A low-sulfur filamentous high-nickel ternary precursor and its preparation method

Abstract

The present invention provides a low-sulfur filamentous high-nickel ternary precursor and a preparation method thereof. By adopting the preparation method of the present invention, high-nickel ternary precursor particles with low sulfur and sodium contents and filamentous surfaces can be prepared with a simple process flow. The preparation method comprises the following steps: 1.1) in a nucleation stage, controlling the pH in the reactor to be 10.20-10.60 and the complexing agent concentration to be 0.05 mol / L-0.2 mol / L, wherein the nucleation stage is performed until the material in the reactor grows to a particle size D50 that reaches 30-40% of the target particle size, and then entering the growth stage; 1.2) in the growth stage, controlling the pH in the reactor to be 9.40-10.00 and the complexing agent concentration to be 0.05 mol / L-0.2 mol / L; and, when the reaction liquid in the reactor reaches a first preset liquid level, circulating the reaction liquid in the reactor between the reactor and a concentrator; and when the liquid level in the concentrator reaches a second preset liquid level, controlling the pH in the concentrator to be 11.0-12.0.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparing ternary positive electrode precursors for lithium-ion batteries, specifically to the technical field of preparing high-nickel ternary precursors, and further to a low-sulfur filamentous high-nickel ternary precursor and a preparation method thereof. Background Art

[0002] With the advent of the new energy era, lithium-ion batteries are increasingly being used in new energy vehicles such as electric vehicles (EVs) and hybrid electric vehicles (EVs). As a new type of secondary battery, lithium-ion batteries offer significant advantages over lead-acid batteries in terms of operating voltage, energy density, and cycle life. In lithium-ion batteries, the cathode material is a key component that determines their performance. In the commercialized cathode material market, high-nickel ternary materials offset the low energy density of lithium iron phosphate, becoming the most promising cathode material for lithium-ion batteries.

[0003] The quality of the precursor significantly impacts the performance of high-nickel ternary cathode materials. Factors such as the size, morphology, and structure of the ternary precursor are crucial to the production of ternary cathodes. Co-precipitation is currently the primary method used by manufacturers to mass-produce ternary precursors.

[0004] The raw materials for the co-precipitation method are typically sulfates of nickel, cobalt, and manganese. During the reaction, sulfate ions are not only adsorbed on the particle surface but also become trapped within the particles. This is particularly true when preparing precursors for large-particle polycrystalline materials. These trapped sulfate ions are difficult to remove during alkaline washing and can remain during cathode sintering, ultimately impacting battery performance.

[0005] In response to the problem of high sulfur content in precursors, CN112591808A discloses a method for preparing a low-sodium-sulfur nickel-cobalt-manganese ternary precursor. Through the multiple steps of "seed preparation-seed growth-stop reaction-increase pH-solution replacement-start reaction-particle growth reaches target value-stop reaction-increase pH-solution replacement-filter pressing and washing-drying and demagnetization", the problem of high sodium-sulfur impurity content in the precursor currently prepared by co-precipitation is solved. However, the process flow of this method is cumbersome, and the reaction must be interrupted during the preparation process to wash and replace the mother liquor, which affects the crystallinity and consistency of the precursor growth. CN113683130B controls the structure of the precursor so that the precursor has radial cracks from the particle surface to the core, and reduces the impurity content of the product by cracking-washing-repairing. However, the precursor particles prepared by this method have low strength and are prone to secondary cracking at the repaired cracks during post-processing and sintering, thereby affecting the performance of the positive electrode. Summary of the Invention

[0006] The present invention provides a low-sulfur filamentous high-nickel ternary precursor and a preparation method thereof. By adopting the preparation method of the present invention, high-nickel ternary precursor particles with low sulfur and sodium contents and a filamentous surface can be prepared with a simple process flow. At the same time, the preparation method adopted is conducive to ensuring the continuity and crystallinity of growth.

[0007] To achieve its purpose, the present invention provides the following technical solutions:

[0008] On one hand, the present invention provides a method for preparing a low-sulfur filamentous high-nickel ternary precursor, wherein the high-nickel ternary precursor is prepared by coprecipitation reaction and post-treatment of raw materials comprising a salt solution, an alkali, and a complexing agent solution, wherein the salt solution is an aqueous solution of nickel, cobalt, and manganese sulfates, preferably an aqueous solution of nickel, cobalt, and manganese sulfates; the preparation method comprises the following steps:

[0009] 1) Synthesis of the high nickel ternary precursor

[0010] The salt solution, the base and the complexing agent solution are introduced into the reactor to synthesize the high nickel ternary precursor through the nucleation stage and the growth stage in sequence; wherein,

[0011] 1.1) During the nucleation stage, the pH in the reactor is controlled to be 10.20-10.60, and the concentration of the complexing agent is controlled to be 0.05 mol / L-0.2 mol / L. The nucleation stage is continued until the material in the reactor grows to a particle size D50 that reaches 30-40% of the target particle size, and then the growth stage is entered;

[0012] 1.2) During the growth phase: controlling the pH in the reactor to 9.40-10.00 and the complexing agent concentration to 0.05 mol / L-0.2 mol / L; and, when the reaction liquid in the reactor reaches a first preset liquid level, circulating the reaction liquid in the reactor between the reactor and the concentrator;

[0013] When the liquid level in the concentrator reaches a second preset liquid level, controlling the pH in the concentrator to be 11.0-12.0;

[0014] 2) When the particle size D50 of the material in the reactor reaches the target particle size during the growth stage, the liquid in the reactor and the concentrator is post-processed to obtain the high-nickel ternary precursor.

[0015] The present invention improves the preparation process of the existing high-nickel ternary precursor. In the nucleation stage, the pH is controlled to 10.20-10.60, the complexing agent concentration is controlled to 0.05mol / L-0.2mol / L, and after the material grows to 30-40% of the target particle size, it enters the growth stage and controls the pH to 9.40-10.00, the complexing agent concentration is controlled to 0.05mol / L-0.2mol / L, and the concentrator pH is controlled to 11.0-12.0 when the concentrator liquid level reaches the predetermined level. Based on the control of the above growth conditions, a high-nickel ternary precursor with low sulfur and low sodium content can be obtained in a simple process flow without interrupting the reaction midway, and the high-nickel ternary precursor has a filamentous surface. Using the preparation method of the present invention, the high-nickel ternary precursor forms a loose radial structure and a large specific surface area during the growth process, and the particle surface is filamentous. During the process, low pH growth and high pH concentration are adopted, and the growth environment conditions of the reactor are controlled during the nucleation stage, and the environmental conditions of the reactor and the concentrator are synchronously controlled during the growth stage. This not only takes into account the acquisition of particles with target morphology, but also can more fully replace the sulfate ions and sodium ions attached to the inside of the particles. Under the process operation that ensures the continuity and crystallinity of growth, low-sodium and low-sulfur products with target morphology are obtained.

[0016] In some embodiments, in step 1), during the nucleation stage, water, the base, and the complexing agent solution are pre-added to the reactor as a reaction base solution; preferably, the pH of the reaction base solution is 10.20-10.60, and the complexing agent concentration is 0.05 mol / L-0.2 mol / L. The present invention utilizes a reaction base solution with the above-described conditions to enter the nucleation stage, enabling nucleation at a lower pH. This, combined with the subsequent process flow and condition control of the present invention, facilitates obtaining a product with the target particle size and morphology, while also taking into account low sulfur and low sodium content.

[0017] In a preferred embodiment, in step 1), during the nucleation stage, the stirring speed of the reactor is 540-600 rpm. During the growth stage, when the particle size D50 of the material in the reactor reaches 50%-80% of the target particle size, the stirring speed of the reactor is reduced to 400-480 rpm. This preferred speed control facilitates the formation of uniform spherical particles and avoids cracking.

[0018] In the present invention, preferably, in step 1), the flow rate of the salt solution added to the reactor is 1 L / h to 2 L / h. When the particle size D50 of the material in the reactor reaches 50% to 80% of the target particle size, the flow rate of the salt solution added to the reactor is increased, preferably to 2 L / h to 4 L / h. This preferred flow rate control facilitates sufficient crystal growth, improves particle strength, and prevents crystal nucleation during growth.

[0019] In some embodiments, in step 1), during the growth stage, the first preset liquid level refers to the reaction liquid in the reactor reaching 80%-90% of the height of the reactor cavity, or the first preset liquid level refers to the reaction liquid in the reactor reaching the overflow port of the reactor and entering the concentrator through the overflow port. Specifically, the overflow port of the reactor can be set at 80-90% of the height of the reactor cavity.

[0020] In some embodiments, in step 1), during the growth stage, the second preset liquid level refers to the liquid level in the concentrator reaching 40%-60% of the height of the concentrator cavity.

[0021] More specifically, in step 1), the concentrator is equipped with a filter element and a clear liquid outlet. The filter element is used to filter the feed liquid in the concentrator and retain particulate matter in the feed liquid within the concentrator. The clear liquid outlet is used to discharge the clear liquid obtained after filtration by the filter element. Preferably, the filter element includes an upper filter rod (specifically, which can be located at a position corresponding to the upper portion of the concentrator) and a lower filter rod (specifically, located below the upper filter rod, for example, in the area from the lower portion to the middle portion of the concentrator). The concentrator used in the present invention can directly adopt a concentrator that has corresponding filtering and clear liquid discharge functions in the art. The concentrator equipped with the upper and lower filter rods can also directly adopt a corresponding concentrator in the art.

[0022] In some embodiments, the second preset liquid level refers to the position where the liquid in the concentrator reaches or submerges the lower filter rod. Specifically, for example, as described above, this position corresponds to 40-60% of the height of the concentrator cavity.

[0023] In some embodiments, when the liquid in the concentrator passes through the filter element, specifically, for example, when it passes through the position of the upper filter rod, the filter element is filtered and the clear liquid is discharged; this operation is also called "clearing" in the art.

[0024] More specifically, the salt solution described in the present invention can be the corresponding salt solution commonly used in the art for preparing high-nickel ternary precursors, and there is no particular limitation on this. In some embodiments, the molar ratio of nickel, cobalt and manganese in the salt solution is x:y:z, where x+y+z=1, and 0.60 <x<0.96,0.01<y<0.30,0.01<z<0.30;

[0025] In the present invention, the alkali used can be the corresponding alkali solution commonly used in the art. In some embodiments, the alkali is one or more of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and barium hydroxide aqueous solution, preferably sodium hydroxide aqueous solution. The concentration of the alkali is preferably 6.0 to 10.0 mol / L.

[0026] In the present invention, the complexing agent used can be a corresponding complexing agent commonly used in the art. In some embodiments, the complexing agent is selected from one or more of ammonia water, ammonium sulfate, ammonium acetate, ammonium carbonate, ammonium nitrate, ammonium chloride, urea, sodium citrate, and EDTA, and can be used in the form of an aqueous solution. Preferably, the complexing agent is ammonia water. In some embodiments, the concentration of the complexing agent solution is 8.0 to 13.0 mol / L.

[0027] In some embodiments, the total concentration of nickel, cobalt, and manganese ions in the salt solution is 1.5 to 2.5 mol / L.

[0028] Furthermore, in step 1), the reaction temperature of the reactor is preferably controlled to be 50-70°C, more preferably 60°C.

[0029] In some embodiments, in step 2), the post-treatment includes: centrifuging the feed liquid in the reactor and the concentrator, alkali washing and water washing, and then drying. In some embodiments, after drying, screening, iron removal and other treatments may also be performed. Preferably, the washing liquid used for the alkali washing is a hot alkaline solution, preferably the temperature of the washing liquid is 60-80°C, and the concentration of the washing liquid is preferably 2-4 mol / L. In some embodiments, the washing liquid is selected from one or more of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and barium hydroxide aqueous solution.

[0030] Specifically, the pH of the reactor and the concentrator is adjusted by adjusting the amount of alkali added. Preferably, both the reactor and the concentrator are equipped with an automatic pH feedback control system capable of controlling the flow rate of the alkali according to the set pH value. The pH automatic feedback control system adjusts the amount of alkali added to the reactor or concentrator, thereby achieving corresponding pH regulation. Specifically, the pH automatic feedback control system can directly adopt a control system with corresponding functions existing in the art, such as a PLC-based automatic pH control module, which is commercially available.

[0031] In the present invention, preferably, the target particle size (D50) is 10-16 μm.

[0032] In this article, the allowable error of the pH value involved is ±0.03, and the allowable error of the complexing agent concentration is ±0.02 mol / L.

[0033] The second aspect of the present invention provides a low-sulfur filamentous high-nickel ternary precursor prepared according to the preparation method described above; preferably, the D50 of the high-nickel ternary precursor is 10-16μm; preferably, the sulfur content of the high-nickel ternary precursor is <1200ppm.

[0034] The technical solution provided by the present invention has the following beneficial effects:

[0035] (1) The present invention controls the pH and complexing agent concentration of the reactor in the nucleation stage and the growth stage within a specific range, controls the crystallization process of the precursor growth stage, and makes the prepared high-nickel secondary balls have a loose filamentous structure. At the same time, the pH of the concentrator in the growth stage is controlled within a specific range, and the slurry is circulated between the reactor and the concentrator, which can more thoroughly replace the sulfate ions inside the particles, ensuring the continuous growth process of the precursor while solving the problem of high sulfur and sodium impurity content inside the precursor. At the same time, it is beneficial to take into account the acquisition of products with target morphology (surface filamentous) and target particle size (e.g., 10-16 μm). The precursor material obtained by the process of the present invention is beneficial for sintering to obtain a positive electrode material with better structural stability, which is beneficial for improving the capacity and cycle stability of the positive electrode material.

[0036] (2) The solution provided by the present invention does not require the introduction of a large number of processes and equipment, and the process control is simple, which is conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Shown is a schematic diagram of a process device system in one embodiment.

[0038] Figure 2-6 The following are scanning electron microscope images of the precursors prepared in Example 1 of the present invention and Comparative Examples 4-7, respectively.

[0039] Figure 1 In the middle: 1 is a reactor, 2 is a concentrator, 3 is a filter rod assembly, 4 is a feed pipeline for the metal salt solution, alkali, and complexing agent solution of the reactor, 5 is a alkali feed pipeline of the concentrator, and 6 is a circulation pump. DETAILED DESCRIPTION

[0040] In order to facilitate the understanding of the present invention, the present invention will be further described below in conjunction with examples. It should be understood that the following examples are only for a better understanding of the present invention and do not mean that the present invention is limited to the following examples.

[0041] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in the art can be used. Reagents or instruments used without specifying the manufacturer are all commercially available conventional products.

[0042] In the following examples or comparative examples, the raw materials used are described as follows:

[0043] Nickel sulfate: nickel sulfate hexahydrate NiSO4·6H2O, battery grade, Chizhou Xien;

[0044] Manganese sulfate: manganese sulfate monohydrate MnSO4·H2O, battery grade, Qinzhou Nanhai Chemical;

[0045] Cobalt sulfate: cobalt sulfate heptahydrate CoSO4·7H2O, Guangdong Ghana Energy.

[0046] Description of the detection method:

[0047] Sodium and sulfur content detection method: Quantitative analysis of elements in lithium battery layered materials (ICP-OES method), refer to the method specified in YS / T1006.2-2014 for determination.

[0048] Particle size D50 test: Laser diffraction method was used, with reference to the method specified in GB / T 19077-2016. The testing equipment was Malvern Mastersizer 3000 particle size analyzer.

[0049] In the following examples, the process device system diagram used is as follows Figure 1 As shown. Specifically, the process device system includes a reactor 1 and a concentrator 2, and the reactor 1 is provided with a stirring paddle. The concentrator 2 is provided with a filter element, which is specifically a filter rod assembly 3 provided in the concentrator, specifically including an upper filter rod and a lower filter rod; the clear liquid outlet is located on the side wall of the concentrator corresponding to the position of the filter rod assembly; the concentrator is an existing device in the art, for example, by providing a nitrogen inlet and a pressure relief port in the concentrator. According to the clearing demand, the pressure in the concentrator is increased by the introduction of nitrogen to increase the pressure in the concentrator, thereby performing the filtering operation of the filter rod assembly and discharging the clear liquid through the clear liquid outlet; conversely, the pressure is released through the pressure relief port to stop the clearing. An overflow port is provided at the top of the reactor 1, and a liquid inlet is provided at the top of the concentrator 2. The overflow port of the reactor 1 and the liquid inlet of the concentrator 2 are connected by a pipeline. A liquid inlet is provided at the top of the reactor 1, and a liquid outlet is provided at the bottom of the concentrator 2. The liquid inlet of the reactor 1 and the liquid outlet of the concentrator 2 are connected by a pipeline, and a circulating pump 6 is provided on the pipeline. The reactor 1 is connected to a plurality of feeding lines 4 for feeding alkali (e.g., aqueous sodium hydroxide solution), complexing agent solution, and metal salt solution into the reactor. The reactor 1 is equipped with an automatic pH feedback adjustment system (not shown in the figure) that can adjust the rate of addition of alkali according to the set pH. The concentrator 2 is connected to an alkali inlet line 5, which is equipped with an automatic pH feedback adjustment system (not shown in the figure) that can adjust the rate of addition of alkali according to the set pH. The above-mentioned various devices and components are all existing devices and components in the art, and the existing devices and components with corresponding functions in the art can be directly used.

[0050] Example 1

[0051] This embodiment prepares a low-sulfur filamentous high-nickel ternary precursor.

[0052] The preparation steps are as follows:

[0053] 1) Synthesis of high nickel ternary precursor

[0054] Solution preparation: Prepare 10 mol / L sodium hydroxide aqueous solution as a precipitant, 13 mol / L ammonia aqueous solution as a complexing agent solution, and a metal salt solution with a metal ion concentration of 2.5 mol / L (i.e., a mixed aqueous solution of nickel, cobalt, and manganese sulfates (Ni:Co:Mn=0.95:0.03:0.02, molar ratio)).

[0055] The above-mentioned metal salt solution, sodium hydroxide aqueous solution, and ammonia aqueous solution are introduced into the reactor to synthesize the high-nickel ternary precursor through the nucleation stage and growth stage. Both the reactor and the concentrator are equipped with an automatic pH feedback control system to adjust the feed rate of the sodium hydroxide aqueous solution and thus the pH. The specific requirements for the nucleation stage and the growth stage are as follows:

[0056] 1.1) Core-building stage:

[0057] Water, sodium hydroxide aqueous solution and ammonia solution were introduced into a 100L reactor to prepare 50L of alkaline bottom liquid with a pH of 10.20 and an ammonia concentration of 0.10mol / L. The temperature of the reaction system in the reactor was controlled by water bath heating to maintain at 60±0.5℃, and the stirring speed was 540rpm. The metal salt solution was evenly pumped into the reactor at a rate of 2L / h through a peristaltic pump, and the feed rate of sodium hydroxide aqueous solution (precipitant) was adjusted by the pH automatic feedback adjustment system to control the pH of the reaction system in the reactor to 10.2±0.03. The feed rate of ammonia solution was controlled to maintain the ammonia concentration in the reactor at 0.10±0.02mol / L. The entire nucleation stage lasted for 0.5h, and the particle size D50 of the material in the reactor reached 6μm, and the nucleation stage ended.

[0058] 1.2) Growth stage:

[0059] After the nucleation phase, the pH in the reactor was lowered to 10.0 at a rate of 0.05 mol / h, transitioning to the crystal growth phase. The pH in the reactor was then maintained at 9.6 ± 0.03 for the duration of the reaction, and the ammonia concentration in the reactor was maintained at 0.10 ± 0.02 mol / L. The metal salt solution was then uniformly pumped into the reactor at a rate of 2 L / h.

[0060] When the liquid level in the reactor reaches the overflow port (located at about 85% of the reactor cavity height), the material in the reactor overflows into the concentrator, and the pump is started to circulate the material between the concentrator and the reactor;

[0061] When the liquid level in the concentrator is below the lower filter rod (located at about 50% of the height of the inner cavity of the concentrator), the pH automatic feedback adjustment system of the concentrator is turned on to control the amount of sodium hydroxide aqueous solution added to the concentrator so that the pH in the concentrator is 11.5; when the liquid level in the concentrator is below the upper filter rod of the concentrator, the clearing operation is started (i.e., the upper and lower filter rods of the concentrator are filtered and the clear liquid outlet is opened to discharge the filtered clear liquid), and the liquid level in the concentrator is maintained at a height just above the upper filter rod.

[0062] When the material in the reactor is D 50 When the particle size D is 8 μm, the stirring rate of the reactor is reduced to 420 rpm, and the feeding rate of the metal salt solution is increased to 4 L / h. 50 When the particle size reaches 16 μm (target particle size), the feed is stopped.

[0063] (4) Post-processing:

[0064] After the reaction is completed, the materials in the reactor and the concentrator are put into a centrifuge and washed with a 70°C sodium hydroxide aqueous solution (concentration 3 mol / L) for 30 minutes, then washed with pure water for 1.5 hours and dehydrated; the washed and centrifugally dehydrated materials are placed in an oven for drying. After drying, the obtained materials are sieved with a 200-mesh vibrating screen and then deironed with a magnetic rod to obtain a low-sulfur filamentous high-nickel ternary precursor material Ni 0.95 Co 0.03 Mn 0.02 (OH)2.

[0065] Example 2

[0066] This embodiment prepares a low-sulfur filamentous high-nickel ternary precursor.

[0067] The preparation steps are as follows:

[0068] 1) Synthesis of high nickel ternary precursor

[0069] Solution preparation: Prepare 8 mol / L sodium hydroxide aqueous solution as a precipitant, 10 mol / L ammonia aqueous solution as a complexing agent solution, and a metal salt solution with a metal ion concentration of 2.0 mol / L (i.e., a mixed aqueous solution of nickel, cobalt, and manganese sulfates (Ni:Co:Mn=0.90:0.05:0.05, molar ratio)).

[0070] The above-mentioned metal salt solution, sodium hydroxide aqueous solution, and ammonia aqueous solution are introduced into the reactor to synthesize the high-nickel ternary precursor through the nucleation stage and growth stage. Both the reactor and the concentrator are equipped with an automatic pH feedback control system to adjust the feed rate of the sodium hydroxide aqueous solution and thus the pH. The specific requirements for the nucleation stage and the growth stage are as follows:

[0071] 1.1) Core-building stage:

[0072] Water, sodium hydroxide aqueous solution and ammonia solution were introduced into a 100L reactor to prepare 50L of alkaline bottom liquid with a pH of 10.40 and an ammonia concentration of 0.15mol / L. The temperature of the reaction system in the reactor was controlled by water bath heating to maintain at 60±0.5℃, and the stirring speed was 580rpm. The metal salt solution was evenly pumped into the reactor at a rate of 1L / h through a peristaltic pump, and the feed rate of sodium hydroxide aqueous solution (precipitant) was adjusted by the pH automatic feedback adjustment system to control the pH of the reactor reaction system to 10.4±0.03. The feed rate of ammonia solution was controlled to maintain the ammonia concentration in the reactor at 0.15±0.02mol / L. The entire nucleation stage lasted for 1h, and the particle size D50 of the material in the reactor reached 4.5μm, and the nucleation stage ended.

[0073] 1.2) Growth stage:

[0074] After the nucleation phase, the pH in the reactor was lowered to 10.0 at a rate of 0.05 mol / h, transitioning to the crystal growth phase. The pH in the reactor was then maintained at 9.8 ± 0.03 for the duration of the reaction, and the ammonia concentration in the reactor was maintained at 0.15 ± 0.02 mol / L. The metal salt solution was continuously pumped into the reactor at a rate of 1 L / h.

[0075] When the liquid level in the reactor reaches the overflow port (located at about 85% of the reactor cavity height), the material in the reactor overflows into the concentrator, and the pump is started to circulate the material between the concentrator and the reactor;

[0076] When the liquid level of the concentrator is below the lower filter rod (located at about 50% of the height of the concentrator cavity), the pH automatic feedback adjustment system of the concentrator is turned on to control the amount of sodium hydroxide aqueous solution added to the concentrator so that the pH in the concentrator is 11.5; when the liquid level of the concentrator is below the upper filter rod of the concentrator, the clearing is turned on to maintain the liquid level in the concentrator just above the upper filter rod.

[0077] When the material in the reactor is D 50 When the particle size D is 7 μm, the stirring rate of the reactor is reduced to 460 rpm, and the feeding rate of the metal salt solution is increased to 2 L / h. 50 When the particle size reaches 12 μm (target particle size), the feed is stopped.

[0078] (4) Post-processing:

[0079] After the reaction is completed, the materials in the reactor and the concentrator are put into a centrifuge and washed with a 70°C sodium hydroxide aqueous solution (concentration 3 mol / L) for 30 minutes, then washed with pure water for 1.5 hours and dehydrated; the washed and centrifugally dehydrated materials are placed in an oven for drying. After drying, the obtained materials are sieved with a 200-mesh vibrating screen and then deironed with a magnetic rod to obtain a low-sulfur filamentous high-nickel ternary precursor material Ni 0.90 Co 0.05 Mn 0.05 (OH)2.

[0080] Example 3

[0081] This embodiment prepares a low-sulfur filamentous high-nickel ternary precursor.

[0082] The preparation steps are as follows:

[0083] 1) Synthesis of high nickel ternary precursor

[0084] Solution preparation: prepare 6 mol / L sodium hydroxide aqueous solution as precipitant, 8 mol / L ammonia aqueous solution as complexing agent solution, and a metal salt solution with a metal ion concentration of 1.5 mol / L (i.e., a mixed aqueous solution of nickel, cobalt, and manganese sulfates (Ni:Co:Mn=0.83:0.12:0.05, molar ratio)).

[0085] The above-mentioned metal salt solution, sodium hydroxide aqueous solution, and ammonia aqueous solution are introduced into the reactor to synthesize the high-nickel ternary precursor through the nucleation stage and growth stage. Both the reactor and the concentrator are equipped with an automatic pH feedback control system to adjust the feed rate of the sodium hydroxide aqueous solution and thus the pH. The specific requirements for the nucleation stage and the growth stage are as follows:

[0086] 1.1) Core-building stage:

[0087] Water, sodium hydroxide aqueous solution and ammonia solution were introduced into a 100L reactor to prepare 50L of alkaline bottom liquid with a pH of 10.60 and an ammonia concentration of 0.20mol / L. The temperature of the reaction system in the reactor was controlled by water bath heating to maintain at 60±0.5℃, and the stirring speed was 600rpm. The metal salt solution was evenly pumped into the reactor at a rate of 1L / h through a peristaltic pump, and the feed rate of sodium hydroxide aqueous solution (precipitant) was adjusted by the pH automatic feedback adjustment system to control the pH of the reaction system in the reactor to 10.6±0.03. The feed rate of ammonia solution was controlled to maintain the ammonia concentration in the reactor at 0.2±0.02mol / L. The entire nucleation stage lasted for 1h, and the particle size D50 of the material in the reactor reached 3.5μm, and the nucleation stage ended.

[0088] 1.2) Growth stage:

[0089] After the nucleation phase, the pH in the reactor was lowered to 10.0 at a rate of 0.05 per hour, transitioning to the crystal growth phase. The pH in the reactor was then controlled to maintain at 10.0 ± 0.03 for the reaction, and the ammonia concentration in the reactor was maintained at 0.20 ± 0.02 mol / L. The metal salt solution was continuously pumped into the reactor at a rate of 1 L / h.

[0090] When the liquid level in the reactor reaches the overflow port (located at about 85% of the reactor cavity height), the material in the reactor overflows into the concentrator, and the pump is started to circulate the material between the concentrator and the reactor;

[0091] When the liquid level of the concentrator is below the lower filter rod (located at about 50% of the height of the concentrator cavity), the pH automatic feedback adjustment system of the concentrator is turned on to control the amount of sodium hydroxide aqueous solution added to the concentrator so that the pH in the concentrator is 12.0; when the liquid level of the concentrator is below the upper filter rod of the concentrator, the clearing is turned on to maintain the liquid level in the concentrator just above the upper filter rod.

[0092] When the material in the reactor is D 50 When the particle size D is 6 μm, the stirring rate of the reactor is reduced to 480 rpm, and the feeding rate of the metal salt solution is increased to 2 L / h. 50 When the particle size reaches 10 μm (target particle size), the feed is stopped.

[0093] (4) Post-processing:

[0094] After the reaction is completed, the materials in the reactor and the concentrator are put into a centrifuge and washed with a 70°C sodium hydroxide aqueous solution (concentration 3 mol / L) for 30 minutes, then washed with pure water for 1.5 hours and dehydrated; the washed and centrifugally dehydrated materials are placed in an oven for drying. After drying, the obtained materials are sieved with a 200-mesh vibrating screen and then deironed with a magnetic rod to obtain a low-sulfur filamentous high-nickel ternary precursor material Ni 0.83 Co 0.12 Mn 0.05 (OH)2.

[0095] Comparative Example 1

[0096] This comparative example is carried out with reference to Example 1, and the similarities are not repeated here, and only the differences are described below:

[0097] In the growth stage 1.2), when the liquid level in the concentrator is below the lower filter rod, the pH automatic feedback adjustment system of the concentrator is not activated, and the pH in the concentrator is not adjusted. The remaining operations are the same as in Example 1.

[0098] Comparative Example 2

[0099] This comparative example is carried out with reference to Example 2, and the similarities are not repeated here, and only the differences are described below:

[0100] In the growth stage 1.2), when the liquid level in the concentrator is below the lower filter rod, the pH automatic feedback control system of the concentrator is not activated, and the pH in the concentrator is not adjusted. The remaining operations are the same as in Example 2.

[0101] Comparative Example 3

[0102] This comparative example is carried out with reference to Example 3, and the similarities are not repeated here. Only the differences are described below:

[0103] In the growth stage 1.2), when the liquid level in the concentrator is below the lower filter rod, the pH automatic feedback control system of the concentrator is not activated, and the pH in the concentrator is not adjusted. The remaining operations are the same as in Example 3.

[0104] Comparative Example 4

[0105] The process was carried out in accordance with Example 1, except that: in 1.1) the nucleation stage, the pH of the alkaline base solution was controlled at 10.8 and the ammonia concentration was 0.1 mol / L; and after the metal salt solution was pumped in, the pH in the reactor was continued to be controlled at 10.8 and the ammonia concentration was continued to be 0.1 mol / L.

[0106] Experimental results: Scanning electron microscopy revealed that the filamentous morphology of the primary particles obtained in the nucleation stage was coarser than that of Examples 1-3, and that the secondary particles obtained in the growth stage were cracked and had seeding.

[0107] Comparative Example 5

[0108] The process was carried out in accordance with Example 1, except that: in 1.1) the nucleation stage, the pH of the alkaline base solution was controlled at 10.0 and the ammonia concentration was 0.1 mol / L; and after the metal salt solution was pumped in, the pH in the reactor was continued to be controlled at 10.0 and the ammonia concentration was continued to be 0.1 mol / L.

[0109] Experimental results: The particles are severely agglomerated and the sphericity of the secondary particles is extremely poor.

[0110] Comparative Example 6

[0111] The process is carried out in accordance with Example 1, except that: in 1.1) the nucleation stage, when the particle size D50 of the material in the reactor reaches 3 μm (20% of the target particle size (D50 = 16 μm)), the nucleation stage is terminated and the growth stage is entered.

[0112] Experimental results: Seeds appeared during the particle growth process, the particle uniformity was poor, the particle size distribution became significantly wider, and it was difficult to obtain a product with D50 meeting the target particle size requirement (lower than the target particle size D50) during the growth stage.

[0113] Comparative Example 7

[0114] The process is carried out in accordance with Example 1, except that: in 1.1) the nucleation stage, when the particle size D50 of the material in the reactor reaches 8 μm (50% of the target particle size (D50=16 μm)), the nucleation stage is terminated and the growth stage is entered.

[0115] Experimental results: The nucleation time was too long, the number of particles in the kettle was too large, and the solid content was too high in the later stage, resulting in particle cracking and seeding.

[0116] The contents of the impurity elements Na and S were detected for the high nickel ternary precursors prepared in the above embodiments and comparative examples. The results are shown in Table 1.

[0117] Table 1 Precursor impurity element content data

[0118] Na content / ppm S content / ppm Example 1 108 901 Example 2 109 885 Example 3 118 898 Comparative Example 1 106 2234 Comparative Example 2 112 1901 Comparative Example 3 107 1962 Comparative Example 4 116 918 Comparative Example 5 116 1108 Comparative Example 6 112 904 Comparative Example 7 108 934

[0119] During the preparation process of Examples 1-3, there was no obvious phenomenon of seeding and particle agglomeration. The high nickel ternary precursors obtained in Examples 1-3 were examined by scanning electron microscopy, with Example 1 as a representative example. The results are shown in Figure 2 As can be seen from the left figure, the particle surface has a rich filamentous morphology, no cracks on the surface, uniform particle size distribution, and good sphericity; the scanning electron microscopy results of the other examples are similar to those of Example 1. The obtained particles have a filamentous surface morphology, no cracks on the surface, relatively uniform particle size, and good sphericity. The scanning electron microscopy test results of Comparative Example 4 can be found in Figure 3 As can be seen from the figure, the particle size distribution uniformity of the particles obtained in Comparative Example 4 is poor, and there is cracking. The results of the scanning electron microscope test of Comparative Example 5 can be found in Figure 4 , it can be seen from the figure that the particles are seriously agglomerated and have poor sphericity. Figure 5 As can be seen from the figure, the particle size uniformity is very poor and the particle size distribution is obviously wide. Figure 6 ,As can be seen from the figure, there is cracking in the particles and the ,particle size distribution is not uniform.

[0120] It can be seen from the above experimental results that Examples 1-3 adopt the "low pH growth-high pH concentration" preparation process provided by the present invention, which significantly reduces the sulfur content of the high-nickel ternary precursor without increasing the Na impurity content, and the obtained particles have better uniformity and sphericity. During the preparation process, there is no obvious agglomeration of the particles, and the obtained particles do not crack, and have better structural strength; at the same time, particles with a filamentous surface of the target particle size can be obtained.

[0121] It will be readily understood that the above embodiments are merely examples for clarity of description and are not intended to limit the present invention to these examples. Those skilled in the art will readily appreciate that other variations or modifications based on the above description are possible. It is not necessary and impossible to provide an exhaustive list of all possible implementations. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a low-sulfur filamentous high-nickel ternary precursor, characterized in that: The high-nickel ternary precursor is prepared by coprecipitation reaction and post-treatment of raw materials including a salt solution, an alkali and a complexing agent solution, wherein the salt solution is an aqueous solution of inorganic salts of nickel, cobalt and manganese; the preparation method comprises the following steps: 1) Synthesis of the high nickel ternary precursor The salt solution, the base and the complexing agent solution are introduced into the reactor to synthesize the high nickel ternary precursor through the nucleation stage and the growth stage in sequence; wherein, 1.1) During the nucleation stage, the pH in the reactor is controlled to be 10.20-10.60, and the concentration of the complexing agent is controlled to be 0.05 mol / L-0.2 mol / L. The nucleation stage is continued until the material in the reactor grows to a particle size D50 that reaches 30-40% of the target particle size, and then the growth stage is entered; 1.2) During the growth phase: controlling the pH in the reactor to 9.40-10.00 and the complexing agent concentration to 0.05 mol / L-0.2 mol / L; and, when the reaction liquid in the reactor reaches a first preset liquid level, circulating the reaction liquid in the reactor between the reactor and the concentrator; When the liquid level in the concentrator reaches a second preset liquid level, controlling the pH in the concentrator to be 11.0-12.0; 2) When the particle size D50 of the material in the reactor reaches the target particle size during the growth stage, the liquid in the reactor and the concentrator is post-processed to obtain the high-nickel ternary precursor.

2. The preparation method according to claim 1, characterized in that The salt solution is an aqueous solution of nickel, cobalt and manganese sulfates.

3. The preparation method according to claim 1, characterized in that In step 1), during the nucleation stage, water, the base and the complexing agent solution are added into the reactor in advance as a reaction base solution.

4. The preparation method according to claim 3, characterized in that In step 1), during the nucleation stage, the pH of the reaction base solution is 10.20-10.60, and the concentration of the complexing agent is 0.05 mol / L-0.2 mol / L.

5. The preparation method according to claim 1, characterized in that In step 1), during the nucleation stage, the stirring speed of the reactor is 540-600 rpm; During the growth stage, when the particle size D50 of the material in the reactor reaches 50%-80% of the target particle size, the stirring speed of the reactor is reduced to 400-480 rpm.

6. The preparation method according to any one of claims 1 to 5, characterized in that In step 1), the flow rate of adding the salt solution to the reactor is 1 L / h-2 L / h, and when the particle size D50 of the material in the reactor reaches 50%-80% of the target particle size, the flow rate of adding the salt solution to the reactor is increased.

7. The preparation method according to claim 6, characterized in that The method of increasing the flow rate of the salt solution added to the reactor is to increase the flow rate to 2 L / h-4 L / h.

8. The preparation method according to any one of claims 1 to 5, characterized in that In step 1), during the growth stage, the first preset liquid level refers to the reaction liquid in the reactor reaching 80%-90% of the height of the reactor cavity, or the first preset liquid level refers to the reaction liquid in the reactor reaching the overflow port of the reactor and entering the concentrator through the overflow port.

9. The preparation method according to any one of claims 1 to 5, characterized in that In step 1), during the growth stage, the second preset liquid level refers to the liquid level in the concentrator reaching 40%-60% of the height of the concentrator cavity.

10. The preparation method according to any one of claims 1 to 5, characterized in that: In step 1), the concentrator is equipped with a filter element and a clear liquid outlet. The filter element is used to filter the feed liquid in the concentrator and retain the particulate matter in the feed liquid in the concentrator. The clear liquid outlet is used to discharge the clear liquid obtained after being filtered by the filter element.

11. The preparation method according to claim 10, characterized in that: The filter element comprises an upper filter rod and a lower filter rod.

12. The preparation method according to claim 11, characterized in that The second preset liquid level refers to the position where the liquid in the concentrator reaches or submerges the lower filter rod.

13. The preparation method according to claim 11, characterized in that When the liquid in the concentrator submerges the filter element, the filter element performs a filtering operation and discharges the clear liquid.

14. The preparation method according to claim 13, characterized in that The phrase "when the feed liquid in the concentrator has submerged the filter element" means when the feed liquid in the concentrator has submerged the position of the upper filter rod.

15. The preparation method according to any one of claims 1 to 5, characterized in that: The molar ratio of nickel, cobalt and manganese in the salt solution is x:y:z, wherein x+y+z=1, and 0.60 <x<0.96,0.01<y<0.30,0.01<z<0.30; and / or, the base is one or more of a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, and a barium hydroxide aqueous solution; And / or, the complexing agent is selected from one or more of ammonia water, ammonium sulfate, ammonium acetate, ammonium carbonate, ammonium nitrate, ammonium chloride, urea, sodium citrate, and EDTA; and / or, the concentration of the complexing agent solution is 8.0 to 13.0 mol / L; And / or, the total concentration of nickel, cobalt and manganese ions in the salt solution is 1.5 to 2.5 mol / L.

16. The preparation method according to claim 15, characterized in that The alkali is an aqueous solution of sodium hydroxide; And / or, the complexing agent is aqueous ammonia.

17. The preparation method according to claim 15, characterized in that The concentration of the alkali is 6.0 to 10.0 mol / L.

18. The preparation method according to any one of claims 1 to 5, characterized in that: In step 1), the reaction temperature of the reactor is controlled at 50-70°C; And / or, in step 2), the post-treatment comprises: centrifuging, alkali washing and water washing the liquid in the reactor and the concentrator, and then drying; And / or, the pH of the reactor and the concentrator are both adjusted by adjusting the amount of the alkali added.

19. The preparation method according to claim 18, characterized in that In step 1), the reaction temperature of the reactor is controlled at 60°C; And / or, in step 2), the washing liquid used for the alkali washing in the post-treatment is a hot alkaline solution, the temperature of the washing liquid is 60-80° C., and the concentration of the washing liquid is 2-4 mol / L; And / or, the reactor and the concentrator are both equipped with a pH automatic feedback adjustment system capable of controlling the flow rate of the alkali according to a set pH value.

20. The preparation method according to claim 19, characterized in that In step 2), the washing solution used in the post-treatment is selected from one or more of a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, and a barium hydroxide aqueous solution.

21. A low-sulfur filamentous high-nickel ternary precursor prepared according to the preparation method according to any one of claims 1 to 20.

22. The low-sulfur filamentous high-nickel ternary precursor according to claim 21, characterized in that The D50 of the high-nickel ternary precursor is 10-16 μm.

23. The low-sulfur filamentous high-nickel ternary precursor according to claim 21, characterized in that The sulfur content of the high-nickel ternary precursor is less than 1200 ppm.

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