Nickel-based single-crystal hydroxide precursor, single-crystal cathode material and preparation method thereof

Abstract

This invention provides a nickel-based single-crystal hydroxide precursor, a single-crystal cathode material, and a method for preparing the same. The precursor preparation method includes: preparing a mixed salt solution containing nickel, cobalt, and manganese salts; adding the mixed salt solution, ammonia solution, and sodium hydroxide solution concurrently to a reactor containing a base liquid under an inert atmosphere and stirring conditions, controlling the pH to carry out a staged nucleation-ripening reaction; after the reaction, adjusting the pH of the system, waiting for the nickel-based single-crystal hydroxide nuclei to grow to a predetermined particle size, and then aging, filtering, washing, and drying to obtain the nickel-based single-crystal hydroxide precursor. The single-crystal cathode material preparation method includes uniformly mixing the precursor with a lithium source, and then sintering in stages under an oxygen atmosphere to obtain the single-crystal cathode material. This invention enables the controllable preparation of highly dispersed, large-sized single-crystal hydroxide precursors; the prepared cathode material has advantages such as high specific capacity, good rate performance, and excellent reversibility.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode material technology, and more specifically, relates to a nickel-based single-crystal hydroxide precursor, a single-crystal cathode material, and a method for preparing the same. Background Technology

[0002] High-nickel ternary cathode materials are an important component of lithium-ion batteries, possessing unique advantages in terms of energy density and cost. However, the large-scale application of high-nickel (Ni≥80%) ternary cathode materials, especially ultra-high-nickel (Ni>90%) cathode materials, is severely restricted by poor electrochemical performance and insufficient safety performance caused by structural and thermodynamic instability.

[0003] Currently, large-particle polycrystalline spherical structures and single-crystal structures are two common particle structures in high-nickel cathode materials. Large-particle polycrystalline spherical particles are formed by the agglomeration of anisotropic primary nanocrystalline single-crystal particles, exhibiting good flowability and a low specific surface area. However, these secondary particles, agglomerated by intermolecular forces, are prone to breakage during electrode rolling. Furthermore, the disordered volume effect of the anisotropic primary particles during charge-discharge cycling leads to the generation and propagation of intergranular and lattice cracks, exacerbating interfacial side reactions and drastically reducing the volumetric energy density, structural stability, and thermal stability of large-particle polycrystalline layered nickel-based oxide cathode materials. This is a major problem currently facing commercially available polycrystalline and agglomerated cathode materials.

[0004] Single-crystal particle structures can improve the structural stability of materials, effectively solving the aforementioned problems of polycrystalline materials. The particle structure of nickel-based hydroxide precursors directly affects the sintering process of single-crystal high-nickel cathode materials. In its previous research on the synthesis of single-crystal NCA cathode materials, the applicant discovered [Journal of Alloys and Compounds, 2017, 695:91-99] that Ni… 0.8 Co 0.15 Al 0.05 The particle size and specific surface area of ​​the (OH)₂ precursor determine the size and electrochemical performance of the single-crystal finished material. Small particle size (3–5 μm) and high specific surface area (approximately 40 m²) are desirable. 2 Due to its high reactivity, the precursor (e.g., 1 / g) can be used to prepare monodisperse single-crystal NCA cathode materials at a sintering temperature of 800℃ and a lithium ratio of 1.15. These materials exhibit superior volumetric energy density and electrochemical stability compared to large-particle polycrystalline spherical structures. However, this method still requires high-temperature, high-lithium-over-ratio sintering, and the reversibility, rate performance, and cycle performance of the resulting single-crystal cathode materials remain insufficient.

[0005] To address the aforementioned issues, various improvement approaches have been explored. For example, polycrystalline precursors are wet-mixed, dried, and sintered in a rotary furnace; however, the resulting particles have irregular morphologies and excessively large sizes, hindering performance. Another approach involves adding inorganic or organic dispersants during co-precipitation to obtain single-crystal precursors, but this requires additional dispersants and ethanol washing, and the products are prone to agglomeration. Yet another method involves preparing single-crystal doped nickel hydroxide precursors with relatively large primary particles via ammonia complexation-boiling precipitation; however, this method yields precursors that are large, sheet-like primary particles agglomerated into spherical / quasi-spherical shapes, requiring the resulting single-crystal cathode material to be crushed and graded. Furthermore, the reaction rate under boiling conditions is too fast, making controllable preparation impossible, and ammonia volatilization is difficult to control.

[0006] Therefore, in order to improve the performance and scale up the application of ultra-high specific capacity and high rate nickel-based oxide cathode materials, it is urgent to develop a controllable preparation technology for highly dispersed single crystal precursors. Summary of the Invention

[0007] In view of the shortcomings of the prior art, one of the objectives of this invention is to solve one or more problems existing in the prior art. For example, one objective of this invention is to provide a method for the controllable preparation of highly dispersed, large single-crystal hydroxide precursors.

[0008] To achieve the above objectives, one aspect of the present invention provides a method for preparing a nickel-based single-crystal hydroxide precursor, which may include the following steps: preparing a mixed salt solution containing nickel, cobalt, and manganese salts; under an inert atmosphere and stirring conditions, adding the mixed salt solution, ammonia solution, and sodium hydroxide solution in parallel to a reactor containing a base liquid, controlling the pH to 12.5–13.0, and carrying out a staged feeding nucleation-ripening reaction; wherein, during the nucleation stage, the three solutions are fed in parallel, and during the ripening stage, the feeding is stopped, and the total reaction time is 1–10 hours; after the reaction is completed, adjusting the pH of the system to 10.5–11.5, and waiting for the nickel-based single-crystal hydroxide nucleus particle size to reach a predetermined value, and then aging, filtering, washing, and drying to obtain the nickel-based single-crystal hydroxide precursor Ni. 1-x- y Co x Mn y (OH)2, where 0≤x≤0.2, 0≤y≤0.2.

[0009] Furthermore, the ratio of nucleation time to ripening time can be 1:(0.9~1.1).

[0010] Furthermore, in the stepped feeding nucleation-ripening reaction process and the growth of nickel-based single-crystal hydroxide nuclei, the ammonia concentration in the reaction system can be 1.5 mol / L ~ 2.5 mol / L, and the reaction temperature can be 60 ℃ ~ 90 ℃.

[0011] Furthermore, the flow rate for adding the mixed salt solution can be 10 mL / min to 2 L / min, the flow rate for adding the ammonia solution can be 5 mL / min to 1 L / min, and the flow rate for adding the sodium hydroxide solution can be 5 mL / min to 1 L / min; the stirring speed can be 500 rpm to 900 rpm.

[0012] Furthermore, the nickel salt can be NiSO4·6H2O, the cobalt salt can be CoSO4·7H2O, and the manganese salt can be MnSO4·H2O; in the mixed salt solution, Ni 2+ Co 2+ Mn 2+ The sum of ion concentrations can be 1 mol / L to 2 mol / L; the substrate can be an ammonia solution with an ammonia concentration of 1.5 mol / L to 2.5 mol / L, and the predetermined particle size can be 1 μm to 5 μm.

[0013] Another aspect of the present invention provides a nickel-based single-crystal hydroxide precursor, wherein the primary particle size of the precursor can be 1 μm to 5 μm, the morphology can be hexagonal prism or prism-like, and the specific surface area can be <10 m². 2 / g.

[0014] Another aspect of the present invention provides a method for preparing a single-crystal cathode material, which may include the following steps: mixing the nickel-based single-crystal hydroxide precursor prepared above with a lithium source uniformly, and then sintering it in segments under an oxygen atmosphere to obtain the single-crystal cathode material LiNi. 1-x-y Co x Mn y O2, where 0≤x≤0.2, 0≤y≤0.2; segmented sintering includes: holding at 400 ℃~500 ℃ for 2~6h, and then sintering at 680 ℃~750 ℃ ​​for 8~15h.

[0015] Furthermore, the lithium source can be LiOH·H2O, and the ratio of the total molar amount of nickel, cobalt and manganese to the molar amount of lithium in the lithium source can be 1:(1.01~1.05).

[0016] Another aspect of the present invention provides a single-crystal cathode material, wherein the primary particle size of the single-crystal cathode material can be 1 μm to 5 μm, the morphology can be hexagonal prism or prism-like, and the specific surface area can be <2 m². 2 / g high-nickel true single-crystal layered oxide cathode material.

[0017] Compared with the prior art, the beneficial effects of the present invention include at least one of the following: (1) This invention prepares single crystal precursors by synergistic regulation of nucleation-maturation-growth; by step feeding nucleation, the agglomeration of amorphous nanocrystal nuclei is effectively reduced, and micro-nano-scale, highly dispersed and pre-maturated nickel-based single crystal hydroxide nuclei are obtained; then, crystal growth is synergistically controlled to achieve controllable preparation of highly dispersed, large single crystal hydroxide precursors.

[0018] (2) The single crystal precursor prepared by the present invention has a controllable D50 of 1 μm to 5 μm, uniform particle size distribution, uniform morphology, high dispersion, controllable crystal structure, simple process, no need to add additional dispersant, good product consistency, and can be mass-produced; the preparation of single crystal cathode material by using single crystal precursor can avoid the disadvantages of high lithium content and high temperature calcination of traditional methods, save energy and reduce consumption from the source, and is green and economical.

[0019] (3) The single-crystal high-nickel cathode material prepared by the present invention inherits the crystal structure characteristics of the single-crystal precursor, has the lithium storage structure characteristics of few defects or no defects, and has the advantages of high specific capacity, good rate performance and excellent reversibility. Attached Figure Description

[0020] The above and other objects and features of the present invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which: Figure 1 Ni prepared in Example 1 0.89 Co 0.07 Mn 0.04 SEM image of (OH)2 precursor; Figure 2 Ni prepared in Example 2 0.92 Co 0.05 Mn 0.03 SEM image of (OH)2 precursor; Figure 3 Ni prepared in Example 3 0.92 Co 0.05 Mn 0.03 SEM image of (OH)2 precursor; Figure 4 Ni prepared in Example 3 0.92 Co 0.05 Mn 0.03 XRD pattern of (OH)2 precursor material; Figure 5 LiNi prepared in Example 3 0.92 Co 0.05 Mn 0.03 SEM image of O2 cathode material; Figure 6 LiNi prepared in Example 3 0.92 Co 0.05 Mn0.03 Charge-discharge curves of O2 cathode material at 0.1C; Figure 7 The graph shows the cycle performance of the cathode material prepared in Example 3. Detailed Implementation

[0021] In the following, the nickel-based single-crystal hydroxide precursor, single-crystal cathode material and its preparation method according to the present invention will be described in detail with reference to the accompanying drawings and exemplary embodiments.

[0022] Specifically, the method of this invention prepares nickel-based single-crystal hydroxide precursors through synergistic regulation of nucleation, initial maturation, and growth, and prepares single-crystal high-nickel cathode materials through low-temperature, low-over-lithium sintering. Specifically, firstly, micro-nano-scale, highly dispersed, and initially matured nickel-based single-crystal hydroxide nuclei are prepared using a step-feed method under high pH conditions of 12.5–13.0; then, the pH is lowered (10.5–11.5) to the nucleus growth point, allowing the single-crystal nuclei to grow slowly, obtaining micron-scale nickel-based single-crystal hydroxide precursors; finally, the precursors, after aging, washing, and drying, are mixed with lithium hydroxide and sintered to obtain single-crystal high-nickel cathode materials. The method of this invention enables the controllable preparation of precursor composition, primary particle size, aspect ratio, and morphology of nickel-based single-crystal hydroxides. Using this single-crystal precursor, true single-crystal high-nickel cathode materials can be sintered at <800℃ and with an over-lithium ratio of <5%, breaking through the harsh conditions of high temperature and high over-lithium ratio involved in the preparation of traditional single-crystal cathode materials. It avoids crystal defects caused by recrystallization. The prepared single-crystal high-nickel cathode material perfectly inherits the crystal structure of the single-crystal precursor, possesses lithium storage structure characteristics with few or no defects, and has advantages such as high specific capacity, good rate performance, and excellent reversibility.

[0023] One aspect of the present invention provides a method for preparing a nickel-based single-crystal hydroxide precursor, which in some embodiments may include the following steps: S01, prepare a mixed salt solution containing nickel salt, cobalt salt and manganese salt; S02, under inert atmosphere and stirring conditions, a mixed salt solution, ammonia solution and sodium hydroxide solution are added in parallel to a reactor containing a bottom liquid, and the pH is controlled at 12.5-13.0 to carry out a staged feeding nucleation-ripening reaction; wherein, the three solutions are fed in parallel during the nucleation stage, and the feeding is stopped during the ripening stage, and the total reaction time is 1-10 hours; After the reaction of SO3 is completed, the pH of the system is adjusted to 10.5–11.5. Once the particle size of the nickel-based single-crystal hydroxide nuclei reaches the predetermined value, the nickel-based single-crystal hydroxide precursor Ni is obtained after aging, filtration, washing, and drying. 1-x-y Co x Mn y (OH)2, where 0≤x≤0.2, 0≤y≤0.2.

[0024] In some implementations, nickel, cobalt, and manganese salts can be prepared according to the stoichiometric ratio of the nickel-based single-crystal hydroxide precursor chemical formula. The nickel salt can be NiSO4·6H2O, the cobalt salt can be CoSO4·7H2O, and the manganese salt can be MnSO4·H2O.

[0025] In some embodiments, the flow rate of the mixed salt solution added to the reactor in a co-current manner can be 10 mL / min to 2 L / min, the flow rate of the ammonia solution can be 5 mL / min to 1 L / min, and the flow rate of the sodium hydroxide solution can be 5 mL / min to 1 L / min. For example, the flow rate of the mixed salt solution can be 100 mL / min to 1 L / min, the flow rate of the ammonia solution can be 500 mL / min to 800 mL / min, and the flow rate of the sodium hydroxide solution can be 200 mL / min to 800 mL / min. The ammonia solution and sodium hydroxide solution can be used to coordinate the ammonia concentration and pH value of the reaction system. In some embodiments, Ni in the mixed salt solution... 2+ Co 2+ Mn 2+ The sum of ion concentrations can range from 1 mol / L to 2 mol / L. For example, Ni 2+ Co 2+ Mn 2+ The sum of ion concentrations can be a combination of 1.1 mol / L to 1.8 mol / L, 1.3 mol / L to 1.7 mol / L, 1.5 mol / L to 1.6 mol / L, or higher. The concentration of the ammonia solution can be 10 mol / L to 14 mol / L, and the concentration of the sodium hydroxide solution can be 9 mol / L to 11 mol / L. For example, the concentration of the ammonia solution can be 12 mol / L, and the concentration of the sodium hydroxide solution can be 10 mol / L.

[0026] In some embodiments, the base solution can be an aqueous ammonia solution with an ammonia concentration of 1.5 mol / L to 2.5 mol / L. For example, the base solution can be an aqueous ammonia solution with an ammonia concentration of 2.0 mol / L. The volume of the base solution can be 50 to 60% of the reactor volume. The reactor can be a reaction vessel.

[0027] In some implementations, the inert atmosphere may be a nitrogen atmosphere. The stirring speed may be 500 rpm to 900 rpm. For example, the stirring speed may be a combination of 550 rpm to 840 rpm, 610 rpm to 800 rpm, 690 rpm to 720 rpm, or a range above.

[0028] In some implementations, the nucleation-ripening reaction time for the staged feed can be 1 to 10 hours. The ratio of nucleation time to ripening time can be 1:(0.9 to 1.1), for example, a time ratio of 1:1. As another example, the "feed nucleation 30 minutes - ripening 30 minutes" operation can be repeated 1 to 10 times; during the nucleation process, the metal salt solution, alkaline solution, and ammonia are fed in parallel, and the feeding is stopped during the ripening process. During the staged feed nucleation process, the ammonia concentration in the reaction system is maintained at 1.5 mol / L to 2.5 mol / L, the pH value at 12.5 to 13.0, and the reaction system temperature at 60 °C to 90 °C. For example, during the staged feed nucleation process, the ammonia concentration in the reaction system is maintained at 1.7 mol / L to 2.0 mol / L, the pH value at 12.6 to 12.9, and the reaction system temperature at 65 °C to 85 °C. For example, during the staged feeding nucleation process, the ammonia concentration in the reaction system is maintained at 1.8 mol / L, the pH value at 12.8, and the reaction system temperature at 75 ℃.

[0029] In some implementation schemes, after the staged feed nucleation-ripening reaction is completed, the ammonia concentration in the reaction system can be maintained at 1.5 mol / L to 2.5 mol / L, and the system pH can be adjusted to 10.7 to 11.2 to allow nickel-based single-crystal hydroxide nuclei to grow for 20 to 100 hours. The precursor particle size and morphology are monitored throughout the process, and feeding is stopped once the single-crystal precursor particle size reaches the target size. For example, the ammonia concentration can be maintained at 2.0 mol / L, and the system pH can be adjusted to 11 to allow nickel-based single-crystal hydroxide nuclei to grow for 80 hours before feeding is stopped. The predetermined particle size can be 1 μm to 5 μm, for example, 2 μm to 3 μm or 2.2 μm to 2.8 μm.

[0030] In some implementations, aging can be carried out by continuously adding precursor slurry and stirring for 0.5 to 2 hours after stopping the feed. The washing and drying can be carried out by first stirring and washing with a 5% sodium hydroxide solution at 60°C for 30 minutes, and then washing with deionized water at 60°C until the pH value of the washing solution is lower than 10. After solid-liquid separation, the slurry is placed in a forced-air drying oven at 100 to 150°C and dried for 10 to 20 hours to obtain a nickel-based single crystal hydroxide precursor.

[0031] Another aspect of the present invention provides a nickel-based single-crystal hydroxide precursor, which can be prepared by the nickel-based single-crystal hydroxide precursor preparation method described above. In some embodiments, the primary particle size of the precursor can be 1 μm to 5 μm, the morphology can be hexagonal prism or prism-like, and the specific surface area can be <10 m². 2 / g. For example, the primary particle size of the precursor can be 2 μm to 4 μm, and the specific surface area can be 2 to 8 m². 2 / g.

[0032] Another aspect of the present invention provides a method for preparing a single-crystal cathode material. In some embodiments, the method may include the following steps: After uniformly mixing a nickel-based single-crystal hydroxide precursor with a lithium source, the mixture was sintered in sections under an oxygen atmosphere to obtain a high-nickel true single-crystal layered oxide cathode material, LiNi. 1-x-y Co x Mn y O2, where 0 ≤ x ≤ 0.2, 0 ≤ y ≤ 0.2. In some embodiments, segmented sintering may include: holding at 400 ℃ to 500 ℃ for 2 to 6 h, then sintering at 680 ℃ to 750 ℃ ​​for 8 h to 15 h. For example, segmented sintering may include: holding at 420 ℃ to 480 ℃ for 3 h to 5 h, then sintering at 700 ℃ to 720 ℃ for 10 h to 13 h.

[0033] In some implementations, the lithium source can be LiOH·H2O. The molar ratio of the total molar amount of nickel, cobalt, and manganese to the molar amount of lithium in the lithium source can be 1:(1.01 to 1.05).

[0034] Another aspect of the present invention provides a single-crystal cathode material. In some embodiments, the single-crystal cathode material has a primary particle size of 1 μm to 5 μm, a morphology of hexagonal prism or prism-like, and a specific surface area of ​​<2 m². 2 / g of high-nickel true single-crystal layered oxide cathode material. For example, the single-crystal cathode material has a primary particle size of 2 μm to 4 μm, a morphology of hexagonal prism or prism-like, and a specific surface area of ​​<1 m². 2 / g high-nickel true single-crystal layered oxide cathode material.

[0035] To better understand the present invention, specific examples are provided below to further illustrate the content of the present invention, but the content of the present invention is not limited to the examples below. Example 1

[0036] A nickel-based single-crystal hydroxide precursor, a single-crystal cathode material, and a method for preparing the same, wherein the molecular formula of the single-crystal cathode material is LiNi. 0.89 Co 0.07 Mn 0.04 O2 can include the following steps: Step 1: Mix NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O in the order n(Ni) 2+ ): n(Co 2+ ): n(Mn 2+The metal salt mixtures were mixed in a ratio of 89:7:4 to prepare a 2 mol / L total concentration solution; a 10 mol / L sodium hydroxide solution was prepared; and a 10 mol / L ammonia solution was prepared. In a 100L reactor, 45L of deionized water and 11L of ammonia solution were added as a base solution, with the pH controlled at 12.5 and the ammonia concentration at 2 mol / L. After completely sealing the reaction vessel and testing its airtightness, nitrogen gas (0.2 m³ / L) was introduced. 3 / h), to completely replace the oxygen in the reactor with protective gas. When the temperature inside the reactor reaches 80℃, the mixed metal salt solution, sodium hydroxide solution, and ammonia solution are pumped into the reactor at flow rates of 40mL / min, 16mL / min, and 16mL / min, respectively, with the stirring speed controlled at 800r / min. By adjusting the flow rates of the sodium hydroxide solution and ammonia solution, the pH value of the entire reactor is maintained at 12.5, and the ammonia concentration is maintained at 2mol / L. Nucleation is carried out in stages for 8 hours. After the reaction is completed, the flow rate of the alkali solution is reduced, so that the pH of the solution in the reactor slowly decreases to 10.50, while the ammonia concentration remains unchanged. The reaction continues for 20 hours, then all feeding is stopped. After the slurry is aged for 30 minutes, the mother liquor is filtered, washed with 60℃ alkali solution for 30 minutes, and then washed with 60℃ deionized water until the pH is below 10. Then it is filtered and placed in a 100℃ forced-air drying oven for 20 hours to obtain Ni. 0.89 Co 0.07 Mn 0.04 (OH)2 precursor sample, SEM image is shown below. Figure 1 .

[0037] Step 2: The precursor prepared in Step 1 was mixed with LiOH·H2O at a lithiation ratio of 1:1.05 and thoroughly ball-mixed for 60 min to ensure homogeneity. The mixture was then placed in a tube furnace for high-temperature sintering under oxygen-rich conditions. The heating rate was controlled at 3℃ / min; the temperature was raised to 450℃ and held for 3 h, then further raised to 750℃ and held for 12 h. After natural cooling to room temperature, the sample was removed and ground to obtain the single-crystal cathode material LiNi. 0.89 Co 0.07 Mn 0.04 O2. The discharge capacity of this cathode material is 212.25 mAh / g, the discharge capacity at 10C is 163.8 mAh / g, and the cycle capacity retention at 1C is 94.6% (first 50 cycles). Example 2

[0038] A nickel-based single-crystal hydroxide precursor, a single-crystal cathode material, and a method for preparing the same, wherein the molecular formula of the single-crystal cathode material is LiNi. 0.92 Co 0.05 Mn 0.03 O2 can include the following steps: Step 1: Mix NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O in the order n(Ni) 2+ ): n(Co 2+ ): n(Mn 2+ The metal salt mixtures were mixed in a ratio of 92:5:3 to prepare a 1.5 mol / L total concentration solution; a 10 mol / L sodium hydroxide solution was prepared; and a 14 mol / L ammonia solution was prepared. In a 100L reactor, 50L of deionized water and 6L of ammonia solution were added as a base solution, with the pH controlled at 12.7 (±0.05) and the ammonia concentration at 1.5 mol / L. After completely sealing the reaction vessel and testing its airtightness, nitrogen gas (0.2 m³ / L) was introduced. 3 / h), to completely replace the oxygen in the reactor with protective gas. When the temperature inside the reactor reaches 70℃, a mixed metal salt solution, sodium hydroxide solution, and ammonia solution are pumped into the reactor at flow rates of 80 mL / min, 24 mL / min, and 20 mL / min, respectively. The stirring speed is controlled at 800 r / min. The pH value of the entire reactor is maintained at 12.7 (±0.05) and the ammonia concentration is maintained at 1.5 mol / L by adjusting the flow rates of the sodium hydroxide solution and ammonia solution. Nucleation is carried out in stages for 5 hours. After the reaction is completed, the flow rate of the alkali solution is reduced, and the pH of the solution in the reactor is slowly reduced to 11.30 (±0.05). The reaction is continued for 80 hours. After the reaction is completed, the slurry is aged for 1 hour and then washed, filtered, and dried using the same method as in Example 1 above. Ni is obtained. 0.92 Co 0.05 Mn 0.03 (OH)2 precursor sample, SEM image is shown below. Figure 2 .

[0039] Step 2: The precursor prepared in Step 1 was mixed with LiOH·H2O at a lithiation ratio of 1:1.03 and thoroughly ball-mixed for 60 min to ensure homogeneity. The mixture was then placed in a tube furnace and sintered at high temperature under oxygen-enriched conditions. The heating rate was controlled at 3℃ / min; the temperature was raised to 480℃ and held for 4 h, then further raised to 720℃ and held for 12 h. After natural cooling to room temperature, the sample was removed and ground to obtain the single-crystal cathode material LiNi. 0.92 Co 0.05 Mn 0.03 O2. The cathode material has a discharge capacity of 218.6 mAh / g at 0.1C, a discharge capacity of 172.5 mAh / g at 10C, and a cycle capacity retention of 92.5% (first 50 cycles) at 1C. Example 3

[0040] A nickel-based single-crystal hydroxide precursor, a single-crystal cathode material, and a method for preparing the same, wherein the molecular formula of the single-crystal cathode material is LiNi.0.92 Co 0.05 Mn 0.03 O2 can include the following steps: Step 1: Prepare the same metal salt mixed solution, sodium hydroxide solution, and ammonia solution as in Example 2. In a 100L reactor, pre-add 45L of deionized water and 10L of ammonia solution as the base solution, controlling the pH of the base solution to 12.5 and the ammonia concentration to 2.5mol / L. After completely sealing the reaction vessel and testing its airtightness, begin introducing nitrogen gas (0.2m³). 3 / h), to completely replace the oxygen in the reactor with protective gas. When the temperature inside the reactor reaches 80℃, the metal salt mixed solution, sodium hydroxide solution, and ammonia solution are pumped into the reactor at flow rates of 80mL / min, 24mL / min, and 24mL / min, respectively. The stirring speed is controlled at 700r / min. The pH value of the entire reactor is maintained at 12.5 and the ammonia concentration is maintained at 2.5mol / L by adjusting the flow rates of the sodium hydroxide solution and ammonia solution. Nucleation is carried out in stages for 3 hours. After the reaction is completed, the alkaline solution feed is stopped, and the pH of the solution in the reactor is reduced to 10.8 (±0.05). The reaction is continued for 100 hours. After the reaction is completed, the slurry is aged for 1 hour and then washed, filtered, and dried using the same method as in Example 1 above. Ni is obtained. 0.92 Co 0.05 Mn 0.03 (OH)2 precursor sample, SEM image is shown below. Figure 3 The structure of the single-crystal precursor material prepared in Example 3 was characterized using X-ray powder diffraction, and the results are as follows: Figure 4 As shown in the figure, this is a typical XRD pattern of a layered structure, with no other impurity peaks, indicating that the obtained material is a single pure phase.

[0041] Step 2: The precursor prepared in Step 1 was mixed with LiOH·H2O at a lithiation ratio of 1:1.05 and thoroughly ball-mixed for 60 min to ensure homogeneity. The mixture was then placed in a tube furnace and sintered at high temperature under oxygen-enriched conditions. The heating rate was controlled at 3℃ / min; the temperature was raised to 450℃ and held for 4 h, then further raised to 720℃ and held for 12 h. After natural cooling to room temperature, the sample was removed and ground to obtain the single-crystal cathode material LiNi. 0.92 Co 0.05 Mn 0.03 O2, its SEM image can be found here. Figure 5 The discharge capacity of this cathode material is 222.45 mAh / g, and the initial coulombic efficiency is 92.5%. The charge-discharge curves are shown below. Figure 6 The discharge capacity at 10C is 178.5 mAh / g, and the cycle capacity retention at 1C is 95.42% (first 50 cycles). (See...) Figure 7 . Example 4

[0042] A nickel-based single-crystal hydroxide precursor, a single-crystal cathode material, and a method for preparing the same, wherein the molecular formula of the single-crystal cathode material is LiNi. 0.94 Co 0.05 Mn 0.01 O2, including the following steps: Step 1: Mix NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O in the order n(Ni) 2+ ): n(Co 2+ ): n(Mn 2+ The metal salt mixtures were mixed in a ratio of 94:5:1 to prepare a 2 mol / L total concentration solution; a 10 mol / L sodium hydroxide solution was prepared; and a 14 mol / L ammonia solution was prepared. In a 100L reactor, 50L of deionized water and 8L of ammonia solution were added as a base solution, with the pH controlled at 12.6 (±0.10) and the ammonia concentration at 2.0 mol / L. After completely sealing the reaction vessel and testing its airtightness, nitrogen gas (0.2 m³ / L) was introduced. 3 / h), to completely replace the oxygen in the reactor with protective gas. When the temperature inside the reactor reaches 70℃, a mixed metal salt solution, sodium hydroxide solution, and ammonia solution are pumped into the reactor at flow rates of 80 mL / min, 32 mL / min, and 32 mL / min, respectively. The stirring speed is controlled at 600 r / min. By adjusting the flow rates of the sodium hydroxide solution and ammonia solution, the pH value of the entire reactor is maintained at 12.6 (±0.05), and the ammonia concentration is maintained at 2.0 (±0.05) mol / L. Nucleation is carried out in stages for 5 hours. After the reaction is completed, the alkaline feed is stopped, and the pH of the solution in the reactor is reduced to 11.1 (±0.05). The reaction continues for 80 hours. After the reaction is completed, the slurry is aged for 2 hours and then washed, filtered, and dried using the same method as in Example 1 above. Ni is obtained. 0.94 Co 0.05 Mn 0.01 (OH)2 precursor sample.

[0043] Step 2: The precursor prepared in Step 1 was mixed with LiOH·H2O at a lithiation ratio of 1:1.03 and thoroughly ball-mixed for 60 min to ensure homogeneity. The mixture was then placed in a tube furnace and sintered at high temperature under oxygen-enriched conditions. The heating rate was controlled at 3℃ / min; the temperature was raised to 450℃ and held for 4 h, then further raised to 700℃ and held for 12 h; finally, it was allowed to cool naturally to room temperature. The sample was then removed and ground to obtain the single-crystal cathode material LiNi. 0.94 Co 0.05 Mn 0.01 O2, this cathode material has a very good α-NaFeO3 layered structure, good crystallinity, and good cycle stability. Example 5

[0044] A nickel-based single-crystal hydroxide precursor, a single-crystal cathode material, and a method for preparing the same, wherein the molecular formula of the single-crystal cathode material is LiNi. 0.94 Co 0.05 Mn 0.01 O2, including the following steps: Step 1: Prepare the same metal salt mixed solution, sodium hydroxide solution, and ammonia solution as in Example 4. In a 100L reactor, pre-add 50L of deionized water and 8L of ammonia solution as the base solution, controlling the pH of the base solution to 12.70 (±0.10) and the ammonia concentration to 2mol / L. After completely sealing the reaction vessel and testing its airtightness, begin introducing nitrogen gas (0.2m). 3 / h), to completely replace the oxygen in the reactor with protective gas. When the temperature inside the reactor reaches 90℃, a mixed metal salt solution, sodium hydroxide solution, and ammonia solution are pumped into the reactor at flow rates of 80 mL / min, 32 mL / min, and 32 mL / min, respectively. The stirring speed is controlled at 800 r / min. By adjusting the flow rates of the sodium hydroxide solution and ammonia solution, the pH value of the entire reactor is maintained at 12.7 (±0.05), and the ammonia concentration is maintained at 2.0 (±0.05) mol / L. Nucleation is carried out in stages for 2 hours. After the reaction is completed, the alkaline feed is stopped, and the pH of the solution in the reactor is reduced to 10.80 (±0.05). The reaction continues for 80 hours. After the reaction is completed, the slurry is aged for 2 hours and then washed, filtered, and dried using the same method as in Example 1 above. Ni is obtained. 0.94 Co 0.05 Mn 0.01 (OH)2 precursor sample.

[0045] Step 2: The precursor prepared in Step 1 was mixed with LiOH·H2O at a lithiation ratio of 1:1.05 and thoroughly ball-mixed for 60 min to ensure homogeneity. The mixture was then placed in a tube furnace and sintered at high temperature under oxygen-enriched conditions. The heating rate was controlled at 3℃ / min; the temperature was raised to 450℃ and held for 4 h, then further raised to 680℃ and held for 12 h. After natural cooling to room temperature, the sample was removed and ground to obtain the single-crystal cathode material LiNi. 0.94 Co 0.05 Mn 0.01 O2, this cathode material has a very good α-NaFeO3 layered structure, good crystallinity, and good cycle stability.

[0046] Although the invention has been described above in conjunction with exemplary embodiments, those skilled in the art will understand that various modifications and changes can be made to the exemplary embodiments of the invention without departing from the spirit and scope defined by the claims.

Claims

1. A method for preparing a nickel-based single-crystal hydroxide precursor, characterized in that, Includes the following steps: Prepare a mixed salt solution containing nickel, cobalt, and manganese salts; Under inert atmosphere and stirring conditions, a mixed salt solution, ammonia solution, and sodium hydroxide solution are fed in parallel into a reactor containing a bottom liquid, and the pH is controlled at 12.5–13.0 to carry out a staged feeding nucleation-ripening reaction. During the nucleation stage, the three solutions are fed in parallel, and the feeding is stopped during the ripening stage. The total reaction time is 1–10 hours. After the reaction is complete, the pH of the system is adjusted to 10.5–11.

5. Once the nickel-based single-crystal hydroxide nuclei have grown to the predetermined particle size, the nickel-based single-crystal hydroxide precursor Ni is obtained after aging, filtration, washing, and drying. 1-x-y Co x Mn y (OH)2, where 0≤x≤0.2, 0≤y≤0.

2.

2. The method for preparing a nickel-based single-crystal hydroxide precursor according to claim 1, characterized in that, The ratio of nucleation time to ripening time was 1: (0.9~1.1).

3. The method for preparing a nickel-based single-crystal hydroxide precursor according to claim 1 or 2, characterized in that, During the stepped feed nucleation-ripening reaction process and the growth of nickel-based single-crystal hydroxide nuclei, the ammonia concentration in the reaction system was 1.5 mol / L to 2.5 mol / L, and the reaction temperature was 60 ℃ to 90 ℃.

4. The method for preparing a nickel-based single-crystal hydroxide precursor according to claim 1 or 2, characterized in that, The flow rate for adding the mixed salt solution is 10 mL / min to 2 L / min, the flow rate for adding the ammonia solution is 5 mL / min to 1 L / min, and the flow rate for adding the sodium hydroxide solution is 5 mL / min to 1 L / min. The stirring speed is 500 rpm to 900 rpm.

5. The method for preparing a nickel-based single-crystal hydroxide precursor according to claim 1 or 2, characterized in that, Nickel salt is NiSO4·6H2O, cobalt salt is CoSO4·7H2O, and manganese salt is MnSO4·H2O; in the mixed salt solution, Ni 2+ Co 2+ Mn 2+ The sum of ion concentrations is 1 mol / L to 2 mol / L; the substrate is an ammonia solution with an ammonia concentration of 1.5 mol / L to 2.5 mol / L and a predetermined particle size of 1 μm to 5 μm.

6. A nickel-based single-crystal hydroxide precursor prepared by the method for preparing a nickel-based single-crystal hydroxide precursor according to any one of claims 1 to 5, characterized in that, The precursor primary particles have a particle size of 1 μm to 5 μm, a hexagonal or prismatic morphology, and a specific surface area of ​​<10 m². 2 / g.

7. A method for preparing a single-crystal cathode material, characterized in that, Includes the following steps: The nickel-based single-crystal hydroxide precursor prepared by the method described in any one of claims 1 to 5 is mixed uniformly with a lithium source and then sintered in segments under an oxygen atmosphere to obtain the single-crystal cathode material LiNi. 1-x-y Co x Mn y O2, where 0≤x≤0.2, 0≤y≤0.2; segmented sintering includes: holding at 400 ℃~500 ℃ for 2 h~6 h, then raising the temperature to 680 ℃~750 ℃ ​​for 8 h~15 h.

8. The method for preparing single-crystal cathode material according to claim 7, characterized in that, The lithium source is LiOH·H2O, and the ratio of the total molar amount of nickel, cobalt and manganese to the molar amount of lithium in the lithium source is 1:(1.01~1.05).

9. A single-crystal cathode material, characterized in that, Single-crystal cathode materials have primary particle sizes of 1 μm to 5 μm, with hexagonal or prism-like morphologies and a specific surface area of ​​<2 m². 2 / g high-nickel true single-crystal layered oxide cathode material.

Images