High-nickel precursor material for lithium ion battery and preparation method of high-nickel precursor material

Abstract

The invention relates to the technical field of high-nickel precursor materials, in particular to a high-nickel precursor material for a lithium ion battery and a preparation method of the high-nickel precursor material. The method comprises the following steps: (1) preparing a mixed salt solution from soluble nickel salt and soluble cobalt salt; (2) under a protective atmosphere, introducing the mixed salt solution, a doping additive, a precipitator and a complexing agent into a reaction kettle, carrying out constant-temperature co-precipitation, stopping introducing the mixed salt solution and the doping additive after a preset particle size is reached, introducing a coating additive, and carrying out a reaction to form a coating layer, so as to obtain qualified slurry; and the spherical high-nickel precursor material which can bear high pressure and is not easy to collapse and crack is obtained after post-treatment. Primary particles of the precursor can be refined through the tungsten doping agent, a looser and porous precursor can be formed by combining the tungsten doping agent with the double complexing agent, and meanwhile the precursor has better pressure resistance and cracking resistance under the combined action of the aluminum coating layer and the loose and porous interior.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion power battery technology for new energy vehicles, specifically to a high-nickel precursor material for lithium-ion batteries and its preparation method. Background Technology

[0002] With the continued growth in demand for high-energy-density power batteries from the new energy vehicle industry, high-nickel cathode materials (nickel content ≥80mol%) have emerged as a leader due to their significant energy density advantage. These materials not only possess a specific capacity of over 200mAh / g (15%-20% higher than conventional ternary materials), but also effectively increase the energy density of individual battery cells to over 300Wh / kg, thus being widely recognized by the industry as the mainstream technology for next-generation power batteries.

[0003] However, traditional high-nickel precursors have the following defects: (1) the dense structure leads to a long lithium-ion diffusion path, affecting rate performance; (2) high-nickel materials are prone to phase transitions and microcracks during charging and discharging, causing crystal structure collapse. As a key raw material for cathode materials, the performance indicators of the precursor directly determine the core characteristics of the final cathode material. Therefore, to address the above problems, modifying the precursor structure to be porous is an effective strategy. The optimization effect of the porous precursor structure on the cathode material performance is mainly reflected in the following aspects: the porous structure can shorten the lithium-ion diffusion path, reduce internal resistance, and significantly improve the rate performance of the battery; the porous characteristics promote electrolyte penetration and improve the reaction kinetics of the electrode-electrolyte interface; by controlling the degree of porosity, the volume expansion stress during charging and discharging can be alleviated, effectively improving cycle life. However, while the porous structure of the precursor can provide certain advantages, it also poses a greater challenge to the structural stability of the material: the porous structure can severely weaken the mechanical strength and structural integrity of the particles, leading to phenomena such as collapse and cracking of the precursor material in subsequent battery fabrication and application processes, especially those involving high voltage, thus demonstrating a further disadvantage in structural stability.

[0004] Based on this, this invention patent addresses the shortcomings of traditional high-nickel precursor materials, such as structural collapse and cracking, by exploring a method that can be applied on a large scale to prepare a high-nickel precursor material that can withstand high pressure, is not prone to collapse or cracking, and has high structural stability. Summary of the Invention

[0005] Currently, traditional high-nickel precursors suffer from problems such as compact structure, susceptibility to structural collapse and cracking during application. This invention addresses these issues by exploring a method for large-scale application to prepare a high-nickel precursor that can withstand high pressure without easily collapsing or cracking, thus solving the structural stability problems of precursors that are prone to collapse and cracking.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A method for preparing a high-nickel precursor material for lithium-ion batteries includes the following steps: (1) Prepare a mixed salt solution using soluble nickel salt and soluble cobalt salt; (2) Under a protective atmosphere, a mixed salt solution, a tungsten-doped additive, a precipitant and a complexing agent are introduced into a reactor. The solid content in the reactor is continuously increased and constant temperature co-precipitation is carried out at a certain stirring rate. After the preset particle size is reached, the introduction of the mixed salt solution and the doped additive is stopped, and an aluminum-containing coating additive is introduced to react and form a coating layer. After the coating layer reaction is completed, a qualified slurry is obtained. The complexing agent is a double complexing agent of ammonium sulfate and EDTA or its soluble salt. (3) After post-processing the qualified slurry obtained from the reaction, a spherical high-nickel precursor material that can withstand high pressure, is not easy to collapse or crack is obtained.

[0007] The technical solution provided by this invention involves: preparing a mixed salt solution using soluble nickel and cobalt salts; under a protective atmosphere, introducing the mixed salt solution, dopant, precipitant, and complexing agent into a reactor, continuously increasing the solid content in the reactor while maintaining a constant temperature for co-precipitation at a certain stirring rate; after reaching the preset particle size, stopping the introduction of the mixed salt solution and dopant, and introducing a coating additive to react and form a coating layer; after the coating layer reaction is complete, a qualified slurry is obtained; the slurry is then alkali-washed, followed by pure water washing and pressure filtration to obtain a material to be dried; finally, the material to be dried is dried, iron removed, and sieved to obtain a spherical high-nickel precursor material with a porous and loose structure and a suitable specific surface area. In this invention, the use of tungsten dopant can refine the precursor particles in one step, and the combination with dual complexing agents can form a more porous precursor, increasing the pressure resistance of the precursor; the aluminum coating layer can reduce spherical cracking. The aluminum coating layer and the porous interior give the precursor better pressure resistance and crack resistance. Compared with the rigid spherical shape formed by traditional processes, which is prone to cracking and not resistant to pressure, the present invention effectively improves the structural stability of high-nickel precursors.

[0008] Preferably, in step (1), the molar ratio of nickel ions to cobalt ions in the mixed salt solution is x:y; x+y=1, 0.85≤x<1, 0 <y≤0.15。

[0009] Preferably, the total concentration of metal ions (Me:Ni, Co) in the mixed salt solution in step (1) is 0.5~2.5mol / L, more preferably 1.6~2.2mol / L.

[0010] Preferably, the soluble nickel salt and soluble cobalt salt in step (1) can be selected as at least one of the corresponding sulfates, nitrates and hydrochlorides of nickel and cobalt, including nickel sulfate, nickel nitrate, nickel chloride, cobalt sulfate, cobalt nitrate and cobalt chloride; more preferably, the corresponding sulfates.

[0011] Preferably, the protective atmosphere in step (2) is any one or a mixture of inert gases such as nitrogen, argon, and helium.

[0012] Preferably, the precipitant in step (2) is a sodium hydroxide solution; more preferably, the concentration of the sodium hydroxide solution is 2-10 mol / L.

[0013] Preferably, in step (2), the soluble salt of EDTA in the complexing agent includes disodium EDTA; more preferably, the complexing agent in step (2) is a mixture of ammonium sulfate solution and disodium EDTA solution; even more preferably, the concentration of ammonium sulfate solution is 0.1~1.5 mol / L and the concentration of disodium EDTA solution is 0.01~0.3 mol / L.

[0014] Preferably, in step (2), a base liquid is pre-prepared in the reactor. The concentration of the precipitant in the base liquid is 0.0025~0.05mol / L, and the concentration of the complexing agent includes: ammonium sulfate at 0.05~0.5mol / L, disodium EDTA at 0.001~0.03mol / L, the temperature of the base liquid is the same as the reaction temperature, and the stirring rate is 100~450rpm.

[0015] Preferably, in step (2), the mixed salt solution is introduced at a rate of 10-100 L / h, and the complexing agent is introduced at a concentration of 0.05-0.5 mol / L for ammonium sulfate solution and 0.001-0.03 mol / L for disodium EDTA solution in the reactor. The precipitant is introduced at a pH of 10-12 in the doping stage and at a pH of 5.5-7.0 in the coating stage.

[0016] Preferably, the stirring rate of the reactor in step (2) is 100~450 rpm.

[0017] Preferably, in step (2), the solid content in the reactor is continuously increased to 80~900 g / L, more preferably 150~700 g / L. More preferably, the solid content is increased by a concentration device such as a thickener. More preferably, the increase rate can be taken as: mixed salt solution concentration * flow rate * relative molecular weight / effective volume of the reactor.

[0018] Preferably, the reaction temperature in step (2) is 25~75℃, more preferably 45~70℃.

[0019] Preferably, in step (2), the tungsten-containing doping additive in the doping stage is a sodium tungstate solution; the aluminum-containing coating additive in the coating stage is an aluminum sulfate solution; more preferably, the concentration of the aluminum sulfate solution is 0.1~1.5 mol / L, and the concentration of the sodium tungstate solution is 0.1~2.5 mol / L. Even more preferably, the inlet flow rate of the tungsten-containing doping additive is 0.01~1 L / h, and the inlet flow rate of the aluminum-containing coating additive is 0.1~30 L / h.

[0020] Preferably, in step (2), the preset particle size D50 is 9.9~15.9μm, the particle size D50 after coating is 10.0~16.0μm, and the aluminum hydroxide coating thickness is 0.1~0.3μm. Cathode materials prepared from large-particle precursors have better cycle performance and energy density, while cathode materials prepared from small-particle precursors have better rate performance. This preferred particle size is in the middle range, better combining the material's cycle performance, energy density, and rate performance.

[0021] Preferably, the post-treatment in step (3) includes steps such as alkaline washing, water washing, pressure filtration, and drying; more preferably, the alkaline solution for alkaline washing is a 0.5~2mol / L sodium carbonate solution, and the alkaline washing time is 10~30min; more preferably, the temperature of the water for water washing is 60~80℃; more preferably, the temperature of drying is 90~150℃; more preferably, it also includes steps such as iron removal and sieving.

[0022] Preferably, the spherical high-nickel precursor material obtained by the present invention has a particle size D50 of 10.0~16.0μm, an aluminum hydroxide coating thickness of 0.1~0.3μm, and a tungsten doping content of 500~5000ppm.

[0023] The present invention also provides a high-nickel precursor material for lithium-ion batteries prepared by any of the above-mentioned preparation methods.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In this invention, the primary particle structure of the precursor can be effectively refined by using tungsten dopant; (2) In this invention, by combining dual complexing agents to synergistically regulate crystallization kinetics and by combining refined primary particles, a precursor structure with moderately controllable porosity was successfully constructed. (3) In this invention, the aluminum cladding layer and the loose and porous internal structure work together to form a synergistic enhancement effect, which makes the precursor have better pressure resistance and crack resistance, significantly improves the mechanical strength and structural stability of the material, and thus enables it to have excellent electrochemical performance in subsequent applications. (4) At the same time, the preparation method of the present invention has good process controllability, overcomes the common problems of poor structural uniformity and uneven porosity in traditional porosification processes, effectively avoids the risk of mechanical strength reduction and accompanying structural performance deterioration caused by excessive structure or uneven porosity, and ensures that the product has excellent structural consistency and high reproducibility.

[0025] This invention improves the precursor structure through multi-scale synergistic modification, thereby effectively enhancing the structural stability of the precursor material, such as its compressive strength, making it less prone to cracking and collapse, and thus possessing broad market application prospects. Furthermore, the preparation method of this invention is simple, easy to operate and control, and suitable for large-scale industrial production. Attached Figure Description

[0026] Appendix Figure 1 Example 1: SEM image of the high-nickel precursor; Appendix Figure 2 Example 1: SEM image of the cross-section of the high-nickel precursor; Appendix Figure 3 Example 1: SEM images of the high-nickel precursor calcination test; Appendix Figure 4 Example 1: SEM image of high-nickel precursor withstand voltage test. Detailed Implementation

[0027] To better clarify and understand the objectives, process solutions, and advantages of this invention, the technical solutions and implementation methods of this invention will be further described clearly, completely, and in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the embodiments described in this invention are implemented under the premise of the technical solutions of this invention, providing detailed implementation methods and specific operating procedures, but are only some embodiments of this invention, not all embodiments. The specific implementation methods described are limited to illustrating and explaining this invention and do not limit this invention. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0028] Unless otherwise specified, the experimental methods and conditions used in the embodiments of this invention are conventional methods and conditions. The materials, reagents, instruments, and equipment used in the embodiments, unless otherwise specified, are all conventional substances or equipment known to those skilled in the art and can be obtained commercially or prepared by conventional methods. The reaction conditions described in the invention's content can all achieve the stated reactions and obtain the desired products. Due to space limitations, some embodiments are listed below to further illustrate the advantages of the technical solution of this invention.

[0029] Example 1 A mixed salt solution was prepared by mixing nickel sulfate and cobalt sulfate in a nickel ion:cobalt ion molar ratio of 0.9:0.1, resulting in a total metal ion concentration of 2.1 mol / L. The prepared NaOH solution had a concentration of 10 mol / L; ammonium sulfate solution had a concentration of 1.2 mol / L; disodium EDTA solution had a concentration of 0.2 mol / L; sodium tungstate solution had a concentration of 2 mol / L; and aluminum sulfate solution had a concentration of 1 mol / L.

[0030] The prepared mixed salt solution, ammonium sulfate solution, disodium EDTA solution, and sodium tungstate solution were introduced into the reactor at flow rates of 50 L / h, 8 L / h, 2 L / h, and 0.1 L / h, respectively. The flow rate of NaOH solution was controlled by an automated system. Simultaneously, a 1m³ buffer containing a bottom liquid (80% effective volume of the reactor) and a protective gas (nitrogen) was introduced into the reactor. This buffer consisted of a 0.025 mol / L NaOH solution, a 0.006 mol / L disodium EDTA solution, and a 0.15 mol / L ammonium sulfate solution. 3 In the reaction vessel, the stirring speed was controlled at 350 rpm, the reaction pH at 11.2, and the temperature at 60℃. The solid content in the reaction system was increased to 600 g / L at a rate of 9.6 g / L using a thickener (reaction time 62.5 h). When the particle size D50 reached 13.3 μm, the introduction of mixed salt solution and sodium tungstate solution was stopped, and aluminum sulfate solution was continuously introduced at a flow rate of 20 L / h. The reaction pH was maintained at 6.0, and the solid content in the reaction system was increased to 627 g / L. The reaction was stopped when the particle size D50 reached 13.5 μm. The qualified slurry obtained from the reaction was washed with 1 mol / L sodium carbonate solution for 30 min, then washed with 70℃ hot pure water and centrifuged to obtain the material to be dried. After drying at 120℃, the material was sieved through a 400-mesh sieve and then passed through a 12000 gs electromagnetic separator to remove iron, obtaining the doped and coated precursor material.

[0031] Example 2 A mixed salt solution was prepared by mixing nickel sulfate and cobalt sulfate in a nickel ion:cobalt ion molar ratio of 0.9:0.1, resulting in a total metal ion concentration of 2.1 mol / L. The NaOH solution had a concentration of 10 mol / L, the ammonium sulfate solution had a concentration of 1.2 mol / L, the disodium EDTA solution had a concentration of 0.2 mol / L, and the sodium tungstate solution had a concentration of 2 mol / L.

[0032] The prepared mixed salt solution, ammonium sulfate solution, disodium EDTA solution, and sodium tungstate solution were introduced into the reactor at flow rates of 50 L / h, 8 L / h, 2 L / h, and 0.1 L / h, respectively. The flow rate of NaOH solution was controlled by an automated system. Simultaneously, a 1m³ buffer containing a bottom liquid (80% effective volume of the reactor) and a protective gas (nitrogen) was introduced into the reactor. This buffer consisted of a 0.025 mol / L NaOH solution, a 0.006 mol / L disodium EDTA solution, and a 0.15 mol / L ammonium sulfate solution. 3 In the reaction vessel, the stirring speed was controlled at 350 rpm, the reaction pH was 11.2, and the temperature was 60℃. The solid content in the reaction system was increased to 627 g / L at a rate of 9.6 g / L using a thickener (reaction time 65.3 h). The reaction was stopped when the particle size D50 reached 13.5 μm. The qualified slurry obtained from the reaction was washed with 1 mol / L sodium carbonate solution for 30 min, then washed with hot pure water at 70℃ and centrifuged to obtain the material to be dried. After drying at 120℃, the material was sieved through a 400-mesh sieve and then passed through a 12000 gs electromagnetic iron separator to remove iron, obtaining the doped precursor material.

[0033] Example 3 A mixed salt solution was prepared by mixing nickel sulfate and cobalt sulfate in a nickel ion:cobalt ion molar ratio of 0.9:0.1, resulting in a total metal ion concentration of 2.1 mol / L. The NaOH solution had a concentration of 10 mol / L, the ammonia solution had a concentration of 10 mol / L, and the aluminum sulfate solution had a concentration of 1 mol / L.

[0034] The prepared mixed salt solution and ammonia water were introduced into the reactor at flow rates of 50 L / h and 6 L / h, respectively. The flow rate of the NaOH solution was controlled by an automatic control system. Simultaneously, a 1m³ buffer containing a bottom liquid (80% of the effective volume of the reactor) and a protective gas (nitrogen) was introduced into the reactor. This buffer consisted of a 0.025 mol / L NaOH solution and a 0.3 mol / L ammonia solution. 3 In the reaction vessel, the stirring speed was controlled at 350 rpm, the reaction pH was 11.2, and the temperature was 60℃. The solid content in the reaction system was increased to 600 g / L at a rate of 9.6 g / L using a thickener (reaction time 62.5 h). When the particle size D50 reached 13.3 μm, the addition of mixed salt solution was stopped, and aluminum sulfate solution was continuously introduced at a flow rate of 20 L / h. The reaction pH was 6.0, and the solid content in the reaction system was increased to 627 g / L. When the particle size D50 reached 13.5 μm, the reaction was stopped. The qualified slurry obtained from the reaction was washed with 1 mol / L sodium carbonate solution for 30 min, then washed with hot pure water at 70℃ and centrifuged to obtain the material to be dried. After drying at 120℃, the material was sieved through a 400-mesh sieve and then passed through a 12000 gs electromagnetic separator to remove iron, obtaining the coated precursor material.

[0035] Example 4 A mixed salt solution was prepared by mixing nickel sulfate and cobalt sulfate in a nickel ion:cobalt ion molar ratio of 0.9:0.1, resulting in a total metal ion concentration of 2.1 mol / L. The NaOH solution had a concentration of 5 mol / L, and the ammonia solution had a concentration of 10 mol / L.

[0036] The prepared mixed salt solution and ammonia water were introduced into the reactor at flow rates of 50 L / h and 6 L / h, respectively. The flow rate of the NaOH solution was controlled by an automatic control system. Simultaneously, a 1m³ buffer containing a bottom liquid (80% of the effective volume of the reactor) and a protective gas (nitrogen) was introduced into the reactor. This buffer consisted of a 0.025 mol / L NaOH solution and a 0.3 mol / L ammonia solution. 3 In the reaction vessel, the stirring speed was controlled at 350 rpm, the reaction pH was 11.2, and the temperature was 60℃. The solid content in the reaction system was increased to 627 g / L at a rate of 9.6 g / L using a thickener (reaction time 65.3 h). The reaction was stopped when the particle size D50 reached 13.5 μm. The qualified slurry obtained from the reaction was washed with 1 mol / L sodium carbonate solution for 30 min, then washed with hot pure water at 70℃ and centrifuged to obtain the material to be dried. After drying at 120℃, the material was sieved through a 400-mesh sieve and then passed through a 12000 gs electromagnetic iron separator to remove iron, thus obtaining the precursor material.

[0037] The precursor results for Examples 1-4 are shown in Table 1 below:

[0038] Samples from the four examples were subjected to a calcination test at 450°C to assess their crack resistance. Electron microscopy was used to observe the spherical cracking of the calcined precursors; fewer cracks indicated stronger crack resistance. Additionally, samples were subjected to a 5 MPa pressure test to assess their pressure resistance. Under pressure, the precursors fractured, producing fragments that decreased the particle size distribution (D50) and increased the particle size distribution. A smaller decrease in D50 and a smaller increase in particle size distribution indicated greater pressure resistance.

[0039] The results are shown in Table 2 below:

[0040] Through the pressure resistance test data and calcination test data, it can be seen that even though the structural parameters of the precursors of Examples 1 and Examples 2-4 are basically the same, the precursor of Example 1 of the present invention exhibits significantly better pressure resistance and crack resistance. That is, the use of dual complexing agents and tungsten doping, combined with the synergistic effect of aluminum coating, effectively improves the pressure resistance and crack resistance of the precursor, thus having the best structural stability.

[0041] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications may be made without departing from the technical solutions described in the claims.

Claims

1. A preparation method of a high-nickel precursor material for lithium-ion batteries, characterized by the following steps: (1) Prepare a mixed salt solution using a soluble nickel salt and a soluble cobalt salt; (2) Under a protective atmosphere, introduce the mixed salt solution, a tungsten-doped additive, a precipitating agent, and a complexing agent into a reaction kettle, continuously increase the solid content in the reaction kettle, and carry out isothermal co-precipitation at a certain stirring rate. After reaching the preset particle size, stop introducing the mixed salt solution and the doping additive, and introduce an aluminum-coated additive to form a coating layer. After completion, a qualified slurry is obtained; the complexing agent is a double complexing agent of ammonium sulfate and EDTA or its soluble salt; (3) Post-treat the qualified slurry obtained from the reaction to obtain a spherical high-nickel precursor material.

2. The method for preparing a high-nickel precursor material for lithium-ion batteries according to claim 1, characterized in that, In the step (1): the molar ratio of nickel ions to cobalt ions in the mixed salt solution = x:y; x + y = 1, 0.85 ≤ x < 1, 0 < y ≤ 0.15; the metal ion concentration of the mixed salt solution is 0.5 - 2.5 mol / L.

3. The method for preparing a high-nickel precursor material for lithium-ion batteries according to claim 1, characterized in that, In the step (2): the precipitating agent is a sodium hydroxide solution with a concentration of 2 - 10 mol / L.

4. The method for preparing a high-nickel precursor material for lithium-ion batteries according to claim 1, characterized in that, In the step (2): the complexing agent is an ammonium sulfate solution and a disodium EDTA solution; the concentration of the ammonium sulfate solution is 0.1 - 1.5 mol / L, and the disodium EDTA solution is 0.01 - 0.3 mol / L.

5. The method for preparing a high-nickel precursor material for lithium-ion batteries according to claim 1, characterized in that, In the step (2): the tungsten-doped additive is a sodium tungstate solution with a concentration of 0.1 - 2.5 mol / L.

6. The method for preparing a high-nickel precursor material for lithium-ion batteries according to claim 1, characterized in that, In the step (2): the aluminum-coated additive is an aluminum sulfate solution with a concentration of 0.1 - 1.5 mol / L.

7. The method for preparing a high-nickel precursor material for lithium-ion batteries according to claim 1, characterized in that, In the step (2): the temperature range for isothermal co-precipitation is 25 - 75 °C.

8. The method for preparing a high-nickel precursor material for lithium-ion batteries according to claim 1, characterized in that, In the step (2): the range of the solid content in the reaction is 80 - 900 g / L.

9. The method for preparing a high-nickel precursor material for lithium-ion batteries according to claim 1, characterized in that, In the step (2): the stirring rate of the reactor in the reaction is 100 - 450 rpm.

10. A high-nickel precursor material for lithium-ion batteries prepared by the preparation method according to any one of claims 1 - 9.

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