Positive electrode active material and preparation method therefor and use thereof

Abstract

A positive electrode active material and a preparation method therefor and the use thereof. The positive electrode active material comprises a ternary material, which comprises a compound having a chemical formula of Lia(NixCoyMz)O2, wherein 0.9≤a≤1.1, 0.5≤x＜1, 0＜y≤0.5, 0＜z≤0.5, x+y+z=1, and M comprises Mn, Al, etc. The ternary material satisfies: (1) φ=V1 / (V1+V2), and 0.01≤φ≤0.1; and (2) 100≤h003≤250, wherein φ represents the pore volume filling factor of the ternary material, V1 represents the total pore volume of nitrogen adsorption in the ternary material, in cm3 / g, V2 represents the total skeletal volume of the ternary material, in cm3 / g, and h003 represents the number of stacked layers of the (003) crystal plane of the ternary material in the X-ray diffraction pattern, in layers.

Description

Positive electrode active materials, their preparation methods and applications Technical Field

[0001] This application relates to the field of secondary battery technology, specifically to positive electrode active materials, their preparation methods, and applications. Background Technology

[0002] Lithium-ion batteries, as an important component of the new energy family, are widely used in the fields of electronic communications and transportation. For cathode active materials, ternary materials, which have a wide range of applications, have always attracted much attention. Given the market's increasing demands for lightweight and long-range batteries in high-end new energy vehicles, and the growing need for cost reduction in battery cells, increasingly higher requirements are being placed on the specific capacity and cycle performance of ternary materials.

[0003] However, with the increase of Ni content (especially high-nickel ternary materials with Ni content ≥ 80%), the Li material... + / Ni 2+ Increased mixing of pollutants led to Li + Diffusion is hindered within the ternary cathode material structure, leading to increasingly severe irreversible capacity loss and decreased cycle performance.

[0004] The current mainstream methods to improve the capacity and cycle life of ternary cathode materials are optimization of main element content (increasing the content of active Ni and Co, and reducing the content of inactive Mn), doping, and multi-step sintering coating modification. However, the inventors discovered that the aforementioned mainstream methods all have varying degrees of defects—the types of doping and coating modification elements are numerous and the steps are complex. In order to obtain high capacity, the main component content is often a high-Ni, high-Co, low-Mn system (NCM96 / 3 / 1), resulting in high raw material costs. Even so, the final product capacity obtained is only 222.9 mAh / g, which still cannot meet the ultra-high capacity demand of the market. Alternatively, the preparation process requires multiple sintering steps, including preliminary heat treatment, intermediate heat treatment, and final heat treatment. The steps are complex, and the thickness of the core and shell layers of the prepared core-shell structure is difficult to control. The final product has a 0.1C coin cell capacity of ≤225 mAh / g, which is also difficult to meet the ultra-high capacity demand of leading customers. Or, even if an ultra-high capacity of 240 mAh / g is obtained, the current capacity of high-nickel products still falls short of the demand of the high-end electric vehicle market, and cannot meet the iterative demand of downstream customers to further improve capacity and energy density. Moreover, as the capacity is further increased, the capacity decays rapidly during material cycling, and the cycling performance declines significantly.

[0005] Therefore, how to obtain positive electrode active materials with ultra-high capacity, excellent cycle life, and low cost is an urgent technical problem to be solved.

[0006] Summary of the Invention

[0007] Embodiments of the present application provide a positive electrode active material, a preparation method thereof, and an application thereof. The application involves a positive electrode sheet, a secondary battery, and an electrical device.

[0008] In a first aspect, embodiments of the present application provide a positive electrode active material including a ternary material. The ternary material includes a compound with the chemical formula Li a (Ni x Co y M z )O2, where 0.9 ≤ a ≤ 1.1, 0.5 ≤ x < 1, 0 < y ≤ 0.5, 0 < z ≤ 0.5, x + y + z = 1, and M includes at least one of Mn, Al, Ti, Zr, and Mg; the ternary material satisfies:

[0009] (1) and and,

[0010] (2) 100 ≤ h 003 ≤ 250;

[0011] The is the pore volume filling degree of the ternary material;

[0012] The V1 is the total nitrogen adsorption pore volume of the ternary material, with the unit of cm 3 / g;

[0013] The V2 is the total volume of the framework of the ternary material, with the unit of cm 3 / g;

[0014] The h 003 is the stacking layer number of the (003) crystal plane of the ternary material in the X-ray diffraction pattern, with the unit of layer.

[0015] In some embodiments, the V2 is calculated according to the following formula:

[0016] V2 = 1 / ρ,

[0017] The ρ is the true density of the ternary material, g / cm 3 .

[0018] In some embodiments, the ρ satisfies: 4.00 g / cm 3 < ρ < 5.00 g / cm 3 .

[0019] In some embodiments, the V1 is the total nitrogen adsorption pore volume of the ternary material measured by the static volumetric method.

[0020] In some embodiments, the V1 satisfies: 0.0022 cm 3 / g<V1<0.0235cm 3 / g.

[0021] In some embodiments, the h 003 Calculate using the following formula:

[0022] h 003 =D 003 / d 003 ,

[0023] Wherein, the D 003 The average thickness of the ternary material in the X-ray diffraction pattern perpendicular to the (003) crystal plane is expressed in nm; the d 003 The interlayer spacing of the (003) crystal plane of the ternary material described in the X-ray diffraction pattern is in nm.

[0024] In some embodiments, the D 003 Calculated using Scherer's formula.

[0025] In some embodiments, the D 003 Satisfy: 40nm < D 003 <150nm.

[0026] In some embodiments, the d 003 Calculated using the Bragg equation.

[0027] In some embodiments, the d 003 Satisfy: 0.46nm < d 003 <0.48nm.

[0028] In some embodiments, the particle size D50 of the ternary material satisfies: 0 < D50 < 18 μm.

[0029] In some embodiments, the average pore size of the ternary material is d nm, where d satisfies: 0 < d < 100.

[0030] In some embodiments, the specific surface area of ​​the ternary material is bm 2 / g, where b satisfies: 0 < b < 1.

[0031] In some embodiments, the positive electrode active material further includes additives; the additives are doped into the ternary material, or the additives are coated on at least a portion of the surface of the ternary material.

[0032] In some embodiments, the additive comprises a compound containing element R, wherein element R includes, but is not limited to, at least one selected from Ca, Mg, Zr, Sr, Nb, Sb, Sm, Ti, Na, Si, Al, La, W, B, Fe, Cu, K, Si, Ge, Nd, Mo, Y, or Ce. Optionally, element R includes at least one selected from Nb, Sr, Zr, Sb, Sm, Ti, Al, La, W, B, Mo, Y, and Ce.

[0033] In some embodiments, the additive is present in a concentration greater than 0 and less than 10,000 ppm in the positive electrode active material.

[0034] Secondly, embodiments of this application provide a method for preparing a positive electrode active material, comprising:

[0035] The first metal salt solution, the first alkaline solution, and the first complexing agent are simultaneously added to the reaction base liquid under the first stirring condition and the first gas atmosphere to carry out the first reaction and obtain the first product with a honeycomb spherical core structure.

[0036] The second metal salt solution, the second alkaline solution, and the second complexing agent are simultaneously added to the first product under the second stirring condition and in the second gas atmosphere to carry out the second reaction, thereby obtaining the precursor of the ternary material.

[0037] The ternary precursor, lithium source, and additives are mixed to obtain a mixture.

[0038] The mixture is sintered at a multi-stage gradient temperature in an air or oxygen atmosphere to obtain the positive electrode active material.

[0039] The metal salts in both the first and second metal salt solutions are transition metal salts; both the first and second gases include oxygen and an inert gas, with the oxygen volume content in the first gas being 0-20% and the oxygen volume content in the second gas being 10-20%; the first metal salt solution is added at a rate of 100-500 mL / h, the first stirring speed is 200-250 r / min, and the pH of the first reaction is 9.5-10.5; the second metal salt solution is added at a rate of 200-650 mL / h, the second stirring speed is 50-240 r / min, and the pH of the second reaction is 8.8-9.5.

[0040] In some embodiments, the multi-stage gradient temperature sintering includes a heating section, a first isothermal section, a second isothermal section, a third isothermal section, a fourth isothermal section, and a cooling section arranged sequentially. The sintering temperatures of the heating section, the first isothermal section, the second isothermal section, and the third isothermal section increase sequentially, and the sintering temperatures of the third isothermal section, the fourth isothermal section, and the cooling section decrease sequentially.

[0041] In some embodiments, the heating rate of the heating section is 1-5°C / min.

[0042] In some embodiments, the sintering temperature of the first isothermal section is 500-600°C.

[0043] In some embodiments, the sintering temperature of the second isothermal section is 600-700°C.

[0044] In some embodiments, the sintering temperature of the third isothermal section is 700-900°C.

[0045] In some embodiments, the heat preservation time of the third constant temperature section is 5-15 hours.

[0046] In some embodiments, the sintering temperature of the fourth isothermal section is 550-650°C.

[0047] In some embodiments, the heat preservation time of the fourth constant temperature section, the second constant temperature section, and the first constant temperature section is 1-5 hours.

[0048] In some embodiments, the cooling rate of the cooling section is 3-10°C / min.

[0049] In some embodiments, the reaction temperature of both the first reaction and the second reaction is 40-70°C.

[0050] In some embodiments, the reaction time of the first reaction is 1-3 hours.

[0051] In some embodiments, the second reaction is stopped when the volumetric particle size distribution of the ternary material precursor grows to a median particle size of 2-18 μm.

[0052] In some embodiments, the ternary material precursor satisfies:

[0053] (i) and

[0054] (ii) 10≤k 001 ≤50, and k 001 =D 001 / d 001 ;in,

[0055] The V1' is the pore volume filling degree of the ternary material precursor; V1' is the total nitrogen adsorption pore volume of the ternary material precursor measured by the static volumetric method, in cm³. 3 / g; the total volume of the skeleton of the ternary material precursor described in V2', in cm³. 3 / g; the k 001 The number of stacked layers of the (001) crystal plane of the ternary material precursor in the X-ray diffraction pattern is expressed in layers; the D 001 The average thickness of the ternary precursor material perpendicular to the (001) crystal plane, calculated using the Scherer formula in the X-ray diffraction pattern, is given in nm; the d 001 The interlayer spacing of the (001) crystal plane of the ternary material precursor is calculated using the Bragg equation in the X-ray diffraction pattern, and the unit is nm.

[0056] In some embodiments, the reaction base liquid includes a third alkaline solution, a third complexing agent, and pure water, and a third gas is continuously introduced and a third stirring is performed during the preparation of the reaction base liquid; the third gas includes oxygen and an inert gas.

[0057] In some embodiments, the transition metal salt includes nickel salts, cobalt salts, and salts containing element M, wherein M includes at least one selected from Mn, Al, Ti, Zr, and Mg. Optionally, in salts containing element M, M is Mn.

[0058] In some embodiments, the total concentration of the first metal salt solution and the second metal salt solution is 1-5 mol / L.

[0059] In some embodiments, the concentrations of the first alkaline solution, the second alkaline solution, and the third alkaline solution are all 10-35 wt%.

[0060] In some embodiments, the concentrations of the first complexing agent, the second complexing agent, and the third complexing agent are all 0.05-5 mol / L.

[0061] In some embodiments, the concentration of the first complexing agent is less than the concentration of the second complexing agent.

[0062] In some embodiments, the additive includes at least one compound containing element R, wherein element R includes at least one of Ca, Mg, Zr, Sr, Nb, Sb, Sm, Ti, Na, Si, Al, La, W, B, Fe, Cu, K, Si, Ge, Nd, Mo, Y, or Ce.

[0063] In some embodiments, in the mixture, the amount of lithium in the lithium source is e mol, the total amount of transition metals in the ternary material precursor is c mol, and e and c satisfy: 1.0≤e / c≤1.1.

[0064] In some embodiments, the additive content in the mixture is 0-10000 ppm.

[0065] Thirdly, embodiments of this application provide a positive electrode sheet, comprising a positive active material prepared by the method for preparing the positive active material described in any embodiment of the first aspect or the method for preparing the positive active material described in any embodiment of the second aspect.

[0066] Fourthly, embodiments of this application provide a secondary battery, including a positive electrode, a negative electrode, and a separator, wherein the positive electrode is the positive electrode described in the third aspect embodiment.

[0067] Fifthly, embodiments of this application provide an electrical device including the secondary battery described in the fourth aspect.

[0068] The positive electrode active material provided in this application, by controlling the pore volume filling degree of the ternary material and the number of stacked layers of the (003) crystal plane in the X-ray diffraction pattern to conform to the scope of this application, can shorten the internal Li of the ternary material. + The diffusion path of alkali metal ions is optimized, and a suitable pore volume filling degree can provide a channel for stress release during the cycling process of ternary materials, thereby enabling them to achieve higher capacity and better long-cycle performance compared to existing ternary materials.

[0069] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this application, nor is it intended to limit the scope of this application. Other features of this application will become readily apparent from the following description. Attached Figure Description

[0070] The accompanying drawings are provided to better understand this solution and do not constitute a limitation of this application.

[0071] Figure 1 is a schematic flowchart of a method for preparing a positive electrode active material according to an embodiment of this application.

[0072] Figure 2 is a cross-sectional scanning electron microscope (SEM) image of the ternary material precursor in the preparation method of the positive electrode active material in Example 1.

[0073] Figure 3 is a cross-sectional scanning electron microscope (SEM) image of the positive electrode active material prepared by the preparation method of the positive electrode active material in Example 1.

[0074] Figure 4 is a cross-sectional scanning electron microscope (SEM) image of the ternary material precursor in the preparation method of the positive electrode active material of Comparative Example 1.

[0075] Figure 5 shows a cross-sectional scanning electron microscope (SEM) image of the positive electrode active material prepared by the preparation method of Comparative Example 1. Detailed Implementation

[0076] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0077] 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.

[0078] Unless otherwise specified, all raw materials and equipment involved in this application are self-made through commercial means or known methods; and all methods involved are conventional methods unless otherwise specified.

[0079] In this application, pore volume filling degree refers to the percentage of the total pore volume inside the material to the total volume of the secondary spheres.

[0080] In this application, the total volume of the skeleton was measured using a true density meter and is the reciprocal of the true density value.

[0081] In this application, the Scherrer formula is: D = Kλ / (βcosθ), where K is the Scherrer constant, here K = 0.89; λ is the incident X-ray wavelength, which is 0.154056 nm; β is the half-width at half maximum (FWHM) caused by the crystallite size. In the calculation, the value of β is obtained by subtracting the instrument peak width b from the measured FWHM B of the diffraction peak in the XRD pattern (i.e., β = Bb); θ is the diffraction angle, which is expressed in radians (rad) in the calculation.

[0082] In this application, the Bragg equation is: 2dsinθ=nλ, where λ is the wavelength of the incident X-ray, which is 0.154056nm; n is the reflection order, which is taken as 1 here; θ is the diffraction angle, which is expressed in radians (rad) in the calculation.

[0083] <Positive Electrode Active Materials>

[0084] The positive electrode active material in this application embodiment includes a ternary material, wherein the ternary material satisfies the following conditions:

[0085] (1) and and,

[0086] (2) 100≤h 003 ≤250;

[0087] The The pore filling degree of the ternary material;

[0088] V1 represents the total pore volume of nitrogen adsorption in the ternary material, in cm³. 3 / g;

[0089] V2 refers to the total volume of the ternary material's framework, measured in cm³. 3 / g;

[0090] The h 003 The number of stacked layers of the (003) crystal plane of the ternary material in the X-ray diffraction (XRD) pattern is expressed in layers.

[0091] As an optional example, the positive electrode active material in this application embodiment is a ternary material, which satisfies the above conditions (1) and (2).

[0092] For example, the The values ​​can include, but are not limited to, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1.

[0093] In the embodiments of this application, the pore volume filling degree of the ternary material A value of 0.01-0.1 can provide a channel for stress release during the cyclic process of ternary materials; the aforementioned If the value is less than 0.01, the internal structure of the ternary material is too dense, and the Li-P material will exhibit abnormal behavior during charging and discharging. + The long diffusion path of alkali metal ions prevents the electrolyte from fully wetting the material's interior, and the limited pore structure hinders effective stress release during cycling, resulting in low capacity and poor cycling performance in ternary materials. If the value is greater than 0.1, the excessive number of holes during the cycle will cause the spherical structure to collapse, resulting in rapid capacity decay and poor cycle performance.

[0094] For example, the h 003 The possible values ​​include, but are not limited to, 100, 125, 150, 175, 200, 225, or 250.

[0095] In the embodiments of this application, the number of stacked layers (h) of the ternary material (003) crystal plane in the X-ray diffraction pattern is... 003 With 100-250 layers, the suitable and relatively few crystal layer stacking ensures that the ternary material has more and faster Li + The diffusion path allows for higher capacity compared to other ternary cathode materials with the same nickel content; the h 003 If the value is less than 100, it indicates that excessive oxidation during precursor preparation leads to an excessive amount of fine powder in the ternary material, resulting in a low capacity and rapid capacity decay. 003 If it is greater than 250, it will cause the ternary material Li + Due to the limited and slow diffusion pathways, ternary materials exhibit low reversible capacity and poor kinetic performance.

[0096] It should be noted that in the embodiments of this application, conditions (1) and (2) above must be met simultaneously in order for the positive electrode active material to have both high capacity and excellent long cycle performance. If only condition (2) is met and condition (1) is not met, the capacity of the positive electrode active material can be improved, but the long cycle performance cannot be improved; if only condition (1) is met and condition (2) is not met, neither the capacity nor the long cycle performance of the positive electrode active material can be improved.

[0097] In some embodiments, V2 is calculated according to the following formula:

[0098] V2 = 1 / ρ,

[0099] ρ is the true density of the ternary material, in g / cm³. 3 .

[0100] In some embodiments, the ρ satisfies: 4.00 g / cm³ 3 <ρ<5.00g / cm 3 .

[0101] For example, the value of ρ may include, but is not limited to, 4.01 g / cm³. 3 4.1g / cm 3 4.2g / cm 3 4.3g / cm 3 4.4g / cm 3 4.5g / cm 3 4.6g / cm3 4.7g / cm 3 4.8g / cm 3 4.9g / cm 3 Or 4.99g / cm 3 wait.

[0102] In some embodiments, V1 is the total nitrogen adsorption pore volume of the ternary material as measured by the static volumetric method.

[0103] In some embodiments, V1 satisfies: 0.0022 cm 3 / g<V1<0.0235cm 3 / g.

[0104] For example, the value of V1 may include, but is not limited to, 0.0023 cm. 3 / g, 0.0050cm 3 / g, 0.0075cm 3 / g, 0.01cm 3 / g, 0.0125cm 3 / g, 0.0150cm 3 / g, 0.0175cm 3 / g, 0.02cm 3 / g or 0.0234cm 3 / g etc.

[0105] In some embodiments, h003 is calculated according to the following formula:

[0106] h 003 =D 003 / d 003 ,

[0107] Wherein, the D 003 The average thickness of the ternary material in the X-ray diffraction pattern perpendicular to the (003) crystal plane is expressed in nm; the d 003 The interlayer spacing of the (003) crystal plane of the ternary material described in the X-ray diffraction pattern is in nm.

[0108] In some embodiments, the D 003 Calculated using Scherer's formula.

[0109] In some embodiments, the D 003 Satisfy: 40nm < D 003 <150nm.

[0110] For example, D 003The values of include, but are not limited to, 41nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm, 149nm, etc.

[0111] In some embodiments, the d 003 is calculated by the Bragg equation.

[0112] In some embodiments, the d 003 satisfies: 0.46nm < d 003 < 0.48nm.

[0113] Exemplarily, the values of d 003 include, but are not limited to, 0.461nm, 0.465nm, 0.47nm, 0.475nm, 0.479nm, etc.

[0114] In some embodiments, the ternary material includes a compound with the chemical formula Li a (Ni x Co y M z )O2, where 0.9 ≤ a ≤ 1.1, 0.5 ≤ x < 1, 0 < y ≤ 0.5, 0 < z ≤ 0.5, x + y + z = 1, and M includes, but is not limited to, at least one of Mn, Al, Ti, Zr, Mg, etc.

[0115] Exemplarily, the values of a include, but are not limited to, 0.95, 1.0, 1.05, etc.

[0116] Exemplarily, the values of x include, but are not limited to, 0.6, 0.7, 0.8, 0.9, 0.99, etc.

[0117] Exemplarily, the values of y include, but are not limited to, 0.05, 0.1, 0.2, 0.3, 0.4, 0.45, etc.

[0118] Exemplarily, the values of z include, but are not limited to, 0.05, 0.1, 0.2, 0.3, 0.4, 0.45, etc.

[0119] In some embodiments, the particle size D50 of the ternary material satisfies: 0 < D50 < 18μm.

[0120] In the embodiments of the present application, the particle size D50 is also the median particle size.

[0121] Exemplarily, the particle size D50 of the ternary material includes, but is not limited to, 0.1μm, 1μm, 3μm, 5μm, 7μm, 10μm, 13μm, 15μm, 17.9μm, etc.

[0122] In some embodiments, the average pore size of the ternary material is d nm, where d satisfies: 0 < d < 100.

[0123] For example, the average pore size of the ternary material includes, but is not limited to, 1nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, or 99nm.

[0124] In some embodiments, the specific surface area of ​​the ternary material is bm 2 / g, where b satisfies: 0 < b < 1.

[0125] For example, the specific surface area of ​​the ternary material includes, but is not limited to, 0.1 m². 2 / g, 0.2m 2 / g, 0.3m 2 / g, 0.4m 2 / g, 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g or 0.99m 2 / g etc.

[0126] In some embodiments, the positive electrode active material further includes additives.

[0127] In some embodiments, the additive is incorporated into the ternary material.

[0128] In other embodiments, the additive coats at least a portion of the surface of the ternary material. It is understood that when the additive coats at least a portion of the surface of the ternary material, the additive may coat a portion of the surface of the ternary material or the entire surface of the ternary material.

[0129] In some embodiments, the additive includes a compound containing element R, wherein element R includes, but is not limited to, at least one of Ca, Mg, Zr, Sr, Nb, Sb, Sm, Ti, Na, Si, Al, La, W, B, Fe, Cu, K, Si, Ge, Nd, Mo, Y, or Ce.

[0130] As an alternative example, in compounds containing element R, said element R includes at least one of Nb, Sr, Zr, Sb, Sm, Ti, Al, La, W, B, Mo, Y, and Ce.

[0131] In some embodiments, the additive is present in a concentration greater than 0 and less than 10,000 ppm in the positive electrode active material, including but not limited to 0.01 ppm, 10 ppm, 50 ppm, 100 ppm, 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm, 6000 ppm, 7000 ppm, 8000 ppm, 9000 ppm, or 10000 ppm.

[0132] The positive electrode active material provided in this application embodiment, by controlling the pore volume filling degree of the ternary material and the number of stacked layers of the (003) crystal plane in the X-ray diffraction pattern to conform to the scope of this application, can shorten the internal Li of the ternary material. + The diffusion path of alkali metal ions is optimized, and a suitable pore volume filling degree can provide a channel for stress release during the cycling process of ternary materials, thereby enabling them to achieve higher capacity and better long-cycle performance compared to existing ternary materials.

[0133] <Preparation Methods of Positive Electrode Active Materials>

[0134] The method for preparing the positive electrode active material in this application embodiment can be used to prepare the positive electrode active material in this application embodiment.

[0135] Figure 1 is a schematic flowchart of a method for preparing a positive electrode active material according to an embodiment of this application.

[0136] As shown in Figure 1, the preparation method of this positive electrode active material includes the following steps:

[0137] S101. The first metal salt solution, the first alkaline solution, and the first complexing agent are simultaneously added to the reaction base liquid under the first stirring condition and the first reaction is carried out to obtain the first product with a honeycomb spherical core structure.

[0138] In some embodiments, the metal salt in the first metal salt solution is a transition metal salt.

[0139] In some embodiments, the transition metal salt in the first metal salt solution includes nickel salt, cobalt salt, and salt containing element M, wherein M includes at least one of Mn, Al, Ti, Zr, and Mg.

[0140] As an alternative example, in the transition metal salt in the first metal salt solution, M is Mn in the aforementioned salt containing element M.

[0141] As an optional example, the first metal salt solution is a mixed aqueous solution of a water-soluble salt of nickel, a water-soluble salt of cobalt, and a water-soluble salt of manganese.

[0142] For example, the nickel water-soluble salt in the first metal salt solution includes, but is not limited to, at least one of nickel nitrate, nickel chloride, and nickel sulfate.

[0143] For example, the cobalt water-soluble salt in the first metal salt solution includes, but is not limited to, at least one of cobalt nitrate, cobalt chloride, and cobalt sulfate.

[0144] For example, the water-soluble manganese salt in the first metal salt solution includes, but is not limited to, at least one of manganese nitrate, manganese chloride, and manganese sulfate.

[0145] As an alternative example, the first metal salt solution is a mixed aqueous solution of nickel sulfate, cobalt sulfate, and manganese sulfate.

[0146] In some embodiments, the concentration of the first metal salt solution is 1-5 mol / L, including but not limited to 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L.

[0147] It should be noted that, in the embodiments of this application, when the first metal salt solution contains multiple transition metal salts, the total concentration of the transition metal salt solution is 1-5 mol / L.

[0148] In some embodiments, in the first metal salt solution, the molar ratio of nickel salt, cobalt salt, and salt containing element M is as described in the aforementioned ternary material chemical formula Li a (Ni x Co y M z The ratios of x, y, and z in O2 are consistent.

[0149] In some embodiments, the addition rate of the first metal salt solution is 100-500 mL / h, including but not limited to 100 mL / h, 125 mL / h, 150 mL / h, 200 mL / h, 250 mL / h, 300 mL / h, 350 mL / h, 400 mL / h, 450 mL / h, 475 mL / h, or 500 mL / h. In the embodiments of this application, the addition rate of the first metal salt solution is within the above-mentioned range, which can better control the nucleation rate during the precursor synthesis process, thereby synthesizing a honeycomb spherical core structure with a suitable internal structure. This allows the core of the cathode material to inherit a suitable pore volume filling degree, providing a channel for stress release during the cycling process of the ternary material. When the addition rate of the first metal salt solution is less than 100 mL / h, the production capacity is greatly sacrificed, and there is no practical production reference significance. When the addition rate of the metal salt solution is greater than 500 mL / h, the number of seed nuclei is too large, and the primary particles tend to be arranged randomly during the growth process, failing to form a radially ordered loose porous structure. The capacity and cycling performance of the sintered cathode material are both poor.

[0150] As an optional example, the first metal salt solution is added at a rate of 150-400 mL / h.

[0151] In some embodiments, the first alkaline solution includes, but is not limited to, an aqueous solution of NaOH or KOH.

[0152] As an alternative example, the first alkaline solution is an aqueous solution of NaOH.

[0153] In some embodiments, the concentration of the first alkali solution is 10-35 wt%, including but not limited to 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, or 35 wt%.

[0154] In the embodiments of this application, the addition rate of the first alkali solution is adjusted and controlled by feedback of the pH value of the first reaction.

[0155] In some embodiments, the pH of the first reaction is 9.5-10.5, including but not limited to 9.5, 9.6, 9.7, 9.8, 9.9, 10, 10.1, 10.2, 10.3, 10.4, or 10.5. In the embodiments of this application, the pH of the first reaction within the above range can control the number of nuclei and radial growth during precursor synthesis, resulting in filamentous primary precursor particles, and the number of stacked layers k of the (001) crystal plane of the ternary material precursor is [not specified]. 001 The precursor nucleation stage has a relatively small internal structure, resulting in a honeycomb-like spherical core structure with suitable internal density, thereby obtaining the number of stacked layers h of the (003) crystal plane of the cathode material. 003 When the pH is relatively small, the internal pore size of the ternary material is suitable, the lithium-ion diffusion path is short, the material capacity is high, and the cycle performance is excellent. When the pH is less than 9.5, the pore volume filling during the nucleation stage of the precursor is too large, resulting in too many pores in the sintered cathode material, which leads to structural collapse and rapid capacity decay during cycling. When the pH is greater than 10.5, the core formation is too dense, and the capacity and cycle performance of the sintered cathode material cannot be guaranteed.

[0156] As an alternative example, the pH of the first reaction is 10-10.4.

[0157] In some embodiments, the first complexing agent includes, but is not limited to, at least one of ammonia, urea, ammonium acetate, ammonium sulfate, ammonium carbonate, ammonium chloride, and ammonium nitrate.

[0158] As an alternative example, the first complexing agent is ammonia.

[0159] In some embodiments, the concentration of the first complexing agent is 0.05-5 mol / L, including but not limited to 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.11 mol / L, 0.12 mol / L, 0.13 mol / L, 0.14 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, or 5 mol / L.

[0160] As an alternative example, the concentration of the first complexing agent is 0.05-0.15 mol / L.

[0161] In some embodiments, the first complexing agent is added at a rate of 1-20 mL / h, including but not limited to 3.1 mL / h, 9.5 mL / h, or 15.8 mL / h.

[0162] In some embodiments, the first stirring speed is 200-250 r / min, including but not limited to 200 r / min, 210 r / min, 220 r / min, 230 r / min, 240 r / min, or 250 r / min. In the embodiments of this application, the first stirring speed is within the above range, which can reasonably control the degree of agglomeration and order during the precursor nucleation process, obtain a radially ordered macroporous through-pore core structure, thereby making the sintered cathode pore volume distribution orderly, and the material capacity and cycle performance are both better; when the first stirring speed is less than 200 r / min, the agglomeration in the nucleation stage is severe, and the primary particle growth is disordered, the core is too dense, and the precursor core pore volume filling is too low, resulting in the sintered cathode material lacking stress release channels during cycling and poor cycle performance; when the first stirring speed is greater than 250 r / min, the core is too loose, the pore volume filling is too high, and the sintered cathode material has poor cycle performance.

[0163] As an optional example, the speed of the first stirring is 220-240 r / min.

[0164] In some embodiments, the first gas includes, but is not limited to, oxygen (O2) and inert gases.

[0165] For example, the inert gas in the first gas includes, but is not limited to, at least one of argon (Ar), nitrogen (N2), and helium (He).

[0166] As an optional example, the inert gas in the first gas is argon (Ar).

[0167] As an alternative example, the first gas is a mixture of oxygen and argon.

[0168] In some embodiments, the volume content of oxygen in the first gas is 0-20%, including but not limited to 0, 2.5%, 5%, 7.5%, 10%, 12.5%, 15%, 17.5%, or 20%. In the embodiments of this application, the volume content of oxygen in the first gas within the above range can effectively control the degree of oxidation during the precursor synthesis process, thereby controlling the formation of fine filamentous morphology of primary particles, obtaining a precursor with fewer crystal layer stacking layers, and thus inheriting a smaller number of positive electrode crystal layer stacking layers and a higher material capacity; when the volume content of oxygen in the first gas is greater than 20%, the volume content of O2 in the oxidizing atmosphere O2 / Ar mixture is too large, resulting in a nucleation phenomenon during the precursor preparation process, more fine powder, and excessive oxidation leading to a smaller number of (001) crystal layer stacking layers k001 in the prepared precursor, and a smaller number of (003) crystal layer stacking layers (h003) corresponding to the sintered ternary positive electrode material, resulting in too much fine powder in the positive electrode material, lower material capacity, and faster capacity decay.

[0169] As an optional example, the oxygen volume content in the first gas is 5-15%.

[0170] In some embodiments, the reaction temperature of the first reaction is 40-70°C, including but not limited to 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, or 70°C.

[0171] As an optional example, the reaction temperature of the first reaction is 50-60°C.

[0172] In some embodiments, the reaction time of the first reaction is 1-3 hours, including but not limited to 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours.

[0173] In some embodiments, the reaction base liquid includes a third alkaline solution, a third complexing agent, and pure water, and a third gas is continuously introduced and a third stirring is performed during the preparation of the reaction base liquid.

[0174] In some embodiments, the third alkaline solution includes, but is not limited to, aqueous solutions of NaOH or KOH.

[0175] As an optional example, the third alkaline solution is an aqueous solution of NaOH.

[0176] In some embodiments, the concentration of the third alkali solution is 10-35 wt%, including but not limited to 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, or 35 wt%.

[0177] It should be noted that the amount of the third alkaline solution added is controlled by the pH of the reaction substrate.

[0178] As an alternative example, the pH of the reaction substrate is the same as that of the first reaction.

[0179] In some embodiments, the third complexing agent includes, but is not limited to, at least one of ammonia, urea, ammonium acetate, ammonium sulfate, ammonium carbonate, ammonium chloride, and ammonium nitrate.

[0180] As an alternative example, the third complexing agent is ammonia.

[0181] In some embodiments, the concentration of the third complexing agent is 0.05-5 mol / L, including but not limited to 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.11 mol / L, 0.12 mol / L, 0.13 mol / L, 0.14 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, or 5 mol / L.

[0182] In some embodiments, the amount of the third complexing agent added is 0.3-35% of the volume of the reaction substrate.

[0183] For example, the amount of the third complexing agent added is 0.3%, 5%, 10%, 15%, 20%, 25%, 30% or 35% of the volume of the reaction base liquid.

[0184] In some embodiments, the third gas includes, but is not limited to, oxygen (O2) and inert gases.

[0185] For example, the inert gas in the third gas includes, but is not limited to, at least one of argon (Ar), nitrogen (N2), and helium (He).

[0186] As an optional example, the inert gas in the third gas is argon (Ar).

[0187] As an alternative example, the third gas is a mixture of oxygen and argon.

[0188] In some embodiments, the oxygen volume content in the third gas is 5-15%, including but not limited to 5%, 7.5%, 10%, 12.5%, or 15%.

[0189] As an optional example, the oxygen content in the third gas is 10% by volume.

[0190] In some embodiments, the third gas needs to be continuously introduced during the preparation of the reaction base liquid for 4-10 hours, including but not limited to 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours.

[0191] In some embodiments, the speed of the third stirring is 50-250 r / min.

[0192] For example, the speed of the third stirring includes, but is not limited to, 50 r / min, 100 r / min, 150 r / min, 200 r / min or 250 r / min.

[0193] In some embodiments, the third stirring time is 1-3 hours, including but not limited to 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours.

[0194] As an optional example, the method for preparing the reaction base liquid includes: adding the third alkaline solution, the third complexing agent and pure water to a reaction vessel, performing a third stirring, continuously introducing a third gas, and preparing the reaction base liquid.

[0195] S102. The second metal salt solution, the second alkaline solution, and the second complexing agent are simultaneously added to the first product obtained in step S101 under the second stirring condition and in the second gas atmosphere to carry out the second reaction and obtain the precursor of the ternary material.

[0196] It should be noted that in the embodiments of this application, the second reaction and the first reaction in step S101 both belong to the coprecipitation reaction, but are divided into different reaction stages of the coprecipitation reaction. The first reaction in step S101 belongs to the first stage of the coprecipitation reaction, and the second reaction belongs to the second stage of the coprecipitation reaction. The second stage is the radial porous filamentous precursor morphology growth stage.

[0197] In some embodiments, the metal salt in the second metal salt solution is a transition metal salt.

[0198] In some embodiments, the transition metal salt in the second metal salt solution includes nickel salt, cobalt salt, and salt containing element M, wherein M includes at least one of Mn, Al, Ti, Zr, and Mg.

[0199] As an alternative example, in the second metal salt solution, the M in the salt containing element M is Mn.

[0200] As an alternative example, the second metal salt solution is a mixed aqueous solution of a water-soluble salt of nickel, a water-soluble salt of cobalt, and a water-soluble salt of manganese.

[0201] For example, the nickel water-soluble salt in the second metal salt solution includes, but is not limited to, at least one of nickel nitrate, nickel chloride, and nickel sulfate.

[0202] For example, the cobalt water-soluble salt in the second metal salt solution includes, but is not limited to, at least one of cobalt nitrate, cobalt chloride, and cobalt sulfate.

[0203] For example, the water-soluble manganese salt in the second metal salt solution includes, but is not limited to, at least one of manganese nitrate, manganese chloride, and manganese sulfate.

[0204] As an alternative example, the second metal salt solution is a mixed aqueous solution of nickel sulfate, cobalt sulfate, and manganese sulfate.

[0205] In some embodiments, the concentration of the second metal salt solution is 1-5 mol / L, including but not limited to 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L.

[0206] It should be noted that, in the embodiments of this application, when the second metal salt solution contains multiple transition metal salts, the total concentration of the transition metal salt solution is 1-5 mol / L.

[0207] In some embodiments, in the second metal salt solution, the molar ratio of nickel salt, cobalt salt, and salt containing element M is the same as that of the aforementioned ternary material with chemical formula Li. a (Ni x Co y M z The ratios of x, y, and z in O2 are consistent.

[0208] In some embodiments, the addition rate of the second metal salt solution is 200-650 mL / h, including but not limited to 200 mL / h, 225 mL / h, 250 mL / h, 300 mL / h, 350 mL / h, 400 mL / h, 450 mL / h, 500 mL / h, 550 mL / h, 575 mL / h, or 600 mL / h. In the embodiments of this application, the addition rate of the second metal salt solution is within the above-mentioned range, which can better control the stacking and growth rate of hexagonal nanosheets during the precursor synthesis process, thereby obtaining a relatively loose radially porous internal structure of the precursor. This allows the ternary material to inherit a suitable pore volume filling degree and radial structure, providing a channel for stress release during the cycling process of the ternary material. If the addition rate is less than 200 mL / h, the feeding rate is too slow, resulting in an overly compact internal structure and low production capacity. If the addition rate is greater than 650 mL / h, the primary particles tend to be randomly arranged during the growth process, failing to form a radially ordered loose porous structure, resulting in poor capacity and cycling performance of the sintered cathode material.

[0209] As an optional example, the second metal salt solution is added at a rate of 250-500 mL / h.

[0210] In some embodiments, the second alkaline solution includes, but is not limited to, aqueous solutions of NaOH or KOH.

[0211] As an alternative example, the second alkaline solution is an aqueous solution of NaOH.

[0212] In some embodiments, the concentration of the second alkali solution is 10-35 wt%, including but not limited to 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, or 35 wt%.

[0213] In the embodiments of this application, the addition rate of the second alkali solution is adjusted and controlled by feedback of the pH value of the second reaction.

[0214] In some embodiments, the pH of the second reaction is 8.8-9.5, including but not limited to 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, or 9.5. In the embodiments of this application, the pH of the second reaction within the above range can regulate the number of nuclei and radial growth during precursor synthesis, resulting in filamentous primary precursor particles, and the number of stacked layers k of the (001) crystal plane of the ternary material precursor is [not specified]. 001 The number of stacked layers h of the (003) crystal plane of the ternary material is relatively small, thus obtaining the number of stacked layers h of the ternary material. 003 The ternary material has a relatively small internal pore size, a short lithium-ion diffusion path, high material capacity, and excellent cycle performance. However, when the pH is less than 8.8, it does not conform to the actual production scenario, as such a low pH value cannot be obtained under the existing reaction system. When the pH is greater than 9.5, it leads to a decrease in the number of (001) crystal plane stacking layers k of the prepared precursor. 001 If the number of stacked layers h003 corresponding to the (003) crystal plane of the sintered ternary material is too large, the material capacity will be low.

[0215] As an alternative example, the pH of the second reaction is 8.8-9.2.

[0216] In some embodiments, the second complexing agent includes, but is not limited to, at least one of ammonia, urea, ammonium acetate, ammonium sulfate, ammonium carbonate, ammonium chloride, and ammonium nitrate.

[0217] As an alternative example, the second complexing agent is ammonia.

[0218] In some embodiments, the concentration of the second complexing agent is 0.05-5 mol / L, including but not limited to 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.11 mol / L, 0.12 mol / L, 0.13 mol / L, 0.14 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, or 5 mol / L.

[0219] As an alternative example, the concentration of the second complexing agent is greater than 0.15 mol / L and less than 0.3 mol / L.

[0220] In some embodiments, the concentration of the first complexing agent is lower than the concentration of the second complexing agent. This is intended to ensure that, during the nucleation stage, a lower concentration of the first complexing agent promotes the formation of a well-dispersed spherical core structure, while an excessively high concentration of the first complexing agent leads to severe aggregation during the nucleation stage.

[0221] In some embodiments, the second complexing agent is added at a rate of 3-25 mL / h, including but not limited to 6.2 mL / h, 12.5 mL / h, or 20.2 mL / h.

[0222] As an optional example, in the embodiments of this application, the first metal salt solution and the second metal salt solution have the same material composition and concentration, the first alkaline solution, the second alkaline solution and the third alkaline solution have the same material composition and concentration, the first complexing agent, the second complexing agent and the third complexing agent have the same material composition, and the first complexing agent and the second complexing agent have the same concentration.

[0223] In some embodiments, the speed of the second stirring is 50-240 r / min, including but not limited to 50 r / min, 60 r / min, 70 r / min, 80 r / min, 100 r / min, 125 r / min, 150 r / min, 175 r / min, 200 r / min, 210 r / min, 220 r / min, 230 r / min or 240 r / min. In the embodiments of this application, the second stirring speed is within the above-mentioned range, which can reasonably control the degree of agglomeration and order during the precursor growth process, obtain a radially ordered large-pore through-hole structure, thereby making the sintered cathode pore volume distribution orderly, and the material capacity and cycle performance better; when the second stirring speed is less than 50 r / min, the primary particle growth is disordered, the structure is too dense, the precursor pore volume filling is too low, resulting in the sintered cathode material lacking stress release channels during the cycle, and poor cycle performance; when the second stirring speed is greater than 240 r / min, the structure is too loose, the pore volume filling is too high, and the sintered cathode material has poor cycle performance.

[0224] As an optional example, the second stirring speed is 80-200 r / min.

[0225] In some embodiments, the second gas includes, but is not limited to, oxygen (O2) and inert gases.

[0226] For example, the inert gas in the second gas includes, but is not limited to, at least one of argon (Ar), nitrogen (N2), and helium (He).

[0227] As an alternative example, the inert gas in the second gas is argon (Ar).

[0228] As an alternative example, the second gas is a mixture of oxygen and argon.

[0229] In some embodiments, the volume content of oxygen in the second gas is 10-20%, including but not limited to 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%.

[0230] As an optional example, the oxygen volume content in the second gas is 12-18%.

[0231] In some embodiments, the reaction temperature of the second reaction is 40-70°C, including but not limited to 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, or 70°C.

[0232] As an optional example, the reaction temperature of the second reaction is 50-60°C.

[0233] In some embodiments, the second reaction is stopped when the volumetric particle size distribution of the ternary material precursor grows to a median particle size of 2-18 μm.

[0234] For example, the second reaction is stopped when the volumetric particle size distribution of the ternary material precursor grows to a median particle size of, but is not limited to, 2μm, 4μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm or 18μm.

[0235] In some embodiments, the second reaction and the first reaction are carried out in the same reactor.

[0236] In some embodiments, the ternary material precursor satisfies the following conditions:

[0237] (i) and

[0238] (ii) 10≤k 001 ≤50, and k 001 =D 001 / d 001 ;in,

[0239] The V1' is the pore volume filling degree of the ternary material precursor; V1' is the total nitrogen adsorption pore volume of the ternary material precursor measured by the static volumetric method, in cm³. 3 / g; the total volume of the skeleton of the ternary material precursor described in V2', in cm³. 3 / g; the k 001 The number of stacked layers of the (001) crystal plane of the ternary material precursor in the X-ray diffraction pattern is expressed in layers; the D 001 The grain size of the (001) crystal plane of the ternary material precursor, calculated using the Scherer formula in the X-ray diffraction pattern, is expressed in nm; the d 001 The interlayer spacing of the (001) crystal plane of the ternary material precursor is calculated using the Bragg equation in the X-ray diffraction pattern, and the unit is nm.

[0240] In the embodiments of this application, the reason why the ternary material precursor needs to meet the above conditions (i) and (ii) is that: the ternary material has inheritance when the precursor is sintered into a positive electrode; the moderate pore volume filling degree of the precursor ensures that the sintered positive electrode active material can obtain a suitable pore volume filling degree; the suitable and fewer crystal layer stacking layers of the precursor result in fewer crystal layer stacking layers on the 003 crystal plane of the sintered positive electrode active material, thereby ensuring that the capacity and cycle life of the sintered positive electrode active material are both better.

[0241] In some embodiments, V2' is calculated according to the following formula:

[0242] V2'=1 / ρ',

[0243] ρ' is the true density of the ternary material precursor, in g / cm³. 3 .

[0244] In some embodiments, ρ' satisfies: 3.5 g / cm³ 3 <ρ'<4.0g / cm 3 .

[0245] For example, ρ' includes, but is not limited to, 3.55 g / cm³. 3 3.6g / cm 3 3.7g / cm 3 3.8g / cm 3 Or 3.9g / cm 3 wait.

[0246] In some embodiments, V1' satisfies: 0.01cm 3 / g<V1'<0.1cm 3 / g.

[0247] For example, V1' includes, but is not limited to, 0.02m 3 / g, 0.03m 3 / g, 0.05m 3 / g, 0.08m 3 / g or 0.95m 3 / g etc.

[0248] In some embodiments, the D 001 Satisfy: 4nm < D 001 <25nm.

[0249] For example, D 001 Including but not limited to 4.5nm, 8nm, 12nm, 16nm, 20nm or 24nm, etc.

[0250] In some embodiments, the d 001 Satisfy: 0.45nm < d 001 <0.47nm.

[0251] For example, d 001 Including but not limited to 0.455nm, 0.46nm, 0.465nm or 0.469nm.

[0252] In some embodiments, The values ​​include, but are not limited to, 0.05, 0.07, 0.1, 0.13, 0.15, 0.18, 0.20, 0.23, or 0.25.

[0253] In some embodiments, k 001 The possible values ​​include, but are not limited to, 10, 15, 20, 25, 30, 35, 40, 45, or 50.

[0254] In some embodiments, the method for preparing the positive electrode active material further includes the steps of centrifuging, washing, and drying the product of the second reaction.

[0255] S103. Mix the ternary precursor, lithium source and additives obtained in step S102 to obtain a mixture.

[0256] As an optional example, the lithium source is a lithium compound, which includes, but is not limited to, at least one of lithium hydroxide or other lithium salts.

[0257] For example, the lithium salt includes, but is not limited to, at least one of lithium carbonate, lithium sulfate, and lithium chloride.

[0258] In some embodiments, the additive includes, but is not limited to, at least one of compounds containing element R, wherein element R includes, but is not limited to, at least one of Ca, Mg, Zr, Sr, Nb, Sb, Sm, Ti, Na, Si, Al, La, W, B, Fe, Cu, K, Si, Ge, Nd, Mo, Y, or Ce.

[0259] As an optional example, the R element in the above-mentioned R-containing compounds includes at least one of Nb, Sr, Zr, Sb, Sm, Ti, Al, La, W, B, Mo, Y, and Ce.

[0260] In some embodiments, in the mixture, the amount of lithium in the lithium source is e mol, the total amount of transition metals in the ternary material precursor is c mol, and e and c satisfy: 1.0≤e / c≤1.1.

[0261] For example, the values ​​of e / c include, but are not limited to, 1.0, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, or 1.1.

[0262] As an optional example, e and c satisfy: 1.02 ≤ e / c ≤ 1.05.

[0263] In some embodiments, the additive content in the mixture is 0-10000 ppm.

[0264] For example, the additive content in the mixture includes, but is not limited to, 0, 10 ppm, 50 ppm, 100 ppm, 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm, 6000 ppm, 7000 ppm, 8000 ppm, 9000 ppm, or 10000 ppm.

[0265] In some embodiments, the ternary precursor, lithium source and additive obtained in step S102 are mixed in a high-speed mixer.

[0266] S104. The mixture obtained in step S103 is subjected to multi-stage gradient temperature sintering in an air or oxygen atmosphere to obtain the positive electrode active material.

[0267] In some embodiments, the multi-stage gradient temperature sintering includes a heating section, a first isothermal section, a second isothermal section, a third isothermal section, a fourth isothermal section, and a cooling section arranged sequentially. The sintering temperatures of the heating section, the first isothermal section, the second isothermal section, and the third isothermal section increase sequentially, and the sintering temperatures of the third isothermal section, the fourth isothermal section, and the cooling section decrease sequentially.

[0268] In the embodiments of this application, the multi-stage gradient temperature sintering can enable the ternary material in the positive electrode active material to inherit the pore volume structure of the ternary material precursor, ensuring that the pore volume filling degree of the ternary material is within the range defined in this application.

[0269] In some embodiments, the heating rate of the heating section is 1-5℃ / min, including but not limited to 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min or 5℃ / min.

[0270] In some embodiments, the sintering temperature of the first isothermal section is 500-600℃, including but not limited to 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃ or 600℃.

[0271] In some embodiments, the sintering temperature of the second isothermal section is 600-700℃, including but not limited to 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, 660℃, 670℃, 680℃, 690℃ or 700℃.

[0272] In some embodiments, the sintering temperature of the third isothermal section is 700-900℃, including but not limited to 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, or 900℃.

[0273] In some embodiments, the heat preservation time of the third constant temperature section is 5-15 hours, including but not limited to 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours or 15 hours.

[0274] In some embodiments, the sintering temperature of the fourth isothermal section is 550-650℃, including but not limited to 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃ or 650℃.

[0275] In some embodiments, the heat preservation time of the fourth constant temperature section, the second constant temperature section and the first constant temperature section is 1-5h, including but not limited to 1h, 2h, 3h, 4h or 5h.

[0276] In some embodiments, the cooling rate of the cooling section is 3-10℃ / min, including but not limited to 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min or 10℃ / min.

[0277] The method for preparing the positive electrode active material in this application utilizes the inheritance between the ternary material precursor and the ternary material, and by adjusting and optimizing the sintering platform at the sintering end, it is possible to obtain a material with a suitable pore volume filling degree. Ternary materials with fewer stacked layers (h003) thus shorten the internal Li content of the cathode material. + The diffusion pathways of alkali metal ions and the appropriate pore volume filling provide channels for stress release during material cycling, thereby enabling ternary materials to achieve higher capacity and excellent long-cycle performance.

[0278] <Positive Electrode>

[0279] The positive electrode sheet of this application includes the positive active material of any embodiment of this application or the positive active material prepared by the preparation method of the positive active material of any embodiment of this application.

[0280] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes the positive electrode active material of any embodiment of the present application or the positive electrode active material prepared by the preparation method of the positive electrode active material of any embodiment of the present application.

[0281] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on either or both of the two opposite surfaces of the positive electrode current collector.

[0282] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0283] In some embodiments, in addition to the positive electrode active material of the embodiments of the present application, the positive electrode active material can also include other materials capable of absorbing and releasing lithium. For example, lithium manganese phosphate (LiMnPO4), lithium cobalt phosphate (LiCoPO4), lithium iron pyrophosphate (Li2FeP2O7), lithium cobalt oxide (LiCoO2), spinel-type lithium manganate (LiMn2O4), spinel-type lithium nickel manganate (LiNi 0.5 Mn 1.5 O4), layered lithium manganate (LiMnO2), lithium nickel oxide (LiNiO2), lithium niobate (LiNbO2), lithium ferrite (LiFeO2), lithium magnesate (LiMgO2), lithium calcium oxide (LiCaO2), lithium copper oxide (LiCuO2), lithium zinc oxide (LiZnO2), lithium molybdate (LiMoO2), lithium tantalate (LiTaO2), lithium tungstate (LiWO2), lithium nickel cobalt aluminum oxide (LiNi x Co y Al 1-x- y O2, 0 < x < 1, 0 < y < 1, 0 < x + y < 1, for example LiNi 0.8 Co 0.15 Al 0.05 O2), lithium nickel cobalt manganese oxide (LiNi x Co y Mn 1- x-y O2, 0 < x < 1, 0 < y < 1, 0 < x + y < 1, for example LiNi 1 / 3Co 1 / 3 Mn 1 / 3 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 At least one of the following: O2, lithium-rich materials (e.g., lithium-rich nickel-cobalt-manganese oxide), manganese oxide (MnO2), vanadium oxide, sulfur oxide, silicate oxide, and their respective modified compounds. These materials may be used alone or in combination of two or more.

[0284] The modified compounds for the above-mentioned positive electrode active materials can be modified by doping, surface coating, or both doping and coating.

[0285] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0286] In some embodiments, the positive electrode film may optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0287] 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, positive conductive agent, positive 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 current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0288] Secondary batteries

[0289] The secondary battery of this application includes the positive electrode sheet of any embodiment of this application.

[0290] In some embodiments, the secondary battery includes lithium-ion batteries, etc.

[0291] [Negative electrode plate]

[0292] In some embodiments, the secondary battery further includes a negative electrode.

[0293] In some embodiments, 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.

[0294] 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.

[0295] 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.).

[0296] In some embodiments, the negative electrode active material may be a negative electrode active material for batteries known in the art. As an example, these known negative electrode active materials for batteries may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the embodiments of this application are not limited to these materials and may also include other conventional materials that can be used as negative electrode active materials for batteries. These negative electrode active materials may be used alone or in combination of two or more.

[0297] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. The negative electrode 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).

[0298] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. The negative electrode 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.

[0299] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0300] 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, negative electrode conductive agent, negative electrode 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 obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0301] [Isolation membrane]

[0302] In some embodiments, the secondary battery further includes a separator.

[0303] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0304] 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.

[0305] [Electrolytes]

[0306] In some embodiments of this application, the secondary battery further includes an electrolyte.

[0307] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or entirely solid.

[0308] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes electrolyte salts and non-aqueous organic solvents.

[0309] 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.

[0310] In some embodiments, the non-aqueous organic 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.

[0311] In some embodiments, the electrolyte may also optionally include additives. For example, the 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 the overcharge performance of the battery, additives that improve the high-temperature or low-temperature performance of the battery, etc.

[0312] In some embodiments, when the electrolyte is a solid electrolyte, the solid electrolyte includes but is not limited to:

[0313] LISICON type: such as γ-Li3PO4, etc.;

[0314] NASICON type; such as Li (1+x1) Q x M (2-x1) (PO4)3, 0 ≤ x1 < 1, Q includes at least one of Al, Cr, Ba, Fe, Sc, In, Lu, Y, La;

[0315] Garnet type; such as Li (7-x2) La3Zr (2-x2) M x2 O12, etc., 0 ≤ x2 < 1, M includes at least one of Sb, Nb, Ta, Te, W;

[0316] LIPON type: such as Li x3 PO y1 N z1 ; 0 < x3 ≤ 1, 0 < y1 ≤ 1, 0 < z1 ≤ 1;

[0317] Perovskite type: such as Li3 x 4Q (2 / 3-x4) MO3, etc., 0.04 < x4 < 0.17, Q includes at least one of La, Sr, Ba, Nd, M includes at least one of Al, Ti, Ge;

[0318] Anti-Perovskite type: such as Li3OCl, etc.; Thio-LiSICON type: such as Li (3+x5) My2A (1-y2) Q (4-z2) T z2 , where -1 < x5 < 2, 0 ≤ y2 ≤ 1, 0 ≤ z2 ≤ 2, M includes at least one of B, Al, In, Si, Ge, Sn, Ti, W, Mo, A includes at least one of P, As, Sb, Bi, Q includes at least one of S, Se, T includes at least one of F, Cl, Br, I;

[0319] Sulfide solid electrolytes, including: Thiophosphate type: Li3PS4, etc., Argyrodite type: Li6PS5Cl, Halide type: Li3InCl6, Hydride type: 0.7Li(CB9H 10 )-0.3Li(CB 11 H 12 ), and at least one of the following; for example, Li (10+x6) M (1+y3) A (2- y3) Q (12-z3) H z3 type: where -2 < x6 < 2, 0 ≤ y3 ≤ 2, 0 ≤ z3 ≤ 2, M includes at least one of B, Al, In, Si, Ge, Sn, Ti, W, Mo; A includes at least one of P, As, Sb, Bi, Q includes at least one of S, Se, H includes at least one of F, Cl, Br, I: (100 - x7)Li2S·x7M·y4Q type: where 20 ≤ x7 ≤ 30, 0 ≤ y4 ≤ 50, M includes at least one of B2S3, Al2S3, In2S3, SiS2, GeS2, SnS2, P2S5, As2S3, Sb2S5, Bi2S3, WS2, MoS2, Q includes at least one of B2O3, Al2O3, In2O3, SiO2, GeO2, SnO2, P2O5, Sb2O5, Bi2O3, WO2, WO3, MoO2, MoO3, Fe2O3, ZnO, MgO, CuO, CaO, LiN, Li2O, LiF, LiCl, LiBr, LiI; Argyrodite type: Li (6+x8) M y5 A (1-y5) Q (5-z5) T (1+z5) , where -1 ≤ x8 ≤ 1, 0 ≤ y5 ≤ 1, -1 < z5 ≤ 1, M includes at least one of B, Al, In, Si, Ge, Sn, Ti, W, Mo, A includes at least one of P, As, Sb, Bi, Q includes at least one of S, Se, T includes at least one of F, Cl, Br, I; Halide type: Li3MJ or Li2Sc 2 / 3 J; M includes at least one of Y, Er, In, Sc, Ga, J includes at least one of F, Cl, Br, I.

[0320] When the above-mentioned sulfide solid electrolytes are sulfide-type solid electrolytes, they include, but are not limited to: silver-germanium sulfide electrolytes; binary sulfide-type solid systems such as Li2S-P2S5, Li2S-SiS2, Li2S-GeS and Li2S-B2S3; and ternary systems such as Li2S-Me-P2S5, wherein Me is selected from Si, Ge, Sn or Al, etc.

[0321] Specifically, the sulfide electrolyte is selected from at least one of Li2S-P2S5, Li2S-SiS2, Li2S-GeS, Li2S-B2S3 and Li2S-Me-P2S5.

[0322] In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly by a winding process or a stacking process.

[0323] 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.

[0324] In some embodiments, the outer packaging of a secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of a 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.

[0325] The embodiments of this application do not impose any particular limitation on the shape of the secondary battery, which can be cylindrical, square, or any other arbitrary shape.

[0326] <Electrical Appliances>

[0327] The electrical device in the embodiments of this application includes a secondary battery in any embodiment of this application.

[0328] In some embodiments, the aforementioned electrical devices include, but are not limited to, vehicles, lighting devices, electronic devices, etc.

[0329] The positive electrode sheet, secondary battery, and power device of the present application embodiments all have at least the beneficial effects of the positive electrode active material and the preparation method of the positive electrode active material of the present application embodiments.

[0330] The following non-limiting embodiments further illustrate certain features of the present technology.

[0331] I. Examples and Comparative Examples

[0332] The LiOH·H2O used in the following examples and comparative examples is from Ganfeng Lithium Corporation; the additives ZrO2 and Nb2O5 are from Xuancheng Jingrui New Materials Co., Ltd.

[0333] Example 1

[0334] The positive electrode active material in this embodiment is the ternary material Li(Ni) 0.93 Co 0.03 Mn 0.04 O2, the preparation method of which includes the following steps:

[0335] S1, Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 Preparation of (OH)2

[0336] Step 1: Prepare the metal salt solution.

[0337] Nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in deionized water in a molar ratio of 0.93:0.03:0.04 to obtain a 2 mol / L salt solution.

[0338] Step 2: Prepare the reaction base solution.

[0339] 10 mL of 32 wt% sodium hydroxide solution, 110 mL of 4.5 mol / L ammonia water and 5 L of pure water were added to a 10 L reactor and stirred at 230 r / min for 1 h to prepare a reaction base solution with pH 10.0, ammonia concentration of 0.1 mol / L and temperature of 60 °C. During stirring, an O2 / Ar mixture containing 10% O2 was continuously introduced.

[0340] Step 3: Synthesize Ni, the precursor for ternary materials 0.93 Co 0.03 Mn 0.04 (OH)2.

[0341] A method for synthesizing ternary material precursors includes the following steps:

[0342] (1) Generation of honeycomb core structure: The metal salt solution prepared in step 1, 32wt% sodium hydroxide solution and ammonia water with a concentration of 4.5mol / L are simultaneously added to the reaction vessel containing the reaction base liquid obtained in step 2 under the first stirring condition and the first gas atmosphere is continuously introduced to carry out the first reaction and obtain the first product with honeycomb core structure.

[0343] The reaction conditions for the first reaction were as follows: pH value of 10.0, stirring speed of 230 r / min, flow rate of metal salt solution of 300 mL / h, flow rate of ammonia water of 9.5 mL / h, flow rate of sodium hydroxide solution controlled by pH feedback, reaction temperature of 60℃, ammonia concentration of reaction liquid of 0.1 mol / L, first gas of O2 / Ar mixture containing 10% O2 by volume, and reaction time of 2 h.

[0344] (2) Radial porous filament morphology growth: The metal salt solution prepared in step 1, 32wt% sodium hydroxide solution, and 4.5mol / L ammonia water were simultaneously added to the first product obtained in step (1) under a second stirring condition and a continuously introduced second gas atmosphere to carry out the second reaction. After the precursor volume particle size distribution grew to a median particle size of 10μm, it was centrifuged, washed, and dried to obtain the ternary material precursor Ni. 0.93 Co 0.03 Mn 0.04 (OH)2.

[0345] The reaction conditions for the second reaction are as follows: pH value is 9.0, the second stirring speed is 200 r / min, the flow rate of the metal salt solution is 400 mL / h, the flow rate of the ammonia water is 12.5 mL / h, the flow rate of the sodium hydroxide solution is controlled by pH feedback, the reaction temperature is 60℃, the ammonia concentration is 0.2 mol / L, and the second gas is an O2 / Ar mixture containing 15% O2 by volume.

[0346] Figure 2 shows the cross-sectional SEM image of the prepared ternary material precursor, and Table 1 shows the XRD and pore volume filling data of the precursor. As can be seen from Figure 2, the precursor cross-section exhibits a radially porous structure, with most of the pores being large through pores.

[0347] S2, ternary material Li(Ni) 0.93 Co 0.03 Mn 0.04 O2 preparation

[0348] Weigh the above Ni separately 0.93 Co 0.03 Mn 0.04 8.5 kg of (OH)₂ precursor, 4 kg of lithium source LiOH·H₂O, 36 g of additive ZrO₂, and 12 g of additive Nb₂O₅ were mixed uniformly in a high-speed mixer, wherein the lithium in the lithium source reacted with the aforementioned Ni. 0.93 Co 0.03 Mn 0.04 The (OH)2 precursor contains a total transition metal (Ni, Co, Mn) molar ratio of 1.04, a Zr doping concentration of 3000 ppm, and a Nb doping concentration of 1000 ppm. The mixed material is then subjected to multi-stage gradient temperature sintering in an oxygen-filled furnace. First, the temperature is increased to 550°C at a rate of 3°C / min and held for 3 hours. Then, the temperature is increased to 650°C and held for 3 hours, followed by an increase to 730°C and held for 10 hours. The temperature is then decreased to 600°C and held for 3 hours. Finally, the temperature is reduced to room temperature at a rate of 6°C / min to obtain a polycrystalline ternary material (i.e., the positive electrode active material in this embodiment).

[0349] The above-mentioned positive electrode active material was subjected to coarse and fine crushing post-processing to dissociate it into dispersed polycrystalline secondary spherical particles, which were then passed through a 400-mesh sieve to obtain a polycrystalline positive electrode active material with a median particle size D50 of 10-12 μm, named C-1. Figure 3 shows the cross-sectional SEM image of the prepared positive electrode active material, and Table 2 shows the pore volume filling degree and XRD data. As can be seen from Figure 3, the cross-section of the positive electrode active material inherits the pore structure of the precursor well, indicating a porous structure with relatively uniform pore distribution.

[0350] Example 2

[0351] This embodiment is basically the same as embodiment 1, except that:

[0352] In step 2, during the preparation of the reaction base solution, the pH is 10.5;

[0353] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0354] In step (1), the reaction conditions for the first reaction are: pH value is 10.5, the first stirring speed is 200 r / min, the flow rate of the metal salt solution is 100 mL / h, and the flow rate of the ammonia water is 3.1 mL / h.

[0355] In step (2), the reaction conditions for the second reaction are: pH value is 9.5, second stirring speed is 50 r / min, metal salt solution flow rate is 200 mL / h, and ammonia water flow rate is 6.2 mL / h.

[0356] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named C-2.

[0357] Example 3

[0358] This embodiment is basically the same as embodiment 1, except that:

[0359] In step 2, during the preparation of the reaction substrate, the pH is 9.5;

[0360] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0361] In step (1), the conditions for the first reaction are: pH value is 9.5, the first stirring speed is 250 r / min, the flow rate of the metal salt solution is 500 mL / h, and the flow rate of the ammonia water is 15.8 mL / h.

[0362] In step (2), the reaction conditions for the second reaction are: pH value of 8.8, second stirring speed of 240 r / min, metal salt solution flow rate of 650 mL / h, and ammonia water flow rate of 20.2 mL / h.

[0363] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named C-3.

[0364] Example 4

[0365] This embodiment is basically the same as embodiment 1, except that:

[0366] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0367] In step (1), the conditions for the first reaction are: pH value is 9.5.

[0368] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named C-4.

[0369] Example 5

[0370] This embodiment is basically the same as embodiment 1, except that:

[0371] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0372] In step (1), the conditions for the first reaction are: pH value is 10.5.

[0373] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named C-5.

[0374] Example 6

[0375] This embodiment is basically the same as embodiment 1, except that:

[0376] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0377] In step (1), the conditions for the first reaction are: the first stirring speed is 200 r / min.

[0378] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named C-6.

[0379] Example 7

[0380] This embodiment is basically the same as embodiment 1, except that:

[0381] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0382] In step (1), the conditions for the first reaction are: the first stirring speed is 250 r / min.

[0383] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named C-7.

[0384] Example 8

[0385] This embodiment is basically the same as embodiment 1, except that:

[0386] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0387] In step (1), the conditions for the first reaction are: the flow rate of the metal salt solution is 100 mL / h.

[0388] The obtained polycrystalline cathode material with a median particle size D50 of 10-12 μm was named C-8.

[0389] Example 9

[0390] This embodiment is basically the same as embodiment 1, except that:

[0391] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0392] In step (1), the conditions for the first reaction are: the flow rate of the metal salt solution is 500 mL / h.

[0393] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named C-9.

[0394] Example 10

[0395] This embodiment is basically the same as embodiment 1, except that:

[0396] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co0.03 Mn 0.04 During the process of (OH)2:

[0397] In step (2), the conditions for the second reaction are: pH 8.8.

[0398] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named C-10.

[0399] Example 11

[0400] This embodiment is basically the same as embodiment 1, except that:

[0401] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0402] In step (2), the conditions for the second reaction are: pH 9.5.

[0403] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named C-11.

[0404] Example 12

[0405] This embodiment is basically the same as embodiment 1, except that:

[0406] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0407] In step (2), the conditions for the second reaction are: the speed of the second stirring is 240 r / min.

[0408] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named C-12.

[0409] Example 13

[0410] This embodiment is basically the same as embodiment 1, except that:

[0411] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0412] In step (2), the conditions for the second reaction are: the speed of the second stirring is 50 r / min.

[0413] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named C-13.

[0414] Example 14

[0415] This embodiment is basically the same as embodiment 1, except that:

[0416] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0417] In step (2), the conditions for the second reaction are: the flow rate of the metal salt solution is 200 mL / h.

[0418] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named C-14.

[0419] Example 15

[0420] This embodiment is basically the same as embodiment 1, except that:

[0421] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0422] In step (2), the conditions for the second reaction are: the flow rate of the metal salt solution is 650 mL / h.

[0423] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named C-15.

[0424] Example 16

[0425] This embodiment is basically the same as embodiment 1, except that:

[0426] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0427] In step (1), the first gas in the first reaction condition is Ar gas.

[0428] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named C-16.

[0429] Example 17

[0430] This embodiment is basically the same as embodiment 1, except that:

[0431] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0432] In step (1), the conditions for the first reaction are: the first gas is an O2 / Ar mixture containing 20% ​​O2 by volume.

[0433] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named C-17.

[0434] Example 18

[0435] This embodiment is basically the same as embodiment 1, except that:

[0436] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0437] In step (2), the conditions for the second reaction are: the second gas is an O2 / Ar mixture containing 10% O2 by volume.

[0438] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named C-18.

[0439] Example 19

[0440] This embodiment is basically the same as embodiment 1, except that:

[0441] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0442] In step (2), the conditions for the second reaction are: the second gas is an O2 / Ar mixture containing 20% ​​O2 by volume.

[0443] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named C-19.

[0444] Example 20

[0445] This embodiment is basically the same as embodiment 1, except that:

[0446] The positive electrode active material in this embodiment is the ternary material Li(Ni) 0.83 Co 0.12 Mn 0.05 O2;

[0447] The precursor for ternary materials is Ni. 0.83 Co 0.12 Mn 0.05 (OH)2;

[0448] In step 1 of step S1, nickel sulfate, cobalt sulfate, and manganese sulfate are dissolved in deionized water in a molar ratio of 0.83:0.12:0.05 to obtain a 2 mol / L salt solution.

[0449] Step S2: Ternary material Li(Ni) 0.83 Co 0.12 Mn 0.05 In the O2 preparation process: the mixture is sintered in a multi-stage gradient temperature furnace with an oxygen atmosphere. First, the temperature is increased to 550℃ at a rate of 3℃ / min and held for 3h. Then, the temperature is increased to 650℃ and held for 3h. Next, the temperature is increased to 780℃ and held for 10h. Then, the temperature is decreased to 600℃ and held for 3h. Finally, the temperature is decreased to room temperature at a rate of 6℃ / min to obtain a polycrystalline positive electrode active material with a median particle size D50 of 10-12μm, named: C-20.

[0450] Example 21

[0451] This embodiment is basically the same as embodiment 1, except that:

[0452] Step S2: Ternary material Li(Ni) 0.93 Co 0.03 Mn 0.04 During O2 preparation:

[0453] The mixed material was subjected to multi-stage gradient temperature sintering in an oxygen-filled atmosphere furnace. First, the temperature was increased to 500°C at a rate of 1°C / min and held for 3 hours. Then, the temperature was increased to 600°C and held for 3 hours. Next, the temperature was increased to 730°C and held for 10 hours. Then, the temperature was decreased to 550°C and held for 3 hours. Finally, the temperature was decreased to room temperature at a rate of 3°C / min to obtain a polycrystalline ternary material (i.e., the positive electrode active material in this embodiment).

[0454] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named C-21.

[0455] Example 22

[0456] This embodiment is basically the same as embodiment 1, except that:

[0457] Step S2: Ternary material Li(Ni) 0.93 Co 0.03 Mn 0.04 During O2 preparation:

[0458] The mixed material was subjected to multi-stage gradient temperature sintering in an oxygen-filled atmosphere furnace. First, the temperature was increased to 600°C at a rate of 5°C / min and held for 3 hours. Then, the temperature was increased to 700°C and held for 3 hours. Next, the temperature was increased to 730°C and held for 10 hours. Then, the temperature was decreased to 650°C and held for 3 hours. Finally, the temperature was decreased to room temperature at a rate of 10°C / min to obtain a polycrystalline ternary material (i.e., the positive electrode active material in this embodiment).

[0459] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named C-22.

[0460] Comparative Example 1

[0461] This comparative example is basically the same as Example 1, except that:

[0462] In step 2, during the preparation of the reaction substrate, the pH is 11.0;

[0463] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0464] In step (1), the conditions for the first reaction are: pH value is 11.0, first stirring speed is 150 r / min, metal salt solution flow rate is 80 mL / h, and ammonia water flow rate is 2.5 mL / h.

[0465] In step (2), the reaction conditions for the second reaction are: pH value of 10.0, second stirring speed of 40 r / min, metal salt solution flow rate of 180 mL / h, and ammonia flow rate of 5.6 mL / h. The cross-sectional SEM image of the precursor of the prepared ternary material is shown in Figure 4. As can be seen from Figure 4, the precursor has fewer cross-sectional pores and poor radiality.

[0466] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named D-1; the cross-sectional SEM image of the prepared cathode active material is shown in Figure 5. As can be seen from Figure 5, the sintered cathode active material has fewer pores and the pore distribution is uneven.

[0467] Comparative Example 2

[0468] This comparative example is basically the same as Example 1, except that:

[0469] During step 2, when preparing the reaction substrate, the pH is 9.0;

[0470] Step 3: Synthesis of Ni, a ternary material precursor 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0471] In step (1), the conditions for the first reaction are: pH value of 9.0, stirring speed of 300 r / min, flow rate of metal salt solution of 550 mL / h, and flow rate of ammonia water of 17.1 mL / h.

[0472] In step (2), the reaction conditions for the second reaction are: pH 8.6, stirring speed 250 r / min, metal salt solution flow rate 700 mL / h, and ammonia flow rate 21.7 mL / h.

[0473] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named D-2.

[0474] Comparative Example 3

[0475] This comparative example is basically the same as Example 1, except that:

[0476] Step S2: Ternary material Li(Ni) 0.93 Co 0.03 Mn 0.04 During O2 preparation:

[0477] The mixed materials were subjected to multi-stage gradient temperature sintering in an oxygen-filled atmosphere furnace. First, the temperature was increased to 550℃ at a rate of 3℃ / min and held for 3 hours. Then, the temperature was increased to 730℃ and held for 15 hours. Finally, the temperature was reduced to room temperature to obtain a polycrystalline ternary material (i.e., the positive electrode active material of this comparative example).

[0478] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named D-3.

[0479] Comparative Example 4

[0480] This comparative example is basically the same as Example 1, except that:

[0481] Step S1, step 3: Synthesis of ternary material precursor Ni 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0482] In step (1), the conditions for the first reaction are: the oxygen volume content in the O2 / Ar mixture is 25%.

[0483] In step (2), the conditions for the second reaction are: the oxygen volume content in the O2 / Ar mixture is 25%.

[0484] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named D-4.

[0485] Comparative Example 5

[0486] This comparative example is basically the same as Example 1, except that:

[0487] Step S1, step 3: Synthesis of ternary material precursor Ni 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0488] In step (1), the conditions for the first reaction are: the oxygen volume content in the O2 / Ar mixture is 0%.

[0489] In step (2), the conditions for the second reaction are: the oxygen volume content in the O2 / Ar mixture is 0%.

[0490] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named D-5.

[0491] Comparative Example 6

[0492] This comparative example is basically the same as Example 1, except that:

[0493] Step S1, step 3: Synthesis of ternary material precursor Ni 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0494] In step (1), the conditions for the first reaction are as follows: the oxygen volume content in the O2 / Ar mixture is 25%, the first stirring speed is 150 r / min, the flow rate of the metal salt solution is 80 mL / h, and the flow rate of the ammonia water is 2.5 mL / h.

[0495] In step (2), the reaction conditions for the second reaction are: the oxygen volume content in the O2 / Ar mixture is 25%, the second stirring speed is 40 r / min, the flow rate of the metal salt solution is 180 mL / h, and the flow rate of ammonia water is 5.6 mL / h.

[0496] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named D-6.

[0497] Comparative Example 7

[0498] This comparative example is basically the same as Example 1, except that:

[0499] Step S1, step 3: Synthesis of ternary material precursor Ni 0.93 Co 0.03 Mn 0.04 During the process of (OH)2:

[0500] In step (1), the conditions for the first reaction are as follows: the oxygen volume content in the O2 / Ar mixture is 0%, the first stirring speed is 300 r / min, the flow rate of the metal salt solution is 550 mL / h, and the flow rate of the ammonia water is 17.1 mL / h.

[0501] In step (2), the reaction conditions for the second reaction are: the oxygen volume content in the O2 / Ar mixture is 0%, the second stirring speed is 250 r / min, the flow rate of the metal salt solution is 700 mL / h, and the flow rate of the ammonia water is 21.7 mL / h.

[0502] The obtained polycrystalline cathode active material with a median particle size D50 of 10-12 μm was named D-7.

[0503] II. Material Characterization and Performance Testing

[0504] 1. Material Characterization

[0505] The ternary material precursors and positive electrode active materials obtained in the above embodiments and comparative examples were characterized by X-ray diffraction (XRD), N2 adsorption pore volume, and true density.

[0506] Pore ​​filling degree of ternary material precursors Calculate using the following formula (1):

[0507] In formula (1), V1' is the total pore volume of nitrogen (N2) adsorption in the ternary material precursor, measured by the static volumetric method, in cm³. 3 / g; V2' is calculated according to the following formula (2):

[0508] V2'=1 / ρ' Formula (2)

[0509] In formula (2), ρ' is the true density of the ternary material precursor, in g / cm³. 3 .

[0510] Pore ​​filling degree of ternary materials Calculate using the following formula (3):

[0511] In formula (3), V1 is the total pore volume of nitrogen (N2) adsorption in the ternary material as measured by the static volumetric method, in cm³. 3 / g; Total skeletal volume of V2 ternary material, in cm³ 3 / g; V2 is calculated according to the following formula (4):

[0512] V2=1 / ρ Formula (4),

[0513] In formula (4), ρ is the true density of the ternary material, g / cm³.3 .

[0514] The number of stacked layers k of the (001) crystal plane of the ternary material precursor in the XRD pattern 001 (Unit: layer) Calculated according to the following formula (5):

[0515] k 001 =D 001 / d 001 Formula (5)

[0516] In formula (5), D 001 d represents the average thickness of the ternary precursor perpendicular to the (001) crystal plane, calculated using the Scherer formula with Highscore software in the XRD pattern, in nm; 001 The interlayer spacing of the (001) crystal plane of the ternary material precursor was calculated using the Bragg equation with Highscore software in the XRD pattern, and the unit is nm.

[0517] The number of stacked layers h of the (003) crystal plane of the ternary material in the XRD pattern 003 (Unit: layer) Calculated according to the following formula (6):

[0518] h 003 =D 003 / d 003 Formula (6)

[0519] In formula (6), D 003 d represents the average thickness of the ternary material perpendicular to the (003) crystal plane, calculated using the Scherer formula with Highscore software in the XRD pattern, in nm; 003 The interlayer spacing of the (003) crystal plane of the ternary material was calculated using the Bragg equation with Highscore software in the XRD pattern, and the unit is nm.

[0520] Test method:

[0521] In the pore volume filling of the ternary material precursor and the positive electrode active material, the total pore volume of N2 adsorption was determined on a static N2 adsorption-desorption instrument, model JW-BK400, with the adsorption-desorption pressure P / P0 ranging from 0 to 1; the total skeleton volume was determined on a true density instrument, model Ultrapyc 5000, with the value being the reciprocal of the true density value.

[0522] The cross-sectional morphology of the ternary material precursor and the positive electrode active material was characterized by first cutting the cross-section using an argon ion polisher, followed by SEM imaging of the cross-section morphology using a field emission high-resolution electron microscope. The argon ion polisher was a Gatan 697, with a cutting voltage of 5 kV and a cutting time of 45 min. The high-resolution SEM imaging was performed on a JEOL JSM-7900F electron microscope at a voltage of 3 kV.

[0523] XRD tests on ternary precursors and positive electrode active materials were performed on the Aeris instrument, with a test angle 2θ ranging from 15 to 80°.

[0524] The pore volume filling degree and XRD data results of the ternary material precursors of each embodiment and comparative example are shown in Table 1, and the pore volume filling degree and XRD data results of the ternary materials of each embodiment and comparative example are shown in Table 2. The cross-sectional morphology SEM images of the ternary material precursors and positive electrode active materials of Example 1 and Comparative Example 1 are shown in Figures 2-5 above, and will not be repeated here.

[0525] Table 1. Pore filling degree and XRD data of ternary material precursors for each embodiment and comparative example.

[0526] Table 2. Pore filling degree and XRD data of ternary materials in each embodiment and comparative example.

[0527] 2. Electrochemical performance testing

[0528] Test method:

[0529] The positive electrode active materials of each embodiment and comparative example were assembled into coin half-cells for electrochemical performance testing. The specific battery assembly and testing methods are as follows: Polyvinylidene fluoride (PVDF) was selected as the binder, and conductive carbon black Super P was selected as the conductive agent. A certain mass of positive electrode active material, binder, and conductive agent were weighed according to a mass ratio of 95:2:3, and then dissolved in an appropriate amount of N-methylpyrrolidone (NMP) dispersant. The mixture was dispersed in a homogenizer to form a uniform positive electrode slurry, which was then coated onto the positive electrode current collector aluminum foil with a coating thickness of 150 μm. The electrode was then dried in a vacuum oven for battery assembly. For the electrode prepared using the above method, a lithium metal sheet was selected as the counter electrode, a microporous polypropylene membrane (Celgard 2400) was selected as the separator, and the electrolyte was a 1M mixed solution of LiPF6 EC and DEC (V... EC :V DECThe batteries were assembled into CR2025 button cells using a 1:1 ratio of Ar in an Ar-filled glove box (LS800D type, oxygen and water content ≤0.1ppm). Electrochemical performance was tested after the batteries were allowed to stand for 3 hours. The test conditions for the 0.1C first-cycle discharge capacity were: a controlled test temperature of 25℃, a charge / discharge cutoff voltage of 2.8-4.35V, and a discharge current density of 0.1C. The cycle performance test conditions were: after two cycles of 0.1C charge / discharge activation, 200 cycles of 0.33C charge / 1C discharge were performed.

[0530] The electrochemical performance test results of the positive electrode active materials of each embodiment and comparative example are shown in Table 3.

[0531] Table 3. Electrochemical performance test results of the positive electrode active materials in each embodiment and comparative example.

[0532] According to Table 1-3, it can be seen that:

[0533] The embodiments of this application utilize the inheritance between the ternary material precursor and the ternary material, and simultaneously obtain a suitable pore volume filling degree by adjusting and optimizing the sintering platform at the positive electrode sintering end. and fewer stacking layers (h) 003 The ternary materials (Examples 1-22) reduce the internal Li content of the cathode material. + The diffusion path and suitable pore filling degree provide channels for stress release during material cycling, thus enabling higher capacity compared with other ternary materials with the same nickel content, and excellent cycling performance with high capacity retention after 200 cycles.

[0534] Compared to Example 1, Comparative Example 1 had excessively high pH (11.0 and 10.0), excessively low stirring speed (150 r / min and 40 r / min), and excessively low flow rate of metal salt solution addition during the nucleation and growth of the ternary material precursor, resulting in a lower pore volume filling degree in the prepared ternary material precursor. If the pore size is too small, the pore volume filling degree of the sintered positive electrode active material (i.e., ternary material) will be insufficient. If the size is too small, the material's capacity is relatively low, and the capacity decays quickly, resulting in poor cycle life.

[0535] Compared to Example 1, Comparative Example 2 had excessively low pH (9.0 and 8.6), excessively high stirring speed (300 r / min and 250 r / min), and excessively high flow rate of metal salt solution addition (550 mL / h and 700 mL / h) during the nucleation and growth of the ternary material precursor, resulting in a decrease in the pore volume filling degree of the prepared ternary material precursor. If the pore volume is too large, the pore filling degree of the sintered positive electrode active material (i.e., ternary material) will be affected. If the material is too large, although the capacity is relatively high, the excessive pores during cycling will cause the spherical structure to collapse, resulting in rapid capacity decay and poor cycling performance.

[0536] Compared to Example 1, Comparative Example 3, although having identical process conditions in the preparation of the ternary material precursor, showed a significantly higher pore volume filling degree. Similarly, however, the insufficient number of cathode sintering platforms prevents the cathode active material (i.e., ternary material) from inheriting the pore volume structure of the ternary material precursor, resulting in a lower cathode pore volume filling degree. Too low a value results in lower material capacity and poorer cycle performance.

[0537] Compared to Example 1, Comparative Example 4 had the same pH, stirring speed, and metal salt solution flow rate during the nucleation and growth of the ternary material precursor. However, the oxygen volume content in the O2 / Ar mixed gas was too high, leading to excessive oxidation and causing nucleation explosions during precursor preparation. This resulted in more fine powder and, moreover, excessive oxidation reduced the number of (001) crystal plane stacking layers k in the prepared precursor. 001 If the number of stacked layers h003 corresponding to the (003) crystal plane of the sintered positive electrode active material is too small, the capacity of the material will be low and the capacity decay will be too fast.

[0538] Compared with Example 1, although Comparative Example 5 had the same pH, stirring speed, and metal salt solution flow rate during the nucleation and growth process of the ternary material precursor, the oxygen volume content in the mixed gas O2 / Ar was 0%, which resulted in coarse particles in the first-stage preparation of the precursor. The number of stacked layers k001 of the (001) crystal plane of the prepared precursor was still too large, and the number of stacked layers h003 of the (003) crystal plane corresponding to the sintered positive electrode active material was too large, resulting in a low material capacity.

[0539] Compared to Example 1, although Comparative Example 6 had the same pH during the nucleation and growth of the ternary material precursor, the stirring speed and metal salt solution flow rate were too low, and the oxygen volume content in the introduced O2 / Ar mixed gas was too high. This resulted in a smaller pore volume filling degree in the prepared precursor and a smaller number of stacked layers k001 on the (001) crystal plane of the precursor. Consequently, the number of stacked layers h003 on the (003) crystal plane of the sintered positive electrode active material was too small, and the pore volume filling degree was low. If the temperature is too low, the material's capacity and cycle life will be poor.

[0540] Compared to Example 1, although Comparative Example 7 had the same pH during the nucleation and growth of the ternary material precursor, the stirring speed and metal salt solution flow rate were too high, and the oxygen volume content in the O2 / Ar mixed gas was 0%. This resulted in a larger pore volume filling degree in the prepared precursor and an excessively large number of stacked layers k001 on the (001) crystal plane of the precursor. Consequently, the number of stacked layers h003 on the (003) crystal plane of the sintered positive electrode active material was also excessively high, resulting in a smaller pore volume filling degree. If the material is too large, its capacity and cycle life will be poor.

[0541] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0542] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order, or primary and secondary relationship of the indicated technical features.

[0543] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0544] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0545] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces), unless otherwise explicitly specified.

[0546] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0547] In the description of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0548] All embodiments of this application can be executed individually or in combination with other embodiments, and are all considered to be within the scope of protection claimed by this application.

Claims

1. A positive electrode active material, comprising a ternary material, wherein the ternary material comprises a material with the chemical formula Li a (Ni x Co y M z Compounds of O2, in which, 0.9 ≤ a ≤ 1.1, 0.5 ≤ x < 1, 0 < y ≤ 0.5, 0 < z ≤ 0.5, x + y + z = 1, and M includes at least one of Mn, Al, Ti, Zr, and Mg; The ternary material satisfies: (1) and And, (2)100≤h 003 ≤250； The is the pore volume filling degree of the ternary material; V1 represents the total pore volume of nitrogen adsorption in the ternary material, in cm³. 3 / g; V2 refers to the total volume of the ternary material's framework, measured in cm³. 3 / g; The h 003 The number of stacked layers of the (003) crystal plane of the ternary material described in the X-ray diffraction pattern is expressed in layers.

2. The positive electrode active material according to claim 1, wherein, V2 is calculated by the following formula: V2 = 1 / ρ, ρ is the true density of the ternary material, in g / cm³. 3 .

3. The positive electrode active material according to claim 2, wherein, The specified ρ satisfies: 4.00 g / cm³ 3 <ρ<5.00g / cm 3 .

4. The positive electrode active material according to any one of claims 1 to 3, wherein, V1 is the total nitrogen adsorption pore volume of the ternary material measured by the static volumetric method; and / or, The V1 satisfies: 0.0022cm 3 / g<V1<0.0235cm 3 / g.

5. The positive electrode active material according to any one of claims 1 to 4, wherein, h003 is calculated according to the following formula: h 003 =D 003 / d 003 , Wherein, the D 003 The average thickness of the ternary material in the X-ray diffraction pattern perpendicular to the (003) crystal plane is expressed in nm; the d 003 The interlayer spacing of the (003) crystal plane of the ternary material described in the X-ray diffraction pattern is in nm.

6. The positive electrode active material according to claim 5, wherein, The D 003 Calculated using the Scherer formula; and / or, the D 003 Satisfy: 40nm < D 003 <150nm; and / or, The d 003 Calculated using Bragg's equation; and / or, The d 003 Satisfy: 0.46nm < d 003 <0.48nm.

7. The positive electrode active material according to any one of claims 1 to 6, wherein, The particle size D50 of the ternary material satisfies: 0 < D50 < 18 μm; and / or, The average pore diameter of the ternary material is d nm, and d satisfies: 0 < d < 100; and / or, The specific surface area of ​​the ternary material is bm. 2 / g, wherein b satisfies: 0 < b < 1; and / or, The positive electrode active material further includes an additive; the additive is doped in the ternary material, or the additive coats at least part of the surface of the ternary material; and / or, the additive includes a compound containing an R element, and the R element includes at least one of Ca, Mg, Zr, Sr, Nb, Sb, Sm, Ti, Na, Si, Al, La, W, B, Fe, Cu, K, Si, Ge, Nd, Mo, Y, or Ce; and / or, the content of the additive in the positive electrode active material is greater than 0 and not more than 10000 ppm.

8. The positive electrode active material according to claim 7, wherein, The R element includes at least one of Nb, Sr, Zr, Sb, Sm, Ti, Al, La, W, B, Mo, Y, and Ce.

9. A method for preparing a positive electrode active material, comprising: Simultaneously adding a first metal salt solution, a first alkali solution, and a first complexing agent to a reaction bottom solution under the condition of first stirring in a first gas atmosphere to carry out a first reaction to obtain a first product having a honeycomb-like spherical core structure; Simultaneously adding a second metal salt solution, a second alkali solution, and a second complexing agent to the first product under the condition of second stirring in a second gas atmosphere to carry out a second reaction to obtain a precursor of the ternary material; Mixing the ternary precursor, a lithium source, and an additive to obtain a mixed material; Performing multi-stage gradient temperature sintering on the mixed material in an air or oxygen atmosphere to obtain the positive electrode active material; The metal salts in the first metal salt solution and the second metal salt solution are both transition metal salts; the first gas and the second gas both include oxygen and an inert gas, and the volume content of oxygen in the first gas is 0 - 20%, and the volume content of oxygen in the second gas is 10 - 20%; the addition rate of the first metal salt solution is 100 - 500 mL / h, the speed of the first stirring is 200 - 250 r / min, and the pH of the first reaction is 9.5 - 10.5; the addition rate of the second metal salt solution is 200 - 650 mL / h, the speed of the second stirring is 50 - 240 r / min, and the pH of the second reaction is 8.8 - 9.

5.

10. The preparation method according to claim 9, wherein, The multi-stage gradient temperature sintering includes a heating section, a first isothermal section, a second isothermal section, a third isothermal section, a fourth isothermal section, and a cooling section arranged sequentially. The sintering temperatures of the heating section, the first isothermal section, the second isothermal section, and the third isothermal section increase sequentially, while the sintering temperatures of the third isothermal section, the fourth isothermal section, and the cooling section decrease sequentially.

11. The preparation method according to claim 10, wherein, The heating rate of the heating section is 1-5℃ / min; and / or, The sintering temperature of the first isothermal section is 500-600℃; and / or, The sintering temperature of the second isothermal section is 600-700℃; and / or, The sintering temperature of the third isothermal section is 700-900℃; and / or, The heat preservation time of the third constant temperature section is 5-15 hours; and / or, The sintering temperature of the fourth isothermal section is 550-650℃; and / or, The heat preservation time for the fourth constant temperature section, the second constant temperature section, and the first constant temperature section is 1-5 hours; and / or, The cooling rate of the cooling section is 3-10℃ / min.

12. The preparation method according to claim 9, wherein, The reaction temperatures for both the first and second reactions are 40-70°C; and / or, The reaction time of the first reaction is 1-3 hours; and / or, The second reaction is stopped when the volumetric particle size distribution of the ternary material precursor grows to a median particle size of 2-18 μm; and / or, The ternary material precursor satisfies: (i) and (ii) 10≤k 001 ≤50, and k 001 =D 001 / d 001 ;in, The V1' is the pore volume filling degree of the ternary material precursor; V1' is the total nitrogen adsorption pore volume of the ternary material precursor measured by the static volumetric method, in cm³. 3 / g; the total volume of the skeleton of the ternary material precursor described in V2', in cm³. 3 / g; the k 001 The number of stacked layers of the (001) crystal plane of the ternary material precursor in the X-ray diffraction pattern is expressed in layers; the D 001 The average thickness of the ternary precursor material perpendicular to the (001) crystal plane, calculated using the Scherer formula in the X-ray diffraction pattern, is given in nm; the d 001 The interlayer spacing of the (001) crystal plane of the ternary material precursor is calculated using the Bragg equation in the X-ray diffraction pattern, and the unit is nm.

13. The preparation method according to claim 9, wherein, The reaction base solution includes a third alkaline solution, a third complexing agent, and pure water. During the preparation of the reaction base solution, a third gas must be continuously introduced and a third stirring must be performed. The third gas includes oxygen and an inert gas. And / or, the transition metal salt includes nickel salts, cobalt salts, and salts containing element M, wherein M includes at least one of Mn, Al, Ti, Zr, and Mg.

14. The preparation method according to claim 13, wherein, The total concentration of both the first metal salt solution and the second metal salt solution is 1-5 mol / L; and / or, The concentrations of the first alkaline solution, the second alkaline solution, and the third alkaline solution are all 10-35 wt%. And / or, The concentrations of the first complexing agent, the second complexing agent, and the third complexing agent are all 0.05-5 mol / L; and / or, The concentration of the first complexing agent is less than the concentration of the second complexing agent; and / or, M is Mn.

15. The preparation method according to claim 9, wherein, The additive comprises at least one compound containing element R, wherein element R includes at least one of Ca, Mg, Zr, Sr, Nb, Sb, Sm, Ti, Na, Si, Al, La, W, B, Fe, Cu, K, Si, Ge, Nd, Mo, Y, or Ce; and / or, In the mixture, the amount of lithium in the lithium source is e mol, and the total amount of transition metals in the ternary material precursor is c mol, wherein e and c satisfy: 1.0 ≤ e / c ≤ 1.1; and / or, The additive content in the mixture is 0-10000 ppm.

16. A positive electrode sheet, comprising the positive electrode active material as described in any one of claims 1 to 8 or the positive electrode active material prepared by the preparation method of the positive electrode active material as described in any one of claims 9 to 15.

17. A secondary battery, comprising a positive electrode, a negative electrode, and a separator, wherein, The positive electrode is the positive electrode as described in claim 16.

18. An electrical device comprising the secondary battery as described in claim 17.

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