Positive electrode active material precursor as well as preparation method therefor and use thereof

Abstract

The present application provides a positive electrode active material precursor as well as a preparation method therefor and the use thereof. The positive electrode active material precursor comprises secondary particles consisting of primary particles, the primary particles have a curved surface structure, and the curvature of the primary particles is not lower than 0.2. Therefore, the secondary particles consisting of the primary particles have loose inner structures and large specific surface area, which facilitates the intercalation of lithium ions during calcination, remarkably reduces the content of residual lithium on surfaces of positive electrode active materials, and omits a water washing process, thus solving the problem of reductions of direct-current internal resistance and circulating performance of batteries which are caused by water washing.

Description

A positive electrode active material precursor, a preparation method and application thereof

[0001] The present application claims priority to the Chinese patent application No. 202410627314.8, filed on May 20, 2024, and entitled "A positive electrode active material precursor, a preparation method and application thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application belongs to the technical field of lithium ion batteries, and relates to a positive electrode active material precursor, in particular to a positive electrode active material precursor, a preparation method and application thereof. BACKGROUND

[0003] Lithium ion batteries are widely used in electric vehicles, electric vehicles, aerospace, portable electronic devices (such as notebook computers, mobile phones, digital products) and other fields due to their high working voltage, high energy density, high safety performance and environmental friendliness. However, with the continuous development of science and technology, higher requirements are put forward for the cycle life of lithium ion batteries. As an important component of lithium ion batteries, the performance of positive electrode active material undoubtedly affects the electrochemical performance of the battery to a great extent, and the performance of positive electrode active material is mainly determined by the performance of its precursor.

[0004] Generally, an excess of lithium needs to be added during the mixing and calcination process of the positive electrode active material precursor and the lithium-containing compound. The unreacted lithium salt reacts with the moisture and carbon dioxide in the air to generate lithium hydroxide and lithium carbonate again, which remains on the surface of the material, resulting in a high residual lithium content on the surface of the positive electrode active material. If the residual lithium is not treated, the slurry will present a jelly-like state during the pulping or coating process, leading to processing difficulties. Moreover, lithium hydroxide in the residual alkali is prone to react with lithium hexafluorophosphate in the electrolyte to generate hydrofluoric acid, and lithium carbonate will cause the battery to swell, which poses a great safety hazard. Currently, water washing process is usually used to reduce the residual lithium content on the surface of the material. However, during the water washing process, lithium ions in the material will also transfer to the surface of the material and dissolve out, destroying the layered structure of the material, thereby causing the direct current internal resistance of the material to rise and the cycle performance to deteriorate.

[0005] Therefore, in view of the above defects, it is urgent to develop a positive electrode active material precursor to improve the cycle performance of lithium ion batteries. SUMMARY

[0006] In view of the above defects, the present application provides a positive electrode active material precursor. Since the primary particles included in the precursor have a curved surface structure with a curvature not less than 0.2, the direct current internal resistance of the lithium ion battery can be significantly reduced and the cycle performance of the battery can be improved.

[0007] The application also provides a preparation method of the above positive electrode active material precursor, and the positive electrode active material precursor prepared by the preparation method can significantly reduce the direct current resistance of a lithium ion battery and improve the cycle performance of the battery.

[0008] The application also provides a positive electrode active material obtained by mixing and calcining the above positive electrode active material precursor and a lithium-containing compound, so that a lithium ion battery including the positive electrode active material has a lower direct current resistance and a longer cycle life.

[0009] The application provides a positive electrode active material precursor in a first aspect, wherein the positive electrode active material precursor includes secondary particles composed of primary particles; and the primary particles have a curved surface structure.

[0010] The curvature of the primary particles is not less than 0.2.

[0011] The positive electrode active material precursor as described above, wherein the curvature of the primary particles is not less than 0.3.

[0012] The positive electrode active material precursor as described above, wherein the specific surface area of the positive electrode active material precursor is 70-90 m 2 / g.

[0013] The positive electrode active material precursor as described above, wherein the porosity of the positive electrode active material precursor is 50-80%.

[0014] The positive electrode active material precursor as described above, wherein the D50 of the positive electrode active material precursor is 10-20 μm, and / or the D90 is 30-40 μm, and / or the D10 is 1-5 μm.

[0015] The positive electrode active material precursor as described above, wherein the (D90-D10) / D50 of the positive electrode active material precursor is 1.45-4.

[0016] The positive electrode active material precursor as described above, wherein the thickness of the primary particles is not higher than 100 nm, and / or the length is not higher than 3 μm.

[0017] The positive electrode active material precursor as described above, wherein the positive electrode active material precursor includes a chemical composition shown in Formula 1, Ni a Co b Mn c (OH)2 Formula 1

[0018] In Formula 1, 0.5

[0019] or the positive electrode active material precursor includes a chemical composition shown in Formula 2, Nix Co y Mn z CO3 Formula 2

[0020] In Formula 2, 0.5 < x < 1, 0 < y < 0.5, 0 < z < 0.5, and x + y + z = 1.

[0021] The second aspect of the present application provides a preparation method of the positive electrode active material precursor of the first aspect, comprising the following steps:

[0022] mixing the solid phase with deionized water to perform first spray drying to obtain a first product; mixing the first product with deionized water to obtain a dispersion liquid, and performing second spray drying on the dispersion liquid to obtain the positive electrode active material precursor; wherein the solid phase has the chemical composition of the positive electrode active material precursor.

[0023] The average length of the solid phase is not higher than 5 μm, the average width is not higher than 1 μm, and the average thickness is not higher than 100 nm.

[0024] The volume ratio of the solid phase to deionized water is (1-2):10, and the volume ratio of the first product to deionized water is (1-2):10.

[0025] In the first spray drying process, the feeding rate is 3-5 L / h, the frequency of the atomizer is 100-600 Hz, the frequency of the air blower is 20-30 Hz, the frequency of the induced draft fan is 10-40 Hz, the inlet air temperature is 100-250 ℃, and the outlet temperature is 80-150 ℃.

[0026] In the second spray drying process, the feeding rate is 3-5 L / h, the frequency of the atomizer is 400-600 Hz, the frequency of the air blower is 20-30 Hz, the frequency of the induced draft fan is 10-40 Hz, the inlet air temperature is 100-250 ℃, and the outlet temperature is 80-150 ℃.

[0027] The preparation method of the positive electrode active material precursor as described above, wherein the solid phase is subjected to thickening treatment before the first spray drying.

[0028] In the thickening process, the volume ratio of the solid phase to deionized water is 1:(1-10).

[0029] The second aspect of the present application provides a positive electrode active material, which is obtained by mixing and calcining the positive electrode active material precursor of the first aspect or the positive electrode precursor material prepared by the preparation method of the second aspect with a lithium-containing compound.

[0030] The positive electrode active material as described above, wherein the tap density of the positive electrode active material is 1-1.8 g / cm 3.

[0031] The positive electrode active material as described above, wherein the median particle size of the positive electrode active material is 5-10 μm.

[0032] The positive electrode active material precursor in the present application comprises secondary particles composed of primary particles, and the primary particles have a curved surface structure and a curvature not less than 0.2, so that the secondary particles formed therefrom have a loose internal structure and a large specific surface area, which is helpful to the embedding of lithium ions in the calcination process, and thus the content of residual lithium on the surface of the positive electrode active material can be significantly reduced, and the water washing process can be omitted, thereby avoiding the problems of the decrease of the direct current resistance and the cycle performance of the battery caused by water washing. BRIEF DESCRIPTION OF DRAWINGS

[0033] Fig. 1 is a schematic diagram of the primary particles included in the positive electrode active material precursor of the present application;

[0034] Fig. 2 is a schematic diagram of the curvature of the primary particles included in the positive electrode active material precursor of the present application;

[0035] Fig. 3 is an SEM image of the positive electrode active material precursor prepared in Example 2 of the present application at a 2k rate;

[0036] Fig. 4 is an SEM image of the positive electrode active material precursor prepared in Example 1 of the present application at a 1k rate;

[0037] Fig. 5 is an SEM image of the positive electrode active material precursor prepared in Example 1 of the present application at a 5k rate;

[0038] Fig. 6 is an SEM image of the positive electrode active material precursor prepared in Example 1 of the present application at a 50k rate;

[0039] Fig. 7 is a sectional SEM image of the positive electrode active material precursor prepared in Example 2 of the present application;

[0040] Fig. 8 is an SEM image of the positive electrode active material precursor prepared in Comparative Example 1 of the present application at a 50k rate;

[0041] Fig. 9 is an SEM image of the positive electrode active material precursor prepared in Comparative Example 1 of the present application at a 10k rate;

[0042] Fig. 10 is an SEM image of the positive electrode active material precursor prepared in Comparative Example 1 of the present application at a 5k rate. DETAILED DESCRIPTION

[0043] In order to make the objects, technical solutions and advantages of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0044] The first aspect of the present application provides a positive electrode active material precursor, which comprises secondary particles composed of primary particles; the primary particles have a curved surface structure; and the curvature of the primary particles is not less than 0.2.

[0045] As shown in FIG. 1, it is a schematic diagram of the primary particles included in the positive electrode active material precursor of the present application. Since the primary particles have a curved surface structure, the side surface thereof can be regarded as a wave structure formed by alternating distribution of concave portions and convex portions. Each concave portion has a respective concave depth, and each convex portion has a respective convex height, and the present application does not limit the relationship between the concave depths and the convex heights.

[0046] In the present application, the concave depth refers to the straight-line distance between the lowest point X of the concave portion and the connecting line of the concave portion, and the convex height refers to the straight-line distance between the highest point M of the convex portion and the connecting line of the convex portion. The connecting line of the concave portion refers to the connecting line of the highest points N and M of the convex portions on both sides of the concave portion, and the connecting line of the convex portion refers to the connecting line of the lowest points X and Y of the concave portions on both sides of the convex portion, as shown in FIG. 2.

[0047] The curvature of the present application refers to the ratio of the concave depth to the length of the connecting line of the concave portion for the concave portion, and refers to the ratio of the convex height to the length of the connecting line of the convex portion for the convex portion, as shown in FIG. 2, where c / d is the curvature of a certain concave portion in the primary particle, and b / a is the curvature of a certain convex portion in the primary particle. For example, if the primary particle of the present application includes N concave portions and M convex portions, there are N+M curvatures, and the N+M curvatures in the present application are all not less than 0.2.

[0048] The positive electrode active material precursor in the present application comprises secondary particles composed of primary particles, wherein the primary particles have a curved surface structure and the curvature is not less than 0.2, so that the positive electrode active material prepared from the precursor has a lower direct current resistance and a higher cycle performance. The inventors speculate that this may be due to the fact that the curved surface structure can make the internal structure of the secondary particles loose, and there are more pores and channels, so that during the mixing and calcining process of the positive electrode active material precursor and the lithium-containing compound, lithium ions are more easily embedded, thereby effectively reducing the residual lithium content on the surface of the positive electrode active material, without the need for water washing, so that the direct current resistance of the lithium ion battery can be significantly reduced, and the cycle performance of the battery can be improved.

[0049] In addition, the precursor of the present application has more pores and channels, which can increase the specific surface area of the precursor, and thus the irreversible capacity loss during the operation of the battery can be reduced, and the first coulombic efficiency of the battery can be improved.

[0050] Preferably, the primary particles with curved surface structure are arranged and agglomerated in a certain form to obtain secondary particles with spherical-like "flower cluster" structure. The secondary particles with such special structure can make the prepared positive active material particles more uniform, and effectively improve the cycle performance and rate performance of the battery.

[0051] In a specific embodiment, the curvature of the primary particles is not less than 0.3. Specifically, the curvature of the primary particles can be further improved by controlling the volume ratio of the solid phase to deionized water, the volume ratio of the first product to deionized water, the feeding rate, the frequency of the atomizer, the frequency of the induced fan, the frequency of the air blower, the inlet air temperature and the outlet air temperature in the first and second spray drying processes, so that the internal structure of the positive active material precursor including the primary particles is more loose, has more pores, promotes the insertion of lithium ions during calcination, and further reduces the residual lithium content on the surface of the positive active material without the need for a water washing step, so that the battery has a lower direct current resistance and higher cycle performance.

[0052] In a specific embodiment, the specific surface area of the positive active material precursor is 70-90 m 2 / g. In this range, the structure of the precursor is more loose and porous, which is more conducive to the migration and diffusion of lithium ions during calcination, not only can the water washing step be omitted, but also the cycle performance of the battery can be effectively improved, and the residual lithium content on the surface of the positive active material can be further reduced, so that the lithium ion battery has a lower direct current resistance and a longer cycle life.

[0053] Illustratively, the specific surface area of the positive active material precursor can be 70 m 2 / g, 72 m 2 / g, 74 m 2 / g, 76 m 2 / g, 78 m 2 / g, 80 m 2 / g, 82 m 2 / g, 84 m 2 / g, 86 m 2 / g, 88 m 2 / g, 90 m 2 / g, or a range formed by any two of the above values.

[0054] In an embodiment, the porosity of the positive electrode active material precursor is 50-80%. In this range, the positive electrode active material precursor has more pores and channels, which can further increase the specific surface area of the precursor, increase the amount of lithium ion insertion during calcination, and further reduce the amount of residual lithium on the surface of the positive electrode active material, thereby reducing the direct current resistance of the battery and improving the cycle performance.

[0055] For example, the porosity of the positive electrode active material precursor can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, or a range defined by any two of these values.

[0056] In this application, the "specific surface area" and "porosity" can be measured by a TriStar II 3020 full-automatic three-station specific surface area and porosity analyzer.

[0057] In an embodiment, the D50 of the positive electrode active material precursor is 10-20 μm, and / or the D90 is 30-40 μm, and / or the D10 is 1-5 μm. The D50 represents the median particle size of the positive electrode active material precursor, i.e., the particle size corresponding to a cumulative particle size distribution percentage of 50% of the material; the D90 represents the particle size corresponding to a cumulative particle size distribution percentage of 90% of the positive electrode active material precursor; and the D10 represents the particle size corresponding to a cumulative particle size distribution percentage of 10% of the positive electrode active material precursor, which can be measured by a laser particle size analyzer. In this range, it is beneficial to form single-crystal positive electrode active materials of large size during sintering, thereby improving the tap density and the volume capacity of the lithium ion battery.

[0058] For example, the D50 can be 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, or a range defined by any two of these values; the D90 can be 30 μm, 32 μm, 34 μm, 36 μm, 38 μm, 40 μm, or a range defined by any two of these values; and the D10 can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or a range defined by any two of these values.

[0059] In an embodiment, the (D90-D10) / D50 of the positive electrode active material precursor is 1.45-4. At this time, the particle size distribution of the positive electrode active material precursor is good, and the particle size distribution of the positive electrode active material obtained by sintering the precursor is also suitable, which can form a structure in which small particles fill the gaps between large particles in the positive electrode active layer, thereby improving the compaction density of the positive electrode sheet and the energy density of the battery.

[0060] For example, the (D90-D10) / D50 can be 1.45, 1.5, 2, 2.5, 3, 3.5, 4, or a range defined by any two of the values.

[0061] In one embodiment, the tap density of the positive electrode active material is 1-1.8. In this case, the positive electrode sheet has a high tap density, and thus the energy density of the battery can be effectively improved.

[0062] For example, the tap density can be 1 g / cm 3 , 1.1 g / cm 3 , 1.2 g / cm 3 , 1.3 g / cm 3 , 1.4 g / cm 3 , 1.5 g / cm 3 , 1.6 g / cm 3 , 1.7 g / cm 3 , 1.8 g / cm 3 , or a range defined by any two of the values.

[0063] In the present application, the "tap density" is tested by the following method:

[0064] At room temperature 25°C, the dried positive electrode active material powder is weighed, and a tap density tester is used to tap the powder to a stable volume according to the standard parameters (250 times / minute, 500 times of vibration). The tap density is calculated by the ratio of the mass to the tap volume, and the unit is g / cm 3 .

[0065] In one embodiment, the thickness of the primary particles is not higher than 100 nm, and / or the length of the primary particles is not higher than 3 μm. When the thickness and / or the length of the primary particles are within the above range, the formation of the curved surface structure of the primary particles is facilitated, the primary particles have a higher curvature, the number of internal pores and channels of the precursor is increased, the specific surface area is improved, and thus the lithium ions can better diffuse and migrate during the calcination process, the lithium intercalation amount is increased, the positive electrode active material with a low residual lithium content can be obtained without water washing, and the cycle performance of the battery is effectively improved and the direct current resistance is reduced.

[0066] For example, the thickness of the primary particles can be 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, or a range defined by any two of the values; and the length can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, or a range defined by any two of the values.

[0067] The thickness and length of the primary particles in the present application can be obtained by a scanning electron microscope (SEM) test, in which 20 primary particles are selected from the SEM photos, the thickness and length of each particle are measured and counted, and the average values are obtained as the thickness and length of the primary particles.

[0068] In a specific embodiment, the positive electrode active material precursor comprises a chemical composition shown in Formula 1, Ni a Co b Mn c (OH)2 Formula 1

[0069] In Formula 1, 0.5

[0070] Alternatively, the positive electrode active material precursor comprises a chemical composition shown in Formula 2, Ni x Co y Mn z CO3 Formula 2

[0071] In Formula 2, 0.5

[0072] The second aspect of the present application provides a preparation method of the positive electrode active material precursor of the first aspect, comprising the following steps:

[0073] mixing the solid phase with deionized water to obtain a dispersion liquid, and performing second spray drying on the dispersion liquid to obtain the positive electrode active material precursor; wherein the solid phase has the chemical composition of the positive electrode active material precursor;

[0074] The average length of the solid phase is not higher than 5 μm, the average width is not higher than 1 μm, and the average thickness is not higher than 100 nm;

[0075] The volume ratio of the solid phase to deionized water is (1-2):10, and the volume ratio of the first product to deionized water is (1-2):10;

[0076] In the first spray drying process, the feeding rate is 3-5 L / h, the frequency of the atomizer is 100-600 Hz, the frequency of the air blower is 20-30 Hz, the frequency of the induced draft fan is 10-40 Hz, the inlet air temperature is 100-250 ℃, and the outlet temperature is 80-150 ℃;

[0077] In the second spray drying process, the feeding rate is 3-5 L / h, the frequency of the atomizer is 400-600 Hz, the frequency of the air blower is 20-30 Hz, the frequency of the induced draft fan is 10-40 Hz, the inlet air temperature is 100-250 ℃, and the outlet temperature is 80-150 ℃.

[0078] Specifically, the solid phase with the chemical composition of the positive electrode active material precursor is mixed with deionized water at a volume ratio of (1-2):10, and then first spray drying is performed to obtain a first product. In the first spray drying process, the feeding rate is controlled to be 3-5 L / h, the atomizer frequency is controlled to be 100-600 Hz, the blower frequency is controlled to be 20-30 Hz, the induced draft frequency is controlled to be 10-40 Hz, the air inlet temperature is controlled to be 100-250 ℃, and the outlet temperature is controlled to be 80-150 ℃. In addition, the average length of the solid phase is not higher than 5 μm, the average width is not higher than 1 μm, and the average thickness is not higher than 100 nm. Subsequently, the first product is mixed with deionized water at a volume ratio of (1-2):10 to obtain a dispersion liquid, and then the dispersion liquid is subjected to second spray drying to obtain the positive electrode active material precursor. In the second spray drying process, the feeding rate is controlled to be 3-5 L / h, the atomizer frequency is controlled to be 400-600 Hz, the blower frequency is controlled to be 20-30 Hz, the induced draft frequency is controlled to be 10-40 Hz, the air inlet temperature is controlled to be 100-250 ℃, and the outlet temperature is controlled to be 80-150 ℃.

[0079] Exemplarily, the volume ratio of the solid phase to deionized water can be 1:10, 1.2:10, 1.4:10, 1.6:10, 1.8:10, 2:10, or a range formed by any two of the above values. The volume ratio of the first product to deionized water can be 1:10, 1.2:10, 1.4:10, 1.6:10, 1.8:10, 2:10, or a range formed by any two of the above values.

[0080] Exemplarily, in the first spray drying process, the feeding rate can be 3 L / h, 3.5 L / h, 4 L / h, 4.5 L / h, 5 L / h, or a range formed by any two of the above values. The atomizer frequency can be 100 Hz, 200 Hz, 300 Hz, 400 Hz, 500 Hz, 600 Hz, or a range formed by any two of the above values. The blower frequency can be 20 Hz, 22 Hz, 24 Hz, 26 Hz, 28 Hz, 30 Hz, or a range formed by any two of the above values. The induced draft frequency can be 10 Hz, 15 Hz, 20 Hz, 25 Hz, 30 Hz, 35 Hz, 40 Hz, or a range formed by any two of the above values. The air inlet temperature can be 100 ℃, 130 ℃, 160 ℃, 190 ℃, 220 ℃, 250 ℃, or a range formed by any two of the above values. The outlet temperature can be 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, or a range formed by any two of the above values.

[0081] Exemplarily, in the second spray drying, the feed rate can be 3 L / h, 3.5 L / h, 4 L / h, 4.5 L / h, 5 L / h or a range formed by any two of the numerical values; the atomizer frequency can be 400 Hz, 420 Hz, 440 Hz, 460 Hz, 480 Hz, 500 Hz, 520 Hz, 540 Hz, 560 Hz, 580 Hz, 600 Hz or a range formed by any two of the numerical values; the blower frequency can be 20 Hz, 22 Hz, 24 Hz, 26 Hz, 28 Hz, 30 Hz or a range formed by any two of the numerical values; the induced draft frequency can be 10 Hz, 15 Hz, 20 Hz, 25 Hz, 30 Hz, 35 Hz, 40 Hz or a range formed by any two of the numerical values; the air inlet temperature can be 100℃, 130℃, 160℃, 190℃, 220℃, 250℃ or a range formed by any two of the numerical values; and the outlet temperature can be 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃ or a range formed by any two of the numerical values.

[0082] The average length, the average width and the average thickness of the solid phase substance in the present application can be obtained by SEM photos obtained by scanning electron microscope (SEM) test and test by combining Nano Measurer 1.2 software.

[0083] Further, the specific surface area of the first product is preferably 40-60 m 2 / g, which helps to increase the specific surface area of the positive active material precursor, so that the specific surface area of the precursor is between 70-90 m 2 / g.

[0084] Exemplarily, the specific surface area of the first product can be 40 m 2 / g, 42 m 2 / g, 44 m 2 / g, 46 m 2 / g, 48 m 2 / g, 50 m 2 / g, 52 m 2 / g, 54 m 2 / g, 56 m 2 / g, 58 m 2 / g, 60 m 2 / g or a range formed by any two of the numerical values.

[0085] The test method of the specific surface area of the first product in the present application can be consistent with the test method of the specific surface area of the positive active material precursor described above, which is not described herein.

[0086] Further, the amount of nitrogen gas in the first spray drying and the second spray drying is 0.1-10 L / h.

[0087] Illustratively, the amount of nitrogen gas can be 0.1 L / h, 1 L / h, 2 L / h, 4 L / h, 6 L / h, 8 L / h, 10 L / h, or a range defined by any two of the values.

[0088] The application does not make specific limitation to the preparation method of the solid phase, and only requires that the prepared solid phase has the above-mentioned flaky structure and the chemical composition of the positive electrode active material precursor, for example, can be prepared by the following steps:

[0089] The nickel salt, the cobalt salt, and the manganese salt are mixed with deionized water to obtain a mixed salt solution, a precipitant is mixed with deionized water to prepare a precipitant solution, the precipitant solution is added to the mixed salt solution to obtain a mixed solution with a pH of 8-12, and after reaction at 20-85°C for 1-12 h, the reaction product is washed and solid-liquid separated to obtain the solid phase.

[0090] Illustratively, the pH can be 8, 9, 10, 11, 12, or a range defined by any two of the values; the reaction temperature can be 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 85°C, or a range defined by any two of the values; and the reaction time can be 1 h, 2 h, 4 h, 6 h, 8 h, 10 h, 12 h, or a range defined by any two of the values.

[0091] The application does not make specific limitation to the molar concentration of metal ions in the mixed salt solution, and preferably, the molar concentration of metal ions in the mixed salt solution is 0.1-3 mol / L.

[0092] Illustratively, the molar concentration of metal ions in the mixed salt solution can be 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, or a range defined by any two of the values.

[0093] The application does not make specific limitation to the molar concentration of the precipitant solution, and preferably, the molar concentration of the precipitant solution is 0.5-10 mol / L.

[0094] Illustratively, the molar concentration of the precipitant solution can be 0.5 mol / L, 1 mol / L, 2 mol / L, 4 mol / L, 6 mol / L, 8 mol / L, 10 mol / L, or a range defined by any two of the values.

[0095] The application does not make specific limitation to the adding speed of the precipitant solution, and preferably, the adding speed of the precipitant solution is 1-10 L / h.

[0096] For example, the feeding speed can be 1 L / h, 2 L / h, 4 L / h, 6 L / h, 8 L / h, 10 L / h or a range defined by any two of the above values.

[0097] The application does not make specific limitations on the types of nickel salt, cobalt salt, manganese salt and precipitant. For example, the nickel salt includes at least one of nickel sulfate, nickel chloride, nickel acetate, nickel carbonate and nickel nitrate; the cobalt salt includes at least one of cobalt sulfate, cobalt chloride, cobalt acetate, cobalt carbonate and cobalt nitrate; the manganese salt includes at least one of manganese sulfate, manganese chloride, manganese acetate, manganese carbonate and manganese nitrate; and the precipitant includes sodium carbonate or sodium hydroxide.

[0098] The application does not make specific limitations on the sources of nickel salt, cobalt salt, manganese salt and precipitant. For example, commercially available products or products prepared by conventional preparation methods known to those skilled in the art can be used.

[0099] The application does not make specific limitations on the washing and solid-liquid separation methods. For example, the reaction product can be washed with deionized water and / or aqueous sodium hydroxide solution, and then subjected to solid-liquid separation by centrifugation or filtration. The above steps can be repeated 1-3 times.

[0100] The preparation method of the positive electrode active material precursor in the application controls the feeding speed, atomizer frequency, induced fan frequency, air blower frequency, air inlet temperature, outlet temperature and the volume ratio of solid phase to deionized water in the first spray drying process, and the feeding speed, atomizer frequency, induced fan frequency, air blower frequency, air inlet temperature, outlet temperature and the volume ratio of the first product to deionized water in the second spray drying process, so that the primary particles included in the prepared precursor have a curved surface structure. This curved surface structure can make lithium ions more easily embedded during the mixing and calcination process with lithium-containing compounds, effectively increase the embedded amount of lithium ions, and greatly reduce the residual lithium content on the surface of the positive electrode active material. Therefore, the positive electrode active material with low residual lithium content can be obtained without water washing, thereby significantly reducing the direct current resistance of the lithium ion battery and improving its cycle performance.

[0101] In a specific embodiment, the solid phase is subjected to thickening treatment before the first spray drying. In the thickening process, the volume ratio of the solid phase to deionized water is 1:(1-10). Preferably, the water feeding rate during the thickening treatment is 10-30 L / h. By subjecting the solid phase to thickening treatment and controlling the volume ratio of the solid phase to deionized water within the above range, the morphology of the solid phase can be more uniform, and the agglomeration degree of the solid phase can be reduced, which is conducive to the formation of a curved surface structure of the primary particles during the spray drying process and improves the curvature of the primary particles, thereby further improving the specific surface area of the precursor, reducing the direct current resistance of the battery and improving the cycle performance of the battery.

[0102] Exemplarily, in the thickening process, the volume ratio of the solid phase to the deionized water can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, or a range formed by any two of the above ratios; the water inlet rate in the thickening process can be 10 L / h, 15 L / h, 20 L / h, 25 L / h, 30 L / h, or a range formed by any two of the above values.

[0103] The third aspect of the present application provides a positive electrode active material, which is obtained by mixing and calcining the positive electrode active material precursor of the first aspect or the positive electrode precursor material prepared by the preparation method of the second aspect and a lithium-containing compound. Since the primary particles included in the positive electrode active material precursor have a curved surface structure and the curvature is not less than 0.2, lithium ions in the lithium-containing compound can be better embedded in the calcination process, effectively increasing the lithium content in the positive electrode active material and reducing the residual lithium content on the surface of the material. When the positive electrode active material is applied to a lithium ion battery, the direct current resistance of the battery can be significantly reduced and the cycle performance of the battery can be improved.

[0104] The present application does not limit the type of lithium-containing compound. For example, the lithium-containing compound includes at least one of lithium hydroxide, lithium carbonate, and lithium hydroxide hydrate.

[0105] The present application does not specifically limit the source of the lithium-containing compound. For example, commercially available products or products prepared by conventional preparation methods known to those skilled in the art can be used.

[0106] In a specific embodiment, the positive electrode active material is obtained by a preparation method comprising the following processes:

[0107] After mixing the positive electrode active material precursor and the lithium-containing compound, calcination is performed under oxygen conditions, the calcination temperature in the calcination process is 400-1100℃, the heating rate is 2-5℃ / min, the calcination time is 5-20h, and after calcination, the positive electrode active material is obtained after crushing, sieving, and iron removal.

[0108] Exemplarily, the calcination temperature can be 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, 1100℃, or a range formed by any two of the above values; the heating rate can be 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, or a range formed by any two of the above values; and the reaction time can be 5h, 8h, 11h, 14h, 17h, 20h, or a range formed by any two of the above values.

[0109] In one specific embodiment, the median particle size of the positive electrode active material is 5-10 μm. Within this range, the positive electrode active material has high strength and low direct current internal resistance, which can improve the cycle performance of the battery.

[0110] For example, the median particle size of the positive electrode active material can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or a range defined by any two of these values.

[0111] The median particle size of the positive electrode active material in the present application can be obtained by a laser particle size analyzer.

[0112] In the following, the positive electrode active material precursor of the present application is described in detail through specific examples.

[0113] Example 1

[0114] (1) NiSO4, CoSO4 and MnSO4 were mixed with deionized water at a molar ratio of 60:20:20 to obtain 60 L of a mixed salt solution with a molar concentration of 1 mol / L. 14 L of 10 mol / L NaOH was added at a rate of 2 L / h to obtain a mixed solution with a pH of 10. After reaction at 60°C for 5 h, the precipitate was obtained by centrifugal separation, and the precipitate was concentrated using a thickener at a rate of 20 L / h for 15 h. During the concentration process, the volume ratio of the precipitate to deionized water was 1:5. After concentration, the solid phase Ni 0.6 Co 0.2 Mn 0.2 (OH)2 was obtained by centrifugal washing. The average length of the solid phase was 5.12 μm, the average width was 1.54 μm, and the average thickness was 137 nm.

[0115] (2) The solid phase was mixed with deionized water at a volume ratio of 2:10 to perform first spray drying. The feeding rate was 4 L / h, the atomizer frequency was 400 Hz, the inlet air temperature was 200°C, the outlet temperature was 120°C, the frequency of the air blower was 25 Hz, the frequency of the induced draft fan was 30 Hz, and the nitrogen flow was 0.1 L / h to obtain a first product. The first product was mixed with deionized water at a volume ratio of 2:10 to perform second spray drying. The feeding rate was 5 L / h, the atomizer frequency was 400 Hz, the inlet air temperature was 200°C, the outlet temperature was 130°C, the frequency of the air blower was 25 Hz, the frequency of the induced draft fan was 30 Hz, and the nitrogen flow was 0.1 L / h to obtain the positive electrode active material precursor Ni 0.6 Co 0.2 Mn 0.2 (OH)2 of the present example. The D50 of the precursor was 14.3 μm, the D10 was 3.4 μm, the D90 was 33.5 μm, and (D90-D10) / D50 was 2.10.

[0116] Example 2

[0117] (1) NiCl2, CoCl2and MnCl2were mixed with deionized water at a molar ratio of 50:20:30 to obtain a mixed salt solution of 60 L with a molar concentration of 1 mol / L, 15 L of 10 mol / L NaOH was added at a rate of 2 L / h to obtain a mixed solution with a pH of 10, after reaction at 60°C for 5 h, the precipitate was obtained by centrifugal separation, and the precipitate was thickened using a thickener for 15 h at a water inlet rate of 20 L / h, during the thickening process, the volume ratio of the precipitate to deionized water was 1:5; after the thickening was completed, centrifugal washing was performed to obtain a solid phase material Ni 0.5 Co 0.2 Mn 0.3 (OH)2, the average length of the solid phase material was 5.07 μm, the average width was 1.52 μm, and the average thickness was 121 nm;

[0118] (2) The above solid phase material was mixed with deionized water at a volume ratio of 2:10 to perform first spray drying, the feeding rate was 4 L / h, the atomizer frequency was 400 Hz, the inlet air temperature was 200°C, the outlet temperature was 120°C, the frequency of the air blower was 25 Hz, the frequency of the induced draft fan was 30 Hz, the nitrogen amount was 0.1 L / h, to obtain a first product; the first product was mixed with deionized water at a volume ratio of 2:10 to perform second spray drying, the feeding rate was 5 L / h, the atomizer frequency was 400 Hz, the inlet air temperature was 200°C, the outlet temperature was 130°C, the frequency of the air blower was 25 Hz, the frequency of the induced draft fan was 30 Hz, the nitrogen amount was 0.1 L / h, to obtain the positive electrode active material precursor Ni 0.5 Co 0.2 Mn 0.3 (OH)2of the present embodiment, the D50 of the precursor was 13.7 μm, the D10 was 3.6 μm, the D90 was 35.4 μm, and the (D90-D10) / D50 was 2.32.

[0119] Example 3

[0120] (1) NiCl2, CoCl2and MnCl2were mixed with deionized water at a molar ratio of 83:12:5 to obtain a mixed salt solution of 60 L with a molar concentration of 1 mol / L, 18 L of 10 mol / L NaOH was added at a rate of 2 L / h to obtain a mixed solution with a pH of 10, after reaction at 60°C for 5 h, the precipitate was obtained by centrifugal separation, and the precipitate was thickened using a thickener for 15 h at a water inlet rate of 20 L / h, during the thickening process, the volume ratio of the precipitate to deionized water was 1:5; after the thickening was completed, centrifugal washing was performed to obtain a solid phase material Ni 0.8 Co0.23 Mn 0.05 (OH)2, the average length of the solid phase was 5.14 μm, the average width was 1.54 μm, and the average thickness was 115 nm;

[0121] (2) The solid phase was mixed with deionized water at a volume ratio of 2:10 to perform first spray drying, the feeding rate was 4 L / h, the atomizer frequency was 400 Hz, the inlet air temperature was 200 ℃, the outlet temperature was 120 ℃, the frequency of the air blower was 24 Hz, the frequency of the induced draft fan was 32 Hz, the nitrogen amount was 0.1 L / h, and a first product was obtained; the first product was mixed with deionized water at a volume ratio of 2:10 to perform second spray drying, the feeding rate was 5 L / h, the atomizer frequency was 400 Hz, the inlet air temperature was 200 ℃, the outlet temperature was 130 ℃, the frequency of the air blower was 24 Hz, the frequency of the induced draft fan was 32 Hz, and the nitrogen amount was 0.1 L / h, and the positive electrode active material precursor Ni 0.83 Co 0.12 Mn 0.5 (OH)2, the D50 of the precursor was 15.6 μm, the D10 was 4.0 μm, the D90 was 32.9 μm, and (D90-D10) / D50 was 1.85.

[0122] Example 4

[0123] (1) NiSO4, CoSO4 and MnSO4 were mixed with deionized water at a molar ratio of 60:20:20 to obtain 60 L of mixed salt solution with a molar concentration of 1 mol / L, 14 L of 10 mol / L NaOH was added at a rate of 2 L / h to obtain a mixed solution with a pH of 10, after reaction at 60 ℃ for 10 h, centrifugal separation was performed to obtain a precipitate, and the precipitate was concentrated using a thickener for 20 h, the water inlet rate was 15 L / h, and the volume ratio of the precipitate to deionized water during the concentration process was 1:5; after the concentration was completed, centrifugal washing was performed to obtain a solid phase Ni 0.6 Co 0.2 Mn 0.2 (OH)2, the average length of the solid phase was 5.14 μm, the average width was 1.54 μm, and the average thickness was 115 nm;

[0124] (2) The solid phase is mixed with deionized water at a volume ratio of 2:10 to perform first spray drying, the feeding rate is preferably 4 L / h, the atomizer frequency is 300 Hz, the inlet air temperature is 180℃, the outlet temperature is 120℃, the frequency of the air blower is 23 Hz, the frequency of the induced draft fan is 30 Hz, the nitrogen amount is 0.1 L / h, to obtain the first product; the first product is mixed with deionized water at a volume ratio of 2:10 to perform second spray drying, the feeding rate is preferably 4 L / h, the atomizer frequency is 300 Hz, the inlet air temperature is 160℃, the outlet temperature is 120℃, the frequency of the air blower is 23 Hz, the frequency of the induced draft fan is 30 Hz, the nitrogen amount is 0.1 L / h, to obtain the positive electrode active material precursor Ni 0.6 Co 0.2 Mn 0.2 (OH)2of this embodiment.

[0125] Example 5

[0126] (1) NiSO4, CoSO4and MnSO4are mixed with deionized water at a molar ratio of 60:20:20 to obtain 60 L of mixed salt solution with a molar concentration of 1 mol / L, 14 L of 10 mol / L NaOH is added at a rate of 2 L / h to obtain a mixed solution with a pH of 10, after reaction at 60℃ for 5 h, centrifugal separation is performed to obtain a precipitate, the precipitate is concentrated using a thickener for 20 h, the water inlet rate is 15 L / h, and during the concentration process, the volume ratio of the precipitate to deionized water is 1:5; after the concentration is completed, centrifugal washing is performed to obtain a solid phase Ni 0.6 Co 0.2 Mn 0.2 (OH)2, the average length of the solid phase is 4.99 μm, the average width is 1.53 μm, and the average thickness is 94 nm;

[0127] (2) The solid phase is mixed with deionized water at a volume ratio of 2:10 to perform first spray drying, the feeding rate is preferably 4 L / h, the atomizer frequency is 300 Hz, the inlet air temperature is 180℃, the outlet temperature is 120℃, the frequency of the air blower is 23 Hz, the frequency of the induced draft fan is 30 Hz, the nitrogen amount is 0.1 L / h, to obtain the first product; the first product is mixed with deionized water at a volume ratio of 2:10 to perform second spray drying, the feeding rate is preferably 4 L / h, the atomizer frequency is 300 Hz, the inlet air temperature is 160℃, the outlet temperature is 120℃, the frequency of the air blower is 23 Hz, the frequency of the induced draft fan is 30 Hz, the nitrogen amount is 0.1 L / h, to obtain the positive electrode active material precursor Ni 0.6 Co0.2 Mn 0.2 The D50 of the precursor is 16.4 μm, the D10 is 2.6 μm, the D90 is 34.7 μm, and (D90-D10) / D50 is 1.96.

[0128] Example 6

[0129] (1) NiSO4, CoSO4 and MnSO4 were mixed with deionized water in a molar ratio of 60:20:20 to obtain 60 L of mixed salt solution with a molar concentration of 1 mol / L, 14 L of 10 mol / L NaOH was added at a rate of 2 L / h to obtain a mixed solution with a pH of 10, and after reaction at 60°C for 5 h, the precipitate was obtained by centrifugal separation, and the precipitate was concentrated by using a thickener for 6 h at an inflow rate of 20 L / h, and the volume ratio of the precipitate to deionized water was 1:2 during the concentration process; after the concentration was completed, centrifugal washing was performed to obtain a solid-phase material Ni 0.6 Co 0.2 Mn 0.2 The average length of the solid-phase material is 8.31 μm, the average width is 2.51 μm, and the average thickness is 221 nm;

[0130] (2) The solid-phase material was mixed with deionized water in a volume ratio of 2:10 to perform first spray drying, the feeding rate was preferably 4 L / h, the atomizer frequency was 350 Hz, the inlet air temperature was 195°C, the outlet temperature was 120°C, the frequency of the air blower was 25 Hz, the frequency of the induced draft fan was 32 Hz, the nitrogen amount was 0.1 L / h, and the first product was obtained; the first product was mixed with deionized water in a volume ratio of 2:10 to perform second spray drying, the feeding rate was preferably 4 L / h, the atomizer frequency was preferably 350 Hz, the inlet air temperature was 195°C, the outlet temperature was 120°C, the frequency of the air blower was 25 Hz, the frequency of the induced draft fan was 32 Hz, the nitrogen amount was 0.1 L / h, and the positive electrode active material precursor Ni 0.6 Co 0.2 Mn 0.2 The D50 of the precursor is 10.7 μm, the D10 is 2.3 μm, the D90 is 31.5 μm, and (D90-D10) / D50 is 2.73.

[0131] Example 7

[0132] (1) NiSO4, CoSO4 and MnSO4 are mixed with deionized water according to a molar ratio of 60:20:20 to obtain 60 L of mixed salt solution with a molar concentration of 1 mol / L, 14 L of 10 mol / L NaOH is added at a rate of 2 L / h to obtain a mixed solution with a pH of 10, after reaction at 60 °C for 5 h, the precipitate is obtained by centrifugal separation, and the precipitate is thickened for 24 h using a thickener, the water inlet rate is 20 L / h, and the volume ratio of the precipitate to deionized water during the thickening process is 1:8; after the thickening is completed, centrifugal washing is performed to obtain a solid-phase material Ni 0.6 Co 0.2 Mn 0.2 (OH)2, the average length of the solid-phase material is 4.51 μm, the average width is 1.12 μm, and the average thickness is 76 nm;

[0133] (2) The above solid-phase material is mixed with deionized water according to a volume ratio of 2:10 to perform first spray drying, the feeding rate is preferably 4 L / h, the atomizer frequency is 500 Hz, the inlet air temperature is 210 °C, the outlet temperature is 120 °C, the frequency of the air blower is 24 Hz, the frequency of the induced draft fan is 29 Hz, the nitrogen amount is 0.1 L / h, and the first product is obtained; the first product is mixed with deionized water according to a volume ratio of 2:10 to perform second spray drying, the feeding rate is preferably 4 L / h, the atomizer frequency is preferably 500 Hz, the inlet air temperature is 210 °C, the outlet temperature is 120 °C, the frequency of the air blower is 24 Hz, the frequency of the induced draft fan is 29 Hz, the nitrogen amount is 0.1 L / h, and the positive electrode active material precursor Ni 0.6 Co 0.2 Mn 0.2 (OH)2 of the present embodiment is obtained, the D50 of the precursor is 18.7 μm, the D10 is 4.3 μm, the D90 is 38.4 μm, and (D90-D10) / D50 is 1.82.

[0134] Example 8

[0135] (1) NiSO4, CoSO4 and MnSO4 are mixed with deionized water according to a molar ratio of 60:20:20 to obtain 60 L of mixed salt solution with a molar concentration of 1 mol / L, 14 L of 10 mol / L Na2CO3 is added at a rate of 2 L / h to obtain a mixed solution with a pH of 10, after reaction at 60 °C for 5 h, the precipitate is obtained by centrifugal separation, and the precipitate is thickened for 15 h using a thickener, the volume ratio of the precipitate to deionized water during the thickening process is 1:5; after the thickening is completed, centrifugal washing is performed to obtain a solid-phase material Ni 0.6 Co 0.2 Mn 0.2Ni0.6Co0.2Mn0.2(OH)2, the average length of the solid phase was 5.01 μm, the average width was 1.59 μm, and the average thickness was 113 nm;

[0136] (2) The solid phase was mixed with deionized water at a volume ratio of 2:10 to perform first spray drying, the feeding rate was 4 L / h, the atomizer frequency was 400 Hz, the inlet air temperature was 200 ℃, the outlet temperature was 120 ℃, the nitrogen amount was 0.1 L / h, the blower frequency was 25 Hz, and the induced draft fan frequency was 30 Hz to obtain a first product; the first product was mixed with deionized water at a volume ratio of 2:10 to perform second spray drying, the feeding rate was 5 L / h, the atomizer frequency was 400 Hz, the inlet air temperature was 200 ℃, the outlet temperature was 130 ℃, the blower frequency was 25 Hz, the induced draft fan frequency was 30 Hz, and the nitrogen amount was 0.1 L / h to obtain the positive electrode active material precursor Ni 0.6 Co 0.2 Mn 0.2 Ni0.6Co0.2Mn0.2(OH)2, the D50 of the precursor was 11.7 μm, the D10 was 2.3 μm, the D90 was 31.5 μm, and (D90-D10) / D50 was 2.50.

[0137] Example 9

[0138] (1) NiSO4, CoSO4 and MnSO4 were mixed with deionized water at a molar ratio of 60:20:20 to obtain 60 L of mixed salt solution with a molar concentration of 1 mol / L, 14 L of 10 mol / L NaOH was added at a rate of 2 L / h to obtain a mixed solution with a pH of 10, after reaction at 60 ℃ for 5 h, the precipitate was obtained by centrifugal separation, and the solid phase Ni 0.6 Co 0.2 Mn 0.2 Ni0.6Co0.2Mn0.2(OH)2, the average length of the solid phase was 11.37 μm, the average width was 2.86 μm, and the average thickness was 531 nm;

[0139] (2) The solid phase was mixed with deionized water at a volume ratio of 2:10 to perform first spray drying, the feeding rate was 4 L / h, the atomizer frequency was 400 Hz, the inlet air temperature was 200 ℃, the outlet temperature was 120 ℃, the blower frequency was 25 Hz, the induced draft fan frequency was 30 Hz, and the nitrogen amount was 0.1 L / h to obtain a first product; the first product was mixed with deionized water at a volume ratio of 2:10 to perform second spray drying, the feeding rate was 5 L / h, the atomizer frequency was 400 Hz, the inlet air temperature was 200 ℃, the outlet temperature was 130 ℃, the blower frequency was 25 Hz, the induced draft fan frequency was 30 Hz, and the nitrogen amount was 0.1 L / h to obtain the positive electrode active material precursor Ni0.6 Co 0.2 Mn 0.2 (OH)2, the D50 of the precursor is 10.7 μm, the D10 is 2.7 μm, the D90 is 44.5 μm, and (D90-D10) / D50 is 3.91.

[0140] Comparative Example 1

[0141] In the present comparative example, the Ni 0.6 Co 0.2 Mn 0.2 (OH)2precursor was prepared by a traditional co-precipitation method, specifically including the steps of:

[0142] A mixed salt solution of NiSO4, CoSO4and MnSO4was prepared at 2 mol / L, wherein the molar ratio of Ni, Co and Mn was 60:20:20, 10 mol / L NaOH was prepared as a precipitant, and 8 mol / L ammonia was prepared as a complexing agent; 60 L of the mixed salt solution was added to the reactor, the temperature was raised to 60°C, and stirring was performed at a stirring speed of 550 r / min; NaOH was added to the reactor at a feeding speed of 1 L / h until the pH of the reaction system was 9, then the complexing agent was continuously added to the reactor at a feeding speed of 0.1 L / h until the pH was 12 to stop the reaction, and the ternary positive electrode precursor Ni 0.6 Co 0.2 Mn 0.2 (OH)2was obtained. The D50 of the precursor was 3.80 μm, the D10 was 2.70 μm, the D90 was 5.20 μm, and (D90-D10) / D50 was 0.66.

[0143] Comparative Example 2

[0144] In the present comparative example, the Ni 0.5 Co 0.2 Mn 0.3 (OH)2precursor was prepared by a traditional co-precipitation method, specifically including the steps of:

[0145] A mixed salt solution of NiSO4, CoSO4and MnSO4was prepared at 2 mol / L, wherein the molar ratio of Ni, Co and Mn was 60:20:20, 10 mol / L NaOH was prepared as a precipitant, and 8 mol / L ammonia was prepared as a complexing agent; 60 L of the mixed salt solution was added to the reactor, the temperature was raised to 60°C, and stirring was performed at a stirring speed of 550 r / min; NaOH was added to the reactor at a feeding speed of 1 L / h until the pH of the reaction system was 9, then the complexing agent was continuously added to the reactor at a feeding speed of 0.1 L / h until the pH was 12 to stop the reaction, and the ternary positive electrode precursor Ni 0.5 Co 0.2 Mn0.3 The precursor has a D50 of 3.4 pm, a D10 of 2.3 pm, a D90 of 5.3 pm, and a (D90-D10) / D50 of 0.88.

[0146] Comparative Example 3

[0147] In this comparative example, the Ni 0.83 Co 0.12 Mn 0.05 The precursor has a D50 of 3.4 pm, a D10 of 2.3 pm, a D90 of 5.3 pm, and a (D90-D10) / D50 of 0.88.

[0148] A 2 mol / L mixed salt solution of NiSO4, CoSO4 and MnSO4 was prepared, wherein the molar ratio of Ni, Co and Mn was 83:12:5. A 10 mol / L NaOH solution was prepared as a precipitant, and an 8 mol / L ammonia solution was prepared as a complexing agent. 60 L of the mixed salt solution was added to a reactor, and the temperature was raised to 60°C. The solution was stirred at a speed of 550 r / min. The NaOH solution was added to the reactor at a rate of 1 L / h until the pH of the reaction system reached 9. Then the complexing agent was added to the reactor at a rate of 0.1 L / h until the pH reached 12, and the reaction was stopped. Thus, a ternary positive electrode precursor Ni 0.83 Co 0.12 Mn 0.05 The precursor has a D50 of 3.4 pm, a D10 of 2.3 pm, a D90 of 5.3 pm, and a (D90-D10) / D50 of 0.88.

[0149] Comparative Example 4

[0150] The product prepared in Comparative Example 1 was subjected to two spray drying processes. The feed rate, atomizer frequency, inlet air temperature, outlet temperature, and nitrogen amount in the first spray drying and the second spray drying were consistent with those in Example 1. The prepared precursor has a D50 of 3.9 pm, a D10 of 2.6 pm, a D90 of 4.8 pm, and a (D90-D10) / D50 of 0.56.

[0151] Comparative Example 5

[0152] The product prepared in Comparative Example 2 was subjected to two spray drying processes. The feed rate, atomizer frequency, inlet air temperature, outlet temperature, and nitrogen amount in the first spray drying and the second spray drying were consistent with those in Example 1. The prepared precursor has a D50 of 3.7 pm, a D10 of 2.5 pm, a D90 of 5.1 pm, and a (D90-D10) / D50 of 0.70.

[0153] Comparative Example 6

[0154] The product prepared in Comparative Example 3 was subjected to two spray drying processes, the feed rate, atomizer frequency, inlet air temperature, outlet temperature, and nitrogen amount in the first spray drying and the second spray drying were consistent with Example 1. The prepared precursor had a D50 of 3.4 μm, a D10 of 2.3 μm, a D90 of 5.2 μm, and a (D90-D10) / D50 of 0.85.

[0155] Comparative Example 7

[0156] The preparation method of the positive electrode active material precursor in the present comparative example was basically consistent with that of Example 1, except that the solid phase obtained in step (1) was only subjected to the first spray drying to obtain the positive electrode active material precursor Ni 0.6 Co 0.2 Mn 0.2 (OH)2in the present comparative example. The prepared precursor had a D50 of 12.9 μm, a D10 of 6.1 μm, a D90 of 36.5 μm, and a (D90-D10) / D50 of 2.36.

[0157] Comparative Example 8

[0158] The preparation method of the positive electrode active material precursor in the present comparative example was basically consistent with that of Example 1, except that the volume ratio of the solid phase to deionized water in step (2) and the volume ratio of the first product to deionized water were changed, specifically, the volume ratio of the solid phase to deionized water was adjusted to 5:10, and the volume ratio of the first product to deionized water was adjusted to 5:10, to obtain the positive electrode active material precursor Ni 0.6 Co 0.2 Mn 0.2 (OH)2in the present comparative example. The prepared precursor had a D50 of 18.7 μm, a D10 of 4 μm, a D90 of 49.8 μm, and a (D90-D10) / D50 of 2.45.

[0159] Comparative Example 9

[0160] The preparation method of the positive electrode active material precursor in the present comparative example was basically consistent with that of Example 1, except that in step (2), the parameters in the first spray drying were adjusted, specifically, the feed rate was adjusted to 1 L / h, the atomizer frequency was adjusted to 50 Hz, the frequency of the air blower was adjusted to 10 Hz, the frequency of the induced draft fan was adjusted to 5 Hz, the inlet air temperature was adjusted to 80°C, and the outlet temperature was adjusted to 40°C, to obtain the positive electrode active material precursor Ni 0.6 Co 0.2 Mn 0.2 (OH)2in the present comparative example.

[0161] Comparative Example 10

[0162] The preparation method of the positive electrode active material precursor in the present comparative example is basically the same as that in Embodiment 1, except that in step (2), the parameters in the second spray drying are adjusted, specifically, the feeding rate is adjusted to 9 L / h, the atomizer frequency is adjusted to 800 Hz, the blower frequency is adjusted to 40 Hz, the air intake frequency is adjusted to 50 Hz, the air intake temperature is adjusted to 300 DEG C, and the outlet temperature is adjusted to 230 DEG C, to obtain the positive electrode active material precursor Ni 0.6 Co 0.2 Mn 0.2 (OH)2.

[0163] Comparative Example 11

[0164] The positive electrode active material precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2prepared in Comparative Example 3 is mixed with lithium hydroxide to obtain a positive electrode active material, which is then washed with water to reduce the residual lithium content on the surface of the positive electrode active material.

[0165] Test Example

[0166] 1. The positive electrode active material precursors prepared in the above embodiments and comparative examples are subjected to physicochemical property characterization, and the characterization results are shown in Table 1.

[0167] Table 1

[0168] From Table 1, it can be seen that:

[0169] The primary particles included in the positive electrode active material precursors in Embodiments 1-9 all have a curved surface structure, and the curvature is not less than 0.2, while the positive electrode active material precursors in Comparative Examples 1-11 all do not have a curved surface structure or the curvature is less than 0.2. It can be known that the curved surface structure in the positive electrode active material precursor of the present application can significantly increase the specific surface area and porosity thereof, so that lithium ions are more easily embedded in the process of mixing and sintering with lithium-containing compounds.

[0170] 2. The positive electrode active material precursors prepared in the above embodiments and comparative examples are mixed with lithium-containing compounds to perform calcination, to obtain positive electrode active materials, and the median particle size and residual lithium content of the prepared positive electrode active materials are detected, including the following steps:

[0171] The positive electrode active material precursors prepared in the above embodiments and comparative examples are uniformly mixed with lithium hydroxide according to a molar ratio of 1:1.01, and placed in a muffle furnace to perform calcination, with a temperature rising rate of 2 DEG C / min, a calcination temperature of 950 DEG C, and a holding time of 12 h. After calcination, the calcination product is cooled to obtain a calcination product, which is crushed, sieved, and iron-removed to obtain a positive electrode active material.

[0172] Median particle size: The positive active material was tested using a laser particle size analyzer, HORIBA LA-960 dispersion mode: wet (automatic circulation system), refractive index setting: sample and dispersion medium refractive index difference > 0.1, obscuration: 10% (wet), circulation speed: 3000 rpm (to prevent sedimentation).

[0173] Residual lithium content test: 10 g of sample (accurate to 0.01 g) was weighed into a beaker at 25°C, 100 mL of distilled water was added; a clean magnetic rotor was placed in the beaker, and after sealing with a sealing film, it was placed on a magnetic stirrer for stirring at a rate of 500 r / min for 15 min of leaching, and after standing, the sample solution was filtered using a vacuum filtration device; 1 mL to 10 mL of the test filtrate was accurately transferred into a 100 ml beaker using a corresponding size pipette, 50 ml of distilled water was added, and it was placed in a potentiometric titrator. According to the test results, the contents of lithium hydroxide and lithium carbonate can be obtained, and the test results are shown in Table 2.

[0174] 3. The positive active material prepared above was applied to a button cell, and the direct current resistance and cycle performance of the button cell were tested, including the following steps:

[0175] The positive active material prepared above, SuperP, and polyvinylidene fluoride were mixed and stirred uniformly at a mass ratio of 90:5:5 with N-methyl pyrrolidone to prepare a positive electrode slurry with a solid content of 40%; the positive electrode slurry was coated on both functional surfaces of an aluminum foil, and the coating surface density was 1.5 g / 100 cm 2 After drying at 105°C, the dried electrode sheet was rolled at room temperature to obtain an electrode sheet with a compacted density of 3.3 g / cm 3 The electrode sheet was then punched and cut into a circular sheet with a diameter of 14 mm to form a positive electrode sheet.

[0176] The assembly of the button cell was carried out in a glove box, and the assembly was carried out in the order of "negative electrode shell-foam nickel-lithium sheet-8 drops of electrolyte-separator-8 drops of electrolyte-positive electrode sheet-positive electrode shell", wherein the electrolyte includes 1.0 M LiPF6 and organic solvents ethylene carbonate (EC), methyl ethyl carbonate (EMC), and dimethyl carbonate (DMC), and the volume ratio of EC: EMC: DMC is 1:1:1.

[0177] (1) Direct current resistance test

[0178] The charge-discharge cycle performance of the above button cell was detected at 25°C by using a blue electric test cabinet, 0.1C constant current charging to 4.45V, then constant voltage charging to 0.02C at 4.45V, standing for 5min, recording the first charge capacity as C0; 0.1C discharging to 2.8V, standing for 5min, recording the first discharge capacity as C1; according to the foregoing charge-discharge process, after 300 cycles, discharging at 4C for 30S, recording the data, and calculating the direct current internal resistance by using the formula R=U / I.

[0179] (2) Cycle performance test

[0180] The charge-discharge cycle performance of the above button cell was detected at 25°C by using a blue electric test cabinet, 0.1C constant current charging to 4.45V, then constant voltage charging to 0.02C at 4.45V, standing for 5min, recording the first charge capacity as C0; 0.1C discharging to 2.8V, standing for 5min, recording the first discharge capacity as C1; according to the foregoing charge-discharge process, after 200 cycles, recording the discharge capacity after cycle as C2; then the capacity retention rate and the first coulombic efficiency can be calculated by formula 1 and formula 2 respectively,

[0181] Capacity retention rate (%) = (C2 / C1) x 100% Formula 1

[0182] First coulombic efficiency (%) = (C1 / C0) x 100% Formula 2

[0183] The calculation results are shown in Table 2.

[0184] Table 2

[0185] From Table 2, it can be seen that:

[0186] Compared with Comparative Examples 1-11, Examples 1-9 have lower residual lithium content, and thus have higher first coulombic efficiency, lower direct current internal resistance and higher capacity retention rate. In Examples 1-9, the first coulombic efficiency is as high as 91.8%, the direct current internal resistance is as high as 169.46Ω, and the cycle capacity retention rate is as high as 94.62%, and the battery performance is obviously better than that of Comparative Examples 1-11. Therefore, the positive active material precursor of the present application can effectively improve the direct current internal resistance and cycle performance of the lithium ion battery due to its curved surface structure.

[0187] 4. The positive active material precursor prepared in the above examples and comparative examples was subjected to SEM test, and the test results are shown in Figures 3-10.

[0188] Fig. 3 is an SEM image of the positive electrode active material precursor prepared in Example 2 at a 2k magnification, Fig. 4 is an SEM image of the positive electrode active material precursor prepared in Example 1 at a 1k magnification, Fig. 5 is an SEM image of the positive electrode active material precursor prepared in Example 1 at a 5k magnification, and Fig. 6 is an SEM image of the positive electrode active material precursor prepared in Example 1 at a 50k magnification. As can be seen from Figs. 3-6, the positive electrode active material precursor is composed of countless primary particles with curved surface structures, in a "flower cluster" shape, with loose surface structures and a large number of pores and channels. Fig. 7 is a cross-sectional SEM image of the positive electrode active material precursor prepared in Example 2. As can be seen from Fig. 7, the internal structure of the precursor is also loose and porous, allowing a large number of pores and channels to be formed, which can effectively increase the specific surface area of the precursor. Fig. 8 is an SEM image of the positive electrode active material precursor prepared in Comparative Example 1 at a 50k magnification, Fig. 9 is an SEM image of the positive electrode active material precursor prepared in Comparative Example 1 at a 10k magnification, and Fig. 10 is an SEM image of the positive electrode active material precursor prepared in Comparative Example 1 at a 5k magnification. As can be seen from Figs. 8-10, the precursor prepared by the traditional co-precipitation method has a closed strip structure.

[0189] Therefore, the precursor of the present application has a higher specific surface area than the precursor in Comparative Example 1, can significantly increase the lithium intercalation amount during calcination, reduce the surface residual lithium content of the positive electrode active material, effectively reduce the direct current resistance of the battery and improve its cycle performance.

[0190] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent replacements to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

A positive electrode active material precursor, wherein, The positive electrode active material precursor comprises secondary particles composed of primary particles; the primary particles have a curved surface structure; The curvature of the primary particles is not less than 0.

2. The positive electrode active material precursor according to claim 1, wherein, The curvature of the primary particles is not less than 0.

3. The positive electrode active material precursor according to claim 1 or 2, wherein, The specific surface area of the positive electrode active material precursor is 70 to 90 m 2 / g. The positive electrode active material precursor according to any one of claims 1 to 3, wherein The porosity of the positive electrode active material precursor is 50-80%. The positive electrode active material precursor according to any one of claims 1 to 4, wherein The D50 of the positive electrode active material precursor is 10-20 μm, and / or the D90 is 30-40 μm, and / or the D10 is 1-5 μm. The positive electrode active material precursor according to claim 5, wherein, The (D90-D10) / D50 of the positive electrode active material precursor is 1.45-4. The positive electrode active material precursor according to any one of claims 1 to 6, wherein The thickness of the primary particles is not higher than 100 nm, and / or the length is not higher than 3 μm. The positive electrode active material precursor according to any one of claims 1 to 7, wherein The positive electrode active material precursor comprises a chemical composition shown in Formula 1, Ni a Co b Mn c (OH)2 Formula 1 In Formula 1, 0.5 Or, the positive electrode active material precursor comprises a chemical composition shown in Formula 2, Ni x Co y Mn z CO3 Formula 2 In Formula 2, 0.5 A method for producing the positive electrode active material precursor according to any one of claims 1 to 8, wherein The steps comprise the following: The solid phase is mixed with deionized water, and then first spray drying is performed to obtain a first product; the first product is mixed with deionized water to obtain a dispersion liquid, and then second spray drying is performed on the dispersion liquid to obtain the positive electrode active material precursor; wherein the solid phase has a chemical composition of the positive electrode active material precursor; The average length of the solid phase is not higher than 5 μm, the average width is not higher than 1 μm, and the average thickness is not higher than 100 nm; The volume ratio of the solid phase to deionized water is (1-2):10, and the volume ratio of the first product to deionized water is (1-2):10; In the first spray drying process, the feeding rate is 3-5 L / h, the frequency of the atomizer is 100-600 Hz, the frequency of the air blower is 20-30 Hz, the frequency of the induced draft fan is 10-40 Hz, the inlet air temperature is 100-250 ℃, and the outlet temperature is 80-150 ℃; In the second spray drying process, the feeding rate is 3-5 L / h, the frequency of the atomizer is 400-600 Hz, the frequency of the air blower is 20-30 Hz, the frequency of the induced draft fan is 10-40 Hz, the inlet air temperature is 100-250 ℃, and the outlet temperature is 80-150 ℃. The method for producing a positive electrode active material precursor according to claim 9, wherein The solid phase is subjected to thickening treatment before the first spray drying; In the thickening process, the volume ratio of the solid phase to deionized water is 1:(1-10). A positive electrode active material, wherein, The positive electrode active material is obtained by mixing and calcining the positive electrode active material precursor of any one of claims 1-8, or the positive electrode precursor material prepared by the preparation method of claim 9 or 10, and a lithium-containing compound. The positive electrode active material according to claim 11, characterized in that The tap density of the positive electrode active material is 1 to 1.8 g / cm3 3 . The positive electrode active material according to claim 11 or 12, characterized in that, The median particle size of the positive electrode active material is 5-10 μm.

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