Ternary precursor, preparation method thereof and ternary positive electrode material

Abstract

The invention relates to the technical field of battery materials, in particular to a ternary precursor, a preparation method thereof and a ternary positive electrode material. The preparation method of the ternary precursor comprises the following steps: preparing a mixed metal salt solution containing a nickel source, a cobalt source and a manganese source; the mixed metal salt solution, alkali liquor and a complexing agent are added into the base solution for a coprecipitation reaction, and the coprecipitation reaction comprises the steps that a nucleation reaction is conducted when the pH value of a reaction system ranges from 12 to 13, and then the pH value is gradually reduced to 11 or above along with the growth reaction till product particles reach the target particle size, in the process of gradually reducing the pH value to 11 or above, at least two times of pH value constant time exist, and the pH value constant time of one time is 40 hours or above; and carrying out solid-liquid separation on the product after the coprecipitation reaction is finished to obtain the ternary precursor. According to the preparation method, the ternary precursor material which is narrow in span distribution, small in particle and stable can be obtained.

Description

Technical Field

[0001] The present application belongs to the technical field of battery materials, and in particular relates to a ternary precursor and a preparation method thereof, and a ternary positive electrode material. Background Art

[0002] Lithium-ion batteries (LIBs) have the advantages of high energy density, long cycle life and low self-discharge. They are an ideal chemical power source and are widely used in digital electronic products, power tools, electric vehicles, energy storage devices and other fields.

[0003] As the requirements for lithium-ion battery capacity continue to increase, more and more companies and R&D teams are taking high-nickel ternary cathode materials as one of the mainstream directions for the development of the lithium-ion battery market. The ternary precursor, nickel-cobalt-manganese hydroxide, is an important upstream material for ternary cathode materials. For example, single-crystal ternary cathode materials with excellent stability are mainly prepared using small-particle ternary precursor materials.

[0004] Ternary precursors are secondary particles that are agglomerated from primary particles into spherical particles. There are many methods for preparing them, and the most commonly used method is the efficient and low-cost chemical coprecipitation method. However, during the preparation of ternary precursors, agglomerate crystal nuclei are easily formed in the early stage of the reaction, which can easily lead to small particle products with poor sphericity and too wide particle size distribution. Currently, there are ways to optimize them by improving equipment, using multi-stage screening, and optimizing process flow. However, the resulting ternary precursors either have a wide particle size distribution or are unstable with a large number of abnormally small particles. Summary of the invention

[0005] The purpose of this application is to provide a ternary precursor and a preparation method thereof, and a ternary positive electrode material, aiming to solve the technical problem of how to obtain a ternary precursor material with a narrow particle size distribution, small particles and stability.

[0006] In order to achieve the above application purpose, the technical solution adopted in this application is as follows:

[0007] In a first aspect, the present invention provides a method for preparing a ternary precursor, comprising the following steps:

[0008] preparing a mixed metal salt solution containing a nickel source, a cobalt source and a manganese source;

[0009] A mixed metal salt solution, an alkali solution and a complexing agent are added to a base solution for a coprecipitation reaction, wherein the coprecipitation reaction comprises: a nucleation reaction is performed in a pH range of 12 to 13 in the reaction system, and then the pH value is gradually reduced to above 11 as the growth reaction proceeds until the product particles reach a target particle size, and there are at least two pH constant times during the process of the pH value gradually decreasing to above 11, one of which is a pH constant time of more than 40 hours;

[0010] The product after the coprecipitation reaction is completed is subjected to solid-liquid separation to obtain a ternary precursor.

[0011] In one embodiment, the process of gradually reducing the pH value to above 11 includes:

[0012] When the pH value drops to 11.8, keep the pH constant for 60 to 70 hours; when the pH value drops to 11.7, keep the pH constant for 9 to 20 hours; or

[0013] When the pH value drops to 11.8, the pH value is kept constant for 40 to 50 hours. When the pH value drops to 11.7, the pH value is kept constant for 4 to 10 hours. When the pH value drops to 11.6, the pH value is kept constant for 4 to 10 hours.

[0014] In one embodiment, while the pH value of the reaction system in the coprecipitation reaction is gradually reduced to above 11, the stirring speed of the reaction system is gradually reduced from high to low within the range of 800 to 1500 rpm until the product particles reach the target particle size.

[0015] In one embodiment, the target particle size D50 is 2 to 3 μm, and the obtained diameter distribution of the ternary precursor is (D90-D10) / D50≤0.65;

[0016] And / or, the pH value is gradually reduced to above 11 with each reduction of 0.05 to 0.1 pH value.

[0017] In one embodiment, the pH value of the reaction system is controlled by adjusting the flow rate of added liquid alkali during the coprecipitation reaction; and / or,

[0018] In the coprecipitation reaction, the concentration of the complexing agent in the reaction system is controlled by adjusting the complexing agent addition flow rate.

[0019] In one embodiment, one or more of the following (1) to (3) are satisfied:

[0020] (1) The temperature of the nucleation reaction is 55-65°C, and the temperature of the growth reaction is 55-65°C;

[0021] (2) The nucleation reaction time is 2 to 4 hours, and the total growth reaction time is 90 to 120 hours;

[0022] (3) The concentration of the complexing agent in the nucleation reaction is 4.0-5.0 g / l, and the concentration of the complexing agent in the growth reaction is 3.0-3.5 g / l.

[0023] In a second aspect, the present invention provides a ternary precursor, the chemical formula of which is Ni x Co y Mn z(OH)2, wherein 0.75≤x≤0.95, 0.03≤y≤0.20, 0.03≤z≤0.20, x+y+z=1;

[0024] The particle size D50 of the ternary precursor is 2 to 3 μm, and the diameter distribution (D90-D10) / D50≤0.65.

[0025] In one embodiment, the ternary precursor satisfies one or more of the following (1) to (4):

[0026] (1) Tap density is 1.8 to 2.0 g / cm 3 ;

[0027] (2) Specific surface area is 3 to 5 m 2 / g;

[0028] (3) The ratio of specific surface area to tap density is 1.5×10 4 ~2.8×10 4 cm 5 / g 2 ;

[0029] (4) The peak ratio of the 101 crystal plane to the 001 crystal plane in the XRD spectrum is 0.7-1.0, the half-peak width corresponding to the 001 crystal plane is 0.48-0.52, the half-peak width corresponding to the 100 crystal plane is 0.27-0.30, and the half-peak width corresponding to the 101 crystal plane is 0.52-0.56.

[0030] In one embodiment, the ternary precursor is prepared by the above-mentioned preparation method of the embodiment of the present application.

[0031] In the third aspect, an embodiment of the present application provides a ternary positive electrode material, which is obtained by sintering a mixture of a lithium salt and a precursor material, and the precursor material includes the ternary precursor prepared by the preparation method provided in the first aspect of the embodiment of the present application and / or the ternary precursor provided in the second aspect of the embodiment of the present application.

[0032] The preparation method of the ternary precursor provided in the first aspect of the embodiment of the present application is a method for preparing a ternary precursor material with a narrow particle size distribution, small particles and stability by chemical co-precipitation method. The preparation method includes two processes: nucleation reaction and growth reaction. The nucleation reaction is carried out in the pH value range of 12 to 13, and the pH value of the growth reaction will gradually decrease, and the target particle size is obtained when the pH value is above 11. There are at least two constant pH times during the gradual decrease of the pH value of the growth reaction, and one of the constant pH times is above 40 hours. In such a high pH nucleation reaction and growth reaction process, the solution supersaturation of the reaction system is large, the formation rate of crystal nuclei is fast, and the growth rate of the precursor particles is slow. Therefore, the generation of crystal nuclei can be controlled, and the sphericity of the ternary precursor particles is optimized through a long-term high pH growth reaction stage, and finally a ternary precursor material with a narrow diameter distribution, small particles and stability is obtained.

[0033] The ternary precursor provided in the second aspect of the embodiment of the present application is characterized by its parameters to be a ternary precursor material with narrow diameter distribution, small particles and stability. Therefore, such a ternary precursor can be used to prepare a stable ternary positive electrode material with uniform particles.

[0034] The ternary positive electrode material provided in the third aspect of the embodiment of the present application is obtained by sintering a mixture of a lithium source and a ternary precursor unique to the embodiment of the present application. Based on the narrow diameter distribution, small and stable particles of the ternary precursor, the obtained ternary positive electrode material has good particle uniformity and stability, and can significantly improve the electrochemical performance of the battery when used in a secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 It is a schematic diagram of the preparation method of the ternary precursor provided in the embodiment of the present application;

[0037] Figure 2 is an electron microscope image of the ternary precursor provided in Example 1 of the present application;

[0038] Figure 3 This is an electron microscope image of a particle cross section of the ternary precursor provided in Example 1 of the present application;

[0039] Figure 4 is the XRD pattern of the ternary precursor provided in Example 1 of the present application;

[0040] Figure 5 This is an electron microscope image of the ternary precursor provided in Example 2 of the present application;

[0041] Figure 6 This is an electron microscope image of a particle cross section of the ternary precursor provided in Example 2 of the present application;

[0042] Figure 7 is the XRD pattern of the ternary precursor provided in Example 2 of the present application;

[0043] Figure 8 This is an electron microscope image of the ternary precursor provided in Comparative Example 1 of the present application;

[0044] Fig. 9 This is an electron microscope image of the ternary precursor provided in Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0045] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application 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 application and are not used to limit the present application.

[0046] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0047] In the present application, "at least one" means one or more, "more than one" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items.

[0048] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0049] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0050] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0051] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0052] The ternary precursor is nickel-cobalt-manganese hydroxide Ni x Co y Mn z (OH)2 is an important upstream material for ternary positive electrode materials, and good ternary precursor materials can obtain ternary positive electrode materials with excellent performance. However, generally small-sized ternary precursor particles are prone to agglomeration and wide diameter distribution, and the effect of current optimization methods is not ideal. The main problem is: in the process of maintaining high pH, ​​it is easy to have an abnormally large number of small particles due to pH deviation from the process range, so the stability control of the reaction is required to be high; therefore, the embodiment of the present application explores the problem of poor sphericity and wide diameter distribution of small-particle ternary precursors under high pH conditions.

[0053] To this end, the first aspect of the present application provides a method for preparing a ternary precursor, such as Figure 1 As shown, the preparation method comprises the following steps:

[0054] S01: preparing a mixed metal salt solution containing a nickel source, a cobalt source and a manganese source;

[0055] S02: adding a mixed metal salt solution, an alkali solution and a complexing agent to a base solution for a coprecipitation reaction, wherein the coprecipitation reaction comprises: performing a nucleation reaction in a pH range of 12 to 13 in the reaction system, and then gradually reducing the pH value to above 11 as the growth reaction proceeds until the product particles reach a target particle size, and during the process of gradually reducing the pH value to above 11, there are at least two pH constant times, one of which is more than 40 hours;

[0056] S03: performing solid-liquid separation on the product after the coprecipitation reaction to obtain a ternary precursor.

[0057] The coprecipitation method is a method for preparing a ternary precursor. The ternary precursor is generated by mixing a ternary mixed metal salt solution, an alkali solution, and a complexing agent in a certain proportion through a coprecipitation reaction. The ternary precursor material is a ternary cathode material precursor product, which is a nickel-cobalt-manganese hydroxide Ni prepared from nickel source, cobalt source, and manganese source as raw materials. x Co y Mn z (OH)2, nickel, cobalt and manganese are ternary, and the specific proportion can be adjusted according to actual needs.

[0058] The preparation method of the embodiment of the present application is to prepare the ternary precursor by coprecipitation, wherein the coprecipitation reaction includes two processes: (1) nucleation reaction, and (2) growth reaction. The nucleation reaction mainly generates an initial core, and the growth reaction mainly grows further on the initial core until the ternary precursor of the target particle size is obtained, and both processes are carried out under relatively high pH conditions.

[0059] Different pH values ​​have a significant effect on the nucleation rate and growth rate of crystals. When the pH value is low, the growth rate of the precursor particles is greater than its nucleation rate due to the low supersaturation in the solution, and the precursor grows faster. Under high pH conditions, the supersaturation in the solution system is large, the crystal nucleus formation rate is very fast, and the growth rate of the precursor particles is slow. In the embodiment of the present application, the nucleation reaction is carried out in the pH value range of 12 to 13, and the growth reaction will gradually decrease on the basis of the initial pH value, and the target particle size particle product is obtained when the pH value is above 11. In this way, during the nucleation reaction and growth reaction at a high pH value, the solution supersaturation of the reaction system is relatively large, the crystal nucleus formation rate is fast, and the growth rate of the precursor particles is slow. Therefore, the generation of crystal nuclei can be controlled, and at the same time, through a long-term high pH growth reaction stage, that is, the pH value of the growth reaction gradually decreases, there are at least two constant pH times, and one of the constant pH times is more than 40 hours. In this way, the sphericity of the ternary precursor particles can be optimized, and finally a ternary precursor material with a narrow diameter distribution, small particles and stability is obtained.

[0060] Step S01: In the preparation method of the embodiment of the present application, the prepared mixed metal salt solution is a mixed metal salt solution prepared by dissolving soluble raw materials of nickel source, cobalt source and manganese source in a solvent (such as water), and the ratio of nickel source, cobalt source and manganese source is added according to the required ratio of nickel, cobalt and manganese in the final ternary precursor.

[0061] The nickel source may be a soluble nickel salt, including at least one of nickel chloride, nickel nitrate, nickel oxalate, and nickel sulfate; the cobalt source may be a soluble cobalt salt, including at least one of cobalt chloride, cobalt nitrate, cobalt oxalate, and cobalt sulfate; the manganese source may be a soluble manganese salt, including at least one of manganese chloride, manganese nitrate, manganese oxalate, and manganese sulfate. The nickel source, cobalt source, and manganese source are dissolved in an aqueous solvent to obtain a uniform mixed metal salt solution.

[0062] In one embodiment, the mixed metal salt solution may be Ni 2+ 、Co 2+ , Mn 2+ A nickel-cobalt-manganese sulfate solution with a total metal concentration of 130 g / L to 140 g / L is prepared in a molar ratio of (92 ± 0.5): (4 ± 0.5): (4 ± 0.5). x Co y Mn z The values ​​of x, y and z in (OH)2 are selected from the mixed metal salt solution of Ni 2 + 、Co 2+ , Mn 2+ The molar ratio of .

[0063] Step S02: coprecipitation reaction.

[0064] The alkaline solution used in the coprecipitation reaction includes at least one of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, and sodium bicarbonate solution; specifically, the corresponding alkaline reagent can be dissolved in water to obtain a concentration of 8 to 12 mol / L. The complexing agent used includes ammonia water, specifically, ammonia gas can be dissolved in water to obtain a concentration of 8 to 12 mol / L.

[0065] The coprecipitation reaction can be carried out in a reactor. The bottom liquid is prepared in the reactor and N2 is introduced. The temperature of the reaction bottom liquid is 55-65°C. The conditions for preparing the reactor bottom liquid are as follows: the bottom liquid can be prepared by adding water, liquid alkali and a complexing agent into the reactor.

[0066] Furthermore, the flow rate of N2 in the bottom liquid is 200-500 ml / min, the amount of pure water added is 30%-50% of the volume of the reactor, the amount of complexing agent such as ammonia water added is 0.5%-0.8% of the volume of the reactor, and the amount of liquid alkali added is 0.2-0.5% of the volume of the reactor. In the bottom liquid, the ammonia concentration is 2-5 g / L, the pH is 12-13; the volume of the reactor is 5L.

[0067] In one embodiment, the pH value of the reaction system is controlled by adjusting the flow rate of liquid alkali added in the coprecipitation reaction; the concentration of the complexing agent in the reaction system is controlled by adjusting the flow rate of the complexing agent added in the coprecipitation reaction. In the embodiment of the present application, the process adopts the form of controlling the flow rate of liquid alkali and the flow rate of complexing agent to make the offline pH value and the concentration of complexing agent reach the target value, which has the following advantages: ① Better control of the amount of nucleation in the early stage of the kettle opening with clear water, higher repeatability; ② Because the offline pH meter test frequently causes electrode attenuation, the present application only needs to adjust the flow rate of liquid alkali within a fixed time, which can reduce the frequency of use of the offline pH meter, and this method is more accurate. Specifically, the flow rate of adding the mixed metal salt solution is 2 to 5 mL / min.

[0068] In one embodiment, the nucleation reaction time is 2 to 4 hours, and the total growth reaction time is 90 to 120 hours; for example, the nucleation reaction time can be 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, etc., and the total growth reaction time can be 90 hours, 95 hours, 98 hours, 100 hours, 105 hours, 110 hours, 112 hours, 118 hours, 120 hours, etc. Since the formation rate of the crystal nuclei in the embodiment of the present application is fast and the growth rate of the precursor particles is slow, the nucleation reaction time can be relatively short, and the growth reaction time can be relatively long, so as to obtain the required ternary precursor.

[0069] In one embodiment, the concentration of the complexing agent in the nucleation reaction is 4.0-5.0 g / l, and the concentration of the complexing agent in the growth reaction is 3.0-3.5 g / l. Since liquid alkali is added to the base liquid, the concentration of the complexing agent in the nucleation reaction can be relatively high. As the reaction proceeds, the pH begins to decrease, and the concentration of the complexing agent can be relatively low accordingly.

[0070] In one embodiment, the temperature of the nucleation reaction is 55-65°C, and the temperature of the growth reaction is 55-65°C; the entire co-precipitation reaction of the embodiment of the present application is relatively mild, and the nucleation reaction and the growth reaction can be carried out under the same temperature conditions within the above temperature range.

[0071] In one embodiment, the process of gradually decreasing the pH value to above 11 includes: when the pH value drops to 11.8, the pH value is kept constant for 60 to 70 hours, and when the pH value drops to 11.7, the pH value is kept constant for 9 to 20 hours; or, the process of gradually decreasing the pH value to above 11 includes: when the pH value drops to 11.8, the pH value is kept constant for 40 to 50 hours, when the pH value drops to 11.7, the pH value is kept constant for 4 to 10 hours, and when the pH value drops to 11.6, the pH value is kept constant for 4 to 10 hours. By slowly growing the ternary precursor particles under the above conditions, a ternary precursor material with narrow diameter distribution, small particles and stability can be obtained. Because the longer the maintenance time under high pH conditions, the better the sphericity and particle size distribution of the generated particles, therefore, the embodiment of the present application can choose to keep the pH value constant for 60 to 70 hours when the pH value drops to 11.8, so that a ternary precursor material with better particle sphericity and particle size distribution can be obtained.

[0072] In one embodiment, the pH value is gradually reduced to above 11, and the pH value is reduced by 0.05 to 0.1 pH value each time. For example, the nucleation reaction is constant at a pH value in the range of 12 to 13, and the pH value of the growth reaction begins to decrease, decreasing by 0.1 every 1 to 2 hours; when the pH value drops to 11.8, the pH value is kept constant for 60 to 70 hours, and when the pH value drops to 11.7, the pH value is kept constant for 9 to 20 hours, and then it is reduced by 0.1 every 1 to 2 hours until the product particles reach the target particle size. Alternatively, the pH value of the nucleation reaction is constant at a value in the range of 12 to 13, and the pH value of the growth reaction begins to decrease, decreasing by 0.1 every 1 to 2 hours; when the pH value drops to 11.8, the pH value is kept constant for 40 to 50 hours, when the pH value drops to 11.7, the pH value is kept constant for 4 to 10 hours, and when the pH value drops to 11.6, the pH value is kept constant for 4 to 10 hours, and then it is reduced by 0.1 every 1 to 2 hours until the product particles reach the target particle size. In this way, a ternary precursor material with narrow diameter distribution, small particles and stability can be better obtained.

[0073] In one embodiment, while the pH value of the reaction system in the coprecipitation reaction is gradually reduced to above 11, the stirring speed of the reaction system is gradually reduced from high to low in the range of 800 to 1500 rpm until the product particles reach the target particle size. By continuously reducing the stirring speed, the generated particles can be continuously enlarged. For example, the stirring is adjusted according to the particle size value, and the stirring is maintained at 1500 rpm at the beginning; when the particles grow, the stirring is maintained at 1400 rpm; then the stirring is maintained at 1300 rpm; and finally the stirring is maintained at 1150 rpm.

[0074] In one embodiment, the target particle size D50 is 2 to 3 μm, and the diameter distribution of the obtained ternary precursor is (D90-D10) / D50≤0.65. Specifically, maintaining a relatively high pH value in the early stage of the reaction can effectively improve the sphericity and diameter distribution of the precursor, and most of the particles in the embodiment of the present application are single spheres and exist independently, and the diameter distribution (D90-D10) / D50≤0.65.

[0075] Step S03 is a solid-liquid separation process, in which the slurry of the coprecipitation reaction is washed and dried to obtain a nickel-cobalt-manganese ternary precursor with narrow diameter distribution, small particles and stability.

[0076] In a second aspect, the present invention provides a ternary precursor, the chemical formula of which is Ni x Co y Mn z (OH)2, wherein 0.75≤x≤0.95, 0.03≤y≤0.20, 0.03≤z≤0.20, x+y+z=1;

[0077] The particle size D50 of the ternary precursor is 2 to 3 μm, and the diameter distribution (D90-D10) / D50≤0.65.

[0078] The ternary precursor provided in the embodiment of the present application is characterized by its parameters and is a ternary precursor material with narrow diameter distribution, small particles and stability. Therefore, such a ternary precursor can be used to prepare a stable ternary positive electrode material with uniform particles.

[0079] Specifically, the tap density of the ternary precursor can be 1.8 to 2.0 g / cm 3 , the specific surface area can be 3 to 5m 2 / g, further, the ratio of specific surface area to tap density can be 1.5×10 4 ~2.8×10 4 cm 5 / g 2 Furthermore, in the XRD spectrum of the ternary precursor, the peak ratio of the 101 crystal plane to the 001 crystal plane is 0.7-1.0, the half-peak width corresponding to the 001 crystal plane is 0.48-0.52, the half-peak width corresponding to the 100 crystal plane is 0.27-0.30, and the half-peak width corresponding to the 101 crystal plane is 0.52-0.56.

[0080] Specifically, in the ternary precursor, the Na content is ≤60ppm, and the S content is ≤1200ppm.

[0081] Specifically, the particles of the ternary precursor have Dmin: 0.8-1.0 μm, D10: 1.4-1.7 μm, D90: 3-3.2 μm, D100: 4-6 μm, and D50 < 1 μm account for < 6%.

[0082] D100 particle size, D90 particle size, D50 particle size, and D10 particle size are the equivalent diameters of the largest particles when the cumulative distribution in the particle size distribution curve is 100%, 90%, 50%, and 10%, respectively. (D90-D10) / D50 is the diameter distribution, which represents the consistency of particle size. The smaller the value, the more uniform the particle distribution and the better the consistency of particle size. The larger the value, the wider the particle distribution and the worse the consistency of particle size.

[0083] In the ternary precursor, the ratio of the core size to the ternary precursor size is 20% to 60%, which can be specifically seen from the cross-sectional electron microscope image in the embodiment, that is, the ratio of the core diameter to the precursor diameter. The core is the relatively loose and relatively porous part in the middle of the cross-sectional electron microscope image. The product electron microscope morphology is spherical, and the size distribution is uniform, without agglomeration.

[0084] In one embodiment, the ternary precursor is prepared by the above-mentioned preparation method of the embodiment of the present application.

[0085] In the third aspect, an embodiment of the present application provides a ternary positive electrode material, which is obtained by sintering a mixture of a lithium salt and a precursor material, and the precursor material includes the ternary precursor prepared by the preparation method provided in the first aspect of the embodiment of the present application and / or the ternary precursor provided in the second aspect of the embodiment of the present application.

[0086] The ternary positive electrode material of the embodiment of the present application is obtained by sintering a mixture of a lithium source and a ternary precursor unique to the embodiment of the present application. Since the ternary precursor has a narrow diameter distribution and small and stable particles, the obtained ternary positive electrode material has good particle uniformity and stability, and can significantly improve the electrochemical performance of the battery when used in a secondary battery.

[0087] Specifically, the lithium salt can be a lithium salt commonly used in the preparation of ternary positive electrode materials, and the related sintering process is also a commonly used sintering process.

[0088] The following describes the invention in conjunction with specific embodiments.

[0089] Example 1

[0090] A method for preparing a high-nickel ternary precursor comprises the following steps:

[0091] Step 1: Weigh a certain amount of nickel sulfate, cobalt sulfate, and manganese sulfate to prepare Ni 2+ :Co 2+ :Mn2+ A nickel-cobalt-manganese sulfate solution with a molar ratio of 92:4:4, wherein the total concentration of nickel-cobalt-manganese metal ions is 136 g / L. The nickel-cobalt-manganese sulfate solution is then sieved with a 500-mesh screen and placed in a metal salt solution storage tank for standby use. A sodium hydroxide solution with a concentration of 10.5 mol / L is prepared, and an ammonia solution with a concentration of 10.5 mol / L is prepared.

[0092] Step 2: Preparation of base liquid: ① First clean the reactor and make sure the equipment can operate; ② Stir the reactor to 1500rpm and add 2L of water; introduce nitrogen at 300mL / min above the liquid for more than 6h; set the temperature to 60℃; ③ Add 32mL of ammonia water and adjust the ammonia concentration to 3.5±0.5g / L; ④ Add 15mL of sodium hydroxide solution and adjust the pH to 12.10; ⑤ Test the ammonia concentration and pH value before feeding and record them.

[0093] Step 3: Add the mixed metal salt solution, sodium hydroxide solution and ammonia water prepared in step 1 into the bottom liquid of the reactor in step 2 through a peristaltic pump for initial nucleation reaction. The reaction time is 4 hours, the reaction temperature is 60°C, the pH value is 12.10, the ammonia concentration is 4.5±0.5g / l, and the nitrogen flow rate is 300ml / min.

[0094] Step 4: Growth reaction, ammonia concentration dropped to 3.5 g / l, reaction temperature 60 ° C, nickel cobalt manganese sulfate solution flow rate 3 ml / min (two holes point feed, each hole 1.5 ml / min), pH value by adjusting the flow of sodium hydroxide solution, 4-5h (starting from the initial nucleation reaction of step 3), pH dropped to 12.00; 5-6h, pH dropped to 11.90; 6-7h, pH dropped to 11.80; 7-50h to maintain pH at 11. 80; 50-51h, pH dropped to 11.70; 51-55h, pH maintained at 11.70; 55-56h, pH dropped to 11.60; 56-64h, pH maintained at 11.60; 64-65h, pH dropped to 11.50; 65-66h, pH dropped to 11.40; 66-67h, pH dropped to 11.30; 67-68h, pH dropped to 11.20; after 68h, pH maintained at 11.20, and the reaction continued for 32h. During this process, the stirring speed was adjusted according to the particle size value, 0-2μm, stirring maintained at 1500rpm; 2-2.2μm, stirring maintained at 1400rpm; 2.2-2.25μm, stirring maintained at 1300rpm; 2.25-2.3μm, stirring maintained at 1150rpm. When the particle size reached 2.3 μm, the feeding was stopped to obtain a slurry.

[0095] Step 5: Wash and dry the obtained slurry, and then sieve it after drying. After demagnetization, a ternary precursor with a D50 of 2.3 μm is obtained.

[0096] The particle size distribution of the ternary precursor is (D90-D10) / D50=0.647 (the particle size is tested by Malvern 3000 instrument). The particle size value of the ternary precursor is shown in Table 1 below. Other physical and chemical parameters are shown in Table 2, and the corresponding XRD data are shown in Table 3. The electron microscope image magnified 10,000 times is shown in Figure 2 As shown, the electron microscope image of the particle cross section is as follows Figure 3 As shown, the XRD spectrum is Figure 4 shown.

[0097] Table 1 Particle size distribution of ternary precursors

[0098] Dmin(μm) D10(μm) D50(μm) D90(μm) D100(μm) Particle size 0.995 1.685 2.336 3.196 5.105 0.647

[0099] Table 2 Physicochemical parameters of ternary precursors

[0100] <![CDATA[BET(m 2 / g)]]> <![CDATA[TD(g / cm 3 )]]> <![CDATA[BET / TD(cm 5 / g 2 )]]> Na(ppm) S(ppm) 4.3 1.86 23118 50 1113

[0101] Table 3 XRD patterns of ternary precursors

[0102] I101 / I001 FWHM(001) FWHM(100) FWHM(101) 0.8000 0.514 0.291 0.557

[0103] Example 2

[0104] A method for preparing a high-nickel ternary precursor is as follows:

[0105] Step 1: Weigh a certain amount of nickel sulfate, cobalt sulfate, and manganese sulfate to prepare Ni 2+ :Co 2+ :Mn 2+ The molar ratio of nickel, cobalt and manganese is 92:4:4, and the total metal ion concentration is 136g / L. Then the solution is sieved with a 500-mesh screen and added to the metal salt solution storage tank for standby use. Prepare a sodium hydroxide solution with a concentration of 10.5mol / L and ammonia water with a concentration of 10.5mol / L.

[0106] Step 2: Preparation of base liquid ① First, confirm that the reactor has been cleaned and the equipment is running normally. ② Stir the reactor to 1500rpm and add 2L of water. Pass nitrogen gas above the liquid at 300mL / min for more than 6h. Set the temperature to 60℃ at the same time. ③ Add 32mL of ammonia water and adjust the ammonia concentration to 3.5±0.5g / L. ④ Add 18mL of liquid alkali and adjust the pH to 12.20. ⑤ Before feeding, the ammonia concentration and pH value must be tested and recorded.

[0107] Step 3: Add the mixed metal salt solution, sodium hydroxide solution and ammonia water prepared in step 1 into the bottom liquid of the reactor in step 2 through a peristaltic pump for initial nucleation reaction. The nucleation time is 2h, the reaction temperature is 60°C, the pH value is 12.20, the ammonia concentration is 4.5±0.5g / l, and the nitrogen flow rate is 300ml / min.

[0108] Step 4: Growth reaction, ammonia concentration dropped to 3.5 g / l, reaction temperature 60 ° C, nickel cobalt manganese sulfate solution flow rate of 3 ml / min (two holes point feed, each hole 1.5 ml / min), pH value by adjusting the flow rate of sodium hydroxide solution, 2-3h (starting from the initial nucleation reaction of step 3), pH dropped to 12.10; 3-4h, pH dropped to 12.00; 4-5h, pH dropped to 11.90; 5-6h, pH dropped to 11.80 ; From 6th to 70th hour, pH was maintained at 11.80; From 70th to 71st hour, pH dropped from 11.80 to 11.70; From 71st to 80th hour, pH was maintained at 11.70; From 80th to 82nd hour, pH dropped to 11.60; From 82nd to 84th hour, pH dropped to 11.50; From 84th to 86th hour, pH dropped to 11.40; From 86th to 88th hour, pH dropped to 11.30; From 88th to 90th hour, pH dropped to 11.20; After 90th hour, pH was maintained at 11.20 for 10 hours. Stirring was adjusted according to the particle size value, 0-2μm, stirring was maintained at 1500rpm; 2-2.2μm, stirring was maintained at 1400rpm; 2.2-2.3μm, stirring was maintained at 1300rpm; 2.3-2.4μm, stirring was maintained at 1200rpm. When the particle size reached 2.3 μm, the feeding was stopped to obtain a slurry.

[0109] Step 5: Wash and dry the obtained slurry, and then sieve it after drying. After demagnetization, a ternary precursor with a D50 of 2.3 μm is obtained.

[0110] The particle size distribution of the ternary precursor is (D90-D10) / D50=0.621 (the particle size is tested by Malvern 3000 instrument). The particle size value of the ternary precursor is shown in Table 4. Other physical and chemical parameters are shown in Table 5. The XRD data are shown in Table 6. The electron microscope image magnified 10,000 times is shown in Figure 5 As shown, the electron microscope image of the particle cross section is as follows Figure 6 As shown, the XRD spectrum is Figure 7 shown.

[0111] Table 4 Particle size distribution of ternary precursors

[0112] Dmin(μm) D10(μm) D50(μm) D90(μm) D100(μm) Particle size 0.996 1.678 2.303 3.109 4.09 0.621

[0113] Table 5 Physicochemical parameters of ternary precursors

[0114] <![CDATA[BET(m 2 / g)]]> <![CDATA[TD(g / cm 3 )]]> <![CDATA[BET / TD(cm 5 / g 2 )]]> Na(ppm) S(ppm)10 4.8 1.89 25396 58 1060

[0115] Table 6 XRD patterns of ternary precursors

[0116] I101 / I001 FWHM(001) FWHM(100) FWHM(101) 0.8368 0.488 0.292 0.535

[0117] Comparative Example 1

[0118] A method for preparing a high-nickel ternary precursor comprises the following steps:

[0119] Step 1: The same as the step in Example 1.

[0120] Step 2: Preparation of base liquid ① First, confirm that the reactor has been cleaned and the equipment is running normally. ② Stir the reactor to 1500rpm and add 2L of water. Pass nitrogen gas at 300mL / min above the liquid, and the nitrogen passing time must be more than 6h. At the same time, set the temperature to 60℃. ③ Add 32mL of ammonia water and adjust the ammonia concentration to 3.5±0.5g / L. ④ Add 20mL of liquid alkali and adjust the pH to 12.20. ⑤ Before feeding, the ammonia concentration and pH value must be tested and recorded.

[0121] Step 3: Add the mixed metal salt solution, sodium hydroxide solution and ammonia water prepared in step 1 into the reactor through a peristaltic pump for initial nucleation reaction. The nucleation time is 3h, the reaction temperature is 60°C, the pH value is 12.20, the ammonia concentration is 4.5±0.5g / l, and the nitrogen flow rate is 300ml / min.

[0122] Step 4: Growth reaction, the ammonia concentration dropped to 3.5 g / l, the reaction temperature was 60°C, the flow rate of nickel-cobalt-manganese sulfate solution was 3 ml / min (feeding was divided into two holes, 1.5 ml / min for each hole), and the pH value was adjusted by adjusting the flow rate of the sodium hydroxide solution. At 3-4 h (starting from the initial nucleation reaction of step 3), the pH dropped to 12.10; at 4-5 h, the pH dropped to 12.00; at 5-6 h, the pH dropped to 11.90; at 6-7 h, the pH was dropped to 11.80; at 7-8 h, the pH was maintained at 11.70; at 8-9 h, the pH dropped to 11.60; after 9 h, the pH was maintained at 11.50 and maintained for 86 h. The stirring speed is adjusted according to the particle size value. For 0-2μm, the stirring speed is maintained at 1500rpm; for 2-2.2μm, the stirring speed is maintained at 1400rpm; for 2.2-2.3μm, the stirring speed is maintained at 1300rpm; for 2.3-2.4μm, the stirring speed is maintained at 1200rpm. When the particle size reaches 2.3μm, the feeding is stopped to obtain the slurry.

[0123] Step 5: Wash and dry the obtained slurry, and then sieve it after drying. After demagnetization, a ternary precursor with a D50 of 2.3 μm is obtained.

[0124] The particle size distribution of the ternary precursor is (D90-D10) / D50=0.902 (the particle size is tested using a Malvern 3000 instrument). The particle size values ​​of the precursor are shown in Table 7 below. The electron microscope image magnified 10,000 times is shown in Figure 8 shown.

[0125] Table 7 Particle size distribution of ternary precursors

[0126] Dmin(μm) D10(μm) D50(μm) D90(μm) D100(μm) Particle size 0.78 1.386 2.292 3.453 5.59 0.902

[0127] Comparative Example 2

[0128] A method for preparing a high-nickel ternary precursor comprises the following steps:

[0129] Step 1: The same as step 1 of Example 1.

[0130] Step 2: The same as step 2 of comparative example 1.

[0131] Step 3: The same as step 3 of comparative example 1.

[0132] Step 4: After the nucleation is completed, the ammonia concentration is reduced to 3.5 g / l, the reaction temperature is 60°C, the flow rate of the nickel-cobalt-manganese sulfate solution is 3 ml / min (feeding is divided into two holes, 1.5 ml / min for each hole), and the pH value is adjusted by adjusting the flow rate of the sodium hydroxide solution. In the 3rd to 4th hour (starting from the initial nucleation reaction in step 3), the pH value is reduced to 12.10; in the 4th to 5th hour, the pH value is reduced to 12.00; in the 5th to 6th hour, the pH value is reduced to 12.00. to 11.90; in the 6th to 7th hour, the pH was reduced to 11.80; in the 7th to 8th hour, the pH was maintained at 11.70; in the 8th to 9th hour, the pH was reduced to 11.60; in the 9th to 10th hour, the pH was reduced to 11.50; in the 10th to 11th hour, the pH was reduced to 11.40; in the 11th to 20th hour, the pH was maintained at 11.40; in the 20th to 21st hour, the pH was reduced to 11.30; after the 21st hour, the pH was maintained at 11.30 and maintained for 94 hours. The stirring was adjusted according to the particle size value, 0-2μm, stirring was maintained at 1500rpm; 2-2.2μm, stirring was maintained at 1400rpm; 2.2-2.3μm, stirring was maintained at 1300rpm; 2.3-2.4μm, stirring was maintained at 1200rpm. When the particle size reached 2.3μm, the feeding was stopped to obtain the slurry.

[0133] Step 5: Wash and dry the obtained slurry, and then sieve and remove the magnetism to obtain a ternary precursor with a D50 of 2.3 μm.

[0134] The particle size distribution of the ternary precursor is (D90-D10) / D50=0.851 (the particle size is tested using a Malvern 3000 instrument). The particle size values ​​of the ternary precursor are shown in Table 8 below. The electron microscope image magnified 10,000 times is shown in Fig. 9 shown.

[0135] Table 8 Particle size distribution of ternary precursors

[0136] Dmin(μm) D10(μm) D50(μm) D90(μm) D100(μm) Particle size 0.80 1.514 2.324 3.491 5.72 0.851

[0137] The particle size in Tables 1 to 8 refers to (D90-D10) / D50.

[0138] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a ternary precursor, It is characterized in that The steps include: preparing a mixed metal salt solution containing a nickel source, a cobalt source and a manganese source; The mixed metal salt solution, alkali solution and complexing agent are added to the base liquid for coprecipitation reaction, wherein the coprecipitation reaction comprises: performing a nucleation reaction in a pH range of 12 to 13 in the reaction system, and then gradually reducing the pH value to above 11 as the growth reaction proceeds until the product particles reach the target particle size, and there are at least two pH constant times during the process of gradually reducing the pH value to above 11, one of which is more than 40 hours; The product after the coprecipitation reaction is completed is subjected to solid-liquid separation to obtain a ternary precursor.

2. The preparation method according to claim 1, It is characterized in that The process of gradually reducing the pH value to above 11 includes: When the pH value drops to 11.8, keep the pH constant for 60 to 70 hours; when the pH value drops to 11.7, keep the pH constant for 9 to 20 hours; or When the pH value drops to 11.8, the pH value is kept constant for 40 to 50 hours. When the pH value drops to 11.7, the pH value is kept constant for 4 to 10 hours. When the pH value drops to 11.6, the pH value is kept constant for 4 to 10 hours.

3. The preparation method according to claim 1, It is characterized in that While the pH value of the reaction system in the coprecipitation reaction is gradually reduced to above 11, the stirring speed of the reaction system is gradually reduced from high to low within the range of 800 to 1500 rpm until the product particles reach the target particle size.

4. The preparation method according to claim 3, It is characterized in that The target particle size D50 is 2 to 3 μm, and the obtained diameter distribution of the ternary precursor is (D90-D10) / D50≤0.65; And / or, during the process of gradually decreasing the pH value to above 11, the pH value is decreased by 0.05 to 0.1 pH value each time.

5. The preparation method according to claim 1, It is characterized in that In the coprecipitation reaction, the pH value of the reaction system is controlled by adjusting the flow rate of the liquid alkali added; and / or, In the coprecipitation reaction, the concentration of the complexing agent in the reaction system is controlled by adjusting the flow rate of the complexing agent added.

6. The preparation method according to any one of claims 1 to 5, It is characterized in that Satisfy one or more of the following (1) to (3): (1) The temperature of the nucleation reaction is 55-65°C, and the temperature of the growth reaction is 55-65°C; (2) The nucleation reaction time is 2 to 4 hours, and the total growth reaction time is 90 to 120 hours; (3) The concentration of the complexing agent in the nucleation reaction is 4.0 to 5.0 g / l, and the concentration of the complexing agent in the growth reaction is 3.0 to 3.5 g / l.

7. A ternary precursor, It is characterized in that The chemical formula of the ternary precursor is Ni x Co y Mn z (OH) 2 , where 0.75≤x≤0.95, 0.03≤y≤0.20, 0.03≤z≤0.20, x+y+z=1; The particle size D50 of the ternary precursor is 2-3 μm, and the particle size distribution (D90-D10) / D50≤0.

65.

8. The ternary precursor according to claim 7, It is characterized in that The ternary precursor satisfies one or more of the following (1) to (4): (1) Tap density is 1.8 to 2.0 g / cm 3 ; (2) Specific surface area is 3 to 5 m 2 / g; (3) The ratio of specific surface area to tap density is 1.5×10 4 ~2.8×10 4 cm 5 / g 2 ; (4) The peak ratio of the 101 crystal plane to the 001 crystal plane in the XRD spectrum is 0.7-1.0, the half-peak width corresponding to the 001 crystal plane is 0.48-0.52, the half-peak width corresponding to the 100 crystal plane is 0.27-0.30, and the half-peak width corresponding to the 101 crystal plane is 0.52-0.

56.

9. The ternary precursor according to claim 7 or 8, It is characterized in that The ternary precursor is prepared by the preparation method described in any one of claims 1-6.

10. A ternary cathode material, It is characterized in that The ternary positive electrode material is obtained by sintering a mixture containing a lithium salt and a precursor material, and the precursor material includes a ternary precursor prepared by the preparation method described in any one of claims 1-6 and / or a ternary precursor described in any one of claims 7-9.

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