Positive electrode active material, method for manufacturing the same, positive electrode sheet, secondary battery, and power storage device

Abstract

The present application relates to a method for preparing a positive electrode active material, comprising the following steps: a step of preparing a core material N1: providing a positive electrode active material precursor, mixing and sintering with a lithium source and a compound C1 containing element M, and then crushing to obtain the core material N1; a step of preparing a product N2: mixing and sintering the core material N1 with a compound C2 containing element Y to obtain the product N2; a step of obtaining a positive electrode active material: mixing and sintering the product N2 with a compound C3 containing element Y to obtain the positive electrode active material. The present application also relates to the positive electrode active material prepared by the method, and a positive electrode sheet, a secondary battery and an electric device comprising the positive electrode material. The secondary battery using the positive electrode active material prepared by the method has improved electrode sheet energy density, cycle performance and safety performance.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and in particular to a positive electrode active material and its preparation method, a positive electrode sheet, a secondary battery, and an electrical device. Background Technology

[0002] Rechargeable batteries are widely used in various consumer electronics and electric vehicles due to their outstanding advantages of being lightweight, pollution-free, and having no memory effect. In the structure of rechargeable batteries, the cathode material is a crucial component of lithium-ion batteries. Common cathode materials currently include layered structures (such as lithium cobalt oxide, lithium manganese oxide, and lithium nickel oxide), spinel structures, polyanionic materials, and ternary materials. Nickel-cobalt-manganese ternary materials have received increasing attention due to their high energy density, low cost, and reliable safety.

[0003] However, the energy density, cycle performance, and safety performance of secondary batteries using existing nickel-cobalt-manganese ternary materials still need further improvement. Summary of the Invention

[0004] This application is made in view of the above-mentioned issues, and its purpose is to provide a positive electrode active material that enables secondary batteries containing it to have improved electrode energy density, cycle performance and safety performance.

[0005] To achieve the above objectives, the first aspect of this application provides a method for preparing a positive electrode active material, comprising the following steps:

[0006] The steps for preparing core material N1 are as follows: a positive electrode active material precursor is provided, which is mixed with a lithium source and a compound C1 containing element M and sintered, and then pulverized to obtain core material N1;

[0007] The steps for preparing product N2 are as follows: core material N1 is mixed with compound C2 containing element Y and sintered to obtain product N2;

[0008] The steps to obtain the positive electrode active material are as follows: the product N2 is mixed with the compound C3 containing element Y and sintered to obtain the positive electrode active material.

[0009] The preparation method of this application can increase the coating amount while making the coating more dense, improving the interfacial stability of the ternary cathode material under high voltage, reducing metal dissolution, reducing the contact area between the electrolyte and the main cathode material, suppressing interfacial side reactions during storage, and reducing DCR growth during cycling. Simultaneously, the preparation method of this application ensures enhanced coating uniformity, reduces polarization caused by large particles, and guarantees the full utilization of its specific capacity.

[0010] In any embodiment, in the step of preparing the core material N1, the lithium source comprises at least one selected from lithium carbonate, lithium hydroxide, and lithium oxalate.

[0011] In any embodiment, in the step of preparing the core material N1, the molar ratio of the precursor to the lithium source is 1:(1.0-3.5), wherein the lithium source is calculated based on the lithium therein.

[0012] In any embodiment, in the step of preparing the core material N1, the element M comprises one or more selected from the elements Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb, W and Al.

[0013] In any embodiment, in the steps of preparing product N2 and obtaining the positive electrode active material, the element Y comprises one or more selected from Co, Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb, W and Al.

[0014] In any embodiment, in the step of preparing core material N1, the amount of compound C1 containing element M is 500ppm-10000ppm, optionally 2000ppm-6000ppm; and / or, in the step of preparing product N2, the amount of compound C2 containing element Y is 500ppm-10000ppm, optionally 2000ppm-6000ppm; and / or, in the step of obtaining positive electrode active material, the amount of compound C3 containing element Y is 500ppm-10000ppm, optionally 2000ppm-6000ppm; each based on the mass of positive electrode active material.

[0015] In any embodiment, in the step of preparing the core material N1, the sintering temperature is 700℃-970℃, and / or the sintering time is 8 hours-15 hours; and / or, in the step of preparing the product N2, the sintering temperature is 500℃-750℃, and / or the sintering time is 4 hours-8 hours; and / or, in the step of obtaining the positive electrode active material, the sintering temperature is 250℃-450℃, and / or the sintering time is 3 hours-8 hours.

[0016] In any embodiment, the positive electrode active material precursor has the general formula Ni a Co b Mn c (OH)2, where 0.3≤a≤0.7, 0.01≤b≤0.3, 0.1≤c≤0.5, and a+b+c=1.

[0017] In any embodiment, in the step of preparing the core material N1, the compound containing element M comprises one or more selected from element M as an element, oxide, boride, phosphate, oxalate, carbonate, and sulfate; and / or, in the step of preparing product N2 and the step of obtaining the positive electrode active material, the compound containing element Y comprises one or more selected from element Y as an element, oxide, boride, phosphate, oxalate, carbonate, and sulfate.

[0018] A second aspect of this application also provides a positive electrode active material prepared by the method described in the first aspect of this application, the positive electrode active material comprising a core and a coating layer disposed on the surface of the core, the core comprising a single-crystal compound having the following general formula: Li x (Ni a Co b Mn c ) d M 1-d O 2-y A y ,

[0019] Where 0.95≤x≤1.3, 0.3≤a≤0.7, 0.01≤b≤0.15, 0.1≤c≤0.5, a+b+c=1, 0.95≤d≤1, 0≤y≤0.1;

[0020] M includes one or more elements selected from Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb, W and Al;

[0021] A contains one or more elements selected from S, N, F, Cl, Br, and I;

[0022] The coating layer contains 3000ppm-15000ppm of element Y in its elemental form, oxide, boride, phosphate, oxalate, carbonate, sulfate and its thermal decomposition products, and based on the mass of the positive electrode active material, the element Y contains one or more selected from Co, Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb, W and Al.

[0023] The positive electrode active material of this application can improve the energy density of the electrode and the cycle performance and safety performance of the secondary battery using it.

[0024] In any embodiment, the particle size Dv50 of the positive electrode active material is 2μm-7μm; and / or, the particle size Dv10 of the positive electrode active material is 1μm-3μm; and / or, the particle size Dv90 of the positive electrode active material is 5μm-15μm.

[0025] By controlling the particle size of the positive electrode active material within the above range, it is possible to ensure that the material has high capacity while maximizing cycle life.

[0026] In any embodiment, the specific surface area (BET) of the positive electrode active material is 0.45 m². 2 / g-0.99m 2 / g; and / or, the compacted density of the 4T powder of the positive electrode active material is 2.5 g / cm³. 3 -4.5g / cm 3 .

[0027] Ternary cathode active materials with the above-mentioned BET and / or compaction density can ensure that they have high energy density and improve the power of secondary batteries.

[0028] The high-stability positive electrode active material of this application can ensure that when the positive electrode active material is applied to a high-voltage system, it can effectively avoid the negative effects of excessive cycle DC resistance (DCR) and severe gas generation caused by the large contact area of ​​the positive electrode electrolyte and the many side reactions during long-cycle processes.

[0029] The ternary cathode material of this application exhibits good interfacial stability under high voltage (e.g., greater than or equal to 4.5V), which can suppress interfacial side reactions during storage, facilitate charge transfer and electrochemical reactions during the reaction process, reduce the growth of DCR during cycling, and thus effectively improve the cycle performance and safety performance of the prepared secondary battery.

[0030] A third aspect of this application provides a positive electrode sheet, which 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 includes a positive electrode active material prepared by the method described in the first aspect of this application or the positive electrode active material described in the second aspect of this application, and the content of the positive electrode active material in the positive electrode film layer is 10% by weight or more, based on the total weight of the positive electrode film layer.

[0031] The fourth aspect of this application provides a secondary battery comprising a positive electrode active material prepared by the method described in the first aspect of this application, or the positive electrode active material described in the second aspect of this application, or the positive electrode sheet described in the third aspect of this application.

[0032] The fifth aspect of this application provides an electrical device including the secondary battery of the fourth aspect of this application.

[0033] Since the electrical device of this application includes the secondary battery provided in this application, it has at least the same advantages as the secondary battery. Attached Figure Description

[0034] Figure 1This is a schematic diagram of a battery cell according to one embodiment of this application.

[0035] Figure 2 yes Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown.

[0036] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0037] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0038] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0039] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0040] Explanation of reference numerals in the attached figures:

[0041] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0042] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode active material, its preparation method, the positive electrode sheet, the secondary battery, and the power application 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.

[0043] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0044] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0045] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0046] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, optionally 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 method may also include step (c), indicating 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.

[0047] 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.

[0048] 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).

[0049] In current technologies, the demand for battery energy density is constantly increasing. This is typically achieved by raising the cutoff voltage to improve energy density. However, increasing the voltage may exacerbate cation mixing during battery charging and discharging, making irreversible phase transitions and crystal structure changes more likely. To address these issues, modification methods such as coating and doping are generally used to improve the crystal structure and electrochemical performance of the materials. However, when the operating voltage of ternary cathode materials is increased to 4.5V, the cycle DCR increases at high voltages, and the long-term cycle DCR increases rapidly, leading to accelerated storage degradation. Conventional coating and doping methods cannot achieve the desired suppression effect.

[0050] Unexpectedly, the inventors discovered in their research that the preparation method of this application can increase the coating amount while making the coating more compact, which can stabilize the interface stability of the ternary cathode material under high voltage, suppress interfacial side reactions during storage, and reduce DCR growth during cycling.

[0051] The first aspect of this application provides a method for preparing the positive electrode active material, which includes the following steps:

[0052] The steps for preparing core material N1 are as follows: a positive electrode active material precursor is provided, which is mixed with a lithium source and a compound C1 containing element M and sintered, and then pulverized to obtain core material N1;

[0053] The steps for preparing product N2 are as follows: core material N1 is mixed with compound C2 containing element Y and sintered to obtain product N2;

[0054] The steps to obtain the positive electrode active material are as follows: the product N2 is mixed with the compound C3 containing element Y and sintered to obtain the positive electrode active material.

[0055] The preparation method of this application can increase the coating amount and make the coating more dense, improve the interfacial stability of the ternary cathode material under high voltage, reduce metal dissolution, reduce the contact area between the electrolyte and the main cathode material, suppress interfacial side reactions during storage, and reduce DCR growth during cycling.

[0056] In some embodiments, in the step of preparing the core material N1, the lithium source comprises at least one selected from lithium carbonate, lithium hydroxide, and lithium oxalate.

[0057] In some embodiments, in the step of preparing the core material N1, the molar ratio of the precursor to the lithium source is 1:(1.0-3.5), optionally 1:(1.05-3), or even optionally 1:(1.06-1.5), wherein the lithium source is calculated based on the lithium therein.

[0058] Most existing methods for preparing ternary cathode active materials use a single sintering process, which is time-consuming and cannot uniformly coat a large amount of material. Unexpectedly, the method of this application not only increases the coating amount but also shortens the sintering time, improves product performance, and increases production efficiency.

[0059] In this application, the precursor of the positive electrode active material can be prepared by methods known in the prior art (e.g., by co-precipitation reaction). For example, by preparing an aqueous solution of nickel sulfate, cobalt sulfate, and manganese sulfate, and then placing the solution in a reaction vessel, the particle size and micromorphology can be adjusted by controlling the reaction time, reaction temperature, pH value, and ammonia concentration, thereby preparing positive electrode active material precursors with different particle sizes.

[0060] In some embodiments, in the step of preparing the core material N1, the positive electrode active material precursor has the general formula Ni. a Co b Mn c (OH)2, where 0.3≤a≤0.7, 0.01≤b≤0.3, 0.1≤c≤0.5, and a+b+c=1.

[0061] In some embodiments, in the step of preparing core material N1, the amount of compound C1 containing element M is 500ppm-10000ppm, optionally 2000ppm-6000ppm, further optionally 2500ppm-4500ppm, and even more optionally 3200ppm-4200ppm; and / or, in the step of preparing product N2, the amount of compound C2 containing element Y is 500ppm-10000ppm, optionally 1500ppm-6000ppm, and even more optionally 2000ppm-4500ppm; and / or, in the step of obtaining positive electrode active material, the amount of compound C3 containing element Y is 500ppm-10000ppm, optionally 1500ppm-6000ppm, further optionally 2000ppm-4500ppm, and even more optionally 3500ppm-4200ppm; each based on the mass of the positive electrode active material.

[0062] In some embodiments, in the step of preparing the core material N1, the sintering temperature is 700℃-970℃, optionally 850℃-950℃; and / or, the sintering time is 8 hours-15 hours, optionally 9 hours-12 hours.

[0063] In some embodiments, in the step of preparing product N2, the sintering temperature is 500℃-750℃, optionally 510℃-600℃; and / or, the sintering time is 4 hours-8 hours, optionally 4.5 hours-6 hours.

[0064] In some embodiments, in the step of obtaining the positive electrode active material, the sintering temperature is 250°C-450°C, optionally 290°C-350°C; and / or, the sintering time is 3 hours-8 hours, optionally 4 hours-6 hours.

[0065] In some embodiments, in the step of preparing the core material N1, the element M comprises one or more selected from the elements Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb, W and Al.

[0066] In some embodiments, during the preparation of the core material N1, the sintered material is pulverized after sintering. Optionally, the pulverization is performed in an air jet mill for 1-10 hours. Optionally, the particle size Dv50 of the core material N1 is 1μm-7μm, optionally 2μm-6μm, and further optionally 3μm-5.5μm; and / or the particle size Dv10 of the core material N1 is 0.5μm-3μm, optionally 1μm–2.5μm, and further optionally 1.5μm–2.5μm; and / or the particle size Dv90 of the core material N1 is 5μm-15μm, optionally 5.5μm-13μm, and further optionally 6μm-12μm.

[0067] In this application, it will be understood that the general formula Li is used herein. x (Ni a Co b Mn c ) d M 1-d O 2-y A yThis refers to the general formula of the core material obtained after the step of preparing core material N1 by the method of this application. The coating material (i.e., a compound containing element Y) added in the steps of preparing product N2 and obtaining the positive electrode active material is attached (optionally uniformly attached) to the surface of the core material particles in a continuous or discontinuous state (usually a point distribution state). The coating layer formed on the surface of the core particles in this application is usually a single layer structure. Through the method of this application, the subsequently sintered coating material (e.g., the coating material added in the step of obtaining the positive electrode active material) can fill the voids between the previously sintered coating material particles, so that the coating layer is more uniformly distributed on the surface of the core particles without significantly changing the particle size of the core particles.

[0068] In this application, compounds C2 and C3 containing element Y are typically nanoscale particles with a particle size Dv50 typically not greater than 30 nm, optionally not greater than 20 nm, and further optionally not greater than 10 nm. Therefore, in some embodiments, the thickness of the coating layer on the surface of the core material particles is typically from 1 nm to 40 nm, optionally from 3 nm to 20 nm.

[0069] In some embodiments, in the steps of preparing product N2 and obtaining the positive electrode active material, the element Y comprises one or more selected from elements Co, Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb, W and Al, and may be selected as at least two or three.

[0070] In some embodiments, in the steps of preparing product N2 and obtaining the positive electrode active material, the compound C2 containing element Y and the compound C3 containing element Y may be the same or different, and may be different.

[0071] In some embodiments, in the step of preparing the core material N1, the compound containing element M comprises one or more elements selected from M, oxides, borides, phosphates, oxalates, carbonates, and sulfates; optionally, the compound containing M comprises oxides selected from M.

[0072] In some embodiments, in the steps of preparing product N2 and obtaining the positive electrode active material, the compound containing element Y comprises one or more selected from elemental form, oxide, boride, phosphate, oxalate, carbonate and sulfate of Y; optionally, the compound containing Y comprises oxide selected from Y.

[0073] In some embodiments, in the step of preparing the core material N1, the compound containing element M contains at least one selected from Al2O3, WO3, and ZrO2, and may be selected from at least two or three.

[0074] In some embodiments, in the steps of preparing product N2 and obtaining the positive electrode active material, the compound containing Y comprises at least one selected from Sb2O5, Nb2O5 and TiO2, and may be selected from at least two or three.

[0075] In some embodiments, in the step of preparing the core material N1, the compound C1 containing element M contains at least two, optionally three, selected from Al2O3, WO3, and ZrO2; optionally, the compound C1 containing element M contains Al2O3, WO3, and ZrO2; further optionally, the compound C1 containing element M contains 500ppm-2000ppm of Al2O3, 1000ppm-3000ppm of WO3, and 500ppm-2000ppm of ZrO2, each based on the mass of the positive electrode active material.

[0076] In some embodiments, in the step of preparing product N2, the compound C2 containing element Y comprises at least two or three selected from Nb2O5, Sb2O5 and TiO2, optionally two; optionally, the compound C2 containing element Y comprises Sb2O5, Nb2O5 and TiO2; and even more optionally, the compound C2 containing element Y comprises 500ppm-2000ppm of Sb2O5 and 500ppm-2000ppm of Nb2O5, each based on the mass of the positive electrode active material.

[0077] In some embodiments, in the step of obtaining the positive electrode active material, the compound C3 containing element Y contains at least two or three selected from Nb2O5, Sb2O5 and TiO2, optionally three; optionally, the compound C3 containing element Y contains Nb2O5, Sb2O5 and TiO2; even more optionally, the compound C3 containing element Y contains 500ppm-2000ppm of Nb2O5, 500ppm-2000ppm of Sb2O5 and 1000ppm-3000ppm of TiO2, each based on the mass of the positive electrode active material.

[0078] In some embodiments, in the steps from preparing the core material N1 to obtaining the positive electrode active material, the sum of the contents of the compound C1 containing element M, the compound C2 containing element Y, and the compound C3 containing element Y is 4000ppm-20000ppm, optionally 5000ppm-15000ppm, also optionally 6000ppm-12000ppm, and further optionally 8000ppm-11000ppm, based on the mass of the positive electrode active material.

[0079] In some embodiments, in the steps from preparing the core material N1 to obtaining the positive electrode active material, the mass ratio of the compound C1 containing element M, the compound C2 containing element Y, and the compound C3 containing element Y is 1:(0.4-2.5):(0.8-2), optionally 1:(0.45-2):(0.9-1.5), and even more preferably 1:(0.48-1):(0.95-1.2).

[0080] In some embodiments, in the step of preparing product N2, after sintering, the obtained product N2 is cooled to 10°C-100°C, optionally 15°C-80°C, and further optionally 20°C-40°C, and then used in the step of obtaining positive electrode active material.

[0081] In some embodiments, in the step of obtaining the positive electrode active material, the particle size Dv50 of the positive electrode active material is 2μm-7μm; and / or, the particle size Dv10 of the positive electrode active material is 1μm-3μm; and / or, the particle size Dv90 of the positive electrode active material is 5μm-15μm.

[0082] In some embodiments, during the step of obtaining the positive electrode active material, the BET of the positive electrode active material is 0.45m. 2 / g-0.99m 2 / g; and / or, the compacted density of the 4T powder of the positive electrode active material is 2.5 g / cm³. 3 -3.3g / cm 3 .

[0083] It is understood that some of the limitations and preferences mentioned in the first aspect of this application also apply to the positive electrode active material described in the second aspect, and vice versa.

[0084] In some embodiments, the mixing in the steps from preparing the core material N1 to obtaining the positive electrode active material is carried out using a mixer, which includes one or more selected from high-speed mixers, sand mill mixers, or plow roller mixers.

[0085] In some embodiments, the sintering is carried out in an air or oxygen atmosphere during the steps from preparing the core material N1 to obtaining the positive electrode active material.

[0086] In some embodiments, from the step of preparing the core material N1 to the step of obtaining the positive electrode active material, the oxygen concentration in the oxygen atmosphere is 80% or more, optionally 90% or more, or optionally 99.9% or more.

[0087] A second aspect of this application also provides a positive electrode active material prepared by the method described in the first aspect of this application, the positive electrode active material comprising a core and a coating layer disposed on the surface of the core, the core comprising a single-crystal compound having the following general formula: Li x (Ni a Co b Mn c ) d M 1-d O 2-y A y ,

[0088] Where 0.95≤x≤1.3, 0.3≤a≤0.7, 0.01≤b≤0.15, 0.1≤c≤0.5, a+b+c=1, 0.95≤d≤1, 0≤y≤0.1;

[0089] M includes one or more elements selected from Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb, W and Al;

[0090] A contains one or more elements selected from S, N, F, Cl, Br, and I;

[0091] The coating layer contains 3000ppm-15000ppm of element Y in its elemental form, oxide, boride, phosphate, oxalate, carbonate, sulfate and its thermal decomposition products, and based on the mass of the positive electrode active material, the element Y contains one or more selected from Co, Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb, W and Al.

[0092] In some embodiments, the coating layer contains 3000ppm-15000ppm, optionally 4000ppm-12000ppm, and also optionally 5000ppm-10000ppm of element Y, including elemental Y, oxides, borides, phosphates, oxalates, carbonates, sulfates, and their thermal decomposition products, based on the mass of the positive electrode active material.

[0093] The positive electrode active material of this application can improve the energy density of the electrode and the cycle performance and safety performance of the secondary battery using it.

[0094] In this application, the content of the coating layer refers to the content of all substances in the coating layer above the core particle material, that is, the sum of all compounds containing element Y (compound C1 containing element Y and compound C2 containing element Y). It should be understood that when the content of the coating layer is too high, for example greater than 20,000 ppm, optionally greater than 30,000 ppm, it will hinder the lithium-ion transport path, leading to a decrease in specific capacity.

[0095] In this application, the core is a single-crystal material, which refers to primary particles with a size greater than 0.9 μm, existing as single particles or several primary particles bonded together without significant agglomeration. In this application, it is understood that the core is electrically neutral.

[0096] In this application, the chemical composition of the core material can be measured by inductively coupled plasma optical emission spectrometry (ICP). For example, the substance to be tested is heated to 500°C and calcined for 2 hours, then cooled to room temperature. Aqua regia is added to dissolve the calcined product, and then elemental analysis is performed by inductively coupled plasma optical emission spectrometry (ICP, Ametek, model: SPECTRO ARCOS ICP-OES). This test can obtain the proportion of each element, and the chemical formula Li can be determined based on the proportion of each element. x (Ni a Co b Mn c ) d M 1-d O 2-y A y x, a, b, c, d, and y.

[0097] In this document, the term "thermal decomposition product" refers to the substance obtained by decomposing oxides, borides, phosphates, oxalates, carbonates, and sulfates of element Y under high-temperature heating (e.g., 200-1000°C, optionally 250-700°C), such as the substance obtained by heating under the conditions of the steps of preparing product N2 and obtaining the positive electrode active material in the method described below in this application.

[0098] Unless otherwise stated, in the above chemical formulas, when M consists of two or more elements, the aforementioned limitation on the range of values ​​for d applies not only to the stoichiometric coefficient of each element as M, but also to the sum of the stoichiometric coefficients of all elements as M. That is, when M consists of two or more elements M1, M2...Mn, the stoichiometric coefficients d1, d2...dn of each of M1, M2...Mn must each fall within the range of values ​​for d defined in this application, and the sum of d1, d2...dn must also fall within this range.

[0099] In some implementation schemes, in general formula Li x (Ni a Co b Mn c ) d M 1-d O 2-y A y Among them

[0100] 0.95≤x≤1.3, optionally, 0.96≤x≤1.28, further optionally, 0.97≤x≤1.25;

[0101] 0.3≤a≤0.7, optionally, 0.4≤a≤0.6, further optionally, 0.50≤a≤0.58;

[0102] 0.01≤b≤0.15, optionally, 0.02≤b≤0.10, further optionally, 0.04≤b≤0.08;

[0103] 0.1≤c≤0.5, optionally, 0.2≤c≤0.45, further optionally, 0.35≤c≤0.42;

[0104] 0.95≤d≤1, optionally, 0.96≤d≤0.999, further optionally, 0.995≤d≤0.999;

[0105] 0≤y≤0.1, optionally, 0≤y≤0.05, and further optionally, 0≤y≤0.02.

[0106] In some embodiments, the particle size Dv50 of the positive electrode active material is 2μm-7μm, optionally, the particle size Dv50 of the positive electrode active material is 3μm-6μm, and even more optionally, the particle size Dv50 of the positive electrode active material is 4μm-5.5μm.

[0107] In some embodiments, the particle size Dv10 of the positive electrode active material is 1 μm–3 μm, and optionally, the particle size Dv10 of the positive electrode active material is 1.5 μm–2.8 μm.

[0108] In some embodiments, the particle size Dv90 of the positive electrode active material is 5μm-15μm, optionally, the particle size Dv90 of the positive electrode active material is 6μm-12μm, and even more optionally, the particle size Dv90 of the positive electrode active material is 8μm-11μm.

[0109] In some embodiments, the SPAN value of the positive electrode active material is ≥0.25, optionally, the SPAN value is ≥0.5 and less than 7, and even more optionally, the SPAN value is ≥1.01 and less than 2.0.

[0110] By controlling the particle size of the positive electrode active material within the above range, it is possible to ensure that the material has high capacity while maximizing cycle life.

[0111] In this application, the particle dispersibility SPAN value is calculated according to the formula SPAN = (Dv90 - Dv10) / Dv50, where Dv10 is the particle size corresponding to a cumulative volume percentage of 10% of the sample, Dv50 is the particle size corresponding to a cumulative volume percentage of 50% of the sample, and Dv90 is the particle size corresponding to a cumulative volume percentage of 90% of the sample.

[0112] In some embodiments, the BET of the positive electrode active material is 0.45m. 2 / g-0.99m 2 / g, optionally, the BET of the positive electrode active material is 0.5m. 2 / g-0.85m 2 / g, and optionally, the BET of the positive electrode active material is 0.55m. 2 / g-0.8m 2 / g; and / or, the compacted density of the 4T powder of the positive electrode active material is 2.5 g / cm³. 3 -4.5g / cm 3 Optionally, the compacted density of the 4T powder of the positive electrode active material is 3 g / cm³. 3 -4g / cm 3 Optionally, the compacted density of the 4T powder of the positive electrode active material is 3.2 g / cm³. 3 -3.6g / cm 3 .

[0113] By setting the specific surface area of ​​the positive electrode active material of this application within the above-mentioned range, the corrosion of the positive electrode active material by the electrolyte can be delayed, ensuring its kinetic performance and making it easy to process.

[0114] In this application, the specific surface area was tested in accordance with GB / T 19587-2017, using a nitrogen adsorption specific surface area analysis test method with a Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, USA, and the specific surface area of ​​the material was calculated using the BET (Brunauer Emmett Teller) method.

[0115] By controlling the 4T powder compaction density of the positive electrode active material within the aforementioned range, the electrode compaction density required for this application can be ensured. Powder compaction density can reflect electrode compaction density to a certain extent; with constant BET and particle size, higher powder compaction density indicates a higher electrode compaction density. The compaction density of the positive electrode active material under 4T pressure (i.e., 4 tons of pressure) is determined according to GB / T 24533-2009. A certain amount of positive electrode active material powder is placed in a special compaction mold, and then the mold is placed on a compaction density instrument. A pressure of 4T is applied, and the thickness of the powder under 4T pressure (the thickness after depressurization) is read on the instrument. The compaction density is calculated using ρ = m / v.

[0116] Ternary cathode active materials with the above-mentioned BET and / or compaction density can ensure that they have high energy density and improve the power of secondary batteries.

[0117] The ternary cathode material of this application exhibits good interfacial stability under high voltage (e.g., greater than or equal to 4.5V), which can suppress interfacial side reactions during storage, facilitate charge transfer and electrochemical reactions during the reaction process, reduce the increase of DC resistance during cycling, and thus effectively improve the cycle performance and safety performance of the prepared secondary battery.

[0118] A third aspect of this application provides a positive electrode sheet, which 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 includes a positive electrode active material prepared by the method described in the first aspect of this application or the positive electrode active material described in the second aspect of this application, and the content of the positive electrode active material in the positive electrode film layer is 10% by weight or more, based on the total weight of the positive electrode film layer.

[0119] In some embodiments, the content of the positive electrode active material in the positive electrode film layer is 95-99.5% by weight, optionally 96-99% by weight, based on the total weight of the positive electrode film layer.

[0120] In some embodiments, the compaction density of the positive electrode sheet is 4.5 g / cm³. 3 Up to 3.5g / cm 3 The option is 3.36 g / cm³. 3 Up to 3.45 g / cm 3 .

[0121] In this application, the compaction density of the positive electrode film layer has a meaning known in the art and can be tested using methods known in the art. For example, take a positive electrode sheet that has been coated on one side and cold-pressed (if it is a double-sided coated positive electrode sheet, the positive active material layer on one side can be wiped off first), cut it into small circular pieces with an area of ​​S1, weigh it, and record its weight as M1. Then wipe off the positive active material layer of the weighed positive electrode sheet, weigh the positive current collector, and record it as M0. The areal density of the positive active material layer = (weight of the positive electrode sheet M1 - weight of the positive current collector M0) / S1. Then divide the areal density by the thickness of the positive active material layer to obtain the compaction density of the positive electrode sheet. To ensure the accuracy of the test results, multiple sets (e.g., 10 sets) of samples can be tested, and the average value can be calculated as the test result.

[0122] The fourth aspect of this application provides a secondary battery comprising a positive electrode active material prepared by the method described in the first aspect of this application, or the positive electrode active material described in the second aspect of this application, or the positive electrode sheet described in the third aspect of this application.

[0123] The fifth aspect of this application provides an electrical device including the secondary battery of the fourth aspect of this application.

[0124] The secondary battery of this application will be described below with appropriate reference to the accompanying drawings. The secondary battery may be in the form of a single battery cell, a battery module, or a battery pack.

[0125] In one embodiment of this application, a battery cell is provided.

[0126] Typically, a battery cell includes 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 of ions 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.

[0127] [Positive electrode plate]

[0128] The positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, wherein the positive electrode film layer includes the positive electrode active material of the second aspect of this application or the positive electrode active material prepared according to the method of the first aspect of this application.

[0129] 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.

[0130] 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.).

[0131] In some embodiments, in addition to the positive electrode active material of the second aspect of this application, the positive electrode active material may also be a positive electrode active material known in the art for use in batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0132] 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.

[0133] In some embodiments, the binder constitutes 0.1% to 4% of the positive electrode film by mass, optionally 0.5% to 2%.

[0134] 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.

[0135] In some embodiments, the conductive agent accounts for 0.1% to 4% of the mass percentage of the positive electrode film, optionally 0.5% to 2%.

[0136] 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.

[0137] [Negative electrode plate]

[0138] 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.

[0139] 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.

[0140] 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.).

[0141] 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.

[0142] In some embodiments, the negative electrode active material accounts for 75% to 99% of the mass percentage of the negative electrode film, optionally 80% to 98%.

[0143] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0144] In some embodiments, the binder constitutes 0.1% to 3.5% of the mass percentage of the negative electrode film, optionally 0.5% to 2.5%.

[0145] 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.

[0146] In some embodiments, the conductive agent accounts for 0.04% to 5% of the mass percentage of the negative electrode film, optionally 0.5% to 3%.

[0147] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0148] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the 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 the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0149] [Electrolytes]

[0150] 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.

[0151] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0152] 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.

[0153] 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.

[0154] In some embodiments, the concentration of the electrolyte salt in the non-aqueous electrolyte is, for example, 0.3 mol / L or more, optionally 0.7 mol / L or less, optionally 1.7 mol / L or less, or optionally 1.2 mol / L or less.

[0155] 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.

[0156] [Isolation membrane]

[0157] In some embodiments, the battery cell also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0158] 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.

[0159] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0160] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0161] In some implementations, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch-type soft pack. The soft pack can be made of plastic, including materials such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0162] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 The example shown is a square-structured battery cell 5.

[0163] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover plate 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 plate 53 can be placed over the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0164] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0165] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3In battery module 4, multiple battery cells 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 battery cells 5 can be fixed in place using fasteners.

[0166] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0167] In some embodiments, the aforementioned battery cells can be assembled into a battery pack. In some embodiments, the aforementioned battery modules 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.

[0168] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The 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.

[0169] In addition, this application also provides an electrical device, which includes the secondary battery provided in this application. The secondary battery 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.

[0170] As for the aforementioned electrical device, a secondary battery can be selected according to its usage requirements.

[0171] Figure 6 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.

[0172] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0173] Example

[0174] 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.

[0175] Preparation of primary and secondary batteries

[0176] Example 1

[0177] 1. Preparation of positive electrode active materials

[0178] Preparation of precursors for positive electrode active materials

[0179] In a continuous stirred tank reactor, nickel sulfate, manganese sulfate, and cobalt sulfate were added to deionized water in a molar ratio of Ni:Co:Mn = 55:6:39 (based on elemental nickel, manganese, and cobalt) to prepare a transition metal salt solution with a total molar concentration of 2 mol / L. 4 mol / L sodium hydroxide was added as a precipitant, and 0.4 mol / L ammonia was added as a complexing agent. The precursor Ni for large-particle lithium single-crystal ternary cathode material was prepared by co-precipitation reaction at pH 11.3 for 24 hours. 0.55 Co 0.06 Mn 0.39 (OH)2, particle size Dv50=4.5μm.

[0180] Preparation of positive electrode active materials

[0181] The steps for preparing the core material N1 are as follows: Ni, the precursor of the above positive electrode active material, is used... 0.55 Co 0.06 Mn 0.39 (OH)2 and lithium carbonate were mixed at a molar ratio of 1:1.07, and 1000ppm Al2O3, 2000ppm WO3 and 1000ppm ZrO2 (based on the mass of the final single crystal ternary cathode active material, the same below) were added and placed in a high-speed mixer for mixing. Then, the mixture was placed in a kiln and sintered at 900℃ for 10h. After cooling to room temperature (25℃), it was mechanically ground by an air jet mill for 5 hours to obtain the core material N1.

[0182] The steps for preparing product N2 are as follows: The core material N1 obtained in the previous step is mixed with a mixture of 1000ppm Sb2O5 and 1000ppm Nb2O5 in a high-speed mixer, and then sintered in a kiln at 550℃ for 5 hours. After cooling to room temperature, product N2 is obtained.

[0183] The steps for obtaining the positive electrode active material are as follows: Product N2 is uniformly mixed with 1000 ppm Nb2O5, 1000 ppm Sb2O5, and 2000 ppm TiO2, and then sintered at 300℃ for 5 h to obtain a densely coated single-crystal ternary positive electrode active material with particle sizes Dv50 of 5 μm, Dv10 of 2.5 μm, Dv90 of 9.8 μm, and BET of 0.582 μm. 2 / g, the compacted density of 4T powder is 3.4g / cm³. 3 .

[0184] 2. Preparation of the positive electrode sheet

[0185] The prepared positive electrode active material, conductive carbon black SP, and binder PVDF were dispersed in N-methylpyrrolidone (NMP) solvent at a weight ratio of 98:1:1 and mixed evenly to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated onto a positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained, with a coating weight (after drying) of 0.27 g / 1540.25 mm². 2 Compacted density 3.4 g / cm³ 3 .

[0186] 3. Preparation of negative electrode materials

[0187] Graphite (negative electrode active material), sodium carboxymethyl cellulose (thickener), styrene-butadiene rubber (binder), and acetylene black (conductive agent) were mixed in a mass ratio of 97:1:1:1. Deionized water was added, and the mixture was stirred under vacuum to obtain a negative electrode slurry. The negative electrode slurry was then uniformly coated onto copper foil. After the copper foil was dried at room temperature, it was transferred to a 120°C oven and dried for 1 hour. The foil was then cold-pressed and slit to obtain negative electrode sheets with a coating weight (after drying) of 0.17 g / 1540.25 mm². 2 .

[0188] 4. Preparation of electrolyte

[0189] The organic solvent is a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC, and DEC is 20:20:60. In an argon-atmosphere glove box with a water content of <10 ppm, thoroughly dried lithium salt is dissolved in the organic solvent and mixed thoroughly to obtain the electrolyte; wherein the concentration of lithium salt LiPF6 is 1 mol / L.

[0190] 5. Preparation of the separating membrane

[0191] A 12μm thick polypropylene separator membrane was selected.

[0192] 6. Preparation of Lithium-ion Batteries

[0193] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. After being wound into a square bare cell, it is placed in an aluminum-plastic film, baked at 80°C to remove water, injected with the appropriate electrolyte, and sealed. After processes such as settling, hot and cold pressing, formation, clamping, and capacity testing, the finished secondary battery is obtained.

[0194] Example 2

[0195] The preparation method is similar to that in Example 1, except that in the preparation of the positive electrode active material, only 1000ppm Al2O3 and 2000ppm WO3 are added in the step of preparing the core material N1; 1000ppm Sb2O5 and 1000ppm Nb2O5 are added in the step of preparing product N2; and 1000ppm Nb2O5, 1000ppm Sb2O5 and 2000ppm TiO2 are added in the step of obtaining the positive electrode active material.

[0196] Example 3

[0197] The preparation method is similar to that in Example 1, except that in the preparation of the positive electrode active material, only 1000ppm Al2O3 and 1000ppm ZrO2 are added in the step of preparing the core material N1; 1000ppm Sb2O5 and 1000ppm Nb2O5 are added in the step of preparing the product N2; and 1000ppm Sb2O5 and 2000ppm TiO2 are added in the step of obtaining the positive electrode active material.

[0198] Example 4

[0199] The preparation method is similar to that in Example 1, except that in the preparation of the positive electrode active material, only 1000ppm Al2O3 and 1000ppm ZrO2 are added in the step of preparing the core material N1; 1000ppm Sb2O5 and 1000ppm Nb2O5 are added in the step of preparing the product N2; and 1000ppm Sb2O5 and 1000ppm TiO2 are added in the step of obtaining the positive electrode active material.

[0200] Example 5

[0201] The preparation method is similar to that in Example 1, except that the sintering temperature of the step of preparing the core material N1 is 700°C and the sintering temperature of the step of obtaining the positive electrode active material is 280°C.

[0202] Example 6

[0203] The preparation method is similar to that in Example 1, except that the sintering time for the step of preparing core material N1 is 8 hours and the sintering time for the step of preparing product N2 is 3 hours.

[0204] Example 7

[0205] The preparation method is similar to that of Example 1, except that in the step of preparing the core material N1 during the preparation of the positive electrode active material, the precursor Ni of the above-mentioned positive electrode active material is used... 0.55 Co 0.06 Mn 0.39 (OH)2 and lithium carbonate are mixed in a molar ratio of 1:1.

[0206] Example 8

[0207] The preparation method is similar to that of Example 1, except that in the step of preparing the core material N1 during the preparation of the positive electrode active material, the precursor Ni of the above-mentioned positive electrode active material is used... 0.55 Co 0.06 Mn 0.39 (OH)2 and lithium carbonate are mixed in a molar ratio of 1:3.

[0208] Comparative Example 1

[0209] The preparation method is similar to that in Example 1, except that no dopant is added in the step of preparing the core material N1 when preparing the positive electrode active material (i.e., no 1000ppm Al2O3, 2000ppm WO3 and 1000ppm ZrO2 are added).

[0210] Comparative Example 2

[0211] The preparation method is similar to that in Example 1, except that the step of preparing product N2 is not included in the preparation of the positive electrode active material.

[0212] Comparative Example 3

[0213] The preparation method is similar to that in Example 1, except that the step of obtaining the positive electrode active material is not included in the preparation of the positive electrode active material, and 2000ppm Sb2O5, 2000ppm Nb2O5 and 2000ppm TiO2 are added in the step of preparing product N2.

[0214] Comparative Example 4

[0215] The preparation method is similar to that in Example 1, except that the step of preparing product N2 is not included in the preparation of the positive electrode active material, and the sintering time in the step of obtaining the positive electrode active material is 10 hours.

[0216] Comparative Example 5

[0217] The preparation method is similar to that in Example 1, except that the step of obtaining the positive electrode active material is not included in the preparation of the positive electrode active material, and the sintering time in the step of preparing product N2 is 10 hours.

[0218] Comparative Example 6

[0219] The preparation method is similar to that in Example 1, except that it does not include the steps of preparing product N2 and obtaining positive electrode active material, and only one sintering is used.

[0220]

[0221]

[0222] II. Battery Performance Testing

[0223] Cyclic performance test at 1.25℃

[0224] At 25°C, the lithium-ion battery is charged at a constant current of 1 / 3C to a voltage of 4.5V, then charged at a constant voltage of 4.5V with a current of 0.05C, followed by a constant current discharge of 1C until the final voltage reaches 2.8V and the capacity is C1. This process is repeated until the capacity is measured for the nth cycle, which is Cn. The capacity retention rate (%) is calculated as (nth discharge capacity / first cycle discharge capacity) × 100%. This cycle is continued until the cell capacity retention rate decreases to 80%.

[0225] 2. High-temperature gas production test

[0226] The battery was fully charged to 4.5V at 1C and then left to stand in a 70℃ constant temperature chamber for 30 days. The initial volume and the volume after 30 days of standing were measured by the water displacement method to obtain the battery's volume expansion rate. Battery volume expansion rate (%) = (Volume after 30 days of standing / Initial volume - 1) × 100%.

[0227] 3. Battery capacity test

[0228] The prepared lithium-ion battery was left to stand at a constant temperature of 25°C for 2 hours, then charged at 1 / 3C to 4.5V at 2.8V to 4.5V, and then charged at a constant voltage of 4.5V until the current was ≤0.05mA. After standing for 5 minutes, it was discharged at 1C to 2.8V, and the capacity C of the battery was recorded.

[0229] The specific capacity is equal to the battery capacity C. 放 (mAh) / Mass of positive electrode active material (g).

[0230] 4. High-temperature storage performance test

[0231] At 25℃, the battery was charged at a constant current rate of 0.33C to 4.5V, then charged at a constant voltage rate until the current was less than or equal to 0.05C, and then discharged at a constant current rate of 0.33C to 2.8V. The initial discharge capacity of the battery was measured. At 25℃, the battery was charged at a constant current rate of 0.33C to 4.5V, then charged at a constant voltage rate until the current was less than or equal to 0.05C. The fully charged battery was then stored in a 60℃ oven for 60 days. After 60 days of high-temperature storage, the battery was removed and allowed to cool naturally to 25℃. It was then discharged at a constant current rate of 0.33C to 2.8V, then charged at a constant current rate of 0.33C to 4.5V, then charged at a constant voltage rate until the current was less than or equal to 0.05C, and then discharged at a constant current rate of 0.33C to 2.8V. The discharge capacity of the battery after 60 days of high-temperature storage was measured.

[0232] Battery capacity retention rate (%) after 60 days of high-temperature storage = Discharge capacity after 60 days of high-temperature storage / Initial discharge capacity × 100%.

[0233] Table 2. Test Results

[0234]

[0235] As can be seen from Table 2, secondary batteries using the positive electrode active material prepared by the method of the present invention have improved energy density, cycle performance and safety performance.

[0236] 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 method for preparing a positive electrode active material, comprising the following steps: The steps for preparing core material N1 are as follows: a positive electrode active material precursor is provided, which is mixed with a lithium source and a compound C1 containing element M and sintered, and then pulverized to obtain core material N1; The steps for preparing product N2 are as follows: core material N1 is mixed with compound C2 containing element Y and sintered to obtain product N2, wherein the compound C2 containing element Y contains two or three selected from Nb2O5, Sb2O5 and TiO2. The steps to obtain the positive electrode active material are as follows: the product N2 is mixed with the compound C3 containing element Y and sintered to obtain the positive electrode active material, wherein the compound C3 containing element Y contains two or three selected from Nb2O5, Sb2O5 and TiO2.

2. The method according to claim 1, wherein, In the step of preparing the core material N1, the lithium source comprises at least one selected from lithium carbonate, lithium hydroxide and lithium oxalate.

3. The method according to claim 1 or 2, wherein, In the step of preparing the core material N1, the molar ratio of the precursor to the lithium source is 1:(1.0-3.5), wherein the lithium source is calculated based on the lithium contained therein.

4. The method according to claim 1 or 2, wherein, In the step of preparing the core material N1, the element M includes one or more selected from the elements Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb, W and Al.

5. The method according to claim 1 or 2, wherein, In the step of preparing core material N1, the amount of compound C1 containing element M is 500 ppm-10000 ppm; and / or, in the step of preparing product N2, the amount of compound C2 containing element Y is 500 ppm-10000 ppm; and / or, in the step of obtaining positive electrode active material, the amount of compound C3 containing element Y is 500 ppm-10000 ppm; each based on the mass of positive electrode active material.

6. The method according to claim 5, wherein, In the step of preparing the core material N1, the amount of the compound C1 containing element M is 2000 ppm-6000 ppm, based on the mass of the positive electrode active material.

7. The method according to claim 5, wherein, In the step of preparing product N2, the amount of compound C2 containing element Y is 2000 ppm-6000 ppm.

8. The method according to claim 5, wherein, In the step of obtaining the positive electrode active material, the amount of compound C3 containing element Y is 2000 ppm-6000 ppm, each based on the mass of the positive electrode active material.

9. The method according to claim 1 or 2, wherein, In the step of preparing core material N1, the sintering temperature is 700℃-970℃, and / or the sintering time is 8 hours-15 hours; and / or, in the step of preparing product N2, the sintering temperature is 500℃-750℃, and / or the sintering time is 4 hours-8 hours; and / or, in the step of obtaining positive electrode active material, the sintering temperature is 250℃-450℃, and / or the sintering time is 3 hours-8 hours.

10. The method according to claim 1 or 2, wherein, The positive electrode active material precursor has the general formula Ni a Co b Mn c (OH)2, where 0.3≤a≤0.7, 0.01≤b≤0.3, 0.1≤c≤0.5, and a+b+c=1.

11. The method according to claim 1 or 2, wherein, In the step of preparing the core material N1, the compound containing element M comprises one or more selected from element M as an element, oxide, boride, phosphate, oxalate, carbonate and sulfate.

12. A positive electrode active material prepared by the method of any one of claims 1 to 11, the positive electrode active material comprising a core and a coating layer disposed on the surface of the core, the core comprising a single-crystal compound having the following general formula: Li x (Ni a Co b Mn c ) d M 1-d O2, Where 0.95≤x≤1.3, 0.3≤a≤0.7, 0.01≤b≤0.15, 0.1≤c≤0.5, a+b+c=1, and 0.95≤d≤1; M includes one or more elements selected from Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb, W and Al; The coating layer contains 3,000 ppm to 15,000 ppm of element Y oxide, based on the mass of the positive electrode active material, wherein element Y comprises two or three selected from Ti, Nb, and Sb.

13. The positive electrode active material according to claim 12, wherein the particle size Dv50 of the positive electrode active material is 2 μm-7 μm; and / or, the particle size Dv10 of the positive electrode active material is 1 μm-3 μm; and / or, the particle size Dv90 of the positive electrode active material is 5 μm-15 μm.

14. The positive electrode active material according to claim 12 or 13, wherein the BET of the positive electrode active material is 0.45 m. 2 / g - 0.99 m 2 / g; and / or, the compacted density of the 4T powder of the positive electrode active material is 2.5 g / cm³. 3 - 4.5 g / cm 3 .

15. A positive electrode sheet comprising 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 comprising the positive electrode active material according to any one of claims 12 to 14 or a positive electrode active material prepared by any one of claims 1 to 11, and the positive electrode active material having a content of 10% by weight or more in the positive electrode film layer based on the total weight of the positive electrode film layer.

16. A battery comprising the positive electrode active material according to any one of claims 12 to 14, or the positive electrode active material prepared by any one of claims 1 to 11, or the positive electrode sheet according to claim 15.

17. An electrical device comprising the battery of claim 16.

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