Ternary precursor and preparation method and application thereof

Abstract

The invention provides a ternary precursor and a preparation method and application thereof, the chemical composition of the ternary precursor is NixCoyMz (OH) 2, M is Mn and / or Al, x is more than 0 and less than 1, y is more than 0 and less than 1, z is more than 0 and less than 1, and x + y + z = 1; the sphericity degree R of the ternary precursor is 0.95-0.99, and the agglomeration rate of the ternary precursor is less than 5%. According to the ternary precursor provided by the invention, the sphericity and the agglomeration rate of the ternary precursor are limited, so that the ternary precursor has the advantages of being difficult to agglomerate and relatively high in sphericity, the compaction density, the rate capability and the cycle performance of a positive electrode active material can be improved, and a lithium ion battery can have relatively high energy density; the rate performance and the cycle performance are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and in particular relates to a ternary precursor and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have many advantages such as high operating voltage, light weight, high energy density, and long cycle life, and have been widely used in electric vehicles, digital cameras, mobile phones, laptops, etc. Among them, the positive electrode active material, as the core material in lithium-ion batteries, largely determines the energy density and cost of the battery, and its performance directly affects the performance of lithium-ion batteries.

[0003] Ternary cathode active materials are the cathode active materials for power batteries with the largest market share at present, and have become one of the mainstream choices in the power battery industry. Ternary precursors are important upstream materials for producing ternary cathode active materials. High sphericity ternary precursors can effectively improve the compaction density, rate performance, and cycle performance of cathode active materials. Therefore, improving the sphericity of ternary precursors is one of the important development directions for improving the performance of cathode materials.

[0004] The ternary precursor prepared in the prior art is easy to agglomerate between particles, resulting in poor sphericity of the product, thereby affecting the compaction density, rate performance, and cycle performance of the positive electrode active material. Therefore, providing a ternary precursor material that is not easy to agglomerate and has high sphericity is a technical problem that needs to be solved in the art. Summary of the invention

[0005] The main purpose of the present invention is to provide a ternary precursor which is not easy to agglomerate and has a high sphericity.

[0006] The present invention also provides a method for preparing a ternary precursor, which can prepare the above-mentioned ternary precursor, and has a simple process and low cost.

[0007] The present invention also provides a ternary positive electrode active material, which includes the above-mentioned ternary precursor, so the ternary positive electrode active material has higher compaction density, rate performance and cycle performance.

[0008] The present invention also provides a positive electrode sheet. Since the positive electrode sheet includes the above-mentioned ternary positive electrode active material, the positive electrode sheet is used in a lithium ion battery and can improve the energy density, rate performance and cycle performance of the lithium ion battery.

[0009] The present invention also provides a lithium ion battery. Since the lithium ion battery comprises the above-mentioned positive electrode sheet, the lithium ion battery has higher energy density, rate performance and cycle performance.

[0010] In a first aspect, the present invention provides a ternary precursor, wherein the chemical composition of the ternary precursor is Ni x Co y M z (OH)2, wherein M is Mn and / or Al, 0<x<1, 0<y<1, 0<z<1, x+y+z=1;

[0011] The sphericity R of the ternary precursor is 0.95-0.99, and the agglomeration rate of the ternary precursor is less than 5%.

[0012] The ternary precursor as described above, wherein the ternary precursor comprises uniform particles having a particle size Dmid of 0.8D50<Dmid<1.2D50;

[0013] The number of the uniform particles accounts for ≥90%.

[0014] The ternary precursor as described above has a particle size distribution SPAN of 0.2-0.65.

[0015] As for the ternary precursor as described above, the median particle size D50 of the ternary precursor is 7-15 μm.

[0016] The ternary precursor as described above, wherein the tap density of the ternary precursor is greater than 2.0 g / cm 3 .

[0017] In a second aspect, the present invention provides a method for preparing the ternary precursor as described above, comprising the following steps:

[0018] 1) preparing a first precursor having a median particle size of D50' by a continuous method using a raw material system including a nickel source, a cobalt source, and an M source;

[0019] 2) classifying the first precursor to obtain a target precursor with a median particle size of (0.15-0.5) D50';

[0020] 3) Using the target precursor as a seed, a ternary precursor slurry with a median particle size of D50 is prepared by an intermittent method.

[0021] According to the preparation method described above, the median particle size D50' of the first precursor is 5-15 μm.

[0022] In a third aspect, the present invention provides a ternary positive electrode active material, comprising the above-mentioned ternary precursor or the ternary precursor prepared using the above-mentioned preparation method.

[0023] In a fourth aspect, the present invention provides a positive electrode sheet comprising the above-mentioned ternary positive electrode active material.

[0024] In a fifth aspect, the present invention provides a lithium-ion battery comprising the above-mentioned positive electrode sheet.

[0025] The ternary precursor provided by the present invention has the advantages of being not easy to agglomerate and having a high sphericity by limiting its sphericity and agglomeration rate, thereby improving the compaction density, rate performance and cycle performance of the positive electrode active material, and further enabling the lithium-ion battery to have a higher energy density, rate performance and cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments of the present invention or related technologies. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 A schematic diagram of a device for preparing a ternary precursor provided by the present invention;

[0028] Figure 2 This is a SEM image of the first precursor prepared in Example 1 of the present invention;

[0029] Figure 3 This is a SEM image of the ternary precursor prepared in Example 1 of the present invention;

[0030] Figure 4 This is the SEM image of the ternary precursor prepared in Comparative Example 1 of the present invention.

[0031] Description of reference numerals:

[0032] 100-first reaction device; 110-first reaction device motor; 111-first reaction device stirring shaft; 112-first reaction device upper stirring paddle; 113-first reaction device lower stirring paddle; 200-first aging kettle; 210-first aging kettle motor; 211-first aging kettle stirring shaft; 212-first aging kettle stirring paddle; 300-second aging kettle; 310-second aging kettle motor; 311-second aging kettle stirring shaft; 312-second aging kettle stirring paddle; 400-third aging kettle; 410-third aging kettle motor; 411-third aging kettle stirring shaft; 412-third Aging kettle stirring paddle; 510-first valve; 520-second valve; 600-cyclone; 710-first delivery pump; 720-second delivery pump; 800-second reaction unit; 810-second reaction unit motor; 811-second reaction unit stirring shaft; 812-second reaction unit upper stirring paddle; 813-second reaction unit lower stirring paddle; 900-transfer kettle; 910-transfer kettle motor; 911-transfer kettle stirring shaft; 912-transfer kettle stirring paddle; 1010-thickener; 1011-thickener motor; 1012-thickener stirring shaft; 1013-thickener stirring paddle. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] In a first aspect, the present invention provides a ternary precursor, wherein the chemical composition of the ternary precursor is Ni x Co y M z (OH)2, wherein M is Mn and / or Al, 0<x<1, 0<y<1, 0<z<1, x+y+z=1;

[0035] The sphericity R of the ternary precursor is 0.95-0.99, and the agglomeration rate of the ternary precursor is less than 5%.

[0036] The ternary precursor provided by the present invention is a nickel-cobalt-manganese or nickel-cobalt-aluminum hydroxide ternary precursor, whose sphericity R is 0.95-0.99 and the agglomeration rate is less than 5%. It has the advantages of being not easy to agglomerate and having a high sphericity. The ternary positive electrode active material prepared therefrom has a high compaction density, rate performance and cycle performance, thereby enabling the lithium-ion battery to have a high energy density, rate performance and cycle performance.

[0037] The sphericity R in the present invention refers to the ratio of the surface area of ​​a sphere of the same volume as the material particle to the surface area of ​​the material particle. The larger the ratio, the closer the material particle is to a sphere. The sphericity R in the present invention is calculated by the formula R = 4πS / L 2 Calculated, where S is the area of ​​the cross section of the ternary precursor through the diameter, and L is the circumference of the cross section of the ternary precursor through the diameter. The sphericity of a sphere is 1, and the closer the sphericity is to 1, the better the sphericity of the material. Therefore, the ternary precursor of the present invention has a higher sphericity, rounder particles, and higher dispersibility.

[0038] The agglomeration rate in the present invention refers to the ratio of the number of agglomerated secondary spherical particles to the total number of secondary spherical particles in the prepared sample, that is, agglomeration rate = number of agglomerated particles / total number of particles. The value can be determined by characterizing the sample with a scanning electron microscope (SEM) and then counting the number of agglomerated particles and non-agglomerated particles in the SEM image.

[0039] The ternary precursor provided by the present invention has the advantages of being not easy to agglomerate and having a high sphericity by limiting its sphericity and agglomeration rate, so that it has good fluidity, which helps to achieve better filling and uniform distribution of the positive electrode active material during the molding and sintering process, thereby improving the compaction density, rate performance and cycle performance of the positive electrode active material, and further enabling the lithium-ion battery to have higher energy density, rate performance and cycle performance.

[0040] In some embodiments of the present invention, the ternary precursor comprises uniform particles having a particle size Dmid of 0.8D50 < Dmid < 1.2D50;

[0041] The number of the uniform particles accounts for ≥90%.

[0042] The ternary precursor provided by the present invention includes uniform particles with a particle size Dmid of 0.8D50<Dmid<1.2D50, and the number of uniform particles accounts for ≥90%, indicating that the particle uniformity of the ternary precursor is high. Among them, the number of small particles with a particle size Dmin of 0.6D50≤Dmin≤0.8D50 plus the number of large particles with a particle size Dmax of 1.2D50≤Dmax≤1.4D50 is less than 10%, and there are no particles with a particle size of <0.6D50 and a particle size of >1.4D50 in the ternary precursor. The number ratio of uniform particles can be determined by characterizing the sample by scanning electron microscopy (SEM), and then counting the number of particle sizes Dmid, Dmin and Dmax in the SEM image.

[0043] Among the ternary precursor particles of the present invention, at least 90% of the particles have a particle size Dmid that satisfies 0.8D50<Dmid<1.2D50, that is, close to the median particle size D50, indicating that the particles of the ternary precursor have high uniformity, and can more effectively transfer heat and pressure during the sintering process to prepare the ternary positive electrode active material, reduce sintering defects caused by uneven distribution of materials, help reduce pores and cracks during the sintering process, and improve the density and mechanical properties of the positive electrode active material. The ternary positive electrode active material prepared therefrom is applied to lithium-ion batteries, which can further improve the energy density and cycle performance of lithium-ion batteries.

[0044] In some embodiments of the present invention, the particle size distribution SPAN of the ternary precursor is 0.2-0.65.

[0045] In some embodiments, the particle size distribution SPAN of the ternary precursor is 0.2-0.65, wherein the particle size distribution SPAN of the ternary precursor is calculated according to the formula (D90-D10) / D50. The particle size distribution of the ternary precursor in the present invention is suitable, which can improve the tap density of the material, and is also conducive to ensuring that the stress on the particles is more uniform, avoiding cracking of the particles, and is conducive to further improving the energy density and cycle performance of the battery.

[0046] The present invention does not limit the specific values ​​of D90, D50, and D10 of the ternary precursor, as long as the particle size distribution SPAN of the ternary precursor is ensured to be within the above range.

[0047] The particle size distribution width of the ternary precursor in this embodiment is appropriate, which can increase the tap density of the material and further improve the energy density and cycle performance of the battery.

[0048] In some embodiments of the present invention, the median particle size D50 of the ternary precursor is 7-15 μm.

[0049] The median particle size D50 of the ternary precursor of the present invention is 7-15 μm, which can further improve the sphericity and agglomeration rate of the ternary precursor, thereby improving the compaction density, rate performance and cycle performance of the positive electrode active material, and further enabling the lithium-ion battery to have higher energy density, rate performance and cycle performance.

[0050] In some embodiments of the present invention, the tap density of the ternary precursor is greater than 2.0 g / cm 3 .

[0051] The tap density of the ternary precursor in the present invention is > 2.0 g / cm 3The particles are stacked more closely, and a more stable crystal structure can be formed in the process of preparing positive electrode active materials, reducing deformation and cracking caused by internal stress of the material. It is also beneficial to improve the conductivity and ion transfer efficiency of the ternary positive electrode active materials, and help improve the stability and service life of the positive electrode active materials, thereby improving the energy density and cycle performance of lithium-ion batteries.

[0052] In a second aspect, the present invention provides a method for preparing the ternary precursor as described above, comprising the following steps:

[0053] 1) preparing a first precursor having a median particle size of D50' by a continuous method using a raw material system including a nickel source, a cobalt source, and an M source;

[0054] 2) classifying the first precursor to obtain a target precursor with a median particle size of (0.15-0.5) D50';

[0055] 3) Using the target precursor as a seed, a ternary precursor slurry with a median particle size of D50 is prepared by an intermittent method.

[0056] In the present invention, the ternary precursor provided in the first aspect of the present invention can be prepared by combining the continuous method and the intermittent method.

[0057] Specifically, in step 1), the addition ratio of the nickel source, the cobalt source, and the M source can be determined according to the chemical composition of the ternary precursor to be prepared. For example, the chemical composition of the ternary precursor is Ni x Co y M z (OH)2, the molar ratio of Ni, Co and M in the added nickel source, cobalt source and M source is x:y:z. Figure 1 A schematic diagram of a device for preparing a ternary precursor provided by the present invention is shown in FIG. Figure 1 As shown, the first reaction device 100 is a device for preparing a first precursor with a median particle size of D50' by a continuous method, wherein the pH1 value is 10.5-11.5, the ammonia value is 3-5g / L, the temperature is 40-70°C, the rotation speed R1 is 100-500r / min, the liquid flow rate L1 is 100-1000L / h, and before the stable reaction, the reaction slurry overflows into the first aging kettle 200. After the first reaction device 100 has a stable reaction, a first precursor with a particle size of D50' and a particle size distribution of 1-1.5 is obtained. Because particles of large and small particle sizes coexist in the continuous method, the sphericity of the small particles is better in the process of continuous collision with large particles.

[0058] In step 2), after the first reaction device 100 has reacted stably, the first precursor prepared by the first reaction device 100 is classified by the cyclone 600 to obtain a target precursor with a median particle size of (0.15-0.5) D50', and the target precursor flows into the third aging kettle 400 as a seed for preparing a ternary precursor by the intermittent method in the second reaction device 800, and the particles that do not meet the median particle size of the target precursor flow into the second aging kettle 300, and the particles are discarded. Among them, after the third aging kettle 400, a cyclone and an aging kettle can be added to further classify the target precursor, and a target precursor with a more ideal particle size and particle size distribution can be obtained as a seed.

[0059] In step 3), the target precursor in the third aging kettle 400 is used as a seed of the ternary precursor, and is transported to the second reaction device 800 to form a reaction base liquid, and a ternary precursor with a median particle size of D50 is prepared by an intermittent method. The solid content of the reaction base liquid is 10-70g / L, the pH2 value is 10.5-11.5, the ammonia value is 3-5g / L, the temperature is 40-70°C, the rotation speed R2 is 100-500r / min, and the feed liquid flow rate L2 is 100-1000L / h. Among them, pH1>pH2, R1>R2, L2>L1.

[0060] After the ternary precursor slurry with a median particle size of D50 is prepared, the second reaction device is shut down, and the ternary precursor slurry is washed, filtered, dried, sieved, and iron removed to obtain a ternary precursor product. Among them, the washing, filtering, drying, sieving, and iron removal treatment operations can all refer to conventional operations in the field and will not be repeated here.

[0061] The preparation method of the present invention can prepare the ternary precursor of the first aspect mentioned above. In the stable state of the first reaction device 100, nucleation and growth reactions exist simultaneously. The surface energy of the newly nucleated small particles is large, while the surface energy of the large particles is low. Therefore, the newly nucleated small particles are not easy to agglomerate with the large particles, and the newly nucleated small particles are conducive to being molded into spherical particles under the collision of the large particles. Finally, the first precursor has a higher sphericity and a lower surface energy. The separated target precursor is used as a seed crystal and the reaction is continued in the second reaction device 800. The finally obtained ternary precursor also inherits the characteristics of high sphericity and is not easy to agglomerate.

[0062] In some embodiments of the present invention, the median particle size D50' of the first precursor is 5-15 μm.

[0063] In the present invention, controlling the median particle size D50' of the first precursor to be 5-15 μm is helpful for preparing a ternary precursor with a median particle size D50 of 7-15 μm, which can further improve the sphericity and agglomeration rate of the ternary precursor, thereby improving the compaction density, rate performance and cycle performance of the positive electrode active material, and further enabling the lithium-ion battery to have higher energy density, rate performance and cycle performance.

[0064] In a third aspect, the present invention provides a ternary positive electrode active material, comprising the above-mentioned ternary precursor or the ternary precursor prepared using the above-mentioned preparation method.

[0065] The ternary cathode active material provided by the present invention can be prepared by mixing the ternary precursor provided by the first aspect of the present invention or the ternary precursor prepared by the preparation method provided by the second aspect of the present invention with a lithium source and sintering to obtain the ternary cathode active material. The lithium source can be selected from lithium salts conventionally used in the art, such as lithium hydroxide, lithium carbonate, lithium oxide, etc.; the sintering process can refer to the conventional sintering process in the art, which will not be described here.

[0066] Since the ternary precursor provided by the present invention has the advantages of being not easy to agglomerate and having a high sphericity, the ternary positive electrode active material prepared using the ternary precursor has a high compaction density, rate performance and cycle performance.

[0067] In a fourth aspect, the present invention provides a positive electrode sheet comprising the above-mentioned ternary positive electrode active material.

[0068] The positive electrode sheet of the present invention can be prepared by conventional technical means in the art. Specifically, the above-mentioned positive electrode material, conductive agent, and binder can be uniformly dispersed in a solvent to obtain a positive electrode active layer slurry, and then the positive electrode active layer slurry is coated on at least one functional surface of the positive electrode collector. After drying, the positive electrode sheet of the present invention can be obtained.

[0069] The present invention does not particularly limit the specific types of the conductive agent and the adhesive. The conductive agent, the adhesive and other components can be selected from conventional materials in the field. For example, the conductive agent can be selected from one or more of conductive carbon black, carbon nanotubes, conductive graphite, and graphene, and the adhesive can be selected from one or more of polyvinylidene fluoride (PVDF), acrylic modified PVDF, polyacrylate polymers, polyimide, styrene-butadiene rubber, and styrene-propylene rubber.

[0070] The present invention does not specifically limit the coating method, and any coating method such as gravure coating, extrusion coating, spraying, screen printing, etc. can be used to coat the positive electrode active layer slurry.

[0071] Since the positive electrode sheet provided by the present invention includes the above-mentioned ternary positive electrode active material, the positive electrode sheet is used in a lithium ion battery, which can improve the energy density, rate performance and cycle performance of the lithium ion battery.

[0072] In a fifth aspect, the present invention provides a lithium-ion battery comprising the above-mentioned positive electrode sheet.

[0073] The lithium ion battery of the present invention includes a separator, a negative electrode and an electrolyte in addition to a positive electrode sheet. The composition of the negative electrode sheet can refer to conventional negative electrode sheets in the art, and the separator can also be a separator conventionally used in the art, such as a PP film, a PE film, etc.

[0074] The lithium-ion battery of the present invention can be prepared by conventional methods in the art. Specifically, the positive electrode sheet, the separator and the negative electrode sheet can be stacked in sequence, and then a battery cell can be obtained through a stacking or winding process, and then the above-mentioned lithium-ion battery can be obtained through baking, liquid injection, formation, packaging and other processes.

[0075] Since the lithium ion battery provided by the present invention includes the above-mentioned positive electrode sheet, the lithium ion battery has higher energy density, rate performance and cycle performance.

[0076] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0077] Example 1

[0078] The preparation method of the ternary precursor of this embodiment comprises the following steps:

[0079] 1) Nickel, cobalt and manganese are prepared into nickel-cobalt-manganese sulfate reaction slurry in a molar ratio of 85:10:5, and a first precursor is prepared by a continuous method in a first reaction device 100, wherein pH1 is 11.4-11.5, ammonia value is 3 g / L, temperature T1 is 50°C, rotation speed R1 is 350 r / min, and feed liquid flow rate L1 is 600 L / h; before the stable reaction, the reaction slurry overflows into the first aging kettle 200, and the slurry is regarded as unqualified material; during the stable reaction, pH1 is fine-tuned in the range of 11.4-11.5, and the median particle size D50' of the obtained first precursor is 10 μm;

[0080] 2) After the first reaction device 100 has stably reacted, the first precursor prepared by the first reaction device 100 is classified by the cyclone 600 to obtain a target precursor with a median particle size of 0.5D50'. The target precursor flows into the third aging kettle 400, and the particles that do not meet the median particle size of the target precursor flow into the second aging kettle 300, and these particles are discarded.

[0081] 3) The target precursor is used as a seed of the second reaction device 800 to prepare the ternary precursor by an intermittent method, and is transported to the second reaction device 800 to form a reaction base liquid, wherein the solid content S of the reaction base liquid is 50 g / L, pH2 is 10.7, the ammonia value is 4 g / L, the temperature T2 is 45°C, the rotation speed R2 is 200 r / min, and the feed liquid flow rate L2 is 1000 L / h; the reaction is stopped when the median particle size D50 reaches 10 μm to obtain a ternary precursor slurry;

[0082] 4) The obtained ternary precursor slurry is washed, filtered, dried, sieved, and iron removed to obtain a ternary precursor product, the chemical composition of which is Ni 0.85 Co 0.1 Mn 0.05 (OH)2.

[0083] Example 2

[0084] The preparation method of the ternary precursor in Example 2 is basically the same as that in Example 1, except that L2 in step 3) is changed to 800 L / h. Specific results are shown in Table 1.

[0085] Example 3

[0086] The preparation method of the ternary precursor in Example 3 is basically the same as that in Example 1, except that R1 in step 1) is changed to 450 r / min. Specific results are shown in Table 1.

[0087] Example 4

[0088] The preparation method of the ternary precursor in Example 4 is basically the same as that in Example 1, except that the reaction is stopped when the median particle size D50 in step 3) reaches 7 μm. Specific results are shown in Table 1.

[0089] Example 5

[0090] The preparation method of the ternary precursor in Example 5 is basically the same as that in Example 1, except that the reaction is stopped when the median particle size D50 in step 3) reaches 15 μm. Specific results are shown in Table 1.

[0091] Example 6

[0092] The preparation method of the ternary precursor in Example 6 is basically the same as that in Example 1, except that the rotation speed R1 in step 1) is changed to 500 r / min, the liquid flow rate L1 is changed to 1000 L / h, and the first precursor with D50' of 5 μm is obtained. Specific results are shown in Table 1.

[0093] Example 7

[0094] The preparation method of the ternary precursor in Example 7 is basically the same as that in Example 1, except that the pH 1 in step 1) is changed to 10.5-10.6, the rotation speed is 250 r / min, and the first precursor with a D50' of 15 μm is obtained. Specific results are shown in Table 1.

[0095] Example 8

[0096] The preparation method of the ternary precursor of Example 8 is basically the same as that of Example 1, except that the pH1 in step 1) is changed to 10.5-10.6, the flow rate in step 3) is 700 L / h, and the particle size distribution SPAN of the ternary precursor is obtained to be 0.2. The specific results are shown in Table 1.

[0097] Comparative Example 1

[0098] The preparation methods of the ternary precursors of Comparative Example 1 and Example 1 are basically the same, except that the first precursor is not prepared by a continuous method, and the reaction raw materials are directly introduced into the second reaction device 800 to prepare the ternary precursor by an intermittent method. Specific results are shown in Table 1.

[0099] Comparative Example 2

[0100] The preparation method of the ternary precursor of Comparative Example 2 is basically the same as that of Example 1, except that the first precursor prepared by the continuous method is not graded, and the first precursor is directly introduced into the second reaction device 800 to prepare the ternary precursor by the intermittent method. Specific results are shown in Table 1.

[0101] Comparative Example 3

[0102] Comparative Example 3 is basically the same as the preparation method of the ternary precursor of Example 1, except that the particles (the median particle size does not meet (0.15-0.5) D50') flowing into the second aging kettle 300 after classification treatment are introduced into the second reaction device 800, and the ternary precursor is prepared by an intermittent method, and the reaction is stopped when the median particle size D50 in step 3) reaches 15 μm. The specific results are shown in Table 1.

[0103] Test example:

[0104] 1. Sphericity: Use Metis software to scan the precursor particles in SEM to obtain the projected area S and perimeter L. The sphericity R is calculated as: R = 4πS / L 2 .

[0105] 2. Agglomeration rate: The ternary precursor was characterized by SEM, and the SEM image of the ternary precursor particles at 500 times was obtained. The proportion of the number of agglomerated secondary spherical particles to the total number of secondary spherical particles was counted through the SEM image.

[0106] 3. Angle of repose: Use a protractor to visually measure the angle of the ternary precursor powder pile. The smaller the angle of repose, the better the fluidity.

[0107] 4. Tap density: Put 100g of the ternary precursor into a measuring cylinder, fix the measuring cylinder on a vibration density meter, set the amplitude to 3mm, vibrate 300 times per minute, set the number of vibrations to 3000 times, read the volume reading in the measuring cylinder after the vibration stops, and get the tap density by dividing the mass by the volume.

[0108] 5. Compacted density: The ternary precursors in the above embodiments and comparative examples were mixed with lithium hydroxide monohydrate at a molar ratio of 1:1.04, and heated to 450°C in an oxygen atmosphere at 2°C / min, and kept warm for 4 hours, and then heated to 900°C at 2°C / min, and kept warm for 3 hours, and then cooled to 700°C at 2°C / min, and kept warm for 7 hours. After cooling with the furnace, the ternary positive active material was obtained. At 25°C and normal pressure (0.1MPa), the ternary positive active materials, conductive carbon black, and binder polyvinylidene fluoride (PVDF) of each embodiment and comparative example were respectively stirred and mixed in N-methylpyrrolidone solvent at a mass percentage ratio of 95:3:2 to obtain a positive electrode slurry, and the positive electrode slurry was coated on aluminum foil, and the surface density was controlled at 300mg / cm 2 , the pole piece is roller-pressed to test its compaction density.

[0109] 6. Energy density: According to the method in the charge capacity test, the positive electrode active material is coated into a positive electrode sheet, the negative electrode is made of graphite, and the separator is polypropylene, and the electrolyte (the electrolyte is LiPF6, and the solvent is EC / DMC / EMC) is used to form a full battery. Use a battery charge and discharge tester to charge the battery to 4.5V at 0.2C constant current at 25°C, and then charge it at a constant voltage until the current drops to 0.05C. After standing for 5 minutes, the battery is discharged to 2.5V at 0.2C constant current, and the first discharge capacity Q of the battery is recorded. 放 and the first discharge energy E 放 , weigh the battery mass as W, and calculate the mass energy density ED = E 放 / W.

[0110] 7. Rate performance: According to the method in the withholding capacity test, the positive electrode active material is coated into a positive electrode sheet, the negative electrode is graphite, and the diaphragm polyethylene and the electrolyte (the electrolyte is LiPF6 and the solvent is EC / DMC) form a full battery, which is charged at a constant current of 0.1C rate to a voltage of 4.5V, and then charged at a constant voltage at a voltage of 4.5V to a current equal to 0.05C, then allowed to stand for 5 minutes, and then discharged at a constant current of 0.1C rate to a voltage of 2.5V. The capacity at this time is recorded as the discharge capacity at 0.1C rate; stand for 10 minutes, charge at a constant current of 1C rate to a voltage of 4.5V, and then charge at a constant voltage of 4.5V to a current equal to 0.05C, then allowed to stand for 5 minutes, and then discharged at a constant current of 1C rate to a voltage of 2.5V. The capacity at this time is recorded as the discharge capacity at 1C rate, and the ratio of the discharge capacity at 1C rate to the discharge capacity at 0.1C rate is the 1C rate performance.

[0111] 8. Cycle performance: According to the method in the charge capacity test, the positive electrode active material is coated into a positive electrode sheet, the negative electrode is graphite, and the separator polyethylene and the electrolyte (the electrolyte is LiPF6, the solvent is EC / DMC) form a full battery. At 45°C, it is charged to 4.5V at a constant current of 1C, then charged to 4.5V at a constant voltage of 0.5C, and then discharged to 2.5V at a discharge rate of 1C. Repeat this charge and discharge cycle 300 times, and measure the discharge capacity Q1 at the first cycle and the discharge capacity Q at the 300th cycle. 300 The capacity retention rate after 300 cycles is Q = Q 300 / Q1*100%.

[0112] Figure 2 This is a SEM image of the first precursor prepared in Example 1 of the present invention.

[0113] from Figure 2 It can be seen that the first precursor prepared in Example 1 of the present invention includes particles of different sizes.

[0114] Figure 3 This is the SEM image of the ternary precursor prepared in Example 1 of the present invention.

[0115] from Figure 3 It can be seen that the ternary precursor prepared in Example 1 of the present invention has a lower agglomeration rate, a higher sphericity and better uniformity.

[0116] Figure 4 This is the SEM image of the ternary precursor prepared in Comparative Example 1 of the present invention.

[0117] from Figure 4 It can be seen that the particle size uniformity of the ternary precursor prepared in Comparative Example 1 of the present invention is poor.

[0118] Table 1

[0119]

[0120]

[0121] It can be seen from Table 1 that, compared with the comparative example, the ternary precursor provided by the present invention has the advantages of being not easy to agglomerate and having a higher sphericity, thereby improving the compaction density, rate performance and cycle performance of the positive electrode active material, and thus enabling the lithium-ion battery to have a higher energy density, rate performance and cycle performance.

[0122] From the comparison between Example 1 and Comparative Examples 1-3, it can be seen that the ternary precursor prepared by the present invention has the advantages of being not easy to agglomerate and having a higher sphericity, thereby improving the compaction density, rate performance and cycle performance of the positive electrode active material, and further enabling the lithium-ion battery to have a higher energy density, rate performance and cycle performance.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A ternary precursor, characterized in that: The chemical composition of the ternary precursor is Ni x Co y M z (OH)2, wherein M is Mn and / or Al, 0<x<1, 0<y<1, 0<z<1, x+y+z=1; The sphericity R of the ternary precursor is 0.95-0.99, and the agglomeration rate of the ternary precursor is less than 5%.

2. The ternary precursor according to claim 1, characterized in that: The ternary precursor comprises uniform particles with a particle size Dmid of 0.8D50<Dmid<1.2D50; The number of the uniform particles accounts for ≥90%.

3. The ternary precursor according to claim 1 or 2, characterized in that: The particle size distribution SPAN of the ternary precursor is 0.2-0.

65.

4. The ternary precursor according to any one of claims 1 to 3, characterized in that: The median particle size D50 of the ternary precursor is 7-15 μm.

5. The ternary precursor according to any one of claims 1 to 4, characterized in that: The tap density of the ternary precursor is > 2.0 g / cm 3 .

6. A method for preparing a ternary precursor as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: 1) preparing a first precursor having a median particle size of D50' by a continuous method using a raw material system including a nickel source, a cobalt source, and an M source; 2) classifying the first precursor to obtain a target precursor with a median particle size of (0.15-0.5) D50'; 3) Using the target precursor as a seed, a ternary precursor slurry with a median particle size of D50 is prepared by an intermittent method.

7. The preparation method according to claim 6, characterized in that: The median particle size D50' of the first precursor is 5-15 μm.

8. A ternary positive electrode active material, characterized in that: It comprises the ternary precursor described in any one of claims 1 to 5 or the ternary precursor prepared by the preparation method described in claim 6 or 7.

9. A positive electrode sheet, characterized in that: Comprising the ternary positive electrode active material as described in claim 8.

10. A lithium ion battery, characterized in that: Including the positive electrode sheet as described in claim 9.

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