Ternary precursor, and synthesis method therefor and use thereof

Abstract

Provided in the present disclosure are a ternary precursor, and a synthesis method therefor and the use thereof. The synthesis method comprises: adding a mixed solution containing a metal salt and a complexing agent and liquid caustic soda into a reaction container in a parallel flow manner, so as to perform a first co-precipitation reaction, adjusting the reaction temperature until a reaction product grows to a target particle size, so as to perform a second co-precipitation reaction, and aging same to obtain a nickel-cobalt-manganese precursor, wherein the complexing agent comprises sodium N,N-dicarboxyamino-2-hydroxypropanesulphonate. In the present disclosure, sodium N,N-dicarboxyamino-2-hydroxypropanesulphonate is used as a complexing agent, and the morphology of a sample is adjusted by using different complexing capabilities of the complexing agent to metal ions under high and low temperature conditions, so as to synthesize a product having densely stacked internal primary particles, a loose external morphology and orientated shell whiskers; and the product can have the characteristics of both a large BET specific surface area, a high TD and a relatively low impurity content.

Description

A ternary precursor and its synthesis method and application Technical Field

[0001] The present disclosure belongs to the field of battery technology and relates to a ternary precursor and a synthesis method and application thereof. Background Art

[0002] Developing lithium-ion batteries (LIBs) with high energy density to meet the growing demand of electric vehicles is a global priority. One of the effective strategies to improve the energy density of lithium-ion batteries is to increase the battery capacity, which mainly depends on its cathode material. Common cathode materials include lithium nickel cobalt manganese oxide (LiNi x Co y Mn z O2), lithium iron phosphate or lithium cobalt oxide, among which lithium iron phosphate and lithium cobalt oxide are limited in application due to their relatively low capacity and other issues. The current market is still dominated by ternary positive electrode materials - lithium nickel cobalt manganese oxide.

[0003] Lithium nickel cobalt manganese oxide is obtained by sintering the ternary precursor nickel cobalt manganese hydroxide mixed with lithium. During the charge and discharge process, Li + Volume expansion and contraction caused by deintercalation and intercalation can generate cracks, triggering a series of side reactions that affect battery life. In recent years, significant progress has been made in improving battery electrochemical performance through methods such as element doping, surface coating, and electrolyte optimization. However, these research results have been hindered by challenges in cost control and quality consistency, hindering their industrial application.

[0004] The electrochemical performance of ternary cathode materials is related to various precursor indicators, including size, BET surface area, tap density (TD), morphology, structure, and impurity content (such as sulfur). Generally, a larger BET surface area increases the contact area between the electrolyte and metal ions, improving discharge capacity; a high TD increases the material's tap density, thereby increasing the battery's energy density. A lower impurity content can improve the electrochemical performance of the cathode material.

[0005] Patent CN107611383B discloses a method for preparing a low-sulfur, high-tap-density nickel-cobalt-manganese ternary precursor, but the resulting product fails to simultaneously meet the three properties of low sulfur impurity content, high tap density, and high BET specific surface area. Patent CN115180659A discloses a shell structure with a dense reticular interior and a loose radial shell. This sample has a high BET characteristic, but its TD is relatively low, which is not conducive to improving the energy density of the battery. In addition, the above patent uses high-concentration ammonia as a complexing agent, which is highly volatile and requires additional ventilation equipment to maintain a normal working environment.

[0006] Therefore, there is an urgent need to provide a precursor preparation method that enables the precursor to have a large BET specific surface area, a high TD and a low sulfur impurity content, and can be produced without the need for additional ventilation equipment.

[0007] Summary of the Invention

[0008] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0009] In response to the shortcomings of the prior art, the present invention aims to provide a ternary precursor, its synthesis method, and application. This invention utilizes sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate as a complexing agent, utilizing its varying complexing abilities for metal ions under high and low temperature conditions to adjust the product morphology. Desulfurization is then performed through an aging step, thereby synthesizing a precursor with densely packed primary particles inside, a loose external morphology, and oriented outer shell whiskers. This precursor simultaneously exhibits the characteristics of a large BET specific surface area, a high TD, and a low sulfur impurity content.

[0010] To achieve this goal, the present disclosure adopts the following technical solutions:

[0011] In a first aspect, the present disclosure provides a method for synthesizing a ternary precursor, the method comprising:

[0012] Adding a mixed solution containing a metal salt and a complexing agent and liquid alkali into a reaction vessel in parallel to perform a first coprecipitation reaction, and after the reaction product grows to a target particle size, adjusting the reaction temperature to perform a second coprecipitation reaction, and aging to obtain the ternary precursor;

[0013] Wherein, the complexing agent includes sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate.

[0014] The crystallization process of the ternary precursor precipitation mainly depends on the supersaturation, that is, the - It is related to the concentration of metal ions. When the supersaturation is high, nucleation is easy to form. At this time, under the action of complexing agents under certain conditions, some metal ions are complexed and the supersaturation is moderately reduced, thereby adjusting the growth rate of the crystal and further affecting the crystal morphology and other physical indicators.

[0015] In the present disclosure, the ternary precursor includes but is not limited to a nickel-cobalt-manganese ternary precursor (ie, nickel-cobalt-manganese hydroxide).

[0016] The present disclosure provides a method for synthesizing a ternary precursor, which uses sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate as a complexing agent, utilizes its different complexing abilities for metal ions under high and low temperature conditions to regulate the morphology of the product, and desulfurizes through an aging step, thereby synthesizing a precursor with densely packed primary particles inside, loose external morphology, and oriented outer shell whiskers. The precursor can simultaneously have the characteristics of a large BET specific surface area, a high TD, and a low sulfur impurity content.

[0017] In one embodiment, the metal salt includes but is not limited to at least one of nickel sulfate, nickel chloride, cobalt sulfate, cobalt chloride, manganese sulfate and manganese chloride.

[0018] In one embodiment, the liquid caustic soda comprises sodium hydroxide.

[0019] In one embodiment, based on the target yield of the ternary precursor as 100%, the mass fraction of the complexing agent is 0.1-1.0%, for example, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1.0%, etc.

[0020] In the present disclosure, if the mass fraction of the complexing agent is too low, the complexing effect will be poor, the particles will directly precipitate and grow, and the particles will grow densely inside; if the mass fraction of the complexing agent is too high, the supersaturation will be low, the particles will be loosely stacked, the primary particles will be finer, and they may even be unable to agglomerate into secondary spheres.

[0021] In one embodiment, the temperature of the first coprecipitation reaction is 55-65°C, for example, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C or 65°C.

[0022] In the present disclosure, when the temperature of the first coprecipitation reaction is controlled at 55-65° C., the obtained precursor can have both a higher tap density and a higher BET specific surface area.

[0023] In one embodiment, the pH value of the first coprecipitation reaction is 10-12, for example, 10, 10.5, 11, 11.5 or 12.

[0024] In this disclosure, the high-temperature, high-alkali process conditions of the first coprecipitation reaction can significantly reduce the sulfur content, thereby improving the electrochemical performance of the positive electrode material. The supersaturation within this pH range is within the optimal range for particle growth, which promotes dense sample packing and the formation of thick strips, thereby improving its tap density.

[0025] In one embodiment, the target particle size is 2.0-2.8 μm, for example, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm or 2.7 μm.

[0026] In this disclosure, the target particle size of the reaction product after the first coprecipitation reaction is controlled to 2.0-2.8 μm. This ensures the sphericity of the core, and thus the sphericity of the sample after the second coprecipitation, which helps to improve the sample's compaction density. If the particle size is too small, the surface energy of the small particle sample is relatively high, and the smaller the particles, the more likely they are to agglomerate, resulting in poor sphericity, which in turn affects their compaction density.

[0027] In one embodiment, the temperature of the second coprecipitation reaction is 40-45°C, for example, 40°C, 41°C, 42°C, 43°C, 44°C or 45°C.

[0028] In the present disclosure, after the reaction product grows to the target particle size, the reaction temperature is lowered to perform a second coprecipitation reaction. When the temperature of the second coprecipitation reaction is controlled at 40-45°C, the obtained precursor can have both a high tap density and a high BET specific surface area.

[0029] The present invention uses sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate as a complexing agent, and the mechanism and effect of regulating the morphology by adjusting the reaction temperature are as follows:

[0030] Under the high temperature conditions of the first coprecipitation reaction, due to the esterification reaction of sodium N, N-dicarboxylic acid amino-2-hydroxypropyl sulfonate itself, the complexing sites are reduced and the complexing ability for metal ions is poor. At this stage, the growth and nucleation of crystals in the reaction vessel are carried out simultaneously, which is conducive to the synthesis of primary particles and the growth of thick strips with densely packed particles. Particles with such morphology have a large TD, which is conducive to improving the compaction density of the material. After obtaining the densely packed inner core of the particles through the first coprecipitation reaction, the reaction temperature is lowered. In the second coprecipitation reaction stage, N, Sodium N-dicarboxylic acid amino-2-hydroxypropanesulfonate has a strong complexing ability for metal ions, thereby reducing the supersaturation of the reaction. At low supersaturations, the sample is only in the growth phase, continuing to grow at sites on the surface of the inner core. During this phase, due to the different growth rates of the various crystal faces within the crystal, this difference is more pronounced at lower supersaturations, resulting in the surface of the dense, coarse inner core being transformed into a loose outer shell with whisker-oriented alignment. This loose outer shell with whisker-oriented alignment and the densely packed inner core result in a precursor with both high TD and a large BET surface area. Furthermore, a precursor with a large BET surface area can reduce the temperature of the back-end sintering, thereby reducing costs to a certain extent.

[0031] In one embodiment, after the second coprecipitation reaction, the particle size of the reaction product is 3.45-3.80 μm, for example, 3.45 μm, 3.52 μm, or 3.80 μm.

[0032] In the present disclosure, the particle size of the reaction product after the second coprecipitation reaction is controlled to 3.45-3.80 μm, which has a small particle size range. The small-sized particles require a low temperature during sintering and have excellent low-temperature performance. Moreover, the particle size is also small after being prepared into a positive electrode material at the back end, which can achieve a high rate and improve the cycle performance. This is because the small-particle material has a short Li ion transmission distance and good rate performance during the discharge process; and the small particles can alleviate the microcracks caused by volume expansion and contraction during the charge and discharge process, thereby improving the cycle performance.

[0033] In one embodiment, the aging temperature is 40-45°C, for example, 40°C, 41°C, 42°C, 43°C, 44°C or 45°C.

[0034] In one embodiment, the aging temperature is the same as the temperature of the second coprecipitation reaction.

[0035] In the present disclosure, when the aging temperature is the same as the temperature of the second coprecipitation reaction, potential risks of factors such as increased temperature on sample morphology, such as the generation of micropowder on the surface, can be avoided.

[0036] In one embodiment, the pH value of the aging is 11-12, for example, 11, 11.5 or 12.

[0037] In one embodiment, the pH value of the aging is higher than the pH value of the second coprecipitation reaction.

[0038] According to Fajans adsorption rule, the crystal will preferentially adsorb OH - , which displaces the sulfate, and then OH - Diffusion into the crystal to complete the crystal transformation, sulfate is replaced to the crystal surface adsorption layer. In this disclosure, after the crystal crystallization is completed, the OH in the mother liquor - It has been basically consumed, and alkali solution needs to be added during the aging process to achieve the desulfurization effect. When the pH value of the aging is higher than the pH value of the second coprecipitation reaction, the added OH - It can re-enter the crystal and displace the contained sulfate ions.

[0039] In one embodiment, the aging time is 6-8 hours, for example, 6 hours, 6.5 hours, 7 hours, 7.5 hours or 8 hours.

[0040] In this disclosure, when the aging time is controlled to 6-8 hours, the sulfur entrapped and adsorbed in the precursor can be displaced. If the aging time is too short, the sulfur removal effect will be poor. If the aging time is too long, the sulfur content of the sample has been removed to the upper limit, and further aging will affect experimental efficiency and waste resources.

[0041] As an optional technical solution of the present disclosure, the synthesis method specifically includes:

[0042] (1) adding water to a reaction vessel, heating the mixture to 60° C. in a nitrogen atmosphere while stirring, and then adding an alkali solution to obtain a base solution with a pH of 10-12 (e.g., 10, 10.5, 11, 11.5, or 12);

[0043] (2) adding a mixed solution containing a metal salt and a complexing agent and liquid alkali into a reaction vessel in parallel to perform a first coprecipitation reaction; after the reaction product grows to 2.0-2.8 μm, lowering the reaction temperature to perform a second coprecipitation reaction; after aging, solid-liquid separation, washing, drying and screening are performed in sequence to obtain the ternary precursor, wherein the complexing agent includes sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate.

[0044] In one embodiment, the solid-liquid separation method includes centrifugation.

[0045] In one embodiment, the washing specifically comprises: first washing with 0.5-0.8 mol / L (for example, 0.6 mol / L, 0.65 mol / L or 0.7 mol / L, etc.) NaOH solution, and then washing with pure water.

[0046] In one embodiment, the drying temperature is 80-120°C, such as 80°C, 90°C, 100°C or 110°C, and the drying time is 16-20h, such as 16h, 17h, 18h or 19h.

[0047] In one embodiment, the mesh size of the sieve is 200-400 mesh, for example, 200 mesh, 300 mesh or 400 mesh.

[0048] In a second aspect, the present disclosure provides a ternary precursor, which is prepared by the synthesis method described in the first aspect.

[0049] In one embodiment, the ternary precursor comprises a core and a shell, the core has a higher density than the shell, and the shell has whiskers that are oriented.

[0050] In the present disclosure, the prepared ternary precursor has a tight inner and loose outer morphology, with a tight inner core, a loose outer shell and orientationally arranged whiskers.

[0051] In one embodiment, the tap density of the ternary precursor is 1.68-2.03 g / cm 3 , for example, it can be 1.7 g / cm 3 , 1.8g / cm 3 , 1.9g / cm 3 , 2g / cm 3 wait.

[0052] In one embodiment, the BET specific surface area of ​​the ternary precursor is 17-20 m 2 / g, for example, it can be 17m 2 / g、18m 2 / g、19m 2 / g or 20m 2 / g, etc.

[0053] In one embodiment, the sulfur content in the ternary precursor is 368-562 ppm, for example, 368 ppm, 370 ppm, 380 ppm, 400 ppm, 450 ppm, 500 ppm or 562 ppm.

[0054] In a third aspect, the present disclosure provides a positive electrode material, which is obtained by mixing and sintering the ternary precursor described in the second aspect and a lithium source.

[0055] In one embodiment, the chemical formula of the positive electrode material is LiNi x Co y Mn z O2, where x≥0.2, x+y+z=1.

[0056] In a fourth aspect, the present disclosure provides a lithium-ion battery, wherein the positive electrode of the lithium-ion battery includes the positive electrode material described in the third aspect.

[0057] The numerical range described in the present disclosure includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present disclosure no longer exhaustively lists the specific point values ​​included in the range.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] (1) The present disclosure provides a method for synthesizing a ternary precursor, using sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate as a complexing agent, utilizing its different complexing abilities for metal ions under high and low temperature conditions to regulate the morphology of the product, and performing desulfurization through an aging step, thereby synthesizing a precursor with densely packed primary particles inside, loose morphology outside, and oriented arrangement of outer shell whiskers. The precursor can simultaneously have the characteristics of large BET specific surface area, high TD, and low sulfur impurity content.

[0060] (2) The tap density of the ternary precursor prepared in the present disclosure is 1.68-2.03 g / cm 3 ; BET specific surface area of ​​ternary precursor is 17-20m 2 / g; the sulfur content in the ternary precursor is 356-562ppm.

[0061] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0063] FIG1 is a SEM image and a CP image of the product obtained in step (1) of Example 1 of the present disclosure.

[0064] FIG2 is an SEM image and a CP image of the nickel-cobalt-manganese precursor prepared in Example 1 of the present disclosure.

[0065] FIG3 is an SEM image and a CP image of the product obtained in step (1) of Example 2 of the present disclosure.

[0066] FIG4 is an SEM image and a CP image of the nickel-cobalt-manganese precursor prepared in Example 2 of the present disclosure.

[0067] FIG5 is an SEM image and a CP image of the product obtained in step (1) of Example 3 of the present disclosure.

[0068] FIG6 is an SEM image and a CP image of the nickel-cobalt-manganese precursor prepared in Example 3 of the present disclosure.

[0069] FIG7 is an SEM image and a CP image of the nickel-cobalt-manganese precursor prepared in Comparative Example 1 of the present disclosure.

[0070] FIG8 is an SEM image and a CP image of the nickel-cobalt-manganese precursor prepared in Comparative Example 2 of the present disclosure.

[0071] FIG9 is an SEM image and a CP image of the nickel-cobalt-manganese precursor prepared in Comparative Example 3 of the present disclosure. DETAILED DESCRIPTION

[0072] The technical solution of the present disclosure is further illustrated below through specific implementation methods.

[0073] Example 1

[0074] This embodiment provides a method for synthesizing a nickel-cobalt-manganese precursor, comprising the following specific steps:

[0075] (1) Add water to the overflow port of a 500L reactor, and simultaneously start stirring, nitrogen protection, and heating systems. After the temperature rises to 60°C, add alkali solution to control the pH value to about 12; then add a mixed solution containing a metal salt and a complexing agent and liquid alkali in parallel, wherein the metal salt is a combination of nickel sulfate, cobalt sulfate, and manganese sulfate, the total ion concentration of nickel, cobalt, and manganese in the mixed solution is 114g / L, the complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate, and the content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 0.1wt% of the target yield of nickel, cobalt, and manganese hydroxide; the flow rate of the mixed solution is 25L / h, the liquid alkali is sodium hydroxide solution, and the flow rate is 10L / h. During the parallel flow process, a nitrogen atmosphere is maintained, and the nitrogen flow rate is 15L / min; after 6h of liquid feeding, the pH value is lowered to 10.0 at a rate of 0.05 / 3h. Under the above conditions, liquid feeding is stopped when the product particle size reaches 2.8μm;

[0076] (2) directly lowering the temperature to 40°C and adding a filter rod to the reactor. After reaching the set temperature, start suction filtration and concentration and continue feeding liquid according to the current pH value until the particle size reaches 3.4 μm. After stopping the feeding for 2 hours, increase the pH value to 12 and age for 6 hours to obtain a nickel-cobalt-manganese hydroxide slurry;

[0077] (3) washing the nickel-cobalt-manganese hydroxide slurry with a 0.8 mol / L NaOH solution once for 30 min, and then washing it with pure water once for 1 h. After washing, drying the filter cake in an oven;

[0078] (4) The dried filter cake is sieved on a 200-400 mesh screen to obtain a nickel-cobalt-manganese precursor having a special structure of a compact core, a loose shell, and oriented whiskers, namely nickel-cobalt-manganese hydroxide.

[0079] The morphological and structural characteristics of the product obtained in step (1) of this embodiment are shown in Figure 1, wherein the left figure is a SEM figure and the right figure is a CP figure (i.e., a cross-sectional SEM figure of the sample). It can be seen from the figure that the crystal nuclei synthesized under high temperature conditions are closely arranged strip-shaped primary particles. The cross-sectional figure shows that the internal stacking is tight, there is no hollow structure, and there is no obvious gap between the primary particles. This closely arranged structure is the reason why it has a high TD; the morphological and structural characteristics of the nickel-cobalt-manganese precursor finally obtained in this embodiment are shown in Figure 2, wherein the left figure is a SEM figure and the right figure is a CP figure. It can be seen from the figure that under the action of 0.1wt% of the complexing agent (i.e., sodium N,N-dicarboxylic acid amino-2-hydroxypropyl sulfonate), after lowering the temperature, the strip-shaped primary particles on the surface are layered into thin primary particles, and the primary particles are oriented; the cross-sectional figure shows that the core is tightly packed and the shell is loose. After lowering the temperature, there are obvious gaps between the primary particles in the shell. This loose shell is the reason why the particles have a large BET specific surface area.

[0080] Example 2

[0081] This embodiment provides a method for synthesizing a nickel-cobalt-manganese precursor, comprising the following specific steps:

[0082] (1) Add water to the overflow port of a 500L reactor, and simultaneously start stirring, nitrogen protection, and heating systems. After the temperature rises to 60°C, add alkali solution to control the pH at about 12; then add a mixed solution containing a metal salt and a complexing agent and liquid alkali in parallel, wherein the metal salt is a combination of nickel sulfate, cobalt sulfate, and manganese sulfate, the total ion concentration of nickel, cobalt, and manganese in the mixed solution is 114g / L, the complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate, and the content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 0.5wt% of the target yield of nickel, cobalt, and manganese hydroxide; the flow rate of the mixed solution is 25L / h, the liquid alkali is sodium hydroxide solution, and the flow rate is 10L / h. During the parallel flow process, a nitrogen atmosphere is maintained, and the nitrogen flow rate is 15L / min; after 6h of liquid feeding, the pH value is lowered to 10.0 at a rate of 0.05 / 3h. Under the above conditions, liquid feeding is stopped when the product particle size reaches 2.8μm;

[0083] (2) directly lowering the temperature to 40°C and adding a filter rod to the reactor, then starting the filtration and concentration process and continuing to feed liquid according to the current pH value until the particle size reaches 3.4 μm and then stopping the feeding. After stopping the feeding for 2 hours, the pH value is raised to 12 and aged for 6 hours to obtain a nickel-cobalt-manganese hydroxide slurry;

[0084] (3) The nickel-cobalt-manganese hydroxide slurry was washed once with a 0.8 mol / L NaOH solution for 30 min, and then washed once with pure water for 1 h. After washing, the filter cake was dried in an oven.

[0085] (4) The dried filter cake is sieved on a 200-400 mesh screen to obtain a nickel-cobalt-manganese precursor having a special structure with a tight inner layer, a loose outer shell, and oriented whiskers, namely nickel-cobalt-manganese hydroxide.

[0086] The morphological and structural characteristics of the product obtained in step (1) of this embodiment are shown in FIG3 , wherein the left figure is a SEM figure and the right figure is a CP (sample cross-section SEM) figure. It can be seen from the figure that with the increase of the content of the complexing agent (i.e., sodium N,N-dicarboxylic acid amino-2-hydroxypropyl sulfonate), the primary particles of the crystal core prepared under high temperature conditions are tightly packed, but the degree of compactness is slightly lower than that of Example 1. The internal cross-section shows that the internal stacking is tight, and there is no obvious gap between the primary particles, which is no significant difference from Example 1. The morphological and structural characteristics of the nickel-cobalt-manganese precursor finally obtained in this embodiment are shown in FIG4 , wherein the left figure is a SEM figure and the right figure is a CP figure. It can be seen from the figure that after lowering the temperature, the strip-shaped primary particles are layered into thinner primary particles with oriented arrangement, and the morphology is looser than that of Example 1, so its TD is slightly lower than that of Example 1. The pores between the primary particles in the shell layer are larger in the cross-section, which makes the sample have a larger BET specific surface area.

[0087] Example 3

[0088] This embodiment provides a method for synthesizing a nickel-cobalt-manganese precursor, comprising the following specific steps:

[0089] (1) Add water to the overflow port of a 500L reactor, and simultaneously start stirring, nitrogen protection and heating systems. After the temperature rises to 60°C, add alkali solution to control the pH at about 12; then add a mixed solution containing a metal salt and a complexing agent and liquid alkali in parallel, wherein the metal salt is a combination of nickel sulfate, cobalt sulfate and manganese sulfate, the total ion concentration of nickel, cobalt and manganese in the mixed solution is 114g / L, the complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate, and the content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 1.0wt% of the target yield of nickel, cobalt and manganese hydroxide, the flow rate of the mixed solution is 25L / h, the liquid alkali is sodium hydroxide solution, the flow rate is 10L / h, and a nitrogen atmosphere is maintained during the parallel flow process, with a nitrogen flow rate of 15L / min; after 6h of liquid feeding, the pH value is lowered to 10.0 at a rate of 0.05 / 3h, and liquid feeding is stopped when the product particle size reaches 2.8μm under the above conditions;

[0090] (2) directly lowering the temperature to 40°C and adding a filter rod to the reactor, then starting the filtration and concentration process and continuing to feed liquid according to the current pH value until the particle size reaches 3.4 μm and then stopping the feeding. After stopping the feeding for 2 hours, the pH value is raised to 12 and aged for 6 hours to obtain a nickel-cobalt-manganese hydroxide slurry;

[0091] (3) The nickel-cobalt-manganese hydroxide slurry was washed once with a 0.8 mol / L NaOH solution for 30 min, and then washed once with pure water for 1 h. After washing, the filter cake was dried in an oven.

[0092] (4) The dried filter cake is sieved on a 200-400 mesh screen to obtain a nickel-cobalt-manganese precursor having a special structure with a tight inner layer, a loose outer shell, and oriented whiskers, namely nickel-cobalt-manganese hydroxide.

[0093] The morphological and structural characteristics of the product obtained in step (1) of this embodiment are shown in Figure 5, wherein the left figure is a SEM figure and the right figure is a CP figure. As can be seen from the figure, the content of the complexing agent becomes higher, and the crystal nuclei synthesized under high temperature conditions are arranged as strips of primary particles, which become looser than those in Example 2. In its cross-sectional view, sporadic holes can be observed, which is caused by the primary particles not being tightly packed. The morphological and structural characteristics of the nickel-cobalt-manganese precursor finally obtained in this embodiment are shown in Figure 6, wherein the left figure is a SEM figure and the right figure is a CP figure. As can be seen from the figure, under a high content of complexing agent, the strip-shaped primary particles are layered into thinner primary particles after the temperature is lowered, and the pores between the primary particles are larger and the stacking is looser than in Examples 1 and 2. It can also be observed in its cross-sectional view that the shell is looser, so the TD of this sample is smaller than that of Examples 1 and 2, and the BET specific surface area is larger.

[0094] Example 4

[0095] This embodiment provides a method for synthesizing a nickel-cobalt-manganese precursor, comprising the following specific steps:

[0096] (1) Add water to the overflow port of a 500L reactor, and simultaneously start stirring, nitrogen protection and heating systems. After the temperature rises to 60°C, add alkali solution to control the pH at about 12; then add a mixed solution containing a metal salt and a complexing agent and liquid alkali in parallel, wherein the metal salt is a combination of nickel sulfate, cobalt sulfate and manganese sulfate, the total ion concentration of nickel, cobalt and manganese in the mixed solution is 114g / L, the complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate, and the content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 0.05wt% of the target yield of nickel, cobalt and manganese hydroxide, the flow rate of the mixed solution is 25L / h, the liquid alkali is sodium hydroxide solution, the flow rate is 10L / h, and a nitrogen atmosphere is maintained during the parallel flow process, with a nitrogen flow rate of 15L / min; after 6h of liquid feeding, the pH value is lowered to 10.0 at a rate of 0.05 / 3h, and liquid feeding is stopped when the product particle size reaches 2.8μm under the above conditions;

[0097] (2) directly lowering the temperature to 40°C and adding a filter rod to the reactor, then starting the filtration and concentration process and continuing to feed liquid according to the current pH value until the particle size reaches 3.4 μm and then stopping the feeding. After stopping the feeding for 2 hours, the pH value is raised to 12 and aged for 6 hours to obtain a nickel-cobalt-manganese hydroxide slurry;

[0098] (3) The nickel-cobalt-manganese hydroxide slurry was washed once with a 0.8 mol / L NaOH solution for 30 min, and then washed once with pure water for 1 h. After washing, the filter cake was dried in an oven.

[0099] (4) The dried filter cake is sieved on a 200-400 mesh screen to obtain a nickel-cobalt-manganese precursor having a special structure with a tight inner layer, a loose outer shell, and oriented whiskers, namely nickel-cobalt-manganese hydroxide.

[0100] The sample prepared in this example, synthesized under low complexing agent and high temperature conditions, produced coarse primary particles and dense packing. Complexing activity decreased under high temperature, and further reduction of the complexing agent resulted in denser primary particle growth. Later, as the temperature was lowered and growth continued, the complexing activity of the complexing agent was enhanced at low temperatures, resulting in a thinner, more loosely packed shell of the primary particles. However, the low complexing agent content resulted in a small core-shell difference. This sample, compared to Example 1, had denser overall packing.

[0101] Example 5

[0102] This embodiment provides a method for synthesizing a nickel-cobalt-manganese precursor, comprising the following specific steps:

[0103] (1) Add water to the overflow port of a 500L reactor, and simultaneously start stirring, nitrogen protection, and heating systems. After the temperature rises to 60°C, add alkali solution to control the pH at about 12; then add a mixed solution containing a metal salt and a complexing agent and liquid alkali in parallel, wherein the metal salt is a combination of nickel sulfate, cobalt sulfate, and manganese sulfate, the total ion concentration of nickel, cobalt, and manganese in the mixed solution is 114g / L, the complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate, and the content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 1.5wt% of the target yield of nickel, cobalt, and manganese hydroxide; the flow rate of the mixed solution is 25L / h, the liquid alkali is sodium hydroxide solution, and the flow rate is 10L / h. A nitrogen atmosphere is maintained during the parallel flow process, and the nitrogen flow rate is 15L / min; after 6h of liquid infusion, the pH value is lowered to 10.0 at a rate of 0.05 / 3h. Under the above conditions, liquid infusion is stopped when the product particle size reaches 2.8μm;

[0104] (2) directly lowering the temperature to 40°C and adding a filter rod to the reactor, then starting the filtration and concentration process and continuing to feed liquid according to the current pH value until the particle size reaches 3.4 μm and then stopping the feeding. After stopping the feeding for 2 hours, the pH value is raised to 12 and aged for 6 hours to obtain a nickel-cobalt-manganese hydroxide slurry;

[0105] (3) The nickel-cobalt-manganese hydroxide slurry was washed once with a 0.8 mol / L NaOH solution for 30 min, and then washed once with pure water for 1 h. After washing, the filter cake was dried in an oven.

[0106] (4) The dried filter cake is sieved on a 200-400 mesh screen to obtain a nickel-cobalt-manganese precursor having a special structure with a tight inner layer, a loose outer shell, and oriented whiskers, namely nickel-cobalt-manganese hydroxide.

[0107] The sample prepared in this example, synthesized under high complexing agent and high temperature conditions, exhibited relatively dense primary particle packing, and overall, a looser core than the crystal nucleus in Example 3. Complexing activity decreased under high temperature, and increasing the amount of complexing agent resulted in looser primary particle packing. Later, as the temperature was lowered and growth continued, the complexing activity of the complexing agent was enhanced under low temperature conditions, resulting in a thinner, more loosely packed primary particle stripe. This resulted in a looser core shell than the core. The high complexing agent content resulted in a significant core-shell discrepancy. This sample exhibited a looser overall packing compared to Example 3.

[0108] Example 6

[0109] This embodiment provides a method for synthesizing a nickel-cobalt-manganese precursor, comprising the following specific steps:

[0110] (1) Add water to the overflow port of a 500L reactor, and simultaneously start stirring, nitrogen protection and heating systems. After the temperature rises to 55°C, add alkali solution to control the pH at about 12; then add a mixed solution containing a metal salt and a complexing agent and liquid alkali in parallel, wherein the metal salt is a combination of nickel sulfate, cobalt sulfate and manganese sulfate, the total ion concentration of nickel, cobalt and manganese in the mixed solution is 114g / L, the complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate, and the content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 0.5wt% of the target yield of nickel, cobalt and manganese hydroxide, the flow rate of the mixed solution is 25L / h, the liquid alkali is sodium hydroxide solution, the flow rate is 10L / h, and a nitrogen atmosphere is maintained during the parallel flow process, with a nitrogen flow rate of 15L / min; after 6h of liquid feeding, the pH value is lowered to 10.0 at a rate of 0.05 / 3h, and liquid feeding is stopped when the product particle size reaches 2.8μm under the above conditions;

[0111] (2) directly lowering the temperature to 40°C and adding a filter rod to the reactor, then starting the filtration and concentration process and continuing to feed liquid according to the current pH value until the particle size reaches 3.4 μm and then stopping the feeding. After stopping the feeding for 2 hours, the pH value is raised to 12 and aged for 6 hours to obtain a nickel-cobalt-manganese hydroxide slurry;

[0112] (3) The nickel-cobalt-manganese hydroxide slurry was washed once with a 0.8 mol / L NaOH solution for 30 min, and then washed once with pure water for 1 h. After washing, the filter cake was dried in an oven.

[0113] (4) The dried filter cake is sieved on a 200-400 mesh screen to obtain a nickel-cobalt-manganese precursor having a special structure with a tight inner layer, a loose outer shell, and oriented whiskers, namely nickel-cobalt-manganese hydroxide.

[0114] Compared with Example 2, when the co-precipitation temperature in the first stage of this embodiment is 55°C, the complexing effect of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is higher, the supersaturation in the reactor is lower, the sample grows relatively loose, and a looser core is formed; under the same co-precipitation temperature (40°C) in the second stage, the sample prepared in this embodiment has a slightly smaller TD and a slightly larger BET specific surface area.

[0115] Example 7

[0116] This embodiment provides a method for synthesizing a nickel-cobalt-manganese precursor, comprising the following specific steps:

[0117] (1) Add water to the overflow port of a 500L reactor, and simultaneously start stirring, nitrogen protection, and heating systems. After the temperature rises to 65°C, add alkali solution to control the pH at about 12; then add a mixed solution containing a metal salt and a complexing agent and liquid alkali in parallel, wherein the metal salt is a combination of nickel sulfate, cobalt sulfate, and manganese sulfate, the total ion concentration of nickel, cobalt, and manganese in the mixed solution is 114g / L, the complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate, and the content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 0.5wt% of the target yield of nickel, cobalt, and manganese hydroxide; the flow rate of the mixed solution is 25L / h, the liquid alkali is sodium hydroxide solution, and the flow rate is 10L / h. During the parallel flow process, a nitrogen atmosphere is maintained, and the nitrogen flow rate is 15L / min; after 6h of liquid feeding, the pH value is lowered to 10.0 at a rate of 0.05 / 3h. Under the above conditions, liquid feeding is stopped when the product particle size reaches 2.8μm;

[0118] (2) directly lowering the temperature to 40°C and adding a filter rod to the reactor, then starting the filtration and concentration process and continuing to feed liquid according to the current pH value until the particle size reaches 3.4 μm and then stopping the feeding. After stopping the feeding for 2 hours, the pH value is raised to 12 and aged for 6 hours to obtain a nickel-cobalt-manganese hydroxide slurry;

[0119] (3) The nickel-cobalt-manganese hydroxide slurry was washed once with a 0.8 mol / L NaOH solution for 30 min, and then washed once with pure water for 1 h. After washing, the filter cake was dried in an oven.

[0120] (4) The dried filter cake is sieved on a 200-400 mesh screen to obtain a nickel-cobalt-manganese precursor having a special structure with a tight inner layer, a loose outer shell, and oriented whiskers, namely nickel-cobalt-manganese hydroxide.

[0121] Compared with Example 2, when the co-precipitation temperature in the first stage of this embodiment is 65°C, the complexing effect of sodium N,N-dicarboxylic acid nitrogen-2-hydroxypropane sulfonate is lower, and the growth rate of the sample is accelerated under high temperature conditions. In addition, the supersaturation in the reactor is relatively high, and the sample grows more densely, forming a tighter core; under the same co-precipitation temperature (40°C) in the second stage, the sample prepared in this embodiment has a slightly larger TD and a slightly smaller BET specific surface area.

[0122] Example 8

[0123] This embodiment provides a method for synthesizing a nickel-cobalt-manganese precursor, comprising the following specific steps:

[0124] (1) Add water to the overflow port of a 500L reactor, and simultaneously start stirring, nitrogen protection, and heating systems. After the temperature rises to 60°C, add alkali solution to control the pH at about 12; then add a mixed solution containing a metal salt and a complexing agent and liquid alkali in parallel, wherein the metal salt is a combination of nickel sulfate, cobalt sulfate, and manganese sulfate, the total ion concentration of nickel, cobalt, and manganese in the mixed solution is 114g / L, the complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate, and the content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 0.5wt% of the target yield of nickel, cobalt, and manganese hydroxide; the flow rate of the mixed solution is 25L / h, the liquid alkali is sodium hydroxide solution, and the flow rate is 10L / h. During the parallel flow process, a nitrogen atmosphere is maintained, and the nitrogen flow rate is 15L / min; after 6h of liquid feeding, the pH value is lowered to 10.0 at a rate of 0.05 / 3h. Under the above conditions, liquid feeding is stopped when the product particle size reaches 2.8μm;

[0125] (2) directly lowering the temperature to 45°C and adding a filter rod to the reactor, then starting the filtration and concentration process and continuing to feed liquid according to the current pH value until the particle size reaches 3.4 μm and then stopping the feeding. After stopping the feeding for 2 hours, the pH value is raised to 12 and aged for 6 hours to obtain a nickel-cobalt-manganese hydroxide slurry;

[0126] (3) The nickel-cobalt-manganese hydroxide slurry was washed once with a 0.8 mol / L NaOH solution for 30 min, and then washed once with pure water for 1 h. After washing, the filter cake was dried in an oven.

[0127] (4) The dried filter cake is sieved on a 200-400 mesh screen to obtain a nickel-cobalt-manganese precursor having a special structure with a tight inner layer, a loose outer shell, and oriented whiskers, namely nickel-cobalt-manganese hydroxide.

[0128] Compared with Example 2, when the co-precipitation temperature in the second stage of this embodiment is 45°C, the complexing effect of sodium N,N-dicarboxylic acid nitrogen-2-hydroxypropane sulfonate is lower, forming a shell that is slightly tighter than the shell of Example 2; when the co-precipitation in the first stage is maintained at the same temperature (60°C) as in Example 2, the sample prepared in this example has a slightly larger TD and a slightly smaller BET specific surface area.

[0129] Comparative Example 1

[0130] This comparative example provides a method for synthesizing a nickel-cobalt-manganese precursor, comprising the following specific steps:

[0131] (1) Add water to the overflow port of a 500L reactor, and simultaneously start stirring, nitrogen protection, and heating systems. After the temperature rises to 60°C, add alkali solution to control the pH at about 12; then add a mixed solution containing a metal salt and a complexing agent and liquid alkali in parallel, wherein the metal salt is a combination of nickel sulfate, cobalt sulfate, and manganese sulfate, the total ion concentration of nickel, cobalt, and manganese in the mixed solution is 114g / L, the complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate, and the content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 0.5wt% of the target yield of nickel, cobalt, and manganese hydroxide; the flow rate of the mixed solution is 25L / h, the liquid alkali is sodium hydroxide solution, and the flow rate is 10L / h. During the parallel flow process, a nitrogen atmosphere is maintained, and the nitrogen flow rate is 15L / min; after 6h of liquid feeding, the pH value is lowered to 10.0 at a rate of 0.05 / 3h. Under the above conditions, liquid feeding is stopped when the product particle size reaches 2.8μm;

[0132] (2) Add a filter rod to the reactor, start suction filtration and concentration, and continue to feed liquid according to the current pH value until the particle size reaches 3.4 μm, then stop feeding liquid. After stopping the liquid feeding for 2 hours, raise the pH value to 12 and age for 6 hours to obtain nickel cobalt manganese hydroxide slurry;

[0133] (3) washing the nickel-cobalt-manganese hydroxide slurry with a 0.8 mol / L NaOH solution once for 30 min, and then washing it with pure water once for 1 h. After washing, drying the filter cake in an oven;

[0134] (4) The dried filter cake is sieved on a 200-400 mesh sieve to obtain a densely packed nickel-cobalt-manganese precursor prepared by a batch method at high temperature, namely nickel-cobalt-manganese hydroxide.

[0135] The morphological and structural characteristics of the nickel-cobalt-manganese precursor obtained in this comparative example are shown in Figure 7, with the left image being a SEM image and the right image being a CP image. As can be seen from the figures, the sample synthesized under high temperature conditions throughout the experiment exhibits a densely packed morphology of thick, strip-like primary particles. Its cross-sectional view shows densely packed particles with no hollow structures and no apparent gaps between the primary particles. Compared to Example 2, the sample synthesized under high temperature conditions exhibits a continuous, dense layer structure with a higher TD and a smaller BET.

[0136] Comparative Example 2

[0137] This comparative example provides a method for synthesizing a nickel-cobalt-manganese precursor, comprising the following specific steps:

[0138] (1) Add water to the overflow port of a 500L reactor, and simultaneously start the stirring, nitrogen protection and heating systems. After the temperature rises to 40°C, add alkali solution to control the pH at about 12; then add a mixed solution containing a metal salt and a complexing agent and liquid alkali in parallel, wherein the metal salt is a combination of nickel sulfate, cobalt sulfate and manganese sulfate, the total ion concentration of nickel, cobalt and manganese in the mixed solution is 114g / L, the complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate, and the content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 0.5wt% of the target yield of nickel, cobalt and manganese hydroxide, the flow rate of the mixed solution is 25L / h, the liquid alkali is sodium hydroxide solution, the flow rate is 10L / h, and a nitrogen atmosphere is maintained during the parallel flow process, with a nitrogen flow rate of 15L / min; after 6h of liquid infusion, the pH value is lowered to 10.0 at a rate of 0.05 / 3h;

[0139] (2) When the particle size reaches 2.8 μm under the above conditions, a filter rod is added to the reactor for suction filtration and concentration. When the particle size reaches 3.4 μm, the liquid feed is stopped, and the liquid level is maintained near the overflow port during the suction filtration process; after stopping the liquid feed for 2 hours, the pH value is raised to 12 and aged for 6 hours to obtain a nickel-cobalt-manganese hydroxide slurry;

[0140] (3) washing the nickel-cobalt-manganese hydroxide slurry with a 0.8 mol / L NaOH solution once for 30 min, and then washing it with pure water once for 1 h. After washing, drying the filter cake in an oven;

[0141] (4) The dried filter cake is sieved on a 200-400 mesh sieve to obtain a nickel-cobalt-manganese precursor with loose whisker stacking prepared under low temperature conditions, namely nickel-cobalt-manganese hydroxide.

[0142] The morphological and structural characteristics of the nickel-cobalt-manganese precursor produced in this comparative example are shown in Figure 8, where the left figure is a SEM image and the right figure is a CP image. As can be seen from the figures, the sample synthesized under low temperature conditions throughout the experiment has fine primary particles and a loosely packed morphology, with obvious gaps between the particles in its cross-sectional view. Compared with Example 2, the sample synthesized under low temperature conditions has a loose layered structure, a smaller TD, and a larger BET specific surface area.

[0143] Comparative Example 3

[0144] This comparative example provides a method for synthesizing a nickel-cobalt-manganese precursor, comprising the following specific steps:

[0145] (1) Add water to the overflow port of a 500L reactor, and simultaneously start the stirring, nitrogen protection and heating systems. After the temperature rises to 60°C, add alkali solution to control the pH at about 12; then add a metal salt solution and liquid alkali in parallel, wherein the metal salt is a combination of nickel sulfate, cobalt sulfate and manganese sulfate, and the total ion concentration of nickel, cobalt and manganese in the mixed solution is 114g / L, the flow rate of the metal salt solution is 25L / h, and the liquid alkali is a sodium hydroxide solution with a flow rate of 10L / h. During the parallel flow process, a nitrogen atmosphere is maintained, and the nitrogen flow rate is 15L / min. After 6 hours of liquid addition, the pH value is lowered to 10.0 at a rate of 0.05 / 3h. After reaching a certain particle size, the temperature is lowered to 40°C, and then the pH value is adjusted to control the particle size to around 3.4μm;

[0146] (2) After reaching the target particle size, the material is collected and the prepared product is connected to an aging tank, stirred at the same time, and an alkali solution is added to a pH of 12 and then aged for 6 hours. After the aging is completed, a nickel-cobalt-manganese hydroxide slurry is obtained;

[0147] (3) washing the nickel-cobalt-manganese hydroxide slurry with a 0.8 mol / L NaOH solution once for 30 min, and then washing it with pure water once for 1 h. After washing, drying the filter cake in an oven;

[0148] (4) The dried filter cake is sieved on a 200-400 mesh sieve to obtain a nickel-cobalt-manganese precursor, namely nickel-cobalt-manganese hydroxide, prepared by a conventional continuous method without adding sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate.

[0149] The morphological and structural characteristics of the nickel-cobalt-manganese precursor finally obtained in this comparative example are shown in Figure 9, where the left figure is a SEM image and the right figure is a CP image. It can be seen from the figure that if the complexing agent (i.e., sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate) is not added, the primary particles are finer and the sphericity is poor. The internal stacking in its cross-sectional view is relatively dense, its TD is higher than that of Comparative Example 2, there are obvious pores between the external primary particles, and the BET is larger.

[0150] Physical and chemical indicators:

[0151] The nickel-cobalt-manganese hydroxides prepared in the above examples and comparative examples were tested for physical and chemical indicators, including BET specific surface area, tap density TD, S content, and particle size D50.

[0152] The test results are shown in Table 1.

[0153] Table 1

[0154] analyze:

[0155] As can be seen from the above table, the BET specific surface area and tap density TD of the sample are related to the compactness of the primary particle packing of the sample. The primary particles are loosely packed, and the corresponding BET specific surface area is large and the TD is small. Conversely, the BET specific surface area is small and the TD is large. This can be seen in Comparative Examples 1-3. In Examples 1-3 and 6-8, by constructing a structure with a compact core, a loose shell, and an orientationally arranged shell whisker, a sample with both a large TD and a large BET specific surface area can be obtained. In particular, the orientationally arranged whiskers can maintain the large TD brought by the compact internal crystal core and increase the BET specific surface area of ​​the sample. Among them, when the addition amount of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 0.5wt%, the synergistic effect of BET specific surface area and TD is better. This shows that the process disclosed in the present invention can obtain a nickel-cobalt-manganese precursor with excellent physical indicators such as BET specific surface area, TD, and S content by constructing a structure with a compact core, a loose shell, and an orientationally arranged whisker.

[0156] It can be seen from the data results of Example 2 and Example 4-5 that if the mass fraction of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is too low, the sample will be precipitated directly, avoiding the intermediate step of complexation, and the primary particles thus generated will be coarse and tightly packed. Under this condition, the TD of the sample is large and the BET specific surface area is small; if the mass fraction of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is too high, metal ion complexation will greatly reduce the supersaturation in the kettle, resulting in loose stacking of the primary particles of the sample, smaller TD, and a larger BET specific surface area.

[0157] It can be seen from the data results of Example 2 and Comparative Examples 1-3 that under high temperature conditions throughout the process, the complexing ability of metal ions caused by the esterification reaction of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate at high temperature is greatly reduced, the supersaturation is high, and a tighter stacking is formed, resulting in a larger TD and a smaller BET specific surface area; under low temperature conditions throughout the process, sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate complexes more metals, resulting in a lower supersaturation, which will cause the primary particles to be finer and loosely stacked, resulting in a larger BET specific surface area and a smaller TD; without the addition of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate, the sphericity of the sample is poor, and the TD and BET specific surface area are between Comparative Examples 1 and 3. Compared with Example 2, the sample is unevenly precipitated in the absence of a complexing agent, resulting in poor sphericity.

Claims

1. A method for synthesizing a ternary precursor, comprising: Adding a mixed solution containing metal salts and a complexing agent and liquid alkali into a reaction vessel in a co-current manner to carry out a first co-precipitation reaction. After the reaction product grows to the target particle size, the reaction temperature is adjusted to carry out a second co-precipitation reaction, and the ternary precursor is obtained after aging; wherein, the complexing agent includes sodium N,N-dicarboxyamino-2-hydroxypropylsulfonate.

2. The synthesis method according to claim 1, wherein, Based on the target output of the ternary precursor being 100%, the mass fraction of the complexing agent is 0.1-1.0%.

3. The synthesis method according to claim 1 or 2, wherein, The temperature of the first co-precipitation reaction is 55-65°C.

4. The synthesis method according to any one of claims 1-3, wherein, The pH value of the first co-precipitation reaction is 10-12.

5. The synthesis method according to any one of claims 1-4, wherein, The target particle size is 2.0-2.8 μm.

6. The synthesis method according to any one of claims 1-5, wherein, The temperature of the second co-precipitation reaction is 40-45°C.

7. The synthesis method according to any one of claims 1-6, wherein, After the second co-precipitation reaction, the particle size of the reaction product is 3.45-3.80 μm.

8. The synthesis method according to any one of claims 1-7, wherein, The temperature of the aging is the same as the temperature of the second co-precipitation reaction.

9. The synthesis method according to any one of claims 1-8, wherein, The pH value of the aging is higher than the pH value of the second co-precipitation reaction.

10. The synthesis method according to any one of claims 1-9, wherein, The aging time is 6-8 h.

11. The synthesis method according to any one of claims 1-10, wherein, The synthesis method specifically includes: (1) Adding water into a reaction vessel, heating to 60°C in a nitrogen atmosphere under stirring conditions, and then adding an alkali solution to obtain a bottom solution with a pH value of 10-12; (2) Adding a mixed solution containing metal salts and a complexing agent and liquid alkali into a reaction vessel in a co-current manner to carry out a first co-precipitation reaction. After the reaction product grows to 2.0-2.8 μm, the reaction temperature is lowered to carry out a second co-precipitation reaction. After aging, solid-liquid separation, washing, drying, and sieving are carried out in sequence to obtain the ternary precursor, wherein the complexing agent includes sodium N,N-dicarboxyamino-2-hydroxypropylsulfonate.

12. A ternary precursor prepared by the synthesis method according to any one of claims 1-11.

13. The ternary precursor according to claim 12, wherein, The ternary precursor includes a core and a shell, the compactness of the core is higher than that of the shell, and the whiskers of the shell are arranged in an oriented manner.

14. A cathode material obtained by mixing and sintering the ternary precursor according to claim 12 or 13 and a lithium source.

15. A lithium-ion battery comprising the cathode material according to claim 14.

Images