Precursor with a honeycomb structure in the core, its preparation method, cathode material and lithium-ion battery

Abstract

The present invention belongs to the technical field of lithium-ion battery materials, and discloses a precursor with a honeycomb structure as its core, and its preparation method and application. The precursor is prepared by the co-precipitation method. First, the value of the growth coefficient is determined, and then the flow rate of the mixed salt solution is determined by reverse calculation. At the same time, the pH value, gas atmosphere, etc. of the reaction system in the nucleation stage and the growth stage are determined, and the precursor with a honeycomb structure as its core can be obtained. The preparation idea provided by the present invention greatly simplifies the co-precipitation process control process, and has excellent prospects for industrialization and commercialization. In addition, the core part of the precursor prepared by the present invention has a honeycomb pore structure, which can effectively reduce the number of primary particles in the core part of the precursor, increase the voids in the core part of the hollow material precursor, and is easier to shrink to form a hollow structure during sintering. It is not easy for particles to remain in the hollow part of the hollow material after sintering, which is more conducive to exerting the output characteristics of the hollow material.

Description

Technical Field

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

[0002] Due to the lack of basic charging facilities, pure electric vehicles still have a great deal of range anxiety in actual use. Hybrid electric vehicles (HEV) and plug-in hybrid electric vehicles (PHEV) take into account the characteristics of electric vehicles, such as environmental protection and economy, rapid power response and no range anxiety. For batteries used in HEVs, they need to be charged and discharged frequently in a short period of time, requiring the battery to have excellent rate performance and cycle performance. The hollow ternary precursor material can obtain a positive electrode material with a hollow core during the sintering process. The hollow part can make the electrolyte infiltrated more fully during the cycle, effectively expanding the contact area between the material and the electrolyte, and shortening the Li + Diffusion path, reducing the internal resistance of the material and improving output performance.

[0003] The precursor disclosed in CN114772556A is prepared through two precipitation stages: in the first stage, a carbonate solution is used as the precipitant, and a metal salt solution and the carbonate solution undergo a precipitation reaction to form a loose carbonate core. In step 3, an alkaline solution is switched to the second stage precipitant, and the metal salt solution and the alkaline solution undergo a precipitation reaction to form a hydroxide shell on the surface of the carbonate core, resulting in a porous precursor. After being uniformly mixed with a lithium salt, the carbonate core decomposes during sintering, releasing gas to form a large number of pores, and the loose inner core migrates outward and agglomerates with the outer core. CN110921723A proposes a method for preparing a hollow lithium-ion battery positive electrode material precursor. During the precursor synthesis process, the synthesis reaction is carried out in two stages. The switching point between the first and second stages is determined based on the size requirements of the loose portion within the precursor, and the reaction conditions are adjusted: the stirring linear velocity in the second stage is higher than that in the first stage, and the total metal salt flow rate in the second stage is no greater than that in the first stage; and an inert gas is continuously introduced into the reactor during the synthesis process. CN113979489A discloses a method for preparing a precursor. By controlling the degree of oxidation of the precursor within a specific range during the growth process, the growth of the precursor crystal faces is preferentially changed, and the ratio of (100) and (101) crystal faces of the finished precursor is increased. At the same time, by adjusting the amount of metal salt supplied and the pH during the reaction process, a precursor with the desired morphology is obtained, and a hollow material precursor with controllable crystal faces is obtained. Research on hollow cathode materials and their precursors, especially their preparation methods, is a key focus of researchers. Summary of the Invention

[0004] The first object of the present invention is to provide a precursor having a honeycomb core and a preparation method thereof.

[0005] A second object of the present invention is to provide a positive electrode material.

[0006] A third object of the present invention is to provide a lithium ion battery.

[0007] To achieve the above objectives, the present invention provides the following specific technical solutions.

[0008] First, the present invention provides a method for preparing a precursor, comprising:

[0009] (1) Nucleation stage: A mixed salt solution of transition metals or a mixed salt solution of transition metals and doping elements, a precipitant solution, and a complexing agent solution are introduced into the bottom liquid of the reactor in parallel to carry out a nucleation reaction under an oxidizing atmosphere;

[0010] (2) Growth stage: After the nucleation stage, the growth stage begins. The pH value of the reaction system in the growth stage is lower than that in the nucleation stage. The reaction atmosphere in the growth stage is nitrogen atmosphere or weak oxidizing atmosphere.

[0011] The growth coefficient K during the growth stage is controlled to be 0.01~0.025;

[0012] Define the growth coefficient K , where V1 is the flow rate of the mixed salt solution introduced into the reactor during the nucleation stage, in L / min; V2 is the flow rate of the mixed salt solution introduced into the reactor during the growth stage, in L / min; R1 is the particle size Dv0 of the reaction slurry after the nucleation stage, in μm; t is the nucleation stage time, in min; K is in μm / min;

[0013] (3) The obtained reaction slurry is filtered, washed, and dried to obtain a precursor.

[0014] In a further preferred embodiment, the transition metal includes Ni; preferably, the transition metal includes Ni and includes at least one of Co and Mn.

[0015] In a further preferred embodiment, the doping element is one or more of Al, Mg, Zr and La.

[0016] In a further preferred embodiment, the pH value of the reactor bottom liquid is 11.80-12.60, and the ammonia concentration is 0-22 g / L. Further preferably, the volume of the reactor bottom liquid is 20-70% of the reactor volume.

[0017] In a further preferred embodiment, the total concentration of metal ions in the mixed salt solution is 1.0-2.5 mol / L, preferably 1.8-2.2 mol / L.

[0018] In a further preferred embodiment, the precipitant solution is an alkaline solution, and further preferably, the concentration of the alkaline solution is 5 to 30 wt %.

[0019] In a further preferred embodiment, the complexing agent solution is an ammonia solution, and further preferably, the concentration of the complexing agent solution is 10-30 wt %.

[0020] In a further preferred embodiment, the pH value of the reaction system in the nucleation stage is 11.80-12.60, and the ammonia concentration is 0-22 g / L.

[0021] In a further preferred embodiment, the nucleation stage lasts for 1 to 30 minutes.

[0022] In a further preferred embodiment, the flow rate of the mixed salt solution introduced per minute during the nucleation stage is 0.5-2% of the volume of the bottom liquid of the reactor.

[0023] In a further preferred embodiment, the oxygen concentration in the gas above the liquid surface in the reactor during the nucleation stage is above 10%.

[0024] In a further preferred embodiment, the pH value of the reaction system in the growth stage is 9.90-11.20, and the ammonia concentration is 0-22 g / L.

[0025] In a further preferred embodiment, the oxygen concentration in the gas above the liquid level in the reactor during the growth stage is no higher than 5%.

[0026] In a further preferred embodiment, the oxygen concentration in the gas above the liquid level in the reactor during the growth phase is adjusted to reach a target value within 60 minutes after the nucleation reaction is completed.

[0027] Secondly, the present invention provides a precursor prepared by the above preparation method, wherein the core region of the cross section of the secondary particles of the precursor is a honeycomb hole structure.

[0028] In a further preferred embodiment, the cross-sectional area of the honeycomb pore structure region accounts for 20-70% of the cross-sectional area of the precursor secondary particles, and more preferably 30-60%.

[0029] In a further preferred embodiment, the average pore diameter of the honeycomb pore structure region is 40 nm to 600 nm, and more preferably 100 nm to 300 nm.

[0030] In a further preferred embodiment, the chemical formula of the precursor is Ni x Co y Mn z Me a(OH)2, wherein 0.3≤x≤0.7, 0≤y≤0.4, 0≤z≤0.5, 0≤a≤0.01, x+y+z+a=1, and Me is a doping element.

[0031] In a further preferred embodiment, the Me is one or more of Al, Mg, Zr and La.

[0032] In a further preferred embodiment, the Dv50 of the precursor is 2.0-6.0 μm, the diameter distance is ≤ 0.8, and the specific surface area is 15-60 m 2 / g.

[0033] Based on the same inventive concept, the present invention provides a positive electrode material obtained by sintering the aforementioned precursor mixed with lithium, and also provides a lithium-ion battery comprising the aforementioned positive electrode material.

[0034] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects:

[0035] (1) The core of the precursor prepared by the present invention has a honeycomb pore structure, which can effectively reduce the number of primary particles in the core of the precursor and increase the voids in the core of the hollow material precursor. It is easier to shrink to form a hollow structure during sintering. After sintering, it is not easy for particles to remain in the hollow part of the hollow material, which is more conducive to exerting the output characteristics of the hollow material.

[0036] (2) The present invention limits the growth coefficient, determines the flow rate of the mixed salt solution in the growth stage, and further adjusts the oxygen concentration of the gas above the liquid surface in the reactor during the growth stage to no more than 5%, thereby ensuring a high degree of supersaturation during nucleation, forming loose, fine agglomerated crystal nuclei, and ultimately obtaining a precursor with a honeycomb pore structure in the core.

[0037] (3) The present invention obtains a precursor having a honeycomb pore structure in its core by limiting the growth coefficient to 0.01-0.025. In actual experiments and production processes, the specific value of the growth coefficient is first determined, and then the appropriate flow rate of the mixed salt solution is selected based on the reverse calculation. This is equivalent to establishing a control model for the flow rate of the mixed salt solution during the growth phase. Based on this model, a precursor having a honeycomb pore structure in its core can be obtained, which simplifies the process control process and has excellent prospects for industrialization and commercialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are part of the drawings of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0039] Figure 1 This is a cross-sectional SEM image of the precursor obtained in Example 1.

[0040] Figure 2 This is a cross-sectional SEM image of the precursor obtained in Comparative Example 1.

[0041] Figure 3 This is the cross-sectional SEM image of the precursor obtained in Comparative Example 2.

[0042] Figure 4 This is a cross-sectional SEM image of the precursor obtained in Comparative Example 3.

[0043] Figure 5 This is a cross-sectional SEM image of the precursor obtained in Example 2.

[0044] Figure 6 This is a cross-sectional SEM image of the precursor obtained in Example 3.

[0045] Figure 7 This is a cross-sectional SEM image of the precursor obtained in Example 4.

[0046] Figure 8 This is a cross-sectional SEM image of the precursor obtained in Example 5.

[0047] Figure 9 This is a cross-sectional SEM image of the positive electrode material obtained by calcining the precursor obtained in Example 1.

[0048] Figure 10 This is a cross-sectional SEM image of the positive electrode material obtained by calcining the precursor obtained in Comparative Example 1.

[0049] Figure 11 The DCIR test results of button batteries. DETAILED DESCRIPTION

[0050] The present invention provides a method for preparing a precursor, comprising:

[0051] (1) Nucleation stage: A mixed salt solution of transition metals and doping elements, a precipitant solution, and a complexing agent solution are introduced into the bottom liquid of the reactor in parallel to carry out a nucleation reaction under an oxidizing atmosphere;

[0052] (2) Growth stage: After the nucleation stage, the growth stage begins. The pH value of the reaction system in the growth stage is lower than that in the nucleation stage. The reaction atmosphere in the growth stage is nitrogen atmosphere or weak oxidizing atmosphere.

[0053] The growth coefficient K in the growth stage is controlled to be 0.01~0.025; the growth coefficient K is defined as , where V1 is the flow rate of the mixed salt solution introduced into the reactor during the nucleation stage, in L / min; V2 is the flow rate of the mixed salt solution introduced into the reactor during the growth stage, in L / min; R1 is the particle size Dv0 of the reaction slurry after the nucleation stage, in μm; t is the nucleation stage time, in min; K is in μm / min;

[0054] (3) The obtained reaction slurry is filtered, washed, and dried to obtain a precursor.

[0055] It should be understood by those skilled in the art that in the technical field of lithium-ion battery positive electrode material precursors, the transition metal includes Ni and may include at least one of cobalt and manganese. The transition metal salts and doping element salts used to prepare the mixed salt solution are all soluble salts. For example, nitrates, sulfates, chlorides, acetates, oxalates, carbonates, etc. commonly used in the art meet the requirements for preparing the mixed salt solution. Those skilled in the art can choose according to actual conditions. At the same time, the mixed salt solution is usually prepared according to the set chemical formula of the precursor.

[0056] In the present invention, during the growth phase, by regulating the growth coefficient K within the range of 0.01 to 0.025, the precursor rapidly grows in a nitrogen atmosphere or a weakly oxidizing atmosphere, resulting in a higher degree of crystallinity in the precursor primary particles. Under the influence of the Oswald ripening effect, the fine particles in the loosely agglomerated crystal nuclei formed during the nucleation phase dissolve, and recrystallize on the larger primary particles, thereby forming the core of the honeycomb pore structure. If the growth coefficient is too large, the precursor growth rate is too fast, easily forming loose agglomerates, and it is difficult to achieve a core and shell structure. If the growth coefficient is too small, the precursor growth rate is too slow, the reaction cycle is greatly increased, the crystal nuclei grow uniformly, and it is difficult to form a honeycomb pore structure.

[0057] According to a particularly preferred embodiment of the present invention, the growth coefficient K is 0.020 to 0.025. According to another particularly preferred embodiment of the present invention, the growth coefficient K is 0.01 to 0.018.

[0058] In some specific embodiments of the present invention, the pH value of the reactor bottom liquid is 11.80-12.60, and the ammonia concentration is 0-22 g / L. More preferably, the volume of the reactor bottom liquid is 20-70% of the reactor volume.

[0059] In some specific embodiments of the present invention, the total concentration of metal ions in the mixed salt solution is 1.0-2.5 mol / L, more preferably 1.8-2.2 mol / L.

[0060] In some embodiments of the present invention, the precipitant solution is an alkaline solution, such as at least one of a sodium hydroxide solution, a potassium hydroxide solution, and a lithium hydroxide solution. It is further preferred that the concentration of the alkaline solution is 5 to 30 wt%.

[0061] In some specific embodiments of the present invention, the complexing agent solution is an ammonia solution, and more preferably, the concentration of the ammonia solution is 10 to 30 wt %. It should be understood by those skilled in the art that other complexing agents in the art can also achieve the coprecipitation reaction process and are conventional choices in the art.

[0062] In some specific embodiments of the present invention, the pH value of the reaction system in the nucleation stage is 11.80-12.60, and the ammonia concentration is 0-22 g / L.

[0063] In some specific embodiments of the present invention, the nucleation stage lasts for 1 to 30 minutes.

[0064] In some specific embodiments of the present invention, the flow rate of the mixed salt solution introduced per minute during the nucleation stage is 0.5-2% of the volume of the bottom liquid of the reactor.

[0065] In some specific embodiments of the present invention, the oxygen concentration in the gas above the liquid surface in the reactor during the nucleation stage is above 10%.

[0066] The coordination of the flow rate of the mixed salt solution and the oxygen concentration of the gas above the liquid surface in the reactor can ensure a high degree of supersaturation during nucleation, forming loose, fine agglomerated crystal nuclei.

[0067] In some specific embodiments of the present invention, the pH value of the reaction system in the growth stage is 9.90-11.20, and the ammonia concentration is 0-22 g / L.

[0068] In some specific embodiments of the present invention, the oxygen concentration in the gas above the liquid surface in the reactor during the growth stage is no higher than 5%.

[0069] In some specific embodiments of the present invention, the oxygen concentration in the gas above the liquid surface in the reactor during the growth phase is adjusted to reach a target value within 60 minutes after the nucleation reaction is completed.

[0070] Adjust the nitrogen atmosphere or weak oxidizing properties during the growth phase according to the requirements of the specific surface area and core ratio of the precursor. If the specific surface area and core ratio of the precursor are required to be large, the oxygen concentration in the gas above the liquid surface in the reactor during the growth phase can be adjusted to no more than 5%. The precursor prepared under this condition has a large hollow ratio after sintering and has excellent output characteristics. When the precursor is required to have a higher tap density, a smaller specific surface area and core ratio, the oxygen concentration in the gas above the liquid surface in the reactor during the growth phase can be adjusted to a lower level, below 2%, or non-oxidizing gases such as nitrogen can be introduced. The precursor prepared under this condition has a small hollow ratio after sintering and a larger tap density, which can improve the capacity of the battery while ensuring the output characteristics in the early stage.

[0071] Secondly, the present invention provides a precursor prepared by the above preparation method, wherein the core region of the cross section of the secondary particles of the precursor is a honeycomb hole structure.

[0072] In some specific embodiments of the present invention, the cross-sectional area of the honeycomb pore structure region accounts for 20-70% of the cross-sectional area of the precursor secondary particles, more preferably 30-60%, and even more preferably 30-50%.

[0073] The core part of the precursor has a honeycomb pore structure, which can effectively reduce the number of primary particles in the core part of the precursor, increase the gap in the core part of the precursor, and is more conducive to the formation of a hollow structure during the sintering process, effectively reducing the situation of residual particles in the hollow part of the hollow material.

[0074] In specific practice, the ratio of the interface area of the honeycomb pore structure region to the cross-sectional area of the precursor secondary particles is determined in the following manner: first, the precursor powder is cut with an ion beam and an SEM image of the precursor cross section is taken. Then, the diameter of the precursor core region and the secondary particles is measured using SEM measurement software, such as Nano Measurer. The diameter is then substituted into the circular area formula to calculate the ratio of the honeycomb pore core region area. In order to more accurately reflect the ratio of the core to the secondary particles, when measuring the diameter of the core and the secondary particles, the average value is obtained after measuring more than 10 times from different directions of the precursor cross section as its diameter. Furthermore, the core diameter / secondary particle diameter ratio of more than 10 precursor particles is averaged to calculate the ratio of the core to the secondary particles.

[0075] In some specific embodiments of the present invention, the average pore diameter of the honeycomb pore structure region is 40 nm to 600 nm, and more preferably 100 nm to 300 nm.

[0076] In some specific embodiments of the present invention, the chemical formula of the precursor is Ni x Co y Mn zMe a (OH)2, wherein 0.3≤x≤0.7, 0≤y≤0.4, 0≤z≤0.5, 0≤a≤0.01, x+y+z+a=1, and Me is a doping element.

[0077] In some specific embodiments of the present invention, the Me is one or more of Al, Mg, Zr, and La.

[0078] In some specific embodiments of the present invention, the Dv50 of the precursor is 2.0-6.0 μm, the diameter distance is ≤0.8, and the specific surface area is 15-60 m 2 / g.

[0079] Based on the same inventive concept, the present invention provides a positive electrode material obtained by sintering the aforementioned precursor mixed with lithium, and also provides a lithium-ion battery comprising the aforementioned positive electrode material.

[0080] To facilitate understanding of the present invention, the present invention will be described in more comprehensive and detailed form below in conjunction with the accompanying drawings and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0081] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0082] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0083] Example 1

[0084] Prepare a mixed metal salt solution of nickel sulfate, cobalt sulfate, and manganese sulfate with a total metal concentration of 2 mol / L. The molar ratio of nickel, cobalt, and manganese is 50:20:30. Add 60 L of pure water to a 300 L reactor, followed by liquid caustic soda and industrial ammonia. Adjust the ammonia concentration to 7 g / L, the pH to 12.50, the temperature to 55°C, and the reactor speed to 350 rpm.

[0085] The mixed metal salt solution was introduced into the reactor at a flow rate of 0.9 L / min. At the same time, sodium hydroxide solution, ammonia solution, and compressed air were introduced in parallel to maintain the ammonia concentration of the reaction system at 7 g / L, the pH value at 12.5, and the oxygen concentration in the gas above the liquid surface in the reactor at 18%. After 2 minutes of nucleation, the sodium hydroxide solution was stopped and the growth phase began. At the same time, 50 mL of the slurry was tested and its Dv0 was 0.15 μm. According to K The growth coefficient was limited to 0.025. During the growth phase, the mixed metal salt solution flow rate was maintained at 0.9 L / min. After the pH of the reaction system dropped to 11.2, sodium hydroxide solution was introduced to maintain the pH at 11.2. Thirty-two minutes after the nucleation phase, the oxygen concentration in the gas above the liquid level in the reactor was 5%. The supernatant in the reactor was discharged through a physical settling tank or concentrator. When the reaction slurry reached the target particle size, the feed and reaction were stopped, and the product was discharged. The reaction slurry was filtered, aged, washed, dried, and sieved to obtain the precursor product.

[0086] Figure 1 This is a cross-sectional SEM image of the obtained precursor product. It can be seen from the image that the core of the precursor presents honeycomb-shaped holes.

[0087] Comparative Example 1

[0088] The only difference between Comparative Example 1 and Example 1 is that the nucleation time is 30 min, 50 ml of slurry is taken after the nucleation stage to test its Dv0 is 0.41 μm, the flow rate of the mixed metal salt solution is continued to maintain 0.9 L / min during the growth stage, and K is 0.0045.

[0089] Figure 2 This is a cross-sectional SEM image of the precursor obtained in Comparative Example 1. It can be seen from the figure that the amount of the core material of the precursor is relatively large, the core is relatively dense, and there are no honeycomb-like holes.

[0090] Comparative Example 2

[0091] The only difference between Comparative Example 2 and Example 1 is that during the growth stage, the mixed metal salt solution was introduced into the reactor at a flow rate of 1.5 L / min, and K was 0.0416.

[0092] Figure 3 This is a cross-sectional SEM image of the precursor obtained in Comparative Example 2. It can be seen from the figure that due to the excessively large growth coefficient K, the precursor growth rate is too fast, and eventually loose agglomerates are formed with no boundaries between the inner core and the outer shell.

[0093] Comparative Example 3

[0094] The only difference between Comparative Example 3 and Example 1 is that the oxygen concentration in the gas above the liquid level in the reactor was adjusted to 6% during the growth phase.

[0095] Figure 4 This is a cross-sectional SEM image of the precursor obtained in Comparative Example 3. It can be seen from the figure that due to the high oxygen content above the reactor during the growth stage, the core area of the precursor is severely oxidized, forming a single huge hole.

[0096] Example 2

[0097] Prepare a mixed metal salt solution of nickel sulfate, cobalt sulfate, manganese sulfate, and aluminum sulfate with a total metal concentration of 1.8 mol / L. The molar ratio of nickel, cobalt, manganese, and aluminum is 70:10:19:1. Add 60 L of pure water to a 300 L reactor, followed by liquid caustic soda and industrial ammonia. Adjust the ammonia concentration to 22 g / L, the pH to 12.60, the temperature to 60°C, and the reactor speed to 350 rpm.

[0098] The mixed metal salt solution was introduced into the reactor at a flow rate of 0.8 L / min. At the same time, sodium hydroxide solution, ammonia solution, and compressed air were introduced in parallel to maintain the ammonia concentration of the reaction system at 22 g / L, the pH value at 12.60, and the oxygen concentration in the gas above the liquid surface in the reactor at 18%. After 4 minutes of nucleation, the sodium hydroxide solution was stopped and the growth phase began. At the same time, 50 mL of the slurry was tested and its Dv0 was 0.18 μm. According to K The growth coefficient K was adjusted to 0.017, and the flow rate of the mixed metal salt solution during the growth phase was 0.9 L / min. After the pH of the reaction system dropped to 9.9, sodium hydroxide solution was introduced to maintain the pH of the reaction system at 9.9. At 60 minutes after the nucleation phase, the oxygen concentration in the gas above the liquid surface in the reactor was 2%. The supernatant in the reactor was discharged through a physical sedimentation tank or concentrator. When the reaction slurry reached the target particle size, the feed and reaction were stopped, and the product was discharged. The reaction slurry was filtered, aged, washed, dried, and sieved to obtain the precursor product.

[0099] Figure 5 This is the SEM image of the obtained precursor product. It can be seen from the image that the core of the precursor presents honeycomb-shaped holes.

[0100] Example 3

[0101] Prepare a mixed metal salt solution of nickel sulfate, cobalt sulfate, manganese sulfate, and zirconium nitrate with a total metal concentration of 2.2 mol / L. The molar ratio of nickel, cobalt, manganese, and zirconium is 30:30:39.5:0.5. 3 200 L of pure water was added to the reactor, and then liquid alkali was added, the pH was adjusted to 11.80, the temperature was controlled at 40 ° C, and the speed of the reactor was adjusted to 350 rpm.

[0102] The mixed metal salt solution was introduced into the reactor at a flow rate of 0.48 L / min. At the same time, sodium hydroxide solution, ammonia solution, and compressed air were introduced in parallel to maintain the ammonia concentration of the reaction system at 5 g / L and the pH value at 11.80. The oxygen concentration in the gas above the liquid surface in the reactor was maintained at 10%. After 30 minutes of nucleation, the sodium hydroxide solution was stopped and the growth phase began. At the same time, 50 mL of the slurry was tested and its Dv0 was 0.32 μm. According to the K Adjust the growth coefficient K to 0.01 and increase the salt flow rate to 1.4 L / min. After the pH of the reaction system drops to 11.2, introduce sodium hydroxide solution to maintain the pH at 11.2. 32 minutes after the nucleation phase, adjust the oxygen concentration in the gas above the liquid level in the reactor to 5%. Discharge the supernatant from the reactor via a physical settling tank or concentrator. When the reaction slurry reaches the target particle size, stop feeding and reacting, and discharge the slurry. The reaction slurry is filtered, aged, washed, dried, and sieved to obtain the precursor product.

[0103] Figure 6 This is the SEM image of the obtained precursor product. It can be seen from the image that the core of the precursor presents honeycomb-shaped holes.

[0104] Example 4

[0105] Prepare a mixed metal salt solution of nickel sulfate, cobalt sulfate, manganese sulfate, and lanthanum sulfate with a total metal concentration of 1.0 mol / L. The molar ratio of nickel, cobalt, manganese, and lanthanum is 50:30:19.5:0.5. Add 60 L of pure water to a 300 L reactor, followed by liquid caustic soda. Adjust the pH to 12.0, maintain the temperature at 40°C, and maintain the reactor speed at 350 rpm.

[0106] The mixed metal salt solution was introduced into the reactor at a flow rate of 0.48 L / min. At the same time, sodium hydroxide solution, ammonia solution and compressed air were introduced in parallel to maintain the ammonia concentration of the reaction system at 1 g / L, the pH value at 12.0, and the oxygen concentration in the gas above the liquid surface in the reactor at 10%. After 4 minutes of reaction, the sodium hydroxide solution was stopped and the growth stage began. At the same time, 50 mL of the slurry was taken for testing. Its Dv0 was 0.20 μm. According to K The growth coefficient K was adjusted to 0.021, and the salt flow rate during the growth phase was increased to 0.6 L / min. After the pH of the reaction system dropped to 10.5, sodium hydroxide solution was introduced to maintain the pH at 10.5. Forty minutes after the nucleation phase, the oxygen concentration in the gas above the liquid level in the reactor was 5%. The supernatant in the reactor was discharged through a physical settling tank or concentrator. When the reaction slurry reached the target particle size, the feed and reaction were stopped, and the product was discharged. The reaction slurry was filtered, aged, washed, dried, and sieved to obtain the precursor product.

[0107] Figure 7 This is the SEM image of the obtained precursor product. It can be seen from the image that the core of the precursor presents honeycomb-shaped holes.

[0108] Example 5

[0109] Prepare a mixed metal salt solution of nickel sulfate, cobalt sulfate, manganese sulfate and magnesium chloride with a total metal concentration of 2.5 mol / L. The molar ratio of nickel, cobalt, manganese and magnesium is 46:22:31.5:0.5. 3 400 L of pure water was added to the reactor, and then liquid alkali was added, the pH was adjusted to 12.0, the temperature was controlled at 55° C., and the speed of the reactor was adjusted to 350 rpm.

[0110] The mixed metal salt solution was introduced into the reactor at a flow rate of 1.6 L / min. At the same time, sodium hydroxide solution, ammonia solution, and compressed air were introduced in parallel to maintain the ammonia concentration of the reaction system at 7 g / L and the pH value at 12.0. The oxygen concentration in the gas above the liquid surface in the reactor was maintained at 10%. After 12 minutes of nucleation, the sodium hydroxide solution was stopped and the growth phase began. At the same time, 50 mL of the slurry was tested and its Dv0 was 0.26 μm. According to K Adjust the growth coefficient K to 0.014, increase the salt flow rate to 3.2 L / min, and wait until the pH of the reaction system drops to 10.5 before introducing sodium hydroxide solution to maintain the pH at 10.5. Forty minutes after the nucleation phase, the oxygen concentration in the gas above the liquid level in the reactor is 0.18%. Remove the supernatant from the reactor via a physical settling tank or concentrator. When the reaction slurry reaches the target particle size, stop feeding and reacting, and discharge the slurry. The reaction slurry is filtered, aged, washed, dried, and sieved to obtain the precursor product.

[0111] Figure 8 This is the SEM image of the obtained precursor product. It can be seen from the image that the core of the precursor presents honeycomb-shaped holes.

[0112] The precursor products obtained in Examples 1-5 and Comparative Examples 1-3 were tested for Dv50, tap density, specific surface area, secondary particle cross-sectional diameter, honeycomb interface diameter, and average honeycomb hole diameter, and the diameter pitch and honeycomb area ratio were calculated. The results are shown in Table 1.

[0113] Table 1 Characterization of precursors

[0114]

[0115] The specific sintering process is: the precursor and lithium carbonate are mixed evenly at a molar ratio of 1:0.56, and then calcined at 850° C. in an air atmosphere for 5 hours.

[0116] Figure 9 This is a cross-sectional SEM image of the positive electrode material obtained by sintering the precursor mixed with lithium obtained in Example 1. It can be seen from the figure that there are no particles remaining in the hollow part of the hollow material after sintering.

[0117] Figure 10This is a cross-sectional SEM image of the positive electrode material obtained by sintering the precursor mixed with lithium obtained in Comparative Example 1. It can be seen from the figure that particles remain in the hollow of the hollow material after sintering.

[0118] The obtained positive electrode materials were assembled into button batteries in the following ways:

[0119] The positive electrode active material, acetylene black and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 90:5:5, coated on aluminum foil and dried, and stamped into a positive electrode sheet with a diameter of 12 mm and a thickness of 120 μm using a pressure of 100 MPa. The positive electrode sheet was then placed in a vacuum drying oven and dried at 100°C for 12 hours.

[0120] The negative electrode uses a Li metal sheet with a diameter of 17 mm and a thickness of 1 mm; the separator uses a polyethylene porous membrane with a thickness of 25 μm; and the electrolyte uses an equal mixture of 1 mol / L LiPF6, ethylene carbonate (EC) and diethyl carbonate (DEC).

[0121] The positive electrode, separator, negative electrode, and electrolyte were assembled into a 2025-type button cell in an Ar glove box with water and oxygen contents less than 5 ppm. The button cell was then left to rest for 24 hours. Once the open-circuit voltage stabilized, it was charged at a current density of 0.1C to a cutoff voltage of 4.25V. Constant voltage charging at 4.25V was continued until the cutoff current was less than 0.02C. Discharge was then performed at the same current density to a cutoff voltage of 2.8V. This process was repeated once more to produce an activated cell.

[0122] Perform DCIR performance test on activated batteries: let the fully charged battery stand for 1 hour, use 3C current to adjust the battery to 50% SOC, let it stand for another hour, record the voltage V0 at this time, and finally use 3C discharge current I to discharge for 10S, record the voltage V1 at the 10th second, and obtain the discharge DC internal resistance DCIR=(V0-V1) / I.

[0123] The results are as follows Figure 11 As shown in the figure, it can be seen that the button-type battery assembled with the positive electrode material obtained by calcining the precursor obtained in Example 1 has a significantly lower DCIR than the button-type battery assembled with the positive electrode material obtained by calcining the precursor obtained in Comparative Examples 1 to 3, and has excellent output performance.

[0124] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a precursor, characterized in that: The chemical formula of the precursor is Ni x Co y Mn z Me a (OH)2, wherein 0.3≤x≤0.7, 0≤y≤0.4, 0≤z≤0.5, 0≤a≤0.01, x+y+z+a=1, and Me is a doping element; including: (1) Nucleation stage: A mixed salt solution of transition metals or a mixed salt solution of transition metals and doping elements, a precipitant solution, and a complexing agent solution are introduced into the bottom liquid of the reactor in parallel to carry out a nucleation reaction under an oxidizing atmosphere; (2) Growth stage: After the nucleation stage, the growth stage begins. The pH value of the reaction system in the growth stage is lower than that in the nucleation stage. The reaction atmosphere in the growth stage is nitrogen atmosphere or weak oxidizing atmosphere. The growth coefficient K during the growth stage is controlled to be 0.01~0.025; Define the growth coefficient K , where V1 is the flow rate of the mixed salt solution introduced into the reactor during the nucleation stage, in L / min; V2 is the flow rate of the mixed salt solution introduced into the reactor during the growth stage, in L / min; R1 is the particle size Dv0 of the reaction slurry after the nucleation stage, in μm; t is the time of the nucleation stage, in min; K is in μm / min; (3) The obtained reaction slurry is filtered, washed, and dried to obtain a precursor.

2. The preparation method according to claim 1, wherein The transition metal includes Ni.

3. The preparation method according to claim 1, wherein The transition metal includes Ni and at least one of Co and Mn.

4. The preparation method according to claim 1, wherein The doping element is one or more of Al, Mg, Zr and La.

5. The preparation method according to any one of claims 1 to 4, wherein The pH value of the reaction kettle bottom liquid is 11.80-12.60, and the ammonia concentration is 0-22 g / L.

6. The preparation method according to claim 5, wherein The volume of the reactor bottom liquid is 20-70% of the reactor volume.

7. The preparation method according to claim 1, wherein The total concentration of metal ions in the mixed salt solution is 1.0-2.5 mol / L.

8. The preparation method according to claim 1, wherein The total concentration of metal ions in the mixed salt solution is 1.8-2.2 mol / L.

9. The preparation method according to claim 1, wherein The precipitant solution is an alkaline solution.

10. The preparation method according to claim 9, characterized in that The concentration of the alkaline solution is 5-30 wt %.

11. The preparation method according to claim 1, wherein The complexing agent solution is an ammonia solution.

12. The preparation method according to claim 1 or 11, characterized in that: The concentration of the complexing agent solution is 10-30 wt %.

13. The preparation method according to claim 1, wherein The pH value of the reaction system in the nucleation stage is 11.80-12.60, and the ammonia concentration is 0-22 g / L.

14. The preparation method according to claim 1 or 13, characterized in that: The time of the nucleation stage is 1 to 30 minutes.

15. The preparation method according to claim 1, wherein The flow rate of the mixed salt solution introduced per minute during the nucleation stage is 0.5-2% of the volume of the bottom liquid of the reactor.

16. The preparation method according to claim 1, wherein The oxygen concentration in the gas above the liquid surface in the reactor during the nucleation stage is above 10%.

17. The preparation method according to claim 1, wherein The pH value of the reaction system in the growth stage is 9.90-11.20, and the ammonia concentration is 0-22 g / L.

18. The preparation method according to claim 1 or 17, characterized in that: During the growth stage, the oxygen concentration in the gas above the liquid surface in the reactor is not higher than 5%.

19. The preparation method according to claim 18, characterized in that Within 60 minutes after the end of the nucleation reaction, the oxygen concentration in the gas above the liquid surface in the growth reactor is adjusted to reach the target value.

20. A precursor, characterized in that Prepared by the preparation method according to any one of claims 1 to 19; the core region of the secondary particles of the precursor is a honeycomb hole structure.

21. The precursor according to claim 20, characterized in that The cross-sectional area of the honeycomb hole structure region accounts for 20-70% of the cross-sectional area of the precursor secondary particles.

22. The precursor according to claim 20, wherein The cross-sectional area of the honeycomb hole structure region accounts for 30-60% of the cross-sectional area of the precursor secondary particles.

23. The precursor according to claim 20, characterized in that The average pore diameter of the honeycomb pore structure region is 40 nm to 600 nm.

24. The precursor according to claim 20, characterized in that The average pore diameter of the honeycomb pore structure region is 100-300 nm.

25. The precursor according to any one of claims 20 to 24, characterized in that The Dv50 of the precursor is 2.0-6.0 μm, the diameter distance is ≤0.8, and the specific surface area is 15-60 m 2 / g.

26. A positive electrode material, characterized in that Obtained by sintering the precursor according to any one of claims 20 to 25 mixed with lithium.

27. A lithium ion battery, characterized in that: Comprising the positive electrode material according to claim 26.

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