Positive electrode precursor and preparation method thereof, positive electrode material and lithium ion battery

Abstract

The invention relates to the technical field of lithium battery material preparation, in particular to a positive electrode precursor and a preparation method thereof, a positive electrode material and a lithium ion battery. The positive electrode precursor is composed of secondary particles; the secondary particles are configured from a plurality of sheet-like primary particles. Each secondary particle comprises the following three layers of structures from inside to outside: an inner core layer doped with low-valence cation elements, a middle layer doped with high-valence cation elements and a radial growth layer doped with anion elements; the compactness of the intermediate layer is greater than that of the inner core layer and the radial growth layer. The positive electrode precursor is narrow in particle size distribution, high in crystallinity and good in particle sphericity degree, has a lithium ion high-speed migration path and is also beneficial to internal stress release, and the positive electrode material prepared from the precursor has high energy density, fast charging capacity and long service life.

Description

Technical Field

[0001] This invention relates to the field of lithium battery material preparation technology, and more specifically, to cathode precursors and their preparation methods, cathode materials, and lithium-ion batteries. Background Technology

[0002] In recent years, the new energy vehicle market has continuously increased its demands on battery performance, especially on driving range and charging speed. Current battery systems require higher energy density and rate performance. Furthermore, soaring cobalt prices have prompted companies to reduce cobalt content and shift towards high-nickel / cobalt-free systems (such as NCM811, NCA, and 9-series). While increasing nickel content increases specific capacity (e.g., NCM811 reaches 205 mAh / g), it also leads to significant problems such as increased lithium-nickel mixing, increased surface side reactions, and a sharp drop in cycle performance, exacerbating the challenges to the structural stability of battery materials.

[0003] High-nickel ternary precursors (nickel-cobalt-manganese / aluminum hydroxide) are core raw materials for manufacturing high-nickel cathodes (such as NCM / NCA) for lithium-ion batteries. The crystallinity, sphericity, particle size and distribution, and specific surface area of ​​the precursor significantly affect the electrochemical performance of the cathode material, directly determining the battery's energy density, rate performance, and cycle life. However, the random particle stacking in traditional precursors results in tortuous lithium-ion migration paths, failing to meet the requirement of high-speed ion channels for cathode materials under fast-charging conditions. Furthermore, fast charging intensifies concentration polarization, significantly increasing the risk of lithium plating and posing a high safety hazard. Finally, structural instability in high-nickel materials can lead to a precipitous drop in cycle life and rate performance, all of which urgently require optimization from the precursor source.

[0004] In existing technologies, GEM's ultra-high nickel 9-series core-shell ternary precursor (nickel content core > shell) upgrades the precursor from a one-piece structure to a three-piece structure through micron-level microstructure design. The core is loose and porous, while the shell is dense, which improves cycle life and safety. However, the process is relatively complex and has high requirements for the precursor and cathode sintering equipment. The material side needs to solve the problem of interlayer stress cracking. Yibin Guangyuan's patent CN114573047B discloses a high-power NCM precursor and its preparation method. It uses organic additives such as SDBS (sodium dodecylbenzene sulfonate), AES (sodium fatty alcohol polyoxyethylene ether sulfate), and SAS (sodium secondary alkyl sulfonate) to improve the internal porosity of the precursor, accelerate ion transport, and improve the rate performance of the cathode material. However, the addition of organic matter will undoubtedly increase the cost of wastewater treatment. Other manufacturers use hydrogen peroxide (H2O2) and peracetic acid to replace air / oxygen as oxidants, adjust the dissolved oxygen concentration of the slurry, precisely control the core porosity, and improve lithium-ion transport. However, the use of oxidants increases safety hazards, shortens the service life of equipment, and increases production costs.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a cathode precursor and its preparation method, a cathode material, and a lithium-ion battery. The cathode precursor provided in the embodiments of this invention has a narrow particle size distribution, high crystallinity, good particle sphericity, and a high-speed lithium-ion migration path, which also facilitates internal stress release. The cathode material obtained using this precursor balances high energy density, fast charging capability, and long lifespan.

[0007] This invention is implemented as follows: In a first aspect, the present invention provides a positive electrode precursor, the positive electrode precursor being composed of secondary particles; the secondary particles being composed of a plurality of plate-like primary particles; The secondary particles consist of three layers from the inside out: a core layer doped with low-valence cations, an intermediate layer doped with high-valence cations, and a radial growth layer doped with anions; the intermediate layer is more compact than the core layer and the radial growth layer; the high-valence cations have a higher valence state than the low-valence cations.

[0008] In an optional embodiment, the positive electrode precursor satisfies at least one of the following requirements: (1) The positive electrode precursor is spherical or near-spherical; (2) The sphericity of the positive electrode precursor is 0.7-0.95; (3) The total porosity of the secondary particle profile of the positive electrode precursor is 5%-35%; preferably 8%-20%; (4) The average pore volume of the positive electrode precursor is 0.02-0.11 cm³. 3 / g; (5) The median particle size D50 of the positive electrode precursor is 5-14.5 μm; (6) The particle size distribution of the positive electrode precursor is span=(D90-D10) / D50, and span is 0.3-0.7; (7) The specific surface area BET of the positive electrode precursor is 6-18m². 2 / g; (8) The tap density TD of the positive electrode precursor is 1.5-1.9 g / cm³. 3 ; (9) The positive electrode precursor has a pressure particle size of 0.1-5.3 μm and a fragmentation degree of 1%-20% at 0.75-2T. The pressure particle size refers to the difference between D50 after pressing at 0.75-2T and D50 before pressing, and the fragmentation degree refers to the ratio of pressure particle size to D50 before pressing.

[0009] In an optional embodiment, the molecular formula of the positive electrode precursor is: Ni x Co y Mn z M m N n L p (OH)₂, where x+y+z+m+n+p=1, 0.8≤x≤0.97, 0≤y≤0.10, 0≤z≤0.10, 0≤m≤0.02, 0≤n≤0.02, 0≤n≤0.02, M is a low-valence cation element, doped in the core layer; N is a high-valence cation element, doped in the intermediate layer; L is an anion element, doped in the radial growth layer; Preferably, the low-valent cation element includes any one or a combination of at least two of Mg, Al, Cu, Zn, Sr, and La; The high-valence cation elements include any one or a combination of at least two of Ti, Sb, W, Nb, Zr, and Mo; The anionic element includes any one or a combination of at least two of F, Cl, and B.

[0010] In an optional implementation, the volume ratio of the three-layer structure in the positive electrode precursor meets the following requirements: (1) The volume of the core layer accounts for 5%-10% of the volume of the positive electrode precursor: (2) The volume of the intermediate layer accounts for 10%-15% of the volume of the positive electrode precursor; (3) The volume of the radially grown layer accounts for 75%-85% of the volume of the positive electrode precursor.

[0011] In an optional embodiment, the positive electrode precursor satisfies at least one of the following requirements: (1) I in the XRD pattern 001 / I 101 =0.8-1.3, the preferred orientation degree of the (101) crystal plane is 0.29-0.35, and the preferred orientation index P of the (101) crystal plane is 0.29-0.35. （101） The value is 0.9-1.2; where I represents the peak intensity value of the corresponding crystal plane; I 001 / I 101 This represents the peak intensity ratio between the (001) and (101) crystal planes; (2) The full width at half maximum (FWHM) β of the diffraction peak of the (001) crystal plane corresponding to the diffraction angle 2θ = 19.2 ± 0.5° in the XRD pattern 001 The full width at half maximum (FWHM) β of the diffraction peak on the (101) crystal plane corresponding to a diffraction angle of 0.45-1° and a diffraction angle of 2θ = 38.5 ± 0.5° is 0.45-1°. 101 It is 0.45-0.65°, and β 001 / β 101=0.85-1.8; (3) The effective stacking height Lc along the direction perpendicular to the TM(OH)6 octahedral layer in the microcrystalline structure is 8-18 nm, and the number of microcrystalline wafer layers N on the (001) crystal plane is 8-18 nm. （001） The average diameter La of the stacked layers formed by stacking microwafers is 40-66 nm, and the number of microwafer layers N on the (101) crystal plane is 24-39. （101） It is 5-83, and N 101 / N 001 =1.6-3.4, where TM is at least one of Ni, Co, Mn, low-valence cation elements, anionic elements and high-valence cation elements.

[0012] In an optional implementation, the primary particles meet the following requirements: (1) The length L of the primary particle is 200-800 nm; (2) The thickness H of the primary particles is 20-80 nm; (3) The length-to-thickness ratio of the primary particles: L / H = 2-20; preferably 5-10.

[0013] In a second aspect, the present invention provides a method for preparing the cathode precursor described in the foregoing embodiments, comprising: mixing a metal salt solution A containing a nickel source, a cobalt source and a manganese source, an alkaline solution B, a complexing agent solution C and a doping solution D containing a low-valence cation element to perform a first stage co-precipitation, and then collecting the overflow slurry of the first stage co-precipitation as a first seed crystal; The first seed crystal, the metal salt solution A, the alkaline solution B, the complexing agent solution C, and the doping solution E containing high-valence cation elements are mixed to carry out a second stage of co-precipitation, and then the overflow slurry of the second stage of co-precipitation is collected as the second seed crystal. The second seed crystal, the metal salt solution A, the alkaline solution B, the complexing agent solution C, and the doping solution F containing anionic elements are mixed for concentrated growth and aging.

[0014] In an optional implementation, it includes: S1. Prepare the metal salt solution A, the alkaline solution B, the complexing agent solution C, the doping solution D, the doping solution E, and the doping solution F respectively; S2. The metal salt solution A, the alkaline solution B, the complexing agent solution C, and the doping solution D are mixed with the base liquid under inert gas protection and nucleation is carried out at temperature T1 to obtain reaction solution 1; then, while keeping the complexing agent concentration in reaction solution 1 constant at C1, the pH is lowered to pH1 and maintained until the particle size D50 reaches 1.5-3.5 μm, and the overflow slurry is collected as the first seed crystal; S3. The first seed crystal, the metal salt solution A, the alkaline solution B, the complexing agent solution C and the doping solution E are mixed for a second stage of co-precipitation, wherein the temperature is maintained at T1, the complexing agent concentration is maintained at C2, and the pH is maintained at pH2, until the particle size D50 is 2.5-7.5μm, and the overflow slurry is collected as the second seed crystal. S4. The second seed crystal, the metal salt solution A, the alkaline solution B, the complexing agent solution C, and the doping solution F are mixed and concentrated for growth reaction. The temperature is maintained at T2, the complexing agent concentration is maintained at C3, and the pH is maintained at pH3. After maintaining these conditions for a period of time, the pH is adjusted to pH4 and maintained until the particle size D50 reaches 5-14 μm. Then, the feeding is stopped to obtain a slurry of the positive electrode precursor. The slurry of the positive electrode precursor is then heated and aged. Preferably, the conditions in S1-S4 satisfy at least one of the following requirements: (1) Forming soluble salts of nickel, cobalt and manganese as nickel, cobalt and manganese sources respectively; (2) The total molar concentration of metal ions in the metal salt solution A is 1.5-2.5 mol / L; (3) The concentration of the alkaline solution B is 6-12 mol / L; (4) The alkaline solution B includes a hydroxide solution; (5) The complexing agent solution C includes ammonia water; (6) The concentration of the complexing agent solution C is 5-11 mol / L; (7) The concentration of the doped solution D is 5-20 g / L; (8) The concentration of the doped solution E is 5-20 g / L; (9) The concentration of the doped solution F is 5-20 g / L; (10) The base liquid includes hydroxide, ammonia and water; (11) The pH of the base solution is 10.5-12.5, the concentration of ammonia in the base solution is 0-15 g / L, and the temperature of the base solution is 40-75℃; (12) T1 and T2 are 40-75℃ respectively, and T1 < T2; (13) C1, C2 and C3 are all 0-15 g / L, and C1 < C2 < C3; (14) pH1, pH2, pH3 and pH4 are 9.5-12.2 respectively, and pH1>pH2>pH3>pH4; (15) The rate of introduction of metal salt solution A in S2, S3 and S4 is 1~10% of the volume of the reactor added per hour; and the flow rate of metal salt solution A in S2 = the flow rate of metal salt solution A in S3 ≥ the flow rate of metal salt solution A in S4. The rate at which the alkaline solution B is introduced in S2, S3, and S4 is 0.3% to 4% of the reactor volume per hour, respectively. The infeed rate of the complexing agent solution C in S2, S3 and S4 is 0.2% to 2% of the reactor volume per hour, respectively; The doping solution D, the doping solution E, and the doping solution F are all introduced at a rate of 0.1% to 0.5% of the reactor volume per hour. (16) Add 1%-5% of the volume of alkali to the reactor for aging. The aging temperature is 65-85℃ and the aging time is 3-10h. (17) The amount of the first and second seed crystals added is 50%-80% of the total volume of the reactor.

[0015] Thirdly, the present invention provides a cathode material, which is prepared by the cathode precursor described in the foregoing embodiments.

[0016] Fourthly, the present invention provides a lithium-ion battery comprising the positive electrode material described in the foregoing embodiments.

[0017] The present invention has the following beneficial effects: (1) The cathode precursor provided by this invention has a three-layer structure design consisting of a core layer, an intermediate layer, and a radial growth layer. The three layers are respectively doped with low-valence cation elements, high-valence cation elements, and anion elements, which makes the short, thin, sheet-like primary particles that constitute the secondary particles grow with high uniformity in the radial direction and the porosity between the stacked primary particles growing in an orderly manner in the radial direction is uniformly distributed. This enables the cathode material formed using this cathode precursor to have high-speed lithium-ion transport capability and excellent stress release capability, thereby improving the rate performance and capacity retention of the cathode material. At the same time, the high crystallinity and special crystal microstructure characteristics of this cathode precursor also enable the cathode precursor to have excellent compressive strength, resulting in good cycle performance of the formed cathode material and achieving an organic unity of high energy density, fast charging capability, and long life.

[0018] (2) The embodiments of the present invention adopt an overflow seeding combined with concentrated growth method, which only requires matching the appropriate reaction temperature, ammonia concentration, pH and flow rate to achieve the adjustment of the internal structure of the cathode precursor. At the same time, it has the advantages of high consistency of continuous process and narrow particle size distribution and uniform particle growth of batch process. The production efficiency of cathode precursor preparation using this process is greatly improved, the process control is stable, the batch index stability is high, and it is more suitable for industrial mass production. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The image shows the SEM morphology of the cathode precursor provided in Embodiment 1 of the present invention at 10,000x magnification. Figure 2 This is a cross-sectional morphology image of the positive electrode precursor provided in Embodiment 1 of the present invention at 50,000 magnification. Figure 3 This is a SEM image of the cathode precursor provided in Comparative Example 1 of the present invention at 10,000x magnification. Figure 4 This is a cross-sectional morphology diagram of the positive electrode precursor provided in Comparative Example 1 of the present invention at 50,000x magnification. Figure 5 This is a comparison diagram of the XRD patterns of the cathode precursors provided in Embodiment 1 and Comparative Example 3 of the present invention; Figure 6 The image shows the SEM morphology of the cathode precursor provided in Embodiment 11 of this invention at 10,000x magnification. Figure 7 This is a cross-sectional morphology diagram of the positive electrode precursor provided in Comparative Example 11 of the present invention at 50,000x magnification. Figure 8 This is a cross-sectional morphology diagram of the positive electrode precursor provided in Comparative Example 5 of the present invention at 50,000x magnification. Figure 9 This is a cross-sectional morphology diagram of the positive electrode precursor provided in Comparative Example 6 of the present invention at 50,000x magnification. Figure 10 This is a cross-sectional morphology diagram of the positive electrode precursor provided in Comparative Example 7 of the present invention at 50,000x magnification. Figure 11 Cross-sectional morphology of the cathode precursor provided in Comparative Example 8 of this invention at 50,000x magnification; Figure 12 Cross-sectional morphology of the positive electrode precursor provided in Comparative Example 9 of this invention at 50,000x magnification; Figure 13 Cross-sectional morphology of the cathode precursor provided in Comparative Example 10 of this invention at 50,000x magnification; Figure 14 The cross-sectional morphology of the positive electrode precursor provided in Comparative Example 12 of this invention at 50,000x magnification; Figure 15 Cross-sectional morphology of the cathode precursor provided in Comparative Example 13 of this invention at 50,000x magnification; Figure 16 The cross-sectional morphology of the positive electrode precursor provided in Comparative Example 14 of this invention at 50,000x magnification. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0022] In a first aspect, embodiments of the present invention provide a positive electrode precursor, which is composed of secondary particles. The secondary particles are composed of multiple plate-like primary particles, wherein the primary particles exhibit high radial growth uniformity and uniform porosity distribution among their orderly radially packed arrangement. Furthermore, the secondary particles comprise, from the inside out, the following three-layer structure: a core layer doped with low-valence cations, an intermediate layer doped with high-valence cations, and a radially growing layer doped with anions. The intermediate layer is more compact than the core layer and the radially growing layer. The high-valence cations have a higher valence state than the low-valence cations.

[0023] The porous core facilitates the formation of a hollow structure after sintering, which is beneficial for lithiation and increases lithium-ion transport flux. The relatively dense intermediate layer supports the hollow structure and prevents it from collapsing after sintering shrinkage. The porous radial growth layer provides a rapid lithium-ion transport path, which is beneficial for stress release in the cathode material and alleviates structural instability. The uniform pore distribution ensures a uniform lithium element distribution in the cathode material formed after subsequent lithium mixing and sintering, reducing concentration polarization. The coordinated effect of the three-layer structure of the cathode precursor is one of the key factors in achieving a combination of high energy density, fast charging capability, and long lifespan.

[0024] Furthermore, in the three-layer structure of the positive electrode precursor, the core layer accounts for 5%-10% of the total volume of the positive electrode precursor, for example, any value between 5%, 6%, 7%, 8%, 9%, 10%, or 5%-10%. The intermediate layer accounts for 10%-15% of the total volume of the positive electrode precursor, for example, any value between 10%, 11%, 12%, 13%, 14%, 15%, or 10%-15%. The radial growth layer accounts for 75%-85% of the total volume of the positive electrode precursor, for example, any value between 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, or 75%-85%. The appropriate volume ratio of the above three-layer structure is beneficial for the positive electrode precursor to achieve its performance.

[0025] Furthermore, the primary particle length L of the positive electrode precursor is 200-800 nm, the thickness H is 20-80 nm, and the length-to-thickness ratio L / H is 2-20, with a further preference for 5-10.

[0026] The testing method for the primary particle length L and thickness H is as follows: Using NanoMeasurer software, the length and thickness of the plate-like primary particles on the surface of the secondary particles are measured in SEM images with magnifications of 10,000-50,000x. The longest axis of a single plate-like primary particle is considered its length, and the short axis measured perpendicular to the midpoint of the longest axis is considered its thickness. At least three SEM images at different magnifications are used, and at least ten primary particles are selected for calculation. The average value is taken as the final result.

[0027] Furthermore, the cathode precursor is spherical or near-spherical, with a sphericity of 0.7-0.95. The aforementioned shape and sphericity of the cathode precursor facilitate a more compact deposition of the subsequently formed cathode material, thereby improving battery performance.

[0028] The sphericity of the positive electrode precursor is characterized by roundness, which is defined as the ratio of the area S of the irregular particle to the area S′ of the particle after it is stretched into a circle, i.e., roundness = S / S′ = 4πS / L 2 Where L is the circumference of the circle, the roundness test method is as follows: use Image-ProPlus software to measure the total area S of multiple particles and the total circumference L of the circle in the SEM image with a magnification of 1000-2500 times, and substitute them into the formula to calculate the roundness value. Generally, the average value of 2-3 SEM images is taken as the final result.

[0029] Furthermore, the total porosity of the secondary particle profile (CP) of the cathode precursor is 5%-35%, for example, any value between 5%, 10%, 15%, 20%, 25%, 30%, 35%, or 5%-35%. More preferably, it is 8%-20%.

[0030] In this invention, the porosity calculation uses cross-sectional images of the positive electrode precursor at magnifications of 10,000-50,000. The porosity is directly calculated using ImageJ image analysis software. The porosity is calculated as: Porosity = (Pore area of ​​the selected region in the cross-sectional image / Cross-sectional area of ​​the region in the cross-sectional image) × 100%. In this embodiment, the porosity is the average value obtained from at least three sets of cross-sectional images at different magnifications. The cross-section is taken along the diameter of the secondary particles.

[0031] Furthermore, the average pore volume of the positive electrode precursor is 0.02-0.11 cm³. 3 / g; for example, 0.02cm 3 / g, 0.03cm 3 / g, 0.04cm 3 / g, 0.05cm 3 / g, 0.06cm 3 / g, 0.07cm 3 / g, 0.08cm 3 / g, 0.09cm 3 / g, 0.1cm 3 / g or 0.11cm 3 / g or 0.02-0.11cm 3 Any value between / g.

[0032] The values ​​of pore volume and porosity can, to some extent, reflect the activity level of the cathode precursor. Generally, the larger the pore volume and porosity, the more reaction sites the cathode precursor has, resulting in higher reactivity and easier lithium mixing and sintering. However, excessively high pore volume and porosity can lead to an excessively high specific surface area and an excessively low tap density in the cathode precursor, which is detrimental to the processing and preparation of the cathode material and may even worsen the cycle performance of the cathode material. The porosity and pore volume specified in the embodiments of this invention can simultaneously take into account the reaction sites, specific surface area, and tap density, that is, to balance reactivity and processing performance.

[0033] Furthermore, the median particle size D50 of the cathode precursor is 5-14.5 μm; for example, any value between 5-14.5 μm such as 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm or 14.5 μm.

[0034] Furthermore, the particle size distribution of the cathode precursor is span = (D90 - D10) / D50, where span is 0.3-0.7; for example, any value between 0.3 and 0.7, such as 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, or 0.7. This particle size distribution results in a more uniform particle distribution in the cathode precursor, which is more conducive to filling.

[0035] Furthermore, the specific surface area (BET) of the positive electrode precursor is 6-18 m². 2 / g; for example, 6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g, 10m 2 / g、11m 2 / g、12m 2 / g、13m 2 / g、14m 2 / g, 15m 2 / g, 16m 2 / g、17m 2 / g or 18m 2 / g etc. 6-18m 2 Any value between / g. Using the above specific surface area is beneficial to ensuring the activity of the positive electrode precursor.

[0036] Furthermore, the tap density (TD) of the cathode precursor is 1.5-1.9 g / cm³. 3 For example, 1.5 g / cm³ 3 1.55 g / cm 3 1.6 g / cm 3 1.65 g / cm 3 1.7 g / cm 3 1.75 g / cm 3 1.8 g / cm 3 1.85 g / cm 3 Or 1.9 g / cm 3 1.5-1.9 g / cm³ 3 Any value between these ranges. Using the above-mentioned tap density is beneficial for improving the packing effect.

[0037] Furthermore, the pressure particle size of the cathode precursor at 0.75-2T is 0.1-5.3μm, and the fragmentation degree is 1-20%. The cathode precursor with the above pressure particle size and fragmentation degree has better high-temperature cycling stability.

[0038] In this invention, the concept of pressure particle size is introduced, which is a method to characterize the compressive strength of the cathode precursor. Generally, the smaller the pressure particle size and the smaller the degree of fragmentation, the greater the compressive strength of the cathode precursor, and the better the corresponding high-temperature cycling stability. The testing method is as follows: the particle size of the samples before and after compression is measured using a Malvern 3000 laser particle size analyzer (samples are prepared using an FT-100F powder compaction density analyzer V1.1 under the corresponding pressure). The pressure particle size is the difference between the D50 after compression at 0.75-2T and the D50 before compression, that is, pressure particle size ΔD50 = D50(before compression) - D50(after compression). The degree of fragmentation is the ratio of the pressure particle size to the D50 before compression, that is, the degree of fragmentation = ΔD50 / D50.

[0039] Furthermore, the molecular formula of the positive electrode precursor is: Ni x Co y Mn z M m N n L p(OH)₂, where x+y+z+m+n+p=1, 0.8≤x≤0.97, 0≤y≤0.10, 0≤z≤0.10, 0≤m≤0.02, 0≤n≤0.02, 0≤n≤0.02, M is a low-valence cation element, doped in the core layer; N is a high-valence cation element, doped in the intermediate layer; L is an anion element, doped in the radial growth layer; wherein the low-valence cation element includes any one or at least two combinations of Mg, Al, Cu, Zn, Sr, and La; the high-valence cation element includes any one or at least two combinations of Ti, Sb, W, Nb, Zr, and Mo; and the anion element includes any one or at least two combinations of F, Cl, and B.

[0040] In this invention, the incorporation of low-valent cations into the core of the cathode precursor facilitates the formation of a porous structure. After sintering into the cathode material, the low-valent cations enter the transition metal sites of the cathode material, stabilizing the material structure, suppressing phase transitions, and reducing the formation of internal cracks, thereby improving the cycle stability and thermal stability of the cathode material. The incorporation of high-valent cations into the intermediate layer of the cathode precursor facilitates the formation of a dense structure in the intermediate layer. After sintering into the cathode material, the high-valent cations readily form strong metallic bonds (NO) with oxygen, pinning particle boundaries to reduce interdiffusion and minimize particle coarsening, suppressing Li / Ni mixing, reducing volumetric strain, thereby stabilizing the internal structure and suppressing the formation and propagation of microcracks. After anionic elements are incorporated into the radial growth layer of the cathode precursor, it is beneficial for the primary particles of the cathode precursor to grow radially and form an internal structure with uniformly distributed pores. After sintering into the cathode material, the anionic elements are used to replace oxygen sites, which reduces the dissolution of transition metal elements and the precipitation of lattice oxygen, improves the electronic conductivity and lithium-ion diffusion rate of the cathode material, improves the rate performance of the cathode material, and reduces the risk of lithium plating at high rates.

[0041] Furthermore, in the XRD pattern of the cathode precursor, I 001 / I 101 =0.8-1.3, the preferred orientation degree of the (101) crystal plane is 0.29-0.35, and the preferred orientation index P of the (101) crystal plane is 0.29-0.35. （101） It ranges from 0.9 to 1.2.

[0042] The ratio of peak intensities reflects information about crystal orientation and texture. To further describe the preferred orientation distribution of the crystal, this invention introduces the concepts of preferred orientation degree and preferred orientation index, including the following formulas: Formula 1: R （hkl） =I （hkl） / (I 001 +I 100 +I 101 +I 102 +I110 +I 111 ) Formula 2: P (hkl) =R （hkl） / R 0（hkl） Among them, R （hkl） For the preferred orientation degree of the (hkl) crystal plane, I （hkl） P represents the diffraction intensity of the (hkl) crystal plane in the XRD pattern of the cathode precursor. (hkl) R is the preferred orientation index of the (hkl) crystal plane. 0（hkl） The value is calculated using Formula 1 based on the diffraction intensity of each crystal plane in the PDF card of nickel hydroxide (card number: 14-0117), such as R. 0（101） When P is 0.31, (hkl) When P > 1, the precursor exhibits a preferred orientation of the (hkl) crystal plane. (hkl) The larger the value, the higher its preference degree.

[0043] The preferred orientation of the cathode precursor has a significant impact on the mechanical properties of the cathode material. The tensile strength and flexural fatigue strength of the oriented cathode material are greatly increased in the orientation direction, which improves the mechanical strength of the cathode material. This helps to alleviate the generation and propagation of primary particle microcracks in the cathode material and further improves the cycle stability at high rates.

[0044] Furthermore, the full width at half maximum (FWHM) β of the diffraction peak corresponding to the (001) crystal plane at a diffraction angle of 2θ = 19.2 ± 0.5° in the XRD pattern is... 001 The full width at half maximum (FWHM) β of the diffraction peak on the (101) crystal plane corresponding to a diffraction angle of 0.45-1° and a diffraction angle of 2θ = 38.5 ± 0.5° is 0.45-1°. 101 It is 0.45-0.65°, and β 001 / β 101 =0.85-1.8; the cathode precursor with the above diffraction peak has fewer internal defects, and the cathode material formed after sintering has better overall performance.

[0045] In XRD, peak intensity and full width at half maximum (FWHM) are important indicators of crystal perfection. Narrower and higher peaks indicate larger grains and more perfect crystallization. The better the crystallinity of the precursor, the fewer internal defects, and the better the overall performance of the sintered material.

[0046] Furthermore, the effective stacking height Lc in the microcrystalline structure along the direction perpendicular to the TM(OH)6 octahedral layer (C-axis direction) is 8-18 nm, and the number of microcrystalline layers N on the (001) crystal plane is... （001） The average diameter La of the stacked family of wafers is 40-66 nm, and the number of microcrystal layers N of the (101) crystal plane is 24-39. （101） It is 5-83, and N101 / N 001 =1.6-3.4, where TM is at least one of Ni, Co, Mn, low-valence cation elements, anionic elements and high-valence cation elements.

[0047] The precursor crystal is centered on a transition metal atom TM, surrounded by six hydroxyl groups as ligands, forming a TM(OH)6 octahedron as the basic unit of its crystal structure. Adjacent TM(OH)6 octahedrons are interconnected on the same plane by sharing O atoms, forming a layered structure. Each independent layered structure consists of two hydroxyl layers and a transition metal atom layer sandwiched in between, and the layered structures are interconnected by hydrogen bonds. To further characterize the microcrystalline structure parameters of the precursor, the following formulas are derived using the Scherrer equation and the Bragg equation: Formula 3: Lc = K1λ / (β) （001） ×cosθ (001) ) Formula 4: La = K2λ / (β) （100） ×cosθ (100) ) Formula 5: N (001 ) =Lc / d （001） Formula 6: d (001) =λ / (2sinθ (001) ) Where λ is the wavelength of the target radiation, which is 0.15406 nm; K1 and K2 are shape factors, K1 = 0.89 and K2 = 1.77; β （001） and β （101） The full width at half maximum (FWHM) of the diffraction peaks of the (001) and (100) crystal planes, respectively; θ (001) θ (100) The diffraction angles corresponding to peaks (001) and (100) are respectively; d (001) The interlayer spacing between the (001) crystal plane microcrystal layers is given. The number of (101) crystal plane microcrystal layers mentioned in this article is also calculated by the above formula. Simply replace the (001) related parameters in the formula with the parameters corresponding to the (101) crystal plane.

[0048] It should be noted that in layered structural materials, Li + Diffusion occurs along the a-axis or b-axis, i.e., parallel to the {010} crystal plane family. For single crystal particles, the (104) and (012) sides are the main Li-type surfaces. + The transport plane, polycrystalline material can actually be viewed as an assembly of multiple single-crystal particles, therefore Li + The more transport surfaces are exposed and the smaller the orientation angle of each grain, the more Li will be provided. +Rapid transport paths and channels improve the rate performance of materials. Research has shown that the (101) crystal plane in the precursor XRD pattern evolves into the (104) crystal plane in the cathode material XRD pattern after sintering, which is Li + The critical channel for transmission. Increasing the effective stacking height Lc of the positive electrode precursor, i.e., the effective stacking layer N, is crucial. （001） As the number of crystal layers increases, the average diameter La of the stacked layers decreases, resulting in more and shorter migration paths for lithium ions, thus leading to superior capacity and rate performance of the corresponding cathode material. (101) Number of crystal layers N （101） Increase, and N 101 / N 001 When the ratio is moderate, it can, to some extent, provide Li + The more transmission channels there are, the more Li can be stored. + This reduces the loss of active lithium ions, resulting in lower capacity loss and improved capacity retention in the cathode material. Furthermore, the uniform pore distribution and radially ordered arrangement of particles within the cathode precursor reduce the grain orientation difference angle, which also contributes to the Li... + It provides a smooth and continuous diffusion path, which is conducive to the lithiation of the cathode precursor and the release of stress in the cathode material, thereby improving the rate performance and cycle performance of the cathode material.

[0049] In summary, the cathode precursor provided by this invention has a three-layer structure design consisting of a core layer, an intermediate layer, and a radial growth layer. Each of the three layers is doped with a low-valence cation element, a high-valence cation element, and an anion element, respectively. The primary particles forming the secondary particles exhibit high radial growth uniformity, and the porosity of the radial growth layer is uniformly distributed. This results in cathode materials formed by lithium-ion mixing and sintering using this cathode precursor possessing high-speed lithium-ion transport capabilities and excellent stress release capabilities, reducing lithium-ion concentration polarization, and improving the rate performance and cycle stability of the cathode material. Simultaneously, the high crystallinity and unique crystal microstructure of the cathode precursor also give it excellent compressive strength. The cathode material obtained after sintering achieves a harmonious balance between high energy density, fast charging capability, and long lifespan.

[0050] Secondly, embodiments of the present invention provide a method for preparing a positive electrode precursor, comprising: S1. Prepare metal salt solution A containing nickel source, cobalt source and manganese source, alkaline solution B, complexing agent solution C, doping solution D, doping solution E and doping solution F respectively.

[0051] Specifically, according to the ratio of nickel, cobalt, and manganese in the chemical formula of the positive electrode precursor, nickel, cobalt, and manganese metal salts are mixed with water to prepare a metal salt solution A of appropriate concentration. For example, the metal salt includes one or a combination of at least two soluble salts such as nickel sulfate, cobalt sulfate, and manganese sulfate.

[0052] The total molar concentration of metal ions in metal salt solution A is 1.5~2.5 mol / L, for example, any value between 1.5~2.5 mol / L such as 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L or 2.5 mol / L.

[0053] An alkaline agent is mixed with water to obtain an alkaline solution B of appropriate concentration. Alkaline solution B includes hydroxide solutions, such as, but not limited to, sodium hydroxide solution or potassium hydroxide solution. The concentration of alkaline solution B is 6-12 mol / L; for example, any value between 6 mol / L, 7 mol / L, 8 mol / L, 10 mol / L, or 12 mol / L.

[0054] Prepare a complexing agent solution C of appropriate concentration by mixing the complexing agent with water. The complexing agent solution C includes ammonia water; the concentration of the complexing agent solution C is 5-11 mol / L; for example, any value between 5-11 mol / L, such as 5 mol / L, 6 mol / L, 8 mol / L, 10 mol / L, or 11 mol / L.

[0055] A doped solution D of appropriate concentration is obtained by mixing a metal salt containing a low-valence cation with water. The raw materials forming the doped solution D include one or a combination of at least two soluble salts such as magnesium sulfate, aluminum sulfate, copper sulfate, and zinc sulfate. The concentration of the doped solution D is 5–20 g / L, for example, any value between 5 g / L, 10 g / L, 15 g / L, or 20 g / L.

[0056] A doped solution E of suitable concentration is obtained by mixing a metal salt containing a high-valence cation with water. The raw materials forming the doped solution E include one or a combination of at least two soluble salts such as titanium oxysulfate, strontium chloride, antimony chloride, sodium tungstate, sodium niobate, zirconium sulfate, sodium molybdate, and lanthanum chloride. The concentration of the doped solution E is 5–20 g / L, for example, any value between 5 g / L, 10 g / L, 15 g / L, or 20 g / L.

[0057] A doped solution F of appropriate concentration is obtained by mixing a metal salt containing an anionic element with water. The raw materials forming the doped solution F include one or a combination of at least two soluble substances such as NaF, NaCl, boric acid, or sodium borate. The concentration of the doped solution F is 5~20 g / L, for example, any value between 5 g / L, 10 g / L, 15 g / L, or 20 g / L.

[0058] S2, Kernel Layer Preparation: The metal salt solution A, the alkaline solution B, the complexing agent solution C, and the doped solution D containing low-valence cations were mixed to carry out the first stage of co-precipitation. The overflow slurry of the first stage of co-precipitation was then collected as the first seed crystal.

[0059] Specifically, metal salt solution A, alkaline solution B, complexing agent solution C, and doping solution D are introduced at a certain flow rate into a bottom liquid that accounts for 50-80% of the total volume of the reactor under the protection of an inert gas (e.g., nitrogen) to carry out nucleation, resulting in reaction solution 1. The reaction temperature is set to T1, and nucleation is carried out for the first 0.5-3 hours. After nucleation, the concentration of complexing agent in reaction solution 1 is kept constant at C1, and the pH is lowered to a suitable growth pH (denoted as pH1) and maintained until the target particle size D50 of 1.5-3.5 μm is reached. After the liquid level in the reactor reaches the overflow port, the overflow is opened, and the overflowed precursor slurry is collected and used as the first seed crystal.

[0060] The substrate comprises a hydroxide (e.g., sodium hydroxide), ammonia, and water. Specifically, the pH of the substrate is 10.5-12.5, the concentration of ammonia in the substrate is 0-15 g / L, and the temperature of the substrate is 40-75°C. The hydroxide is used to adjust the pH.

[0061] S3, Intermediate Layer Preparation: The first seed crystal, the metal salt solution A, the alkaline solution B, the complexing agent solution C, and the doping solution E containing high-valence cation elements are mixed to carry out a second stage of co-precipitation, and then the overflow slurry of the second stage of co-precipitation is collected as the second seed crystal.

[0062] Specifically, add the first seed crystal, which accounts for 50-70% of the total volume of the reactor, and keep the metal salt solution A, alkaline solution B and step S2 consistent. Switch the doping solution D to the doping solution E, and continue to pass it into the reactor at a certain flow rate to continue the second stage of co-precipitation reaction. Maintain overflow, keep the reaction temperature at T1, increase the concentration of the complexing agent to C2 and maintain it, and at the same time lower the pH to a suitable growth pH (denoted as pH2) and maintain it until the target particle size D50 2.5-7.5μm is reached. Then collect the overflow slurry as the second seed crystal.

[0063] S4. Preparation of radial growth layer: The second seed crystal, the metal salt solution A, the alkaline solution B, the complexing agent solution C, and the doping solution F containing anionic elements are mixed for concentrated growth and aging.

[0064] Specifically, a second seed crystal, comprising 60-80% of the total volume of the reactor, is added. Metal salt solution A, alkaline solution B, complexing agent solution C, and doping solution F are then introduced into the reactor at a certain flow rate for concentration growth. The reactor overflows, and the solution enters a concentrator for further concentration. The reaction temperature is set to T2. The complexing agent concentration is increased to C3 and maintained. During this process, the pH is lowered in two stages, designated pH3 and pH4. The pH is maintained constant until the target particle size of 5-14.5 μm is reached, at which point the feed is stopped, yielding a precursor slurry. This slurry is then aged with added alkali, followed by centrifugation, washing, drying, batch mixing, demagnetization, and sieving to obtain the positive electrode precursor.

[0065] The conditions for S2, S3, and S4 are as follows: (1) T1 and T2 are 40-75℃ respectively, and T1 < T2. Temperature mainly affects the nucleus generation rate and growth rate. Low temperature is conducive to the formation of nuclei and not conducive to the growth of nuclei, and generally results in fine grains. Crystal precipitation growth is generally carried out under high temperature conditions because there are fewer impurities adsorbed in the high temperature solution, the precipitation time is short, and the product has good crystallinity. However, excessively high temperature will also affect the preparation of the cathode precursor. For example, the volatilization of ammonia and easy oxidation will also deteriorate the quality of the cathode precursor and ultimately deteriorate the performance of the cathode material.

[0066] (2) C1, C2 and C3 are all 0-15 g / L, and C1 < C2 < C3.

[0067] In this embodiment of the invention, ammonia is used as a complexing agent, the main function of which is to complex metal ions, making Ni²⁺… + Co² + Mn² + The precipitation rate of plasma is reduced, and their precipitation rates are made to be on the same order of magnitude, thus achieving the purpose of co-precipitation. Under low ammonia concentration conditions, it is easy to obtain loosely packed and relatively thin primary particles, while under high ammonia concentration conditions, it is easy to obtain densely packed and relatively thick strip-shaped primary particles. However, excessively high ammonia concentration will lead to too many complexed nickel, cobalt, and manganese ions in the solution, which will cause incomplete reaction, causing the proportion of main elements in the positive electrode precursor to deviate from the design value. The loss of metal ions will increase the cost of wastewater treatment.

[0068] (3) pH1, pH2, pH3 and pH4 are 9.5-12.2 respectively, and pH1>pH2>pH3>pH4.

[0069] In this invention, pH value has a significant impact on the growth process and morphology of the precursor. A lower pH value promotes crystal nucleus growth, resulting in thicker and larger primary grains, and secondary particles are prone to agglomeration, leading to irregularly shaped secondary spherical particles. Conversely, a higher pH value promotes crystal nucleus formation, resulting in thin, fine primary grains and mostly spherical secondary particles. Furthermore, stable pH control during the reaction directly affects the particle size distribution of the cathode precursor. If the pH value becomes uncontrolled during the reaction, resulting in excessively high or low pH values, the product quality will drastically decline, leading to substandard products and ultimately affecting the performance of the cathode material.

[0070] (4) The inlet rates of metal salt solution A in S2, S3, and S4 are 1-10% of the reactor volume per hour, respectively; and the flow rate of metal salt solution A in S2 = the flow rate of metal salt solution A in S3 ≥ the flow rate of metal salt solution A in S4. The inlet rates of alkaline solution B in S2, S3, and S4 are 0.3-4% of the reactor volume per hour, respectively. The inlet rates of complexing agent solution C in S2, S3, and S4 are 0.2-2% of the reactor volume per hour, respectively. The inlet rates of doping solution D, doping solution E, and doping solution F are all 0.1-0.5% of the reactor volume per hour.

[0071] (5) Add 1%-5% of the volume of alkali to the reactor for aging. The aging temperature is 65-85℃ and the aging time is 3-10h.

[0072] The main purpose of aging in this embodiment of the invention is to promote crystal form perfection, promote the growth of secondary particles in the precursor during the repair process of large particle cracking of the positive electrode precursor, form pure crystals with uniform particle size, and improve the crystallinity and quality of the positive electrode precursor.

[0073] Thirdly, the present invention provides a cathode material, which is prepared by the cathode precursor described in the foregoing embodiments. Specifically, it includes: mixing and sintering a lithium source with the cathode precursor provided in the embodiments of the present invention to prepare a cathode material, which has better electrochemical performance.

[0074] Fourthly, the present invention provides a lithium-ion battery comprising the positive electrode material described in the foregoing embodiments. Because this positive electrode material includes the positive electrode precursor provided in the embodiments of the present invention, the battery assembled from this positive electrode material has superior electrochemical performance. Optionally, the lithium-ion battery can be a single cell or a battery pack.

[0075] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0076] Example 1 This invention provides a method for preparing a positive electrode precursor, comprising: S1: Prepare a 1.5 mol / L metal salt solution A by mixing nickel sulfate, cobalt sulfate, and manganese sulfate in a metal molar ratio of 82:8:10. Prepare a 6 mol / L sodium hydroxide solution B; a 5 mol / L ammonia solution C; a 20 g / L magnesium sulfate solution D; a 20 g / L titanium oxysulfate solution E; and a 20 g / L sodium fluoride solution F.

[0077] S2: Metal salt solution A (1% L / h of the reactor volume), sodium hydroxide solution B (0.3% L / h of the reactor volume), ammonia solution C (0.2% L / h of the reactor volume), and magnesium sulfate solution D (0.1% L / h of the reactor volume) are introduced into a bottom liquid at a nitrogen-protected atmosphere, with a pH of 10.6-10.8, an ammonia concentration of 1±1 g / L, and a temperature of 40℃, filling 50% of the reactor volume, to promote nucleation. The reaction temperature is maintained at 40℃. After 0.5 hours of nucleation, the ammonia concentration is kept constant at 1±1 g / L, and the pH is lowered to 10.4-10.6 and maintained until the target particle size of 2±0.1 μm is reached. Once the liquid level in the reactor reaches the overflow port, the overflow is opened, and the overflowed precursor slurry is collected as the first seed crystal.

[0078] S3: Add the first seed crystal, which accounts for 50% of the total volume of the reactor. Then, introduce the metal salt solution A at 1% L / h of the reactor volume, the sodium hydroxide solution B at 0.3% L / h of the reactor volume, the ammonia solution C at 0.3% L / h of the reactor volume, and the titanium oxysulfate solution E at 0.1% L / h of the reactor volume into the reactor to continue the second stage of co-precipitation reaction. Maintain overflow and keep the reaction temperature at 40℃. Increase the ammonia concentration to 3±1 g / L and maintain it. Adjust the pH to 10.0-10.2 and maintain growth until the target particle size of 3.8±0.1μm is reached. The overflow precursor slurry is used as the second seed crystal.

[0079] S4: Add a second seed crystal, accounting for 60% of the total volume of the reactor. Introduce metal salt solution A at 1% L / h of the reactor volume, sodium hydroxide solution B at 0.3% L / h of the reactor volume, ammonia solution C at 0.4% L / h of the reactor volume, and sodium fluoride solution F at 0.1% L / h of the reactor volume into the reactor for concentration and growth. Close the overflow, and allow the slurry to circulate and concentrate in a thickener. Set the reaction temperature to 50℃, and increase the ammonia concentration to 5±1 g / L. During this process, first lower the pH to 9.8-10.0 and maintain it for 6 hours, then lower the pH to 9.5-9.7 and maintain this pH until the target particle size of 9±0.1 μm is reached. Stop feeding to obtain the precursor slurry. Heat the slurry to 65℃, add 1% sodium hydroxide alkaline solution (accounting for 1% of the reactor volume), and age for 3 hours. Then centrifuge, wash, dry, mix batches, demagnetize, and sieve to obtain the positive electrode precursor with the molecular formula Ni. 0.81 Co 0.08 Mn 0.09Mg 0.005 Ti 0.00 5F 0.01 (OH)2.

[0080] SEM image of the positive electrode precursor as shown Figure 1 As shown, the SEM cross-sectional image of the positive electrode precursor is as follows. Figure 2 As shown, the positive electrode precursor is composed of spherical secondary particles, which are composed of multiple plate-like primary particles. The primary particles in the cross-section have high radial growth uniformity, and the pores between the primary particles are evenly distributed in an orderly radial stack. The secondary particles have a three-layer structure: a loose core, an intermediate layer, and a radial growth layer.

[0081] Example 2 This invention provides a method for preparing a positive electrode precursor, comprising: S1: Prepare a 1.8 mol / L metal salt solution A by mixing nickel sulfate, cobalt sulfate, and manganese sulfate in a metal molar ratio of 85:7:8. Prepare an 8 mol / L sodium hydroxide solution B; an 8 mol / L ammonia solution C; a 15 g / L aluminum sulfate solution D; a 15 g / L strontium chloride solution E; and a 15 g / L sodium chloride solution F.

[0082] S2: Metal salt solution A at 4% L / h of the reactor volume, sodium hydroxide solution B at 0.4% L / h of the reactor volume, ammonia solution C at 0.2% L / h of the reactor volume, and aluminum sulfate solution D at 0.2% L / h of the reactor volume are introduced into a bottom liquid at 60% of the reactor volume under nitrogen protection. The pH is 11-11.2, the ammonia concentration is 3±1 g / L, the temperature is 50℃, and the bottom liquid occupies 50% of the reactor volume. The reaction temperature is maintained at 50℃. After nucleation for 1 hour, the ammonia concentration is kept constant at 3±1 g / L, and the pH is lowered to 10.8-11.0 and maintained until the target particle size of 3±0.1 μm is reached. After the liquid level in the reactor reaches the overflow port, the overflow is opened, and the overflow precursor slurry is collected as the first seed crystal.

[0083] S3: Add the first seed crystal, which accounts for 60% of the total volume of the reactor. Then, introduce the metal salt solution A at 4% L / h of the reactor volume, the sodium hydroxide solution B at 0.4% L / h of the reactor volume, the ammonia solution C at 0.4% L / h of the reactor volume, and the strontium chloride solution E at 0.2% L / h of the reactor volume into the reactor to continue the second stage of co-precipitation reaction. Maintain overflow, keep the reaction temperature at 50℃, increase the ammonia concentration to 5±1 g / L, and lower the pH to 10.6-10.8 to maintain growth until the target particle size of 6±0.1 μm is reached. Then, transfer the material in the reactor to the third stage for concentration and growth. The overflow precursor slurry is used as the second seed crystal.

[0084] S4: Add a second seed crystal, accounting for 70% of the total volume of the reactor. Introduce metal salt solution A at 3% L / h of the reactor volume, sodium hydroxide solution B at 0.3% L / h of the reactor volume, ammonia solution C at 0.6% L / h of the reactor volume, and sodium chloride solution F at 0.2% L / h of the reactor volume into the reactor for concentration and growth. Close the overflow, and allow the slurry to circulate and concentrate in a thickener. Set the reaction temperature to 60℃, and raise the ammonia concentration to 7±1 g / L. During this process, first lower the pH to 10.4-10.6 and maintain it for 6 hours, then lower the pH to 10.2-10.4 and maintain this pH until the target particle size of 12±0.1 μm is reached. Stop feeding to obtain the precursor slurry. Heat the slurry to 70℃, add 2% alkali solution (by reactor volume), and age for 5 hours. Then centrifuge, wash, dry, mix batches, demagnetize, and sieve to obtain the positive electrode precursor with the molecular formula Ni. 0.84 Co 0.07 Mn 0.07 Al 0.01 Sr 0.01 Cl 0.01 (OH)2.

[0085] Example 3 This invention provides a method for preparing a positive electrode precursor, comprising: S1: Prepare a 2 mol / L metal salt solution A by mixing nickel sulfate and cobalt sulfate at a metal molar ratio of 95:5. Prepare a 10 mol / L sodium hydroxide solution B, an 11 mol / L ammonia solution C, a 10 g / L mixed solution of copper sulfate and zinc sulfate (1:1) D, a 10 g / L mixed solution of antimony chloride and sodium tungstate (1:1) E, and a 10 g / L sodium borate solution F.

[0086] S2: Metal salt solution A is introduced at a rate of 7% L / h of the reactor volume, sodium hydroxide solution B at a rate of 2.8% L / h of the reactor volume, ammonia solution C at a rate of 0.8% L / h of the reactor volume, and copper sulfate and zinc sulfate D at a rate of 0.3% L / h of the reactor volume. Nucleation is carried out in a bottom liquid at a pH of 11.6-11.8, an ammonia concentration of 6±1 g / L, a temperature of 60℃, and a volume of 70% of the reactor volume. The reaction temperature is maintained at 60℃. After nucleation for 2 hours, the ammonia concentration is kept constant at 6±1 g / L, and the pH is lowered to 11.4-11.6 and maintained until the target particle size of 3.5±0.1 μm is reached. Once the liquid level in the reactor reaches the overflow port, the overflow is opened, and the overflowed precursor slurry is collected as the first seed crystal.

[0087] S3: Add the first seed crystal, which accounts for 70% of the total volume of the reactor. Then, introduce the metal salt solution A at 7% L / h of the reactor volume, the sodium hydroxide solution B at 2.8% L / h of the reactor volume, the ammonia solution C at 1% L / h of the reactor volume, and the mixed solution E of antimony chloride and sodium tungstate at 0.3% L / h of the reactor volume into the reactor to continue the second stage of co-precipitation reaction. Maintain overflow, keep the reaction temperature at 60℃, increase the ammonia concentration to 8±1 g / L, and lower the pH to 11.1-11.3 to maintain growth until the target particle size of 7.5±0.1 μm is reached. Then, transfer the material in the reactor to the third stage for concentration and growth, and use the overflow precursor slurry as the second seed crystal.

[0088] S4: Add a second seed crystal, accounting for 80% of the total volume of the reactor. Introduce metal salt solution A at 6% L / h of the reactor volume, sodium hydroxide solution B at 2.5% L / h of the reactor volume, ammonia solution C at 1.2% L / h of the reactor volume, and sodium borate solution F at 0.3% L / h of the reactor volume into the reactor for concentration and growth. Close the overflow, and allow the slurry to circulate and concentrate in a thickener. Set the reaction temperature to 75℃, and raise the ammonia solution to 10±1 g / L. During this process, first lower the pH to 10.9-11.1 and maintain it for 6 hours, then lower the pH to 10.6-10.8 and maintain this pH until the target particle size of 14.0±0.1 μm is reached. Stop feeding to obtain the precursor slurry. Heat the slurry to 85℃, add 5% alkali solution (by reactor volume), and age for 10 hours. Then centrifuge, wash, dry, mix batches, demagnetize, and sieve to obtain the positive electrode precursor with the molecular formula Ni. 0.90 Co 0.05 Cu 0.01 Zn 0.01 Sb 0.01 W 0.01 B 0.02 (OH)2.

[0089] Example 4 This invention provides a method for preparing a positive electrode precursor, comprising: S1: Prepare a 2.5 mol / L metal salt solution A by mixing nickel sulfate and manganese sulfate at a metal molar ratio of 97:3. Prepare a 12 mol / L sodium hydroxide solution B, a 10 mol / L ammonia solution C, a 5 g / L mixed solution of magnesium sulfate and aluminum sulfate (1:1) D, a 5 g / L mixed solution of sodium niobate and zirconium sulfate (1:1) E, and a 5 g / L mixed solution of sodium fluoride and sodium borate (1:1) F.

[0090] S2: Metal salt solution A is introduced at a rate of 10% L / h of the reactor volume, sodium hydroxide solution B at a rate of 4% L / h of the reactor volume, ammonia solution C at a rate of 1.6% L / h of the reactor volume, and a mixed solution of magnesium sulfate and aluminum sulfate D at a rate of 0.5% L / h of the reactor volume. This is done in a bottom liquid at a pH of 12.3-12.5, an ammonia concentration of 10±1 g / L, a temperature of 55℃, and a volume of 80% of the reactor volume, under nitrogen protection. The reaction temperature is maintained at 65℃. After nucleation for 3 hours, the ammonia concentration is kept constant at 10±1 g / L, and the pH is lowered to 12.0-12.2 and maintained until the target particle size of 1.5±0.1μm is reached. Once the liquid level in the reactor reaches the overflow port, the overflow is opened, and the overflowed precursor slurry is collected as the first seed crystal.

[0091] S3: Add the first seed crystal, which accounts for 55% of the total volume of the reactor. Then, introduce the metal salt solution A at 10% L / h of the reactor volume, the sodium hydroxide solution B at 4% L / h of the reactor volume, the ammonia solution C at 1.8% L / h of the reactor volume, and the mixed solution E of sodium niobate and zirconium sulfate at 0.5% L / h of the reactor volume into the reactor to continue the second stage of co-precipitation reaction. Maintain overflow, keep the reaction temperature at 65℃, increase the ammonia concentration to 12±1 g / L, and lower the pH to 11.8-12.0 to maintain growth until the target particle size of 2.5±0.1 μm is reached. The overflow precursor slurry is used as the second seed crystal.

[0092] S4: Add a second seed crystal, accounting for 75% of the total volume of the reactor. Introduce a metal salt solution A at 8% L / h of the reactor volume, a sodium hydroxide solution B at 3.2% L / h of the reactor volume, an ammonia solution C at 2% L / h of the reactor volume, and a mixed solution of sodium fluoride and sodium borate F at 0.5% L / h of the reactor volume into the reactor for concentration and growth. Close the overflow, and the slurry enters a thickener for circulation and concentration. Set the reaction temperature to 70℃, and raise the ammonia solution to 14±1 g / L. During this process, first lower the pH to 11.3-11.5 and maintain it for 6 hours, then lower the pH to 11.0-11.2 and maintain this pH until the target particle size of 5±0.1 μm is reached, at which point the feed is stopped, obtaining the precursor slurry. Heat this slurry to 80℃, add 3% alkali solution (by reactor volume) and age for 7 hours. Then centrifuge, wash, dry, mix batches, demagnetize, and sieve to obtain the positive electrode precursor with the molecular formula Ni. 0.90 Mn 0.05 Mg 0.01 Al 0.01 Nb 0.005 Zr 0.005 B 0.01 F 0.01 (OH)2.

[0093] Example 5 This invention provides a method for preparing a positive electrode precursor, comprising: S1: Prepare a 1.8 mol / L metal salt solution A by mixing nickel sulfate, cobalt sulfate, and manganese sulfate in a metal molar ratio of 88:10:2. Prepare a 12 mol / L sodium hydroxide solution B, a 6 mol / L ammonia solution C, a 10 g / L zinc sulfate and aluminum sulfate (1:1) mixed solution D, a 15 g / L sodium molybdate and lanthanum chloride (1:1) mixed solution E, and a 5 g / L sodium fluoride and boric acid (1:1) mixed solution F.

[0094] S2: Metal salt solution A is introduced at a rate of 5% L / h of the reactor volume, sodium hydroxide solution B at a rate of 2% L / h of the reactor volume, ammonia solution C at a rate of 1% L / h of the reactor volume, and a mixed solution of zinc sulfate and aluminum sulfate D at a rate of 0.5% L / h of the reactor volume. Nucleation is carried out in a bottom liquid at a pH of 11.9-12.1, an ammonia concentration of 7±1 g / L, a temperature of 45℃, and a volume of 65% of the reactor volume under nitrogen protection. The reaction temperature is maintained at 45℃. After nucleation for 1.5 h, the ammonia concentration is kept constant at 7±1 g / L, and the pH is lowered to 11.5-11.7 and maintained until the target particle size of 2.3±0.1 μm is reached. Once the liquid level in the reactor reaches the overflow port, the overflow is opened, and the overflowed precursor slurry is collected as the first seed crystal.

[0095] S3: Add the first seed crystal, which accounts for 65% of the total volume of the reactor. Then, introduce the metal salt solution A at 5% L / h of the reactor volume, the sodium hydroxide solution B at 2% L / h of the reactor volume, the ammonia solution C at 1.3% L / h of the reactor volume, and the mixed solution E of sodium molybdate and lanthanum chloride at 0.4% L / h of the reactor volume into the reactor to continue the second stage of co-precipitation reaction. Maintain overflow and keep the reaction temperature at 45℃. Increase the ammonia concentration to 11±1 g / L and maintain it. Adjust the pH to 11.3-11.5 and maintain growth until the target particle size of 4.5±0.1 μm is reached. Then, transfer the material in the reactor to the third stage for concentration and growth. The overflow precursor slurry is used as the second seed crystal.

[0096] S4: Add a second seed crystal, accounting for 75% of the total volume of the reactor. Introduce a metal salt solution A at 5% L / h of the reactor volume, a sodium hydroxide solution B at 2% L / h of the reactor volume, an ammonia solution C at 1.5% L / h of the reactor volume, and a mixed solution of sodium fluoride and boric acid F at 0.3% L / h of the reactor volume into the reactor for concentration and growth. Close the overflow, and the slurry enters a thickener for circulation and concentration. Set the reaction temperature to 55℃, and raise the ammonia concentration to 13±1 g / L. During this process, first lower the pH to 11.1-11.3 and maintain it for 6 hours, then lower the pH to 10.8-11.0 and maintain this pH until the target particle size of 10±0.1 μm is reached. Stop feeding to obtain the precursor slurry. Heat the slurry to 70℃, add 4% alkali solution (by reactor volume) and age for 6 hours. Then centrifuge, wash, dry, mix batches, demagnetize, and sieve to obtain the positive electrode precursor with the molecular formula Ni. 0.83 Co 0.10 Mn 0.02 Zn 0.005 Al 0.005 Mo 0.015 La 0.015 B 0.005 F 0.005 (OH)2.

[0097] Comparative Example 1 The preparation method of the positive electrode precursor provided in this comparative example differs from the preparation method provided in Example 1 only in that the reaction temperature in steps S2 and S3 is 85°C, while the other conditions and parameters are exactly the same as in Example 1.

[0098] The SEM image of the positive electrode precursor is as follows: Figure 3 As shown, the SEM cross-sectional image of the positive electrode precursor is as follows. Figure 4 As shown in the figure, it can be observed that the primary particles on the surface of the secondary particles of the positive electrode precursor are much thicker, and there is no three-layer structure inside. Although the primary particles grow radially in the cross-section, the porosity between the primary particles along the radial stacking is reduced and unevenly distributed.

[0099] Comparative Example 2 The preparation method of the positive electrode precursor provided in this comparative example differs from the preparation method provided in Example 1 only in that the ammonia concentration in step S2 is greater than that in step S3, which is greater than that in step S4, specifically 7±1 g / L, 5±1 g / L, and 3±1 g / L, respectively. All other conditions and parameters are exactly the same as in Example 1.

[0100] Comparative Example 3 The preparation method of the positive electrode precursor provided in this comparative example differs from the preparation method provided in Example 1 only in that the pH in steps S2, S3 and S4 is less than 9.5, specifically 9.2 and 9.4, respectively. All other conditions and parameters are exactly the same as in Example 1.

[0101] The XRD patterns of the positive electrode precursors of Example 1 and Comparative Example 3 are as follows: Figure 5 As shown, by Figure 5 The comparison shows that the crystallinity of the precursor is relatively poor under low pH conditions, which is manifested by a decrease in peak intensity and an increase in half-width at half-maximum.

[0102] Comparative Example 4 The preparation method of the positive electrode precursor provided in this comparative example differs from the preparation method provided in Example 1 only in that the highest pH in steps S2, S3 and S4 is 12.5, and the other conditions and parameters are exactly the same as in Example 1.

[0103] Comparative Example 5 The preparation method of the positive electrode precursor provided in this comparative example differs from the preparation method provided in Example 1 only in that the core layer of step S2 does not contain doping elements, that is, magnesium sulfate solution is not added in S2. Other conditions and parameters are exactly the same as in Example 1.

[0104] Comparative Example 6 The preparation method of the positive electrode precursor provided in this comparative example differs from the preparation method provided in Example 1 only in that: the compact intermediate layer in step S3 does not contain doping elements, that is, no titanium oxysulfate solution E is added; other conditions and parameters are exactly the same as in Example 1.

[0105] Comparative Example 7 The preparation method of the positive electrode precursor provided in this comparative example differs from the preparation method provided in Example 1 only in that: the loose growth layer in step S4 does not contain doping elements, that is, no sodium fluoride solution is added; other conditions and parameters are exactly the same as in Example 1.

[0106] The cross-sectional views of the cathode precursors described in Comparative Examples 5-7 correspond one-to-one. Figure 8-10 .like Figure 8-10 As shown, it can be observed that after reducing one layer of doping element, the proportion of the three-layer structure inside the precursor changes. Although the primary particles in the cross-section grow radially, the porosity between the primary particles stacked radially is reduced.

[0107] Comparative Example 8 The preparation method of the positive electrode precursor provided in this comparative example differs from the preparation method provided in Example 1 only in that: neither the loose core in step S2 nor the compact intermediate layer in step S3 contains doped elements; the other conditions and parameters are exactly the same as in Example 1.

[0108] Comparative Example 9 The preparation method of the positive electrode precursor provided in this comparative example differs from the preparation method provided in Example 1 only in that: neither the loose core in step S2 nor the loose growth layer in step S4 contains doped elements; all other conditions and parameters are exactly the same as in Example 1.

[0109] Comparative Example 10 The preparation method of the positive electrode precursor provided in this comparative example differs from the preparation method provided in Example 1 only in that: neither the compact intermediate layer in step S3 nor the loose growth layer in step S4 contains doped elements; the other conditions and parameters are exactly the same as in Example 1.

[0110] The cross-sectional views of the cathode precursors described in Comparative Examples 8-10 correspond one-to-one. Figure 11-13 As shown. Figure 11-13 As shown, it can be observed that after reducing the number of doping elements in the second layer, the number of pores inside the precursor increases, the proportion of the compact layer decreases, and the structure is prone to collapse after sintering. Although the primary particles in the cross-section grow radially, the pore distribution between the primary particles in the radial stack is uneven.

[0111] Comparative Example 11 The preparation method of the positive electrode precursor provided in this comparative example differs from the preparation method provided in Example 1 only in that: the loose core in S2, the compact intermediate layer in S3, and the loose growth layer in step S4 do not contain any doped elements; other conditions and parameters are exactly the same as in Example 1.

[0112] The SEM image of the positive electrode precursor is as follows: Figure 6 As shown, the SEM cross-sectional view of the positive electrode precursor is as follows: Figure 7 As shown. Observation shows that after removing all dopants from the three-layer structure, the whiskers on the surface of the precursor become thicker and layered, the average length-to-thickness ratio increases, the proportion of the internal compact layer increases, the radial growth uniformity of the primary particles in the cross-section is low, and the porosity between the primary particles in the radial stacking is reduced and unevenly distributed.

[0113] Comparative Example 12 The preparation method of the positive electrode precursor provided in this comparative example differs from the preparation method provided in Example 1 only in that the doping elements of the loose core in step S2 and the compact intermediate layer in step S3 are interchanged, while other conditions and parameters are exactly the same as in Example 1.

[0114] Comparative Example 13 The preparation method of the positive electrode precursor provided in this comparative example differs from the preparation method provided in Example 1 only in that the doping elements of the compact intermediate layer in step S3 and the loose growth layer in step S4 are interchanged, while other conditions and parameters are exactly the same as in Example 1.

[0115] Comparative Example 14 The preparation method of the positive electrode precursor provided in this comparative example differs from the preparation method provided in Example 1 only in that the doping elements of the loose core in step S2 and the loose growth layer in step S4 are interchanged, while other conditions and parameters are exactly the same as in Example 1.

[0116] The cross-sectional views of the cathode precursors described in Comparative Examples 12-14 correspond one-to-one. Figure 14-16 .like Figure 14-16 As shown, it can be observed that after the doping elements in any two layers are interchanged, the three-layer structure in the precursor body is still retained, but the uniformity of the radial growth of the primary particles in the cross-section is reduced, and the porosity distribution between the primary particles in the radial stack is uneven.

[0117] The performance of the positive electrode precursors of Examples 1-5 and Comparative Examples 1-14 were tested, and the results are shown in Tables 1-3.

[0118] Table 1. Physicochemical parameters of the cathode precursors obtained in Examples 1-5 and Comparative Examples 1-14

[0119] Table 2. Structural characterization parameters of the cathode precursors obtained in Examples 1-5 and Comparative Examples 1-14

[0120] Table 3. Microcrystalline structure parameters of the cathode precursors obtained in Examples 1-5 and Comparative Examples 1-14

[0121] Electrochemical performance testing Method: The positive electrode precursors obtained in Examples 1-5 and Comparative Examples 1-14 were mixed with lithium hydroxide at a molar ratio of 1:1.06 and placed in a tube furnace. Under an oxygen atmosphere, the temperature was increased to 500°C at 5°C / min and held for 4 hours, then increased to 750°C at 5°C / min and held for 10 hours. After cooling to room temperature in the furnace, the mixture was ground to obtain a highly active positive electrode material. The positive electrode material was dissolved in N-methylpyrrolidone at a mass ratio of 90:5:5 with carbon black conductive agent Super P and binder polyvinylidene chloride to form a slurry. This slurry was coated onto aluminum foil and dried at 100°C to obtain the positive electrode sheet. Then, using lithium metal sheet as the negative electrode, a CR2430 coin cell battery module was assembled into a battery. A charge-discharge comparison test was conducted under 4.25V and 4C conditions, and the test results are shown in Table 4.

[0122] Table 4 Battery Test Results

[0123] As shown in Tables 1-4, and as obtained from Examples 1-5, the cathode precursor provided by this invention has a three-layer structure design consisting of a core layer, an intermediate layer, and a radial growth layer. The three layers are sequentially doped with low-valence cations, high-valence cations, and anions, resulting in high radial uniformity of the primary particles constituting the secondary particles and a uniform porosity distribution in the radial growth layer. This allows the cathode material prepared by lithium mixing and sintering using this cathode precursor to possess high-speed lithium-ion transport capabilities and excellent stress release capabilities, improving the rate performance and cycle stability of the cathode material. Simultaneously, the high crystallinity and unique crystal microstructure of the cathode precursor also give it excellent compressive strength. The cathode material obtained after sintering achieves a harmonious balance between high energy density, fast charging capability, and long lifespan. Compared to conventional precursors, the cathode material prepared using this cathode precursor exhibits a discharge capacity ≥180mAh / g under 2.7~4.25V, 4C testing conditions, with a 20-40% improvement in DCR and a capacity retention rate increase of over 4% after 300 cycles.

[0124] Comparing Example 1 and Comparative Example 1, it can be seen that using excessively high reaction temperatures during the preparation of the cathode precursor provided by the present invention can easily reduce the length-to-thickness ratio of the primary particles on the surface of the cathode precursor, make the boundaries of the internal three-layer structure indistinct, reduce the average pore volume and internal porosity, increase the tap density, and decrease the BET. At the same time, Lc decreases and La increases in the microcrystalline structure, and the cathode precursor is prone to breakage under certain pressure, resulting in a deterioration in the capacity and cycle retention rate of the prepared cathode material and a decrease in the DCR improvement rate.

[0125] As can be seen from the comparison between Example 1 and Comparative Example 2, the ammonia concentration during the preparation of the cathode precursor provided by the present invention also affects its performance. When the ammonia concentration of the seed crystal is greater than that during concentrated growth, the cathode precursor is prone to a decrease in internal porosity despite having a larger overall pore volume. At the same time, the length-to-thickness ratio of the primary particles on the surface is too large, and the cathode precursor is also prone to breakage under certain pressure. After sintering, the proportion of the loose layer inside the material decreases, while the proportion of the compact intermediate layer is large, which is not conducive to lithium ion insertion / extraction and stress release. The capacity and cycle performance of the prepared cathode material also decrease significantly.

[0126] As can be seen from the comparison of Example 1 and Comparative Examples 3 and 4, pH control during the preparation of the cathode precursor provided by the present invention affects its performance. If the pH is too low, it will lead to faster growth, particle agglomeration resulting in a wider particle size distribution, thicker whiskers, smaller primary particle length-to-thickness ratio, lower specific surface area, average pore volume, and internal porosity, and poorer crystallinity of the cathode precursor. Under certain pressure, the degree of breakage will be greater, resulting in a significant decrease in the capacity of the prepared cathode material and a deterioration in cycle performance. If the pH is too high, it will lead to slower growth, finer surface whiskers, a larger primary particle length-to-thickness ratio, and higher specific surface area, average pore volume, and internal porosity. Although the capacity of the prepared cathode material will not decrease significantly, the cycle performance will deteriorate significantly, and the DCR improvement rate will be reduced to the lowest level.

[0127] As can be seen from the comparison between Example 1 and Comparative Examples 5-7, after reducing one doping element in the cathode precursor provided by the present invention, the BET and pore volume of the cathode precursor are reduced to varying degrees, the internal structure and crystal structure deteriorate, and the compressive strength deteriorates. As a result, the cathode material obtained lacks a layer of structural protection, and the capacity, cycle retention rate and DCR improvement rate at high rates are all deteriorated, and it is not possible to maintain a good level at the same time.

[0128] As can be seen from the comparison between Example 1 and Comparative Examples 8-10, after reducing the two doping elements in the cathode precursor provided by the present invention, the internal structure and crystal structure of the cathode precursor are further deteriorated, the compressive strength is significantly worse, and the cathode material obtained further decreases in capacity, cycle retention rate and DCR improvement rate at high rates due to the lack of two protective layers.

[0129] Comparing Example 1 and Comparative Example 11, it can be seen that after the three-layer structure of the cathode precursor provided by the present invention does not contain any doping elements, the BET, pore volume, internal structure, surface whiskers and crystal structure of the cathode precursor deteriorate to the extreme. The cathode precursor has the worst compressive strength, and the cathode material obtained lacks three-layer protection. The capacity, cycle retention rate and DCR improvement rate at high rates decrease the most, but it is still better than the cathode material obtained by using conventional precursors on the market.

[0130] As can be seen from the comparison between Example 1 and Comparative Examples 12-14, after the doping elements in the three-layer structure of the cathode precursor provided by the present invention are interchanged, the proportion of each layer structure, the radial growth consistency and the pore uniformity of the precursor deteriorate. The compressive strength of the cathode precursor is deteriorated. Although the capacity, cycle retention rate and DCR improvement rate of the cathode material at high rates can be improved, the improvement is not as obvious as in the examples.

[0131] As can be seen from the comparison between Example 1 and Comparative Examples 5-14, the cathode precursor provided by the present invention can only achieve the best synergistic effect of each element after the core layer, intermediate layer, and radial growth layer are doped with low-valent cation elements, high-valent cation elements, and anionic elements, respectively. The incorporation of low-valent cation elements into the core of the cathode precursor facilitates the formation of a porous structure. After sintering into the cathode material, the dopant elements enter the transition metal sites of the cathode material, stabilizing the material structure, suppressing phase transitions, and reducing the formation of internal cracks, thereby improving the cycle stability and thermal stability of the material. The incorporation of high-valent cation elements into the intermediate layer of the precursor facilitates the formation of a dense structure. After sintering into the material, the dopant elements easily form strong metallic bonds (NO) with oxygen, pinning the particle boundaries to reduce interdiffusion and minimize particle coarsening, suppressing Li / Ni mixing, reducing volumetric strain, thereby stabilizing the internal structure and suppressing the formation and propagation of microcracks. After anionic elements are incorporated into the precursor growth layer, it is beneficial for the primary particles of the cathode precursor to grow radially and form an internal structure with uniformly distributed pores. After sintering into the cathode material, the doping elements replace oxygen sites, reducing the dissolution of transition metal elements and the precipitation of lattice oxygen, improving the electronic conductivity and lithium-ion diffusion rate of the cathode material, improving the rate performance of the cathode material, and reducing the risk of lithium plating at high rates.

[0132] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A positive electrode precursor, characterized in that, The positive electrode precursor is composed of secondary particles; the secondary particles are composed of multiple plate-like primary particles; The secondary particles consist of three layers from the inside out: a core layer doped with low-valence cations, an intermediate layer doped with high-valence cations, and a radial growth layer doped with anions; the intermediate layer is more compact than the core layer and the radial growth layer; the high-valence cations have a higher valence state than the low-valence cations.

2. The positive electrode precursor according to claim 1, characterized in that, The positive electrode precursor satisfies at least one of the following requirements: (1) The positive electrode precursor is spherical or near-spherical; (2) The sphericity of the positive electrode precursor is 0.7-0.95; (3) The total porosity of the secondary particle profile of the positive electrode precursor is 5%-35%; preferably 8%-20%; (4) The average pore volume of the positive electrode precursor is 0.02-0.11 cm³. 3 / g; (5) The median particle size D50 of the positive electrode precursor is 5-14.5 μm; (6) The particle size distribution of the positive electrode precursor is span=(D90-D10) / D50, and span is 0.3-0.7; (7) The specific surface area BET of the positive electrode precursor is 6-18m². 2 / g; (8) The tap density TD of the positive electrode precursor is 1.5-1.9 g / cm³. 3 ; (9) The positive electrode precursor has a pressure particle size of 0.1-5.3 μm and a fragmentation degree of 1%-20% at 0.75-2T. The pressure particle size refers to the difference between D50 after pressing at 0.75-2T and D50 before pressing, and the fragmentation degree refers to the ratio of pressure particle size to D50 before pressing.

3. The positive electrode precursor according to claim 1, characterized in that, The molecular formula of the positive electrode precursor is: Ni x Co y Mn z M m N n L p (OH)2, where x+y+z+m+n+p=1, 0.8≤x≤0.97, 0≤y≤0.10, 0≤z≤0.10, 0≤m≤0.02, 0≤n≤0.02, 0≤n≤0.02, and M is a low-valence cation element doped in the core layer; N is a high-valence cation element, doped in the intermediate layer; L is an anion element, doped in the radial growth layer; Preferably, the low-valent cation element includes any one or a combination of at least two of Mg, Al, Cu, Zn, Sr, and La; The high-valence cation elements include any one or a combination of at least two of Ti, Sb, W, Nb, Zr, and Mo; The anionic element includes any one or a combination of at least two of F, Cl, and B.

4. The positive electrode precursor according to any one of claims 1-3, characterized in that, The volume ratio of the three-layer structure in the positive electrode precursor meets the following requirements: (1) The volume of the core layer accounts for 5%-10% of the volume of the positive electrode precursor: (2) The volume of the intermediate layer accounts for 10%-15% of the volume of the positive electrode precursor; (3) The volume of the radially grown layer accounts for 75%-85% of the volume of the positive electrode precursor.

5. The positive electrode precursor according to any one of claims 1-3, characterized in that, The positive electrode precursor satisfies at least one of the following requirements: (1) I in the XRD pattern 001 / I 101 =0.8-1.3, the preferred orientation degree of the (101) crystal plane is 0.29-0.35, and the preferred orientation index P of the (101) crystal plane is 0.29-0.

35. （101） The value is 0.9-1.2; where I represents the peak intensity value of the corresponding crystal plane; I 001 / I 101 This represents the peak intensity ratio between the (001) and (101) crystal planes; (2) The full width at half maximum (FWHM) β of the diffraction peak of the (001) crystal plane corresponding to the diffraction angle 2θ = 19.2 ± 0.5° in the XRD pattern 001 The full width at half maximum (FWHM) β of the diffraction peak on the (101) crystal plane corresponding to a diffraction angle of 0.45-1° and a diffraction angle of 2θ = 38.5 ± 0.5° is 0.45-1°. 101 It is 0.45-0.65°, and β 001 / β 101 =0.85-1.8; (3) The effective stacking height Lc along the direction perpendicular to the TM(OH)6 octahedral layer in the microcrystalline structure is 8-18 nm, and the number of microcrystalline wafer layers N on the (001) crystal plane is 8-18 nm. （001） The average diameter La of the stacked layers formed by stacking microwafers is 40-66 nm, and the number of microwafer layers N on the (101) crystal plane is 24-39. （101） It is 5-83, and N 101 / N 001 =1.6-3.4, where TM is at least one of Ni, Co, Mn, low-valence cations, anions, and high-valence cations.

6. The positive electrode precursor according to any one of claims 1-3, characterized in that, The primary particles must meet the following requirements: (1) The length L of the primary particle is 200-800 nm; (2) The thickness H of the primary particles is 20-80 nm; (3) The length-to-thickness ratio of the primary particles: L / H = 2-20; preferably 5-10.

7. A method for preparing the positive electrode precursor according to any one of claims 1 to 6, characterized in that, include: A metal salt solution A containing nickel, cobalt, and manganese sources, an alkaline solution B, a complexing agent solution C, and a doping solution D containing low-valence cation elements are mixed to perform the first stage of co-precipitation. The overflow slurry from the first stage of co-precipitation is then collected as the first seed crystal. The first seed crystal, the metal salt solution A, the alkaline solution B, the complexing agent solution C, and the doping solution E containing high-valence cation elements are mixed to carry out a second stage of co-precipitation, and then the overflow slurry of the second stage of co-precipitation is collected as the second seed crystal. The second seed crystal, the metal salt solution A, the alkaline solution B, the complexing agent solution C, and the doping solution F containing anionic elements are mixed for concentrated growth and aging.

8. The preparation method according to claim 7, characterized in that, include: S1. Prepare the metal salt solution A, the alkaline solution B, the complexing agent solution C, the doping solution D, the doping solution E, and the doping solution F respectively; S2. The metal salt solution A, the alkaline solution B, the complexing agent solution C, and the doping solution D are mixed with the base liquid under inert gas protection and nucleation is carried out at temperature T1 to obtain reaction solution 1; then, while keeping the complexing agent concentration in reaction solution 1 constant at C1, the pH is lowered to pH1 and maintained until the particle size D50 reaches 1.5-3.5 μm, and the overflow slurry is collected as the first seed crystal; S3. The first seed crystal, the metal salt solution A, the alkaline solution B, the complexing agent solution C and the doping solution E are mixed for a second stage of co-precipitation, wherein the temperature is maintained at T1, the complexing agent concentration is maintained at C2, and the pH is maintained at pH2, until the particle size D50 reaches 2.5-7.5μm, and the overflow slurry is collected as the second seed crystal. S4. The second seed crystal, the metal salt solution A, the alkaline solution B, the complexing agent solution C, and the doping solution F are mixed and concentrated for growth reaction. The temperature is maintained at T2, the complexing agent concentration is maintained at C3, and the pH is maintained at pH3. After maintaining this for a period of time, the pH is adjusted to pH4 and maintained until the particle size D50 reaches 5-14 μm, at which point the feeding is stopped to obtain a slurry of the positive electrode precursor. The slurry of the positive electrode precursor is then heated and aged. Preferably, the conditions in S1-S4 satisfy at least one of the following requirements: (1) Forming soluble salts of nickel, cobalt and manganese as nickel, cobalt and manganese sources respectively; (2) The total molar concentration of metal ions in the metal salt solution A is 1.5-2.5 mol / L; (3) The concentration of the alkaline solution B is 6-12 mol / L; (4) The alkaline solution B includes a hydroxide solution; (5) The complexing agent solution C includes ammonia; (6) The concentration of the complexing agent solution C is 5-11 mol / L; (7) The concentration of the doped solution D is 5-20 g / L; (8) The concentration of the doped solution E is 5-20 g / L; (9) The concentration of the doped solution F is 5-20 g / L; (10) The base liquid includes hydroxide, ammonia and water; (11) The pH of the base solution is 10.5-12.5, the concentration of ammonia in the base solution is 0-15 g / L, and the temperature of the base solution is 40-75℃; (12) T1 and T2 are 40-75℃ respectively, and T1 < T2; (13) C1, C2 and C3 are all 0-15 g / L, and C1 < C2 < C3; (14) pH1, pH2, pH3 and pH4 are 9.5-12.2 respectively, and pH1>pH2>pH3>pH4; (15) The rate of introduction of metal salt solution A in S2, S3 and S4 is 1% to 10% of the volume of the reactor per hour; and the flow rate of metal salt solution A in S2 = the flow rate of metal salt solution A in S3 ≥ the flow rate of metal salt solution A in S4. The rate at which the alkaline solution B is introduced in S2, S3, and S4 is 0.3% to 4% of the reactor volume per hour, respectively. The infeed rate of the complexing agent solution C in S2, S3 and S4 is 0.2% to 2% of the volume of the reactor added per hour, respectively. The doping solution D, the doping solution E, and the doping solution F are all introduced at a rate of 0.1% to 0.5% of the reactor volume per hour. (16) The aging process involves adding 1%-5% alkali by volume of the reactor, with an aging temperature of 65-85℃ and an aging time of 3-10h. (17) The amount of the first seed crystal and the second seed crystal added is 50%-80% of the total volume of the reactor.

9. A positive electrode material, characterized in that, It is prepared using the positive electrode precursor described in claim 1.

10. A lithium-ion battery, characterized in that, It includes the cathode material as described in claim 9.

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