Small-particle ternary precursor as well as preparation method and application thereof

Abstract

The preparation method comprises the following steps: in an inert atmosphere, taking a mixture of a mixed solution of a ternary solution, ammonia water and liquid caustic soda and a reaction base solution as a reaction system, carrying out a first-stage granulation reaction to obtain a first reaction nucleus with D50 being more than or equal to 0.6 mu m and less than or equal to 1.1 mu m, and adjusting parameters of the first-stage granulation reaction system to carry out a second-stage granulation reaction to obtain a second reaction nucleus with D50 being more than or equal to 0.6 mu m and less than or equal to 1.1 mu m; the reaction base solution contains water, ammonia water and liquid caustic soda, and the ternary solution contains nickel salt, cobalt salt and manganese salt; adjusting parameters of a second-stage granulation reaction system, carrying out a first-stage growth reaction to obtain a third reaction core with D50 larger than 2.8 microns and smaller than or equal to 3.2 microns, and introducing air to carry out a second-stage growth reaction to obtain a small-particle ternary precursor; the tap density of the material is improved in the early growth process, the specific surface area is improved by controlling the oxidation degree in the later growth period, and the tap density and the specific surface area of the ternary precursor are improved at the same time.

Description

Technical Field

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

[0002] Lithium-ion batteries are widely used in electric vehicles, power tools, 3C and other fields due to their advantages such as stable voltage, high capacity, high energy density, low self-discharge, stable cycle, low consumption and environmental friendliness. With the development of science and technology, the energy density and safety requirements of batteries are getting higher and higher. Ternary materials have high reversible specific capacity and can better meet the requirements of increasingly miniaturized and multifunctional electronic products.

[0003] The physical and chemical indicators of the ternary precursor, such as morphology, particle size, specific surface area, and tap density, largely determine the performance of the ternary positive electrode material. However, in the related technology, the energy density and charge and discharge performance of the ternary lithium-ion battery are insufficient. The reason is that it is difficult to improve the tap density and specific surface area of ​​the ternary precursor material at the same time.

[0004] Therefore, it is necessary to provide a solution to simultaneously improve the tap density (TD) and specific surface area (BET) of the ternary precursor material. Summary of the invention

[0005] In view of this, the present application provides a small-particle ternary precursor and a preparation method and application thereof, which are used to solve the problem of how to simultaneously improve the tap density and specific surface area of ​​the ternary precursor.

[0006] In order to achieve the above technical objectives, this application adopts the following technical solutions: In a first aspect, the present application provides a method for preparing a small particle ternary precursor, comprising the following steps: S1. Under an inert atmosphere, a mixture of a ternary liquid, ammonia water, a liquid alkali and a mixture of a reaction base liquid is used as a reaction system to perform a first granulation reaction to obtain a first reaction core of 0.6 μm ≤ D50 ≤ 1.1 μm, and the parameters of the first granulation reaction system are adjusted to perform a second granulation reaction to obtain a second reaction core of 1.1 μm < D50 ≤ 2.8 μm, wherein the reaction base liquid comprises water, ammonia water and liquid alkali, and the ternary liquid comprises nickel salt, cobalt salt and manganese salt; S2. Adjust the parameters of the two-stage granulation reaction system and perform a growth reaction to obtain a third reaction nucleus of 2.8μm<D50≤3.2μm, and then introduce air to perform a two-stage growth reaction to the target particle size, thereby obtaining a small particle ternary precursor.

[0007] Preferably, in step S1, during the first stage of granulation reaction, the ammonium ion concentration of the reaction base liquid is 1.5-2.0 g / L, the pH of the reaction base liquid is 12.05-12.2, and the temperature of the reaction base liquid is 65-70°C.

[0008] Preferably, in step S1, during the first granulation reaction, the molar ratio of nickel salt, cobalt salt and manganese salt in the ternary liquid is (0.602-0.604): (0.0985-0.1025): (0.2935-0.2995) in terms of metal ions, and the total metal ion concentration of the ternary liquid is 1.5-2.0 mol / L.

[0009] Preferably, in step S1, during the first stage of granulation reaction, in the mixed liquid, the flow rate of the ternary liquid is 95-100 L / h, the flow rate of the ammonia water is 1-7 L / h, the flow rate of the liquid alkali is 36-38 L / h, and the stirring rate is 370-400 rpm.

[0010] Preferably, the step of adjusting the parameters of the first-stage granulation reaction system and then performing the second-stage granulation reaction comprises adjusting the ammonium ion concentration to 2.5-3.5 g / L, the pH to 11.7-11.95, and the stirring rate to 370-400 rpm.

[0011] Preferably, the step of adjusting the parameters of the two-stage granulation reaction system and then performing a one-stage growth reaction includes adjusting the flow rate of the ternary liquid to 300-350 L / h, the reaction pH to 11.4-11.6, the ammonium concentration to 3.5-4.5 g / L, and the stirring rate to 300-350 rpm.

[0012] Preferably, in the second-stage growth reaction, the total pressure of the inert gas and air is 1-1.5 MPa, and the air partial pressure is 0.5-0.8 MPa.

[0013] Preferably, in step S2, the target particle size is 3.15 μm ≤ D50 ≤ 3.2 μm.

[0014] In a second aspect, the present application provides a small particle ternary precursor obtained by a preparation method.

[0015] In a third aspect, the present application provides a battery positive electrode material, which is formed by sintering a small particle ternary precursor and a lithium salt.

[0016] The beneficial effects of the present application are as follows: the ternary precursor of the present application has the advantages of large specific surface area and high tap density; the present application improves the tap density of the material by using low concentration of ammonia and high pH in the early growth process, and increases the specific surface area by controlling air oxidation in the later growth stage, thereby facilitating the preparation of a medium-nickel small particle ternary precursor with slender primary particles, small size and high overall consistency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is an electron microscope image of the small particle ternary precursor obtained in Example 1. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] The present application provides a method for preparing a small particle ternary precursor, comprising the following steps: S1. Under an inert atmosphere, a mixture of a ternary liquid, aqueous ammonia, and liquid alkali and a reaction base liquid are pumped into the reactor to perform a first-stage granulation reaction to obtain a first reaction core, and the reaction system is adjusted to continue a second-stage granulation reaction to obtain a second reaction core. The reaction base liquid comprises water, aqueous ammonia, and liquid alkali, and the ternary liquid comprises nickel salt, cobalt salt, and manganese salt. The particle size of the first reaction core is 0.6 μm ≤ D50 ≤ 1.1 μm, and the particle size of the second reaction core is 1.1 μm < D50 ≤ 2.8 μm; S2. Adjust the reaction system and continue to pump the mixture of ternary liquid, ammonia water, liquid alkali and reaction bottom liquid into the reactor for a first growth reaction to obtain the third reaction nucleus, and then introduce air for a second growth reaction. After reaching the target particle size range, stop the reaction to obtain a small particle ternary precursor. The particle size of the third reaction nucleus is 2.8μm<D50≤3.2μm.

[0020] In some embodiments, in step S1, the ammonium concentration of the reaction base solution is 1.5-2.0 g / L, the pH is 12.05-12.2, and the temperature is 65-70°C.

[0021] In some embodiments, in step S1, the molar ratio of nickel salt, cobalt salt and manganese salt in the ternary liquid is (0.602-0.604): (0.0985-0.1025): (0.2935-0.2995) in terms of metal ions, and the total metal ion concentration of the ternary liquid is 1.5-2.0 mol / L. The mass concentrations of ammonia water and liquid caustic soda are 14-18% and 32% respectively.

[0022] In some embodiments, the nickel salt is nickel sulfate, the cobalt salt is cobalt sulfate, and the manganese salt is manganese sulfate. S1 includes steps S11. ternary liquid preparation, S12. base liquid preparation, and S13. granulation stage.

[0023] Specifically, before the first granulation reaction, water, ammonia water and liquid alkali are added into the reactor to form a reaction bottom liquid and an inert gas is introduced, and then the temperature is raised to 65-70°C, and then a mixed liquid of the ternary liquid, ammonia water and liquid alkali is pumped into the reactor to enter the first granulation stage, and the pH and stirring rate are controlled to stabilize the reaction particle size.

[0024] In some embodiments, in the mixed liquid of the first-stage granulation reaction of step S1, the flow rate of the ternary liquid is 95-100 L / h, the flow rate of the ammonia water is 1-7 L / h, the flow rate of the liquid alkali is 36-38 L / h, and the stirring rate is 370-400 rpm, until the particle size of the obtained particles is 0.6 μm ≤ D50 ≤ 1.1 μm, the first-stage granulation is stopped, and the reaction conditions are adjusted to perform the second-stage granulation.

[0025] In some embodiments, in the second-stage granulation reaction of step S1, the ammonium concentration is 2.5-3.5 g / L, the pH is 11.7-11.95, the stirring rate is 370-400 rpm, and after the reactor is full, it enters the thickener for cyclic concentration until the particle size of the obtained particles is 1.1 μm<D50≤2.8 μm, the second-stage granulation stage is stopped, and the reaction conditions are adjusted to enter the first growth stage.

[0026] In some embodiments, in the first growth reaction of step S2, the flow rate of the ternary liquid is 300-350 L / h, the reaction pH is 11.4-11.6, the ammonium concentration is 3.5-4.5 g / L, the stirring rate is 300-350 rpm, and after the reactor is full, it enters the thickener for cyclic concentration until the particle size of the obtained particles is 2.8 μm<D50≤3.2 μm, and then enters the second growth reaction stage.

[0027] In some embodiments, in the second-stage growth reaction of step S2, the total pressure of the inert gas and air is 1-1.5 MPa, the air partial pressure is 0.5-0.8 MPa, and the reaction is continued until the obtained particles reach the target particle size.

[0028] In some embodiments, in step S2, the target particle size is 3.15 μm ≤ D50 ≤ 3.2 μm.

[0029] The small-particle ternary precursor obtained by the preparation method of the present application has a large specific surface area, a high tap density, and the primary particles are slender and small in size, the secondary particles are loose and porous, and the overall consistency is high. When preparing positive electrode materials, it can effectively improve the electrochemical performance of positive electrode materials.

[0030] The present application provides a battery positive electrode material, which is formed by sintering a small particle ternary precursor and a lithium salt.

[0031] The present solution is further described below through specific embodiments.

[0032] Example 1 A method for preparing a small particle ternary precursor comprises the following steps: S11. Ternary liquid preparation: nickel sulfate, cobalt sulfate and manganese sulfate are prepared into a ternary liquid with a total metal concentration of 1.5 mol / L according to 60.4 mol% nickel, 10.05 mol% cobalt and 29.55 mol% manganese; S12. Base liquid preparation: After nitrogen was introduced into the reactor for 30 minutes, pure water was added, followed by ammonia water and liquid alkali, and the mixture was heated to 65°C to obtain a reaction base liquid. The ammonium concentration of the reaction base liquid was measured to be 1.64 g / L, pH = 12.08, and the temperature was 65°C; S13. Granulation stage: A mixture of ternary liquid, ammonia water and liquid alkali was pumped into the reactor containing the reaction base liquid at flow rates of 100 L / h, 6 L / h and 38 L / h, respectively. The ammonium concentration in the reaction system was 1.66 g / L, the pH was 11.92, the stirring rate was 370 rpm, and the particle size was measured after 2 h of reaction to be D50 = 0.836 μm (first reaction core). Within 2 h, the flow rates of ammonia water and liquid alkali were gradually adjusted to make the ammonium concentration in the reaction system 2.59 g / L, the pH was 11.84, the stirring rate was 370 rpm, and the reaction was continued until the particle size D50 = 1.1 μm (second reaction core), completing the granulation stage; S2. After the granulation stage, the flow rates of ternary liquid, ammonia water and liquid alkali were adjusted to 300 L / h, 13 L / h and 100 L / h respectively. The ammonium concentration in the reaction system was 3.68 g / L, the pH was 11.53, the stirring rate was 300 rpm, and the particle size was measured to be D50 = 2.77 μm (third reaction core) after 45 h of reaction. Air was introduced into the reactor, and the total pressure of inert gas and air was controlled at 1.5 MPa, and the air partial pressure was controlled at 0.5 MPa until the particle size reached 3.15 μm = D50, and the reaction was stopped to obtain a small particle ternary precursor, as shown in the electron microscope image. Figure 1 shown.

[0033] Example 2 A method for preparing a small particle ternary precursor comprises the following steps: S11. Ternary liquid preparation: nickel sulfate, cobalt sulfate and manganese sulfate are prepared into a ternary liquid with a total metal concentration of 1.5 mol / L according to 60.4 mol% nickel, 10.05 mol% cobalt and 29.55 mol% manganese; S12. Base liquid preparation: After nitrogen was introduced into the reactor for 30 minutes, pure water was added, followed by ammonia water and liquid alkali, and the mixture was heated to 65°C to obtain a reaction base liquid. The ammonium concentration of the reaction base liquid was measured to be 1.79 g / L, pH = 12.12, and the temperature was 65°C; S13. Granulation stage: A mixture of ternary liquid, ammonia water and liquid alkali was pumped into the reactor containing the reaction base liquid at flow rates of 100 L / h, 5 L / h and 37 L / h, respectively. The ammonium concentration in the reaction system was 1.86 g / L, the pH was 11.73, the stirring rate was 370 rpm, and the particle size was measured after 2 h of reaction to be D50 = 0.918 μm (first reaction core). Within 2 h, the flow rates of ammonia water and liquid alkali were gradually adjusted to make the ammonium concentration in the reaction system 3.1 g / L, the pH was 11.91, the stirring rate was 370 rpm, and the reaction was continued until the particle size D50 = 1.1 μm (second reaction core), completing the granulation stage; S2. After the granulation stage, the flow rates of the ternary liquid, ammonia water and liquid alkali were adjusted to 300 L / h, 13 L / h and 100 L / h respectively. The ammonium concentration in the reaction system was 3.52 g / L, the pH was 11.42, the stirring rate was 300 rpm, and the particle size was measured to be D50 = 2.82 μm (the third reaction core) after 40 hours of reaction. Air was introduced into the reactor, and the total pressure of the inert gas and air was controlled at 1.5 MPa, and the air partial pressure was controlled at 0.6 MPa. The reaction was stopped until the particle size reached 3.2 μm = D50 to obtain a small particle ternary precursor.

[0034] Example 3 A method for preparing a small particle ternary precursor comprises the following steps: S11. Ternary liquid preparation: nickel sulfate, cobalt sulfate and manganese sulfate are prepared into a ternary liquid with a total metal concentration of 1.5 mol / L according to 60.4 mol% nickel, 10.05 mol% cobalt and 29.55 mol% manganese; S12. Base liquid preparation: After nitrogen was introduced into the reactor for 30 minutes, pure water was added, followed by ammonia water and liquid alkali, and the mixture was heated to 65°C to obtain a reaction base liquid. The ammonium concentration of the reaction base liquid was measured to be 1.69 g / L, pH = 12.04, and the temperature was 65°C; S13. Granulation stage: A mixture of ternary liquid, ammonia water and liquid alkali was pumped into the reactor containing the reaction base liquid at flow rates of 100 L / h, 4 L / h and 38 L / h, respectively. The ammonium concentration in the reaction system was 1.57 g / L, the pH was 12.06, the stirring rate was 370 rpm, and the particle size was measured after 2 h of reaction to be D50 = 0.756 μm (first reaction core). Within 2 h, the flow rates of ammonia water and liquid alkali were gradually adjusted to make the ammonium concentration in the reaction system 2.7 g / L, the pH was 11.84, the stirring rate was 370 rpm, and the reaction was continued until the particle size D50 = 1.1 μm (second reaction core), completing the granulation stage; S2. After the granulation stage, the flow rates of the ternary liquid, ammonia water and liquid alkali were adjusted to 300 L / h, 13 L / h and 100 L / h respectively. The ammonium concentration in the reaction system was 4.2 g / L, the pH was 11.55, the stirring rate was 300 rpm, and the particle size was measured after 50 hours of reaction to be D50 = 2.751 μm (the third reaction core). Air was introduced into the reactor, and the total pressure of the inert gas and air was controlled at 1.5 MPa, and the air partial pressure was controlled at 0.6 MPa. The reaction was stopped until the particle size reached 3.15 μm = D50 to obtain a small particle ternary precursor.

[0035] Example 4 A method for preparing a small particle ternary precursor comprises the following steps: S11. Ternary liquid preparation: nickel sulfate, cobalt sulfate and manganese sulfate are prepared into a ternary liquid with a total metal concentration of 2 mol / L according to 60.4 mol% nickel, 10.05 mol% cobalt and 29.55 mol% manganese; S12. Base liquid preparation: After nitrogen was introduced into the reactor for 30 minutes, pure water was added, followed by ammonia water and liquid alkali, and the mixture was heated to 70°C to obtain a reaction base liquid. The ammonium concentration of the reaction base liquid was measured to be 1.84 g / L, pH = 12.06, and the temperature was 70°C; S13. Granulation stage: A mixture of ternary liquid, ammonia water and liquid alkali was pumped into the reactor containing the reaction base liquid at flow rates of 100 L / h, 6 L / h and 38 L / h, respectively. The ammonium concentration in the reaction system was 1.92 g / L, the pH was 12.1, the stirring rate was 370 rpm, and the particle size was measured after 2 h of reaction to be D50 = 0.748 μm (first reaction core). Within 2 h, the flow rates of ammonia water and liquid alkali were gradually adjusted to make the ammonium concentration in the reaction system 2.72 g / L, the pH was 11.91, the stirring rate was 370 rpm, and the reaction was continued until the particle size D50 = 1.1 μm (second reaction core), completing the granulation stage; S2. After the granulation stage, the flow rates of the ternary liquid, ammonia water and liquid alkali were adjusted to 300 L / h, 13 L / h and 100 L / h respectively. The ammonium concentration in the reaction system was 3.84 g / L, the pH was 11.62, the stirring rate was 300 rpm, and the particle size was measured to be D50 = 2.871 μm (the third reaction core) after 55 h of reaction. Air was introduced into the reactor, and the total pressure of the inert gas and air was controlled at 1.5 MPa, and the air partial pressure was controlled at 0.5 MPa. The reaction was stopped until the particle size reached 3.15 μm = D50 to obtain a small particle ternary precursor.

[0036] Example 5 A method for preparing a small particle ternary precursor comprises the following steps: S11. Ternary liquid preparation: nickel sulfate, cobalt sulfate and manganese sulfate are prepared into a ternary liquid with a total metal concentration of 2 mol / L according to 60.4 mol% nickel, 10.05 mol% cobalt and 29.55 mol% manganese; S12. Base liquid preparation: After nitrogen was introduced into the reactor for 30 minutes, pure water was added, followed by ammonia water and liquid alkali, and the mixture was heated to 70°C to obtain a reaction base liquid. The ammonium concentration of the reaction base liquid was measured to be 1.95 g / L, pH = 12.12, and the temperature was 70°C; S13. Granulation stage: A mixture of ternary liquid, ammonia water and liquid alkali was pumped into the reactor containing the reaction base liquid at flow rates of 100 L / h, 6 L / h and 37 L / h, respectively. The ammonium concentration in the reaction system was 1.92 g / L, the pH was 12.06, the stirring rate was 370 rpm, and the particle size was measured after 2 h of reaction to be D50 = 1.089 μm (first reaction core). Within 2 h, the flow rates of ammonia water and liquid alkali were gradually adjusted to make the ammonium concentration in the reaction system 3.2 g / L, the pH was 11.75, the stirring rate was 370 rpm, and the reaction was continued until the particle size D50 = 1.1 μm (second reaction core), completing the granulation stage; S2. After the granulation stage, the flow rates of the ternary liquid, ammonia water and liquid alkali were adjusted to 300 L / h, 13 L / h and 100 L / h respectively. The ammonium concentration in the reaction system was 3.8 g / L, the pH was 11.46, the stirring rate was 300 rpm, and the particle size was measured to be D50 = 2.862 μm (the third reaction core) after 40 h of reaction. Air was introduced into the reactor, and the total pressure of the inert gas and air was controlled at 1.5 MPa, and the air partial pressure was controlled at 0.7 MPa. The reaction was stopped until the particle size reached 3.15 μm = D50 to obtain a small particle ternary precursor.

[0037] Example 6 A method for preparing a small particle ternary precursor comprises the following steps: S11. Ternary liquid preparation: nickel sulfate, cobalt sulfate and manganese sulfate are prepared into a ternary liquid with a total metal concentration of 2 mol / L according to 60.4 mol% nickel, 10.05 mol% cobalt and 29.55 mol% manganese; S12. Base liquid preparation: After nitrogen was introduced into the reactor for 30 minutes, pure water was added, followed by ammonia water and liquid alkali, and the mixture was heated to 70°C to obtain a reaction base liquid. The ammonium concentration of the reaction base liquid was measured to be 1.84 g / L, pH = 12.17, and the temperature was 70°C; S13. Granulation stage: A mixture of ternary liquid, ammonia water and liquid alkali was pumped into the reactor containing the reaction base liquid at flow rates of 100 L / h, 6 L / h and 38 L / h, respectively. The ammonium concentration in the reaction system was 1.93 g / L, the pH was 12.13, the stirring rate was 370 rpm, and the particle size was measured after 2 hours of reaction as D50 = 0.814 μm (first reaction core). Within 2 hours, the flow rates of ammonia water and liquid alkali were gradually adjusted to make the ammonium concentration in the reaction system 3.15 g / L, the pH was 11.75, the stirring rate was 370 rpm, and the reaction was continued until the particle size D50 = 1.1 μm (second reaction core), completing the granulation stage; S2. After the granulation stage, the flow rates of the ternary liquid, ammonia water and liquid alkali were adjusted to 300 L / h, 13 L / h and 100 L / h respectively. The ammonium concentration in the reaction system was 3.5 g / L, the pH was 11.44, the stirring rate was 300 rpm, and the particle size was measured to be D50 = 2.81 μm (the third reaction core) after 45 hours of reaction. Air was introduced into the reactor, and the total pressure of the inert gas and air was controlled at 1.5 MPa, and the air partial pressure was controlled at 0.6 MPa. The reaction was stopped until the particle size reached 3.15 μm = D50 to obtain a small particle ternary precursor.

[0038] Comparative Example 1 A method for preparing a ternary precursor comprises the following steps: S11. Ternary liquid preparation: nickel sulfate, cobalt sulfate and manganese sulfate are prepared into a ternary liquid with a total metal concentration of 1.5 mol / L according to 60.4 mol% nickel, 10.05 mol% cobalt and 29.55 mol% manganese; S12. Base liquid preparation: After nitrogen was introduced into the reactor for 30 minutes, pure water was added, followed by ammonia water and liquid alkali, and the mixture was heated to 70°C to obtain a reaction base liquid. The ammonium concentration of the reaction base liquid was measured to be 1.59 g / L, pH = 12.06, and the temperature was 70°C; S13. Granulation stage: A mixture of ternary liquid, ammonia water and liquid alkali was pumped into the reactor containing the reaction base liquid at flow rates of 100 L / h, 6 L / h and 38 L / h, respectively. The ammonium concentration in the reaction system was 1.63 g / L, the pH was 12.12, the stirring rate was 370 rpm, and the particle size was measured after 2 h of reaction to be D50 = 0.741 μm (first reaction core). Within 2 h, the flow rates of ammonia water and liquid alkali were gradually adjusted to make the ammonium concentration in the reaction system 3.15 g / L, the pH was 11.75, the stirring rate was 370 rpm, and the reaction was continued until the particle size D50 = 1.1 μm (second reaction core), completing the granulation stage; S2. After the granulation stage, the flow rates of the ternary liquid, ammonia water and liquid alkali were adjusted to 300 L / h, 13 L / h and 100 L / h respectively. The ammonium concentration in the reaction system was 3.5 g / L, the pH was 11.44, the stirring rate was 300 rpm, and no air was passed. After 65 hours of reaction, the particle size was measured to be D50 = 3.21 μm, and the ternary precursor was obtained.

[0039] Comparative Example 2 A method for preparing a ternary precursor comprises the following steps: S11. Ternary liquid preparation: nickel sulfate, cobalt sulfate and manganese sulfate are prepared into a ternary liquid with a total metal concentration of 2.0 mol / L according to 60.4 mol% nickel, 10.05 mol% cobalt and 29.55 mol% manganese; S12. Base liquid preparation: After nitrogen was introduced into the reactor for 30 minutes, pure water was added, followed by ammonia water and liquid alkali, and the mixture was heated to 65°C to obtain a reaction base liquid. The ammonium concentration of the reaction base liquid was measured to be 1.69 g / L, pH = 12.08, and the temperature was 65°C; S13. Granulation stage: A mixture of ternary liquid, ammonia water and liquid alkali was pumped into the reactor containing the reaction base liquid at flow rates of 100 L / h, 4 L / h and 38 L / h, respectively. The ammonium concentration in the reaction system was 1.67 g / L, the pH was 12.06, the stirring rate was 370 rpm, and the particle size was measured after 2 h of reaction to be D50 = 0.772 μm (first reaction core). Within 2 h, the flow rates of ammonia water and liquid alkali were gradually adjusted to make the ammonium concentration in the reaction system 2.81 g / L, the pH was 11.84, the stirring rate was 370 rpm, and the reaction was continued until the particle size D50 = 1.1 μm (second reaction core), completing the granulation stage; S2. After the granulation stage, the flow rates of the ternary liquid, ammonia water and liquid alkali were adjusted to 300 L / h, 13 L / h and 100 L / h respectively. The ammonium concentration in the reaction system was 4.2 g / L, the pH was 11.55, the stirring rate was 300 rpm, and no air was passed. After 70 hours of reaction, the particle size was measured to be D50 = 3.151 μm, and the ternary precursor was obtained.

[0040] Test and Evaluation The tap density (TD) and specific surface area (BET) of the ternary precursors obtained in each embodiment and comparative example were tested, and the results are shown in Table 1.

[0041] Table 1 Test results

[0042] The above data show that the present application improves the compaction of the material by using low concentration of ammonia and high pH in the early growth process, and increases the specific surface area by controlling air oxidation in the later growth stage, thereby facilitating the preparation of a medium-nickel small particle ternary precursor with slender primary particles, small size, and high overall consistency. The ternary precursor of the present application has the advantages of large specific surface area and high tap density.

[0043] The above are only preferred specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a small particle ternary precursor, characterized in that: Includes steps: S1. Under an inert atmosphere, a mixture of a ternary liquid, ammonia water, a liquid alkali and a mixture of a reaction base liquid is used as a reaction system to perform a first granulation reaction to obtain a first reaction core of 0.6 μm ≤ D50 ≤ 1.1 μm, and the parameters of the first granulation reaction system are adjusted to perform a second granulation reaction to obtain a second reaction core of 1.1 μm < D50 ≤ 2.8 μm, wherein the reaction base liquid comprises water, ammonia water and liquid alkali, and the ternary liquid comprises nickel salt, cobalt salt and manganese salt; S2. Adjust the parameters of the two-stage granulation reaction system and perform a growth reaction to obtain a third reaction nucleus of 2.8μm<D50≤3.2μm, and then introduce air to perform a two-stage growth reaction to the target particle size, thereby obtaining a small particle ternary precursor.

2. The method for preparing a small particle ternary precursor according to claim 1, characterized in that: In step S1, during the first granulation reaction, the ammonium ion concentration of the reaction base liquid is 1.5-2.0 g / L, the pH of the reaction base liquid is 12.05-12.2, and the temperature of the reaction base liquid is 65-70°C.

3. The method for preparing a small particle ternary precursor according to claim 1, characterized in that: In step S1, during the first granulation reaction, the molar ratio of nickel salt, cobalt salt and manganese salt in the ternary liquid is (0.602-0.604): (0.0985-0.1025): (0.2935-0.2995) in terms of metal ions, and the total metal ion concentration of the ternary liquid is 1.5-2.0 mol / L.

4. The method for preparing a small particle ternary precursor according to claim 1, characterized in that: In step S1, during the first stage of granulation reaction, in the mixed liquid, the flow rate of the ternary liquid is 95-100 L / h, the flow rate of the ammonia water is 1-7 L / h, the flow rate of the liquid alkali is 36-38 L / h, and the stirring rate is 370-400 rpm.

5. The method for preparing a small particle ternary precursor according to claim 1, characterized in that: The step of adjusting the parameters of the first-stage granulation reaction system and then performing the second-stage granulation reaction includes adjusting the ammonium ion concentration to 2.5-3.5 g / L, the pH to 11.7-11.95, and the stirring rate to 370-400 rpm.

6. The method for preparing a small particle ternary precursor according to claim 1, characterized in that: The steps of adjusting the parameters of the second-stage granulation reaction system and then performing a first-stage growth reaction include adjusting the flow rate of the ternary liquid to 300-350 L / h, adjusting the reaction pH to 11.4-11.6, adjusting the ammonium concentration to 3.5-4.5 g / L, and adjusting the stirring rate to 300-350 rpm.

7. The method for preparing a small particle ternary precursor according to claim 1, characterized in that: In the second-stage growth reaction, the total pressure of the inert gas and air is 1-1.5 MPa, and the air partial pressure is 0.5-0.8 MPa.

8. The method for preparing a small particle ternary precursor according to claim 1, characterized in that: In step S2, the target particle size is 3.15 μm ≤ D50 ≤ 3.2 μm.

9. A small particle ternary precursor obtained by the preparation method according to any one of claims 1 to 8.

10. A positive electrode material for a battery, characterized in that: It is formed by sintering the small particle ternary precursor described in claim 9 and lithium salt.

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