A ternary precursor, its synthesis method and application

Abstract

This disclosure provides a ternary precursor, its synthesis method, and its application. The synthesis method includes: adding a mixed solution containing a metal salt and a complexing agent and liquid alkali concurrently to a reaction vessel for a first coprecipitation reaction; after the reaction product grows to the target particle size, adjusting the reaction temperature to carry out a second coprecipitation reaction; and aging to obtain the nickel-cobalt-manganese precursor; wherein the complexing agent includes sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate. This disclosure uses sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate as a complexing agent, utilizing its different complexing abilities for metal ions under high and low temperature conditions to adjust the morphology of the sample, thereby synthesizing a product with dense internal primary particle packing, loose external morphology, and oriented whisker shell. This product can simultaneously possess the characteristics of large BET specific surface area, high TD, and low impurity content.

Description

Technical Field

[0001] This disclosure belongs to the field of battery technology and relates to a ternary precursor, its synthesis method and application. Background Technology

[0002] Developing high-energy-density lithium-ion batteries (LIBs) to meet the growing demand of the electric vehicle market is a global priority. One effective strategy for increasing the energy density of lithium-ion batteries is to improve battery capacity, which primarily depends on the cathode material. Common cathode materials include lithium nickel manganese cobalt oxide (LiNi). x Co y Mn z O2), lithium iron phosphate or lithium cobalt oxide, etc. Among them, lithium iron phosphate and lithium cobalt oxide are limited in application due to problems such as relatively low capacity. The current market is still dominated by ternary cathode material - lithium nickel cobalt manganese oxide.

[0003] Lithium nickel cobalt manganese oxide is obtained by sintering a mixture of lithium nickel cobalt manganese hydroxide, a ternary precursor. During its charge and discharge process, Li... + The volume expansion and contraction caused by insertion / extraction 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 elemental doping, surface coating, and electrolyte optimization. However, these research results have not been able to achieve industrial application due to problems in cost control and quality consistency.

[0004] The electrochemical performance of ternary cathode materials is related to various precursor parameters, including size, BET specific surface area, tap density (TD), morphology, and impurity content (e.g., sulfur). Generally, a larger BET specific 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. Lower impurity content enhances 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 cannot simultaneously satisfy the three characteristics of low sulfur impurity content, high tap density, and high BET specific surface area. Patent CN115180659A discloses a shell structure with a dense internal network and a loose radial shell. This sample has the characteristic of large BET, but its TD is relatively low, which is not conducive to improving the energy density of the battery. In addition, the above patents use high-concentration ammonia water 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 simultaneously possess a large BET specific surface area, high TD, and low sulfur impurity content, while allowing production without additional ventilation equipment. Summary of the Invention

[0007] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0008] To address the shortcomings of existing technologies, the present disclosure aims to provide a ternary precursor, its synthesis method, and its applications. This disclosure uses sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate as a complexing agent. The morphology of the product is adjusted by utilizing its varying complexing abilities for metal ions under high and low temperature conditions. Desulfurization is achieved through an aging process, thereby synthesizing a precursor with densely packed internal primary particles, a loose external morphology, and an oriented whisker shell. This precursor simultaneously possesses a large BET specific surface area, high TD (dimethylsulfate) content, and low sulfur impurity content.

[0009] To achieve this objective, the present disclosure adopts the following technical solution:

[0010] In a first aspect, this disclosure provides a method for synthesizing a ternary precursor, the method comprising:

[0011] A mixed solution containing metal salt and complexing agent is added to a reaction vessel in parallel with liquid alkali to carry out the first coprecipitation reaction. After the reaction product grows to the target particle size, the reaction temperature is adjusted to carry out the second coprecipitation reaction. After aging, the ternary precursor is obtained.

[0012] The complexing agent includes sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate.

[0013] The crystallization process of ternary precursor precipitation mainly depends on supersaturation, i.e., the reaction with metal ions and OH-. - The concentration is related to the crystal growth rate. When the supersaturation is high, nucleation is more likely. At this time, under the action of a complexing agent under certain conditions, some metal ions are complexed and the supersaturation is moderately reduced, thereby regulating the growth rate of the crystal and further affecting the morphology and other physical properties of the crystal.

[0014] In this disclosure, the ternary precursors include, but are not limited to, nickel-cobalt-manganese ternary precursors (i.e., nickel-cobalt-manganese hydroxide).

[0015] This disclosure provides a method for synthesizing a ternary precursor, using sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate as a complexing agent. The morphology of the product is controlled by utilizing the different complexing abilities of sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate for metal ions under high and low temperature conditions. Desulfurization is carried out through an aging step, thereby synthesizing a precursor with dense internal primary particle packing, loose external morphology, and oriented whisker shell. This precursor can simultaneously possess the characteristics of large BET specific surface area, high TD, and low sulfur impurity content.

[0016] 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.

[0017] In one embodiment, the liquid alkali comprises sodium hydroxide.

[0018] In one embodiment, with a target yield of 100% for the ternary precursor, 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.

[0019] In this 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 internal growth of the particles will be dense; if the mass fraction of the complexing agent is too high, the supersaturation will be low, the particles will be loosely packed, the primary particles will be fine, and they may even be unable to aggregate into secondary spheres.

[0020] In one embodiment, the temperature of the first coprecipitation reaction is 55-65°C, for example, it can be 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C or 65°C.

[0021] In this disclosure, when the temperature of the first coprecipitation reaction is controlled at 55-65°C, the resulting precursor can simultaneously have a high tap density and a high BET specific surface area.

[0022] In one embodiment, the pH value of the first coprecipitation reaction is 10-12, for example, it can be 10, 10.5, 11, 11.5 or 12.

[0023] In this disclosure, the high-temperature, high-alkali process conditions of the first co-precipitation reaction can significantly reduce the sulfur content, which is beneficial to improving the electrochemical performance of the cathode material. The supersaturation within this pH range is suitable for particle growth, which is conducive to the compact packing of the sample, resulting in long, coarse strips and improving its tap density.

[0024] In one embodiment, the target particle size is 2.0-2.8 μm, for example, it can be 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, etc.

[0025] In this disclosure, the target particle size of the reaction product after the first coprecipitation reaction is controlled to be 2.0-2.8 μm, which ensures the sphericity of the core and thus the sphericity of the sample after the second coprecipitation. This is beneficial for improving the compaction density of the sample. If the particle size is too small, the surface energy of the small particle sample is relatively high, and the smaller the particle, the easier it is to agglomerate, resulting in poor sphericity and affecting its compaction density.

[0026] 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.

[0027] In this disclosure, after the reaction product grows to the target particle size, the reaction temperature is lowered to carry out a second coprecipitation reaction. When the temperature of the second coprecipitation reaction is controlled at 40-45℃, the resulting precursor can simultaneously have a high tap density and a high BET specific surface area.

[0028] This disclosure uses sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate as a complexing agent. The mechanism and effect of regulating the morphology by adjusting the reaction temperature are as follows:

[0029] Under the high-temperature conditions of the first coprecipitation reaction, the esterification reaction of sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate reduces the number of complexation sites, resulting in poor complexation ability for metal ions. During this stage, crystal growth and nucleation occur simultaneously within the reaction vessel, facilitating the synthesis of primary particles and their growth into coarse, tightly packed morphologies. These particles exhibit a large density (TD), which is beneficial for increasing the material's compaction density. After obtaining the tightly packed nuclei through the first coprecipitation reaction, the reaction temperature is lowered. During the second coprecipitation 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 supersaturation, the sample is only in the growth stage, continuing to grow at the sites on the surface of the core. During this stage, due to the different growth rates of various crystal faces, this difference is more pronounced at lower supersaturation, resulting in the transformation of the coarse, dense core into a loose shell with whisker-oriented morphology. This loose shell with whisker-oriented morphology and the densely packed core give the precursor both high TD and a large BET. Simultaneously, the precursor with a large BET surface area can lower the sintering temperature at the later stage, reducing costs to some extent.

[0030] In one embodiment, after the second coprecipitation reaction, the particle size of the reaction product is 3.45-3.80 μm, for example, it can be 3.45 μm, 3.52 μm or 3.80 μm.

[0031] In this disclosure, the particle size of the reaction product after the second coprecipitation reaction is controlled to be 3.45-3.80 μm. The small particle size range means that the sintering temperature required for small particles is low, resulting in excellent low-temperature performance. Furthermore, the particle size is also small after being prepared into a positive electrode material at the downstream end, which can achieve high rate capability and improve cycle performance. This is because the small particle material has a short Li ion transport distance during discharge, resulting in good rate capability. In addition, the small particles can alleviate the microcracks caused by volume expansion and contraction during charge and discharge, thereby improving cycle performance.

[0032] In one embodiment, the aging temperature is 40-45°C, for example, it can be 40°C, 41°C, 42°C, 43°C, 44°C or 45°C.

[0033] In one embodiment, the aging temperature is the same as the temperature of the second coprecipitation reaction.

[0034] In this disclosure, when the aging temperature is the same as the temperature of the second coprecipitation reaction, the potential risks to the sample morphology caused by factors such as increased temperature can be avoided, such as the formation of micropowder on the surface.

[0035] In one embodiment, the pH value of the aging process is 11-12, for example, it can be 11, 11.5 or 12.

[0036] In one embodiment, the pH value of the aging process is higher than the pH value of the second coprecipitation reaction.

[0037] According to Fajans' adsorption rule, crystals will preferentially adsorb OH-. - It displaces sulfate ions, and then OH... - The ions diffuse into the interior of the crystal to complete the crystal transformation, and sulfate ions are replaced by adsorbed ions on the crystal surface. In this disclosure, after crystal crystallization, the OH- in the mother liquor... - The sulfur dioxide has been largely depleted, and the aging process requires the addition of alkali solution to achieve desulfurization. When the pH value of the aging process is higher than that of the second coprecipitation reaction, OH- is added... - It can re-enter the crystal and displace the encapsulated sulfate ions.

[0038] 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.

[0039] In this disclosure, when the aging time is controlled at 6-8 hours, sulfur trapped and adsorbed in the precursor can be displaced. If the aging time is too short, the desulfurization effect will be poor; if the aging time is too long, the removal of sulfur content in the sample has reached its limit, and continuing aging will affect experimental efficiency and waste resources.

[0040] As an optional technical solution of this disclosure, the synthesis method specifically includes:

[0041] (1) Add water to the reaction vessel and heat it to 60°C under a nitrogen atmosphere while stirring. Then add alkaline solution to obtain a bottom solution with a pH value of 10-12 (e.g., 10, 10.5, 11, 11.5 or 12).

[0042] (2) A mixed solution containing metal salt and complexing agent is added to a reaction vessel in parallel with liquid alkali to carry out the first coprecipitation reaction. After the reaction product grows to 2.0-2.8 μm, the reaction temperature is lowered to carry out the second coprecipitation 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-dicarboxylic acid amino-2-hydroxypropanesulfonate.

[0043] In one embodiment, the solid-liquid separation method includes centrifugation.

[0044] In one embodiment, the washing specifically includes: first washing with a 0.5-0.8 mol / L NaOH solution (e.g., 0.6 mol / L, 0.65 mol / L, or 0.7 mol / L, etc.), and then washing with pure water.

[0045] In one embodiment, the drying temperature is 80-120°C, for example, 80°C, 90°C, 100°C or 110°C, and the drying time is 16-20 hours, for example, 16 hours, 17 hours, 18 hours or 19 hours.

[0046] In one embodiment, the sieve mesh size is 200-400 mesh, for example, it can be 200 mesh, 300 mesh or 400 mesh, etc.

[0047] Secondly, this disclosure provides a ternary precursor, which is prepared by the synthesis method described in the first aspect.

[0048] In one embodiment, the ternary precursor includes a core and a shell, wherein the core has a higher density than the shell, and the shell has whiskers arranged in an oriented manner.

[0049] In this disclosure, the ternary precursor obtained has a morphology of being compact inside and loose outside, with a dense core and a loose outer shell with whiskers arranged in an oriented manner.

[0050] In one embodiment, the tap density of the ternary precursor is 1.68-2.03 g / cm³. 3 For example, it could be 1.7 g / cm³ 3 1.8g / cm 3 1.9g / cm 3 2g / cm 3 wait.

[0051] In one embodiment, the BET specific surface area of ​​the ternary precursor is 17-20 m². 2 / g, for example, could be 17m 2 / g、18m 2 / g、19m 2 / g or 20m 2 / g etc.

[0052] In one embodiment, the sulfur content in the ternary precursor is 368-562 ppm, for example, it can be 368 ppm, 370 ppm, 380 ppm, 400 ppm, 450 ppm, 500 ppm or 562 ppm, etc.

[0053] Thirdly, this disclosure provides a cathode material, which is obtained by sintering the ternary precursor and lithium source as described in the second aspect.

[0054] In one embodiment, the positive electrode material has the chemical formula LiNi. x Co y Mn z O2, where x≥0.2, x+y+z=1.

[0055] Fourthly, this 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.

[0056] The numerical range described in this 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 brevity, this disclosure will not exhaustively list the specific point values ​​included in the range.

[0057] Compared with the prior art, the beneficial effects of this disclosure are as follows:

[0058] (1) This disclosure provides a method for synthesizing a ternary precursor, using sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate as a complexing agent. The morphology of the product is controlled by utilizing the different complexing abilities of sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate under high and low temperature conditions. Desulfurization is carried out through an aging step, thereby synthesizing a precursor with dense internal primary particle packing, loose external morphology and oriented whisker shell. This precursor can simultaneously have the characteristics of large BET specific surface area, high TD and low sulfur impurity content.

[0059] (2) The tap density of the ternary precursor prepared in this disclosure is 1.68-2.03 g / cm³. 3 The BET specific surface area of ​​the ternary precursor is 17-20 m². 2 / g; the sulfur content in the ternary precursor is 356-562ppm.

[0060] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0061] The accompanying drawings are used to provide a further understanding of the technical solutions in this paper and form part of the specification. They are used together with the embodiments of this application to explain the technical solutions in this paper and do not constitute a limitation on the technical solutions in this paper.

[0062] Figure 1 The images shown are SEM and CP images of the product obtained in step (1) of Embodiment 1 of this disclosure.

[0063] Figure 2 The images shown are SEM and CP images of the nickel-cobalt-manganese precursor prepared in Example 1 of this disclosure.

[0064] Figure 3 The images shown are SEM and CP images of the product obtained in step (1) of Embodiment 2 of this disclosure.

[0065] Figure 4 The images shown are SEM and CP images of the nickel-cobalt-manganese precursor prepared in Example 2 of this disclosure.

[0066] Figure 5 The images shown are SEM and CP images of the product obtained in step (1) of Embodiment 3 of this disclosure.

[0067] Figure 6 The images shown are SEM and CP images of the nickel-cobalt-manganese precursor prepared in Example 3 of this disclosure.

[0068] Figure 7 The images shown are SEM and CP images of the nickel-cobalt-manganese precursor prepared in Comparative Example 1 of this disclosure.

[0069] Figure 8 The images shown are SEM and CP images of the nickel-cobalt-manganese precursor prepared in Comparative Example 2 of this disclosure.

[0070] Figure 9 The images shown are SEM and CP images of the nickel-cobalt-manganese precursor prepared in Comparative Example 3 of this disclosure. Detailed Implementation

[0071] The technical solution of this disclosure will be further illustrated below through specific implementation methods.

[0072] Example 1

[0073] This embodiment provides a method for synthesizing a nickel-cobalt-manganese precursor, including the following specific steps:

[0074] (1) Add water to the 500L reactor to the overflow port, and simultaneously turn on the stirring, nitrogen protection and heating system. After the temperature rises to 60℃, add alkali solution to control the pH value at about 12. Then add a mixed solution containing metal salt and complexing agent and liquid alkali in parallel flow. The metal salt is a combination of nickel sulfate, cobalt sulfate and manganese sulfate. The total concentration of nickel, cobalt and manganese ions in the mixed solution is 114 g / L. The complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate. The content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 0.1 wt% of the target yield of nickel, cobalt and manganese hydroxide. The flow rate of the mixed solution is 25 L / h. The liquid alkali is sodium hydroxide solution with a flow rate of 10 L / h. Maintain a nitrogen atmosphere during the parallel flow process with a nitrogen flow rate of 15 L / min. After 6 h of liquid injection, adjust the pH value to 10.0 at a rate of 0.05 / 3 h. Stop liquid injection when the product particle size reaches 2.8 μm under the above conditions.

[0075] (2) The temperature was directly lowered to 40℃ and a filter rod was added to the reactor. After the set temperature was reached, the vacuum filtration and concentration were started, and the liquid was fed in at the current pH value until the particle size reached 3.4μm. The feeding was stopped. After stopping the feeding for 2 hours, the pH value was raised to 12 and aged for 6 hours to obtain nickel cobalt manganese hydroxide slurry.

[0076] (3) Wash the nickel-cobalt-manganese hydroxide slurry once with 0.8 mol / L NaOH solution for 30 min, then wash it once with pure water for 1 h. After washing, dry the filter cake in an oven.

[0077] (4) After the dried filter cake is sieved through a 200-400 mesh screen, a nickel-cobalt-manganese precursor with a special structure of a compact core, a loose outer shell, and an oriented arrangement of whiskers can be obtained, namely nickel-cobalt-manganese hydroxide.

[0078] The morphological and structural characteristics of the product obtained in step (1) of this embodiment are as follows: Figure 1As shown in the figure, the left image is a SEM image, and the right image is a CP image (i.e., a cross-sectional SEM image of the sample). It can be seen from the images that the crystal nuclei synthesized under high-temperature conditions are tightly packed strip-shaped primary particles. The cross-sectional image shows a dense internal packing with no hollow structures, and no obvious gaps between the primary particles. This tightly packed structure is the reason for its high TD (dielectric density). The morphological and structural characteristics of the nickel-cobalt-manganese precursor finally obtained in this embodiment are as follows: Figure 2 As shown in the figure, the left image is a SEM image and the right image is a CP image. It can be seen from the figures that under the action of 0.1 wt% complexing agent (i.e., sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate), after the temperature is reduced, the strip-shaped primary particles on the surface are transformed into thin primary particles, and the primary particles are oriented. The cross-sectional view shows that the internal structure is a tightly packed core and a loosely packed shell. After the temperature is reduced, 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.

[0079] Example 2

[0080] This embodiment provides a method for synthesizing a nickel-cobalt-manganese precursor, including the following specific steps:

[0081] (1) Add water to the 500L reactor to the overflow port, and simultaneously turn on the stirring, nitrogen protection and heating system. After the temperature rises to 60℃, add alkali solution to control the pH at about 12. Then add a mixed solution containing metal salt and complexing agent and liquid alkali in parallel flow. The metal salt is a combination of nickel sulfate, cobalt sulfate and manganese sulfate. The total concentration of nickel, cobalt and manganese ions in the mixed solution is 114 g / L. The complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate. The content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 0.5 wt% of the target yield of nickel, cobalt and manganese hydroxide. The flow rate of the mixed solution is 25 L / h. The liquid alkali is sodium hydroxide solution with a flow rate of 10 L / h. Maintain a nitrogen atmosphere during the parallel flow process with a nitrogen flow rate of 15 L / min. After 6 h of liquid injection, adjust the pH value to 10.0 at a rate of 0.05 / 3 h. Stop liquid injection when the product particle size reaches 2.8 μm under the above conditions.

[0082] (2) The temperature was directly lowered to 40℃ and a filter rod was added to the reactor. Then, the vacuum filtration was started for concentration, and the liquid was fed in at the current pH value until the particle size reached 3.4 μm. After stopping the liquid feeding for 2 hours, the pH value was raised to 12 and aged for 6 hours to obtain nickel-cobalt-manganese hydroxide slurry.

[0083] (3) Wash the nickel-cobalt-manganese hydroxide slurry once with 0.8 mol / L NaOH solution for 30 min, then wash it once with pure water for 1 h. After washing, dry the filter cake in an oven.

[0084] (4) After the dried filter cake is sieved through a 200-400 mesh screen, a nickel-cobalt-manganese precursor with a special structure of a tight inner layer, a loose outer shell, and an oriented arrangement of whiskers can be obtained, namely nickel-cobalt-manganese hydroxide.

[0085] The morphological and structural characteristics of the product obtained in step (1) of this embodiment are as follows: Figure 3 As shown in the figure, the left image is a SEM image, and the right image is a CP (sample cross-sectional SEM) image. It can be seen from the figures that with the increase of the complexing agent (i.e., sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate), the primary particles of the crystal nuclei prepared under high-temperature conditions are more densely packed, but the density is slightly lower than in Example 1. The cross-sectional image shows that the internal packing is dense, with no obvious gaps between the primary particles, showing no significant difference from Example 1. The morphological and structural characteristics of the nickel-cobalt-manganese precursor finally obtained in this example are as follows: Figure 4 As shown, the left image is a SEM image and the right image is a CP image. It can be seen from the images that after the temperature is reduced, the strip-shaped primary particle layer transforms into a thinner primary particle orientation arrangement, and the morphology is more porous than that of Example 1. As a result, its TD is slightly lower than that of Example 1. The cross-sectional image shows that the pores between the primary particles in the shell are larger, which gives the sample a larger BET specific surface area.

[0086] Example 3

[0087] This embodiment provides a method for synthesizing a nickel-cobalt-manganese precursor, including the following specific steps:

[0088] (1) Add water to the 500L reactor to the overflow port, and simultaneously turn on the stirring, nitrogen protection and heating system. After the temperature rises to 60℃, add alkali solution to control the pH at about 12. Then add a mixed solution containing metal salt and complexing agent and liquid alkali in parallel flow. The metal salt is a combination of nickel sulfate, cobalt sulfate and manganese sulfate. The total concentration of nickel, cobalt and manganese ions in the mixed solution is 114 g / L. The complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate. The content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 1.0 wt% of the target yield of nickel, cobalt and manganese hydroxide. The flow rate of the mixed solution is 25 L / h. The liquid alkali is sodium hydroxide solution with a flow rate of 10 L / h. Maintain a nitrogen atmosphere during the parallel flow process with a nitrogen flow rate of 15 L / min. After 6 h of liquid injection, adjust the pH value to 10.0 at a rate of 0.05 / 3 h. Stop liquid injection when the product particle size reaches 2.8 μm under the above conditions.

[0089] (2) The temperature was directly lowered to 40℃ and a filter rod was added to the reactor. Then, the vacuum filtration was started for concentration, and the liquid was fed in at the current pH value until the particle size reached 3.4 μm. After stopping the liquid feeding for 2 hours, the pH value was raised to 12 and aged for 6 hours to obtain nickel-cobalt-manganese hydroxide slurry.

[0090] (3) Wash the nickel-cobalt-manganese hydroxide slurry once with 0.8 mol / L NaOH solution for 30 min, then wash it once with pure water for 1 h. After washing, dry the filter cake in an oven.

[0091] (4) After the dried filter cake is sieved through a 200-400 mesh screen, a nickel-cobalt-manganese precursor with a special structure of a tight inner layer, a loose outer shell, and an oriented arrangement of whiskers can be obtained, namely nickel-cobalt-manganese hydroxide.

[0092] The morphological and structural characteristics of the product obtained in step (1) of this embodiment are as follows: Figure 5 As shown in the figure, the left image is a SEM image, and the right image is a CP image. It can be seen from the figures that with a higher complexing agent content, the primary particles synthesized under high temperature conditions are arranged in strip-like shapes, which are more loosely packed than in Example 2. Scattered pores can be observed in the cross-sectional image, which is caused by insufficient compaction of the primary particles. The morphological and structural characteristics of the nickel-cobalt-manganese precursor finally obtained in this example are as follows: Figure 6 As shown in the figure, the left image is a SEM image and the right image is a CP image. It can be seen from the images that under high complexing agent content, after lowering the temperature, the strip-shaped primary particles transform into a thinner, more oriented primary particle layer. Compared to Examples 1 and 2, the pores between the primary particles are larger, and the packing is more loose. The more porous shell can also be observed in its cross-sectional image. Therefore, the TD of this sample is smaller than that of Examples 1 and 2, and the BET specific surface area is larger.

[0093] Example 4

[0094] This embodiment provides a method for synthesizing a nickel-cobalt-manganese precursor, including the following specific steps:

[0095] (1) Add water to the 500L reactor to the overflow port, and simultaneously turn on the stirring, nitrogen protection and heating system. After the temperature rises to 60℃, add alkali solution to control the pH at about 12. Then add a mixed solution containing metal salt and complexing agent and liquid alkali in parallel flow. The metal salt is a combination of nickel sulfate, cobalt sulfate and manganese sulfate. The total concentration of nickel, cobalt and manganese ions in the mixed solution is 114 g / L. The complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate. The content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 0.05 wt% of the target yield of nickel, cobalt and manganese hydroxide. The flow rate of the mixed solution is 25 L / h. The liquid alkali is sodium hydroxide solution with a flow rate of 10 L / h. Maintain a nitrogen atmosphere during the parallel flow process with a nitrogen flow rate of 15 L / min. After 6 h of liquid injection, adjust the pH value to 10.0 at a rate of 0.05 / 3 h. Stop liquid injection when the product particle size reaches 2.8 μm under the above conditions.

[0096] (2) The temperature was directly lowered to 40℃ and a filter rod was added to the reactor. Then, the vacuum filtration was started for concentration, and the liquid was fed in at the current pH value until the particle size reached 3.4 μm. After stopping the liquid feeding for 2 hours, the pH value was raised to 12 and aged for 6 hours to obtain nickel-cobalt-manganese hydroxide slurry.

[0097] (3) Wash the nickel-cobalt-manganese hydroxide slurry once with 0.8 mol / L NaOH solution for 30 min, then wash it once with pure water for 1 h. After washing, dry the filter cake in an oven.

[0098] (4) After the dried filter cake is sieved through a 200-400 mesh screen, a nickel-cobalt-manganese precursor with a special structure of a tight inner layer, a loose outer shell, and an oriented arrangement of whiskers can be obtained, namely nickel-cobalt-manganese hydroxide.

[0099] The sample prepared in this embodiment, synthesized under low complexing agent and high temperature conditions, had relatively coarse primary particles and dense packing. Under high temperature conditions, the complexing effect decreased, and further reducing the amount of complexing agent resulted in even denser primary particle growth. Later, as the temperature was lowered and growth continued, the complexing effect of the complexing agent increased under low temperature conditions, causing the primary particles to become finer in their strip-like morphology and looser in their packing, forming a shell that was looser than the core. However, the low complexing agent content resulted in little difference between the core and shell. Compared to Example 1, this sample exhibited a denser overall packing.

[0100] Example 5

[0101] This embodiment provides a method for synthesizing a nickel-cobalt-manganese precursor, including the following specific steps:

[0102] (1) Add water to the 500L reactor to the overflow port, and simultaneously turn on the stirring, nitrogen protection and heating system. After the temperature rises to 60℃, add alkali solution to control the pH at about 12. Then add a mixed solution containing metal salt and complexing agent and liquid alkali in parallel flow. The metal salt is a combination of nickel sulfate, cobalt sulfate and manganese sulfate. The total concentration of nickel, cobalt and manganese ions in the mixed solution is 114 g / L. The complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate. The content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 1.5 wt% of the target yield of nickel, cobalt and manganese hydroxide. The flow rate of the mixed solution is 25 L / h. The liquid alkali is sodium hydroxide solution with a flow rate of 10 L / h. Maintain a nitrogen atmosphere during the parallel flow process with a nitrogen flow rate of 15 L / min. After 6 h of liquid injection, lower the pH value to 10.0 at a rate of 0.05 / 3 h. Stop liquid injection when the product particle size reaches 2.8 μm under the above conditions.

[0103] (2) The temperature was directly lowered to 40℃ and a filter rod was added to the reactor. Then, the vacuum filtration was started for concentration, and the liquid was fed in at the current pH value until the particle size reached 3.4 μm. After stopping the liquid feeding for 2 hours, the pH value was raised to 12 and aged for 6 hours to obtain nickel-cobalt-manganese hydroxide slurry.

[0104] (3) Wash the nickel-cobalt-manganese hydroxide slurry once with 0.8 mol / L NaOH solution for 30 min, then wash it once with pure water for 1 h. After washing, dry the filter cake in an oven.

[0105] (4) After the dried filter cake is sieved through a 200-400 mesh screen, a nickel-cobalt-manganese precursor with a special structure of a tight inner layer, a loose outer shell, and an oriented arrangement of whiskers can be obtained, namely nickel-cobalt-manganese hydroxide.

[0106] The sample prepared in this embodiment, synthesized under high complexing agent and high temperature conditions, exhibits relatively dense primary particle packing, but is generally more porous than the crystal nuclei in Example 3. Under high temperature conditions, the complexing effect decreases, and increasing the amount of complexing agent makes the primary particle packing more porous. Later, as the temperature is lowered and growth continues, the complexing effect of the complexing agent is enhanced at low temperatures, resulting in finer, more stringy primary particles and a more porous packing, forming a shell that is more porous than the core. Due to the higher complexing agent content, the core-shell difference is significant. Compared to Example 3, this sample has a more porous overall packing.

[0107] Example 6

[0108] This embodiment provides a method for synthesizing a nickel-cobalt-manganese precursor, including the following specific steps:

[0109] (1) Add water to the 500L reactor to the overflow port, and simultaneously turn on the stirring, nitrogen protection and heating system. After the temperature rises to 55℃, add alkali solution to control the pH at about 12. Then add a mixed solution containing metal salt and complexing agent and liquid alkali in parallel flow. The metal salt is a combination of nickel sulfate, cobalt sulfate and manganese sulfate. The total concentration of nickel, cobalt and manganese ions in the mixed solution is 114 g / L. The complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate. The content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 0.5 wt% of the target yield of nickel, cobalt and manganese hydroxide. The flow rate of the mixed solution is 25 L / h. The liquid alkali is sodium hydroxide solution with a flow rate of 10 L / h. Maintain a nitrogen atmosphere during the parallel flow process with a nitrogen flow rate of 15 L / min. After 6 h of liquid injection, adjust the pH value to 10.0 at a rate of 0.05 / 3 h. Stop liquid injection when the product particle size reaches 2.8 μm under the above conditions.

[0110] (2) The temperature was directly lowered to 40℃ and a filter rod was added to the reactor. Then, the vacuum filtration was started for concentration, and the liquid was fed in at the current pH value until the particle size reached 3.4 μm. After stopping the liquid feeding for 2 hours, the pH value was raised to 12 and aged for 6 hours to obtain nickel-cobalt-manganese hydroxide slurry.

[0111] (3) Wash the nickel-cobalt-manganese hydroxide slurry once with 0.8 mol / L NaOH solution for 30 min, then wash it once with pure water for 1 h. After washing, dry the filter cake in an oven.

[0112] (4) After the dried filter cake is sieved through a 200-400 mesh screen, a nickel-cobalt-manganese precursor with a special structure of a tight inner layer, a loose outer shell, and an oriented arrangement of whiskers can be obtained, namely nickel-cobalt-manganese hydroxide.

[0113] Compared with Example 2, in this example, when the co-precipitation temperature in the first stage is 55°C, the complexation effect of sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate is higher, the supersaturation in the reactor is lower, and the sample grows more loosely, forming a looser core. Under the same co-precipitation temperature in the second stage (40°C), the sample prepared in this example has a slightly smaller TD and a slightly larger BET specific surface area.

[0114] Example 7

[0115] This embodiment provides a method for synthesizing a nickel-cobalt-manganese precursor, including the following specific steps:

[0116] (1) Add water to the 500L reactor to the overflow port, and simultaneously turn on the stirring, nitrogen protection and heating system. After the temperature rises to 65℃, add alkali solution to control the pH at about 12. Then add a mixed solution containing metal salt and complexing agent and liquid alkali in parallel flow. The metal salt is a combination of nickel sulfate, cobalt sulfate and manganese sulfate. The total concentration of nickel, cobalt and manganese ions in the mixed solution is 114 g / L. The complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate. The content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 0.5 wt% of the target yield of nickel, cobalt and manganese hydroxide. The flow rate of the mixed solution is 25 L / h. The liquid alkali is sodium hydroxide solution with a flow rate of 10 L / h. Maintain a nitrogen atmosphere during the parallel flow process with a nitrogen flow rate of 15 L / min. After 6 h of liquid injection, adjust the pH value to 10.0 at a rate of 0.05 / 3 h. Stop liquid injection when the product particle size reaches 2.8 μm under the above conditions.

[0117] (2) The temperature was directly lowered to 40℃ and a filter rod was added to the reactor. Then, the vacuum filtration was started for concentration, and the liquid was fed in at the current pH value until the particle size reached 3.4 μm. After stopping the liquid feeding for 2 hours, the pH value was raised to 12 and aged for 6 hours to obtain nickel-cobalt-manganese hydroxide slurry.

[0118] (3) Wash the nickel-cobalt-manganese hydroxide slurry once with 0.8 mol / L NaOH solution for 30 min, then wash it once with pure water for 1 h. After washing, dry the filter cake in an oven.

[0119] (4) After the dried filter cake is sieved through a 200-400 mesh screen, a nickel-cobalt-manganese precursor with a special structure of a tight inner layer, a loose outer shell, and an oriented arrangement of whiskers can be obtained, namely nickel-cobalt-manganese hydroxide.

[0120] Compared with Example 2, in this example, when the co-precipitation temperature in the first stage is 65°C, the complexation effect of sodium N,N-dicarboxylic acid nitrogen-2-hydroxypropanesulfonate is lower, and the growth rate of the sample is faster under high temperature conditions. In addition, the supersaturation in the reactor is relatively high, resulting in a denser sample growth and a more compact core. Under the same co-precipitation temperature in the second stage (40°C), the sample prepared in this example has a slightly larger TD and a slightly smaller BET specific surface area.

[0121] Example 8

[0122] This embodiment provides a method for synthesizing a nickel-cobalt-manganese precursor, including the following specific steps:

[0123] (1) Add water to the 500L reactor to the overflow port, and simultaneously turn on the stirring, nitrogen protection and heating system. After the temperature rises to 60℃, add alkali solution to control the pH at about 12. Then add a mixed solution containing metal salt and complexing agent and liquid alkali in parallel flow. The metal salt is a combination of nickel sulfate, cobalt sulfate and manganese sulfate. The total concentration of nickel, cobalt and manganese ions in the mixed solution is 114 g / L. The complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate. The content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 0.5 wt% of the target yield of nickel, cobalt and manganese hydroxide. The flow rate of the mixed solution is 25 L / h. The liquid alkali is sodium hydroxide solution with a flow rate of 10 L / h. Maintain a nitrogen atmosphere during the parallel flow process with a nitrogen flow rate of 15 L / min. After 6 h of liquid injection, adjust the pH value to 10.0 at a rate of 0.05 / 3 h. Stop liquid injection when the product particle size reaches 2.8 μm under the above conditions.

[0124] (2) The temperature was directly lowered to 45℃ and a filter rod was added to the reactor. Then, the vacuum filtration was started for concentration, and the liquid was fed in at the current pH value until the particle size reached 3.4 μm. After stopping the liquid feeding for 2 hours, the pH value was raised to 12 and aged for 6 hours to obtain nickel cobalt manganese hydroxide slurry.

[0125] (3) Wash the nickel-cobalt-manganese hydroxide slurry once with 0.8 mol / L NaOH solution for 30 min, then wash it once with pure water for 1 h. After washing, dry the filter cake in an oven.

[0126] (4) After the dried filter cake is sieved through a 200-400 mesh screen, a nickel-cobalt-manganese precursor with a special structure of a tight inner layer, a loose outer shell, and an oriented arrangement of whiskers can be obtained, namely nickel-cobalt-manganese hydroxide.

[0127] Compared to Example 2, in this example, when the co-precipitation temperature in the second stage is 45°C, the complexation effect of sodium N,N-dicarboxylic acid nitrogen-2-hydroxypropanesulfonate is lower, resulting in a slightly denser shell than that in Example 2. Under the condition that the co-precipitation temperature in the first stage is the same as that in Example 2 (60°C), the sample prepared in this example has a slightly larger TD and a slightly smaller BET specific surface area.

[0128] Comparative Example 1

[0129] This comparative example provides a method for synthesizing a nickel-cobalt-manganese precursor, including the following specific steps:

[0130] (1) Add water to the 500L reactor to the overflow port, and simultaneously turn on the stirring, nitrogen protection and heating system. After the temperature rises to 60℃, add alkali solution to control the pH at about 12. Then add a mixed solution containing metal salt and complexing agent and liquid alkali in parallel flow. The metal salt is a combination of nickel sulfate, cobalt sulfate and manganese sulfate. The total concentration of nickel, cobalt and manganese ions in the mixed solution is 114 g / L. The complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate. The content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 0.5 wt% of the target yield of nickel, cobalt and manganese hydroxide. The flow rate of the mixed solution is 25 L / h. The liquid alkali is sodium hydroxide solution with a flow rate of 10 L / h. Maintain a nitrogen atmosphere during the parallel flow process with a nitrogen flow rate of 15 L / min. After 6 h of liquid injection, adjust the pH value to 10.0 at a rate of 0.05 / 3 h. Stop liquid injection when the product particle size reaches 2.8 μm under the above conditions.

[0131] (2) Add a filter rod to the reactor, then start vacuum filtration and concentration, and continue feeding liquid at the current pH value until the particle size reaches 3.4 μm and 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;

[0132] (3) Wash the nickel-cobalt-manganese hydroxide slurry once with 0.8 mol / L NaOH solution for 30 min, then wash it once with pure water for 1 h. After washing, dry the filter cake in an oven.

[0133] (4) After the dried filter cake is sieved through a 200-400 mesh screen, the tightly packed nickel-cobalt-manganese precursor prepared by the high-temperature intermittent method can be obtained, namely nickel-cobalt-manganese hydroxide.

[0134] The morphological and structural characteristics of the nickel-cobalt-manganese precursor finally obtained in this comparative example are as follows: Figure 7 As shown in the figure, the left image is a SEM image and the right image is a CP image. It can be seen from the figures that the sample synthesized under the high-temperature conditions throughout the experiment has a morphology of tightly packed, coarse strip-shaped primary particles. The cross-sectional image shows a densely packed particle structure without hollow structures and no obvious gaps between the primary particles. Compared to Example 2, the sample synthesized under high-temperature conditions has a continuous, compact layer structure with higher TD and lower BET.

[0135] Comparative Example 2

[0136] This comparative example provides a method for synthesizing a nickel-cobalt-manganese precursor, including the following specific steps:

[0137] (1) Add water to the 500L reactor to the overflow port, and simultaneously turn on the stirring, nitrogen protection and heating system. After the temperature rises to 40℃, add alkali solution to control the pH at about 12. Then add a mixed solution containing metal salt and complexing agent and liquid alkali in parallel flow. The metal salt is a combination of nickel sulfate, cobalt sulfate and manganese sulfate. The total concentration of nickel, cobalt and manganese ions in the mixed solution is 114 g / L. The complexing agent is sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate. The content of sodium N,N-dicarboxylic acid amino-2-hydroxypropane sulfonate is 0.5 wt% of the target yield of nickel, cobalt and manganese hydroxide. The flow rate of the mixed solution is 25 L / h. The liquid alkali is sodium hydroxide solution with a flow rate of 10 L / h. Maintain a nitrogen atmosphere during the parallel flow process with a nitrogen flow rate of 15 L / min. After 6 h of liquid addition, adjust the pH value to 10.0 at a rate of 0.05 / 3 h.

[0138] (2) Under the above conditions, when the particle size reaches 2.8 μm, filter rods are added to the reactor for filtration and concentration. When the particle size reaches 3.4 μm, the liquid feeding is stopped. During the filtration process, the liquid level is maintained near the overflow port. After stopping the liquid feeding for 2 hours, the pH value is raised to 12 and aged for 6 hours to obtain nickel-cobalt-manganese hydroxide slurry.

[0139] (3) Wash the nickel-cobalt-manganese hydroxide slurry once with 0.8 mol / L NaOH solution for 30 min, then wash it once with pure water for 1 h. After washing, dry the filter cake in an oven.

[0140] (4) After the dried filter cake is sieved through a 200-400 mesh screen, the nickel cobalt manganese precursor with loosely stacked whiskers prepared under low temperature conditions can be obtained, namely nickel cobalt manganese hydroxide.

[0141] The morphological and structural characteristics of the nickel-cobalt-manganese precursor finally obtained in this comparative example are as follows: Figure 8 As shown in the figure, the left image is the SEM image and the right image is the CP image. It can be seen from the figures that the sample synthesized under low-temperature conditions throughout the experiment has finer primary particles and a loosely packed morphology, with noticeable gaps between particles in the cross-sectional image. Compared to Example 2, the sample synthesized under low-temperature conditions has a loose, layered structure with a smaller TD and a larger BET specific surface area.

[0142] Comparative Example 3

[0143] This comparative example provides a method for synthesizing a nickel-cobalt-manganese precursor, including the following specific steps:

[0144] (1) Add water to the 500L reactor to the overflow port, and at the same time turn on the stirring, nitrogen protection and heating system. After the temperature rises to 60℃, add alkaline solution to control the pH at around 12. Then add metal salt solution and liquid alkali in parallel. The metal salt is a combination of nickel sulfate, cobalt sulfate and manganese sulfate. The total concentration of nickel, cobalt and manganese ions in the mixed solution is 114 g / L. The flow rate of the metal salt solution is 25 L / h. The liquid alkali is sodium hydroxide solution with a flow rate of 10 L / h. During the parallel flow, maintain a nitrogen atmosphere with a nitrogen flow rate of 15 L / min. After 6 hours of liquid injection, lower the pH value to 10.0 at a rate of 0.05 / 3 hours. After reaching a certain particle size, lower the temperature to 40℃. Then adjust the pH value to control the particle size at around 3.4 μm.

[0145] (2) After the target particle size is reached, the material is collected and the prepared product is connected and introduced into the aging tank. At the same time, the stirring is turned on, and the alkali solution is added to pH=12 and then aged for 6 hours. After aging, nickel cobalt manganese hydroxide slurry is obtained.

[0146] (3) Wash the nickel cobalt manganese hydroxide slurry once with 0.8 mol / L NaOH solution for 30 min, then wash it once with pure water for 1 h. After washing, dry the filter cake in an oven.

[0147] (4) After the dried filter cake is sieved through a 200-400 mesh screen, the nickel cobalt manganese precursor, namely nickel cobalt manganese hydroxide, can be obtained by conventional continuous method without the addition of sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate.

[0148] The morphological and structural characteristics of the nickel-cobalt-manganese precursor finally obtained in this comparative example are as follows: Figure 9 As shown in the figure, the left figure is the SEM image and the right figure is the CP image. It can be seen from the figure that if no complexing agent (i.e., sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate) is added, the primary particles are finer and have poorer sphericity. The internal packing in the cross-section is relatively dense, and its TD is higher than that of comparative example 2. There are obvious pores between the primary particles on the outside, and the BET is larger.

[0149] Physicochemical properties:

[0150] The nickel-cobalt-manganese hydroxides prepared in the above examples and comparative examples were subjected to physicochemical tests, including BET specific surface area, tap density TD, S content and particle size D50.

[0151] The test results are shown in Table 1.

[0152] Table 1

[0153]

[0154] analyze:

[0155] As shown in the table above, the BET specific surface area and tap density (TD) of the samples are related to the compactness of the primary particle packing. Loose primary particle packing results in a larger BET specific surface area and a smaller TD, and vice versa, as observed in Comparative Examples 1-3. In Examples 1-3 and 6-8, by constructing a structure with a compact core, a loose outer shell, and oriented whisker arrangement, samples with both a large TD and a large BET specific surface area can be obtained. In particular, the oriented whisker arrangement maintains the large TD resulting from the compact internal nucleus while also increasing the BET specific surface area of ​​the sample. The synergistic effect of BET specific surface area and TD is even better when the amount of sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate added is 0.5 wt%. This indicates that the process disclosed in this paper can obtain nickel-cobalt-manganese precursors with excellent physical properties such as BET specific surface area, TD, and S content by constructing a structure with a compact core, a loose outer shell, and oriented whisker arrangement.

[0156] The data from Examples 2 and 4-5 show that if the mass fraction of sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate is too low, the sample will precipitate directly, avoiding the intermediate step of complexation. The resulting primary particles are coarser and more compactly packed. Under these conditions, the sample has a larger TD and a smaller BET specific surface area. If the mass fraction of sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate is too high, the metal ion complexation will significantly reduce the supersaturation in the reactor, resulting in looser primary particle packing, a smaller TD, and a larger BET specific surface area.

[0157] The data from Example 2 and Comparative Examples 1-3 show that under high-temperature conditions throughout the process, the complexing ability of sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate to metal ions is significantly reduced due to the esterification reaction at high temperatures, resulting in higher supersaturation and denser packing, leading to a larger TD and a smaller BET specific surface area. Under low-temperature conditions throughout the process, sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate complexes more metal ions, resulting in lower supersaturation, which leads to finer primary particles and looser packing, resulting in a larger BET specific surface area and a smaller TD. Without the addition of sodium N,N-dicarboxylic acid amino-2-hydroxypropanesulfonate, the sphericity of the sample is poor, and the TD and BET specific surface area are between those of Comparative Examples 1 and 3. Compared with Example 2, the sample exhibits uneven precipitation without the complexing agent, resulting in poorer sphericity.

Claims

1. A method for synthesizing a ternary precursor, comprising: adding a mixed solution containing a metal salt and a complexing agent into a reaction vessel together with liquid alkali in a parallel flow to perform a first co-precipitation reaction, adjusting the reaction temperature to perform a second co-precipitation reaction after the reaction product grows to a target particle size, and obtaining the ternary precursor after aging; wherein the complexing agent comprises N, N-dicarboxylic acid amino-2-hydroxy propane sulfonic acid sodium; the mass fraction of the complexing agent is 0.1-1.0% based on the target output of the ternary precursor as 100%; the temperature of the first co-precipitation reaction is 55-65℃; the temperature of the second co-precipitation reaction is 40-45℃; the pH value of the aging is higher than that of the second co-precipitation reaction.

2. The method of synthesis of claim 1, wherein, the pH value of the first co-precipitation reaction is 10-12.

3. The method of synthesis of claim 1, wherein, the target particle size is 2.0-2.8μm.

4. The method of synthesis of claim 1, wherein, the particle size of the reaction product after the second co-precipitation reaction is 3.45-3.80μm.

5. The method of synthesis of claim 1, wherein, the temperature of the aging is the same as that of the second co-precipitation reaction.

6. The method of synthesis of claim 1, wherein, the aging time is 6-8h.

7. The method of synthesis of claim 1, wherein, the synthesis method specifically comprises: (1) adding water into the reaction vessel, heating to 60℃ under stirring in a nitrogen atmosphere, and then adding alkali solution to obtain a bottom solution with a pH value of 10-12; (2) adding a mixed solution containing a metal salt and a complexing agent into the reaction vessel together with liquid alkali in a parallel flow to perform a first co-precipitation reaction, adjusting the reaction temperature to perform a second co-precipitation reaction after the reaction product grows to 2.0-2.8μm, and obtaining the ternary precursor after aging, solid-liquid separation, washing, drying and sieving in sequence, wherein the complexing agent comprises N, N-dicarboxylic acid amino-2-hydroxy propane sulfonic acid sodium. 8.A ternary precursor prepared by the synthesis method of any one of claims 1-7.

9. The ternary precursor of claim 8, wherein, The ternary precursor comprises an inner core and an outer shell, the compactness of the inner core is higher than that of the outer shell, and the outer shell is arranged in a whisker orientation. 10.A positive electrode material prepared by mixing and sintering the ternary precursor of claim 8 and a lithium source. 11.A lithium ion battery comprising the positive electrode material of claim 10.

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