Ternary positive electrode material precursor, preparation method thereof, positive electrode material, lithium ion battery and electrical equipment

Abstract

This application provides a ternary cathode material precursor and its preparation method, a cathode material, a lithium-ion battery, and related electrical devices, relating to the field of lithium-ion batteries. The ternary cathode material precursor includes secondary particles, which, from the inside out, comprise a core, an intermediate layer, and a shell. The porosity of the core is higher than that of the intermediate layer, and the porosity of the intermediate layer is higher than that of the shell. Both the core and the intermediate layer contain element M. The molar percentage of element M in the total metal element content of the intermediate layer is higher than that in the total metal element content of the core. M includes at least one of Al, Ti, Zr, Mg, W, and Nb. The core, intermediate layer, and shell in the ternary cathode material precursor of this application work together to improve the structural stability of the material.

Description

Technical Field

[0001] This application relates to the field of lithium-ion batteries, and in particular to a ternary cathode material precursor and its preparation method, cathode material, lithium-ion battery, and electrical equipment. Background Technology

[0002] With the increasing global demand for high-energy-density energy storage devices, research on lithium-ion battery cathode materials has focused on high-nickel layered oxides (such as LiNi). x Co y Mn z O2, where x≥0.8, is referred to as high-nickel NCM. High-nickel NCM materials are considered key materials for realizing next-generation high-energy-density lithium-ion batteries due to their advantages of high specific capacity and low cost.

[0003] However, with the increase in nickel content, a series of inherent technical bottlenecks have become increasingly prominent, severely restricting its commercial application and further development: First, during charging and discharging, especially under deep delithiation (high voltage) conditions, high-nickel materials undergo drastic lattice contraction from the H2 phase to the H3 phase, generating enormous internal stress. This anisotropic lattice stress leads to the generation of numerous radial microcracks within the secondary spherical particles, disrupting the structural integrity of the particles and exposing new active surfaces that undergo continuous side reactions with the electrolyte, accelerating capacity decay and causing a sharp increase in battery internal resistance. Especially under high-temperature environments, these side reactions are further exacerbated, resulting in a significant reduction in battery cycle life.

[0004] To address these challenges, two common strategies are bulk element doping and surface coating. While bulk homogeneous doping can stabilize the crystal structure to some extent, its effect is global and uniform, failing to create localized mechanical strengthening points within the particles. For high-nickel materials during cycling, especially under high voltage and the enormous radial internal stress generated by the H2-H3 phase transition, homogeneous doping cannot effectively resist the initiation and propagation of microcracks caused by stress concentration at grain boundaries. Therefore, after long-term cycling, secondary particles still experience severe structural breakage, leading to a rapid decline in cycle life. Moreover, homogeneous doping suffers from low utilization of functional elements and potential performance sacrifice; only the portion of dopants dispersed throughout the particles at critical defects such as grain boundaries can exert their maximum effect, while the remaining functional parts are not fully utilized. Surface coating primarily acts on the particle surface, improving interfacial stability, but it is powerless against mechanical stress within the particles, especially at grain boundaries, and cannot prevent the generation of microcracks within the particles. Furthermore, once the coating layer is damaged due to volume changes during cycling, its protective effect quickly fails.

[0005] Therefore, existing technologies lack a targeted solution that can effectively suppress microcrack initiation from within the particles and simultaneously improve bulk and interfacial stability. Neither uniform doping nor surface coating can fundamentally solve the mechanical failure problem caused by lattice stress in high-nickel materials during long-term cycling. Summary of the Invention

[0006] The purpose of this application is to provide a ternary cathode material precursor and its preparation method, cathode material, lithium-ion battery and electrical equipment to solve the above-mentioned problems.

[0007] To achieve the above objectives, this application adopts the following technical solution: A ternary cathode material precursor includes secondary particles, wherein the secondary particles comprise, from the inside out, a core, an intermediate layer and a shell. The porosity of the core is higher than that of the intermediate layer, and the porosity of the intermediate layer is higher than that of the shell. Both the core and the intermediate layer contain element M; the molar percentage of element M in the total metal elements of the intermediate layer is higher than the molar percentage of element M in the total metal elements of the core; M includes at least one of Al, Ti, Zr, Mg, W, and Nb.

[0008] According to embodiments of this application, the porosity of the core is 60%~85%, the porosity of the intermediate layer is 20%~40%, and the porosity of the shell layer is 5%~15%. And / or, the D50 particle size of the core is 1.0 μm to 5.0 μm, the thickness of the intermediate layer is 0.5 μm to 2.0 μm, and the thickness of the shell layer is 5.0 μm to 15.0 μm.

[0009] According to an embodiment of this application, the chemical formula of the core is Ni. x1 Co y1 Mn z1 M a1 (OH)2, where 0.50≤x1<1, 0<y1≤0.20, 0<z1≤0.30, 0.01≤a1≤0.08, x1 + y1 + z1 + a1 = 1; And / or, the chemical formula of the intermediate layer is Ni x2 Co y2 Mn z2 M a2 (OH)2, 0.50≤x2<1, 0<y2≤0.20, 0<z2≤0.30, 0.015≤a2≤0.035, x2 + y2 + z2 + a2 = 1, a2>a1; And / or, the chemical formula of the shell is Ni x3Co y3 Mn z3 (OH)2, 0.50≤x3<1, 0<y3≤0.20, 0<z3≤0.30, x3 + y3 + z3 = 1.

[0010] This application also provides a method for preparing the ternary cathode material precursor described above, including: The mixed metal salt solution is mixed with M salt solution, precipitant and complexing agent in the first reaction vessel to carry out the first coprecipitation reaction to obtain seed slurry. The mixed metal salt solution includes nickel salt, cobalt salt and manganese salt. The seed slurry is subjected to a second coprecipitation reaction with a mixed metal salt solution, an M salt solution, a precipitant, and a complexing agent in a second reactor to obtain an intermediate. Stop the flow of M salt solution, and carry out a third coprecipitation reaction with the intermediate, mixed metal salt solution, precipitant, and complexing agent to obtain the ternary cathode material precursor.

[0011] According to an embodiment of this application, in the first coprecipitation reaction, the total concentration of metal ions in the mixed metal salt solution is 1.0-1.8 mol / L; And / or, the precipitant includes a sodium hydroxide solution; And / or, the concentration of the precipitant is 4.0-6.0 mol / L; And / or, the complexing agent comprises an aqueous ammonia solution; And / or, the concentration of the complexing agent is 4.0-8.0 g / L; And / or, the first coprecipitation reaction includes adding a base liquid to a first reaction vessel, and then adding a mixed metal salt solution and an M salt solution, a precipitant, and a complexing agent to the base liquid to carry out the first coprecipitation reaction; And / or, the base solution includes a complexing agent and a precipitating agent, the ammonia concentration of the base solution is 2.0-5.0 g / L, and the pH value of the base solution is 11.5-11.8; And / or, the temperature of the first coprecipitation reaction is 50-60°C; And / or, the stirring speed for the first coprecipitation reaction is 300-500 rpm; And / or, the pH value of the first coprecipitation reaction is 10.2-11.6; And / or, the method further includes: when the particle size of the seed slurry is detected to be 2.2-4.2 μm, the first coprecipitation reaction ends; And / or, the time for the first coprecipitation reaction is 8-18 hours; And / or, in the first coprecipitation reaction, the molar amount of M accounts for 2% to 5% of the total molar amount of all metal elements in the feed liquid.

[0012] According to an embodiment of this application, the second coprecipitation reaction includes: transferring the seed slurry to a second reaction vessel, adding water until the solid content reaches 100-180 g / L, and then adding a mixed metal salt solution, an M salt solution, a precipitant, and a complexing agent to carry out the second coprecipitation reaction; And / or, during the second coprecipitation reaction, the concentration of ammonia in the system is 4.0-7.0 g / L; And / or, the stirring speed for the second coprecipitation reaction is 200-400 rpm; And / or, the temperature of the second coprecipitation reaction is 50-58°C; And / or, the pH value of the second coprecipitation reaction is 10.2-11.6; And / or, the method further includes: when the particle size of the intermediate is detected to be 4.2-8.2 μm, the second coprecipitation reaction ends; And / or, the second coprecipitation reaction takes 2-5 hours; And / or, in the second coprecipitation reaction, the molar amount of M accounts for 1.5% to 3.5% of the total molar amount of all metal elements in the feed liquid.

[0013] According to an embodiment of this application, the pH value of the third coprecipitation reaction is 10.4-11.0; And / or, during the third coprecipitation reaction, the concentration of ammonia in the system is 4.0-7.0 g / L; And / or, the stirring speed for the third coprecipitation reaction is 200-400 rpm; And / or, the temperature of the third coprecipitation reaction is 50-58°C; And / or, the method further includes: when the particle size is detected to be 15.2-39.2 μm, the third coprecipitation reaction ends; And / or, the time for the third coprecipitation reaction is 20-35 hours; And / or, the method further includes: after the third coprecipitation reaction is completed, aging, washing and drying are performed sequentially to obtain a ternary cathode material precursor; And / or, the aging temperature is 50-60°C, and the aging time is 4-10 hours; And / or, the washing includes: washing with hot water at 40-50°C by centrifugation or pressure filtration until the conductivity of the filtrate is <50 μS / cm; And / or, the drying includes: drying the washed filter cake at a temperature of 100-120°C for 10-15 hours.

[0014] This application also provides a cathode material, which is made by lithiation sintering of a ternary cathode material precursor. The ternary cathode material precursor is the ternary cathode material precursor described above or the ternary cathode material precursor prepared by the preparation method described above.

[0015] This application also provides a lithium-ion battery, including the positive electrode material described above.

[0016] This application also provides an electrical device, including the lithium-ion battery described above.

[0017] Compared with the prior art, the beneficial effects of this application include: The cathode precursor of this application has an intermediate layer between the core and the shell, which constitutes a chemical and structural buffer zone. The intermediate layer effectively prevents the lattice strain generated during lithium-ion insertion / extraction from propagating inward, suppresses lattice mismatch and stress concentration, and inhibits the initiation and propagation of radial cracks. At the same time, the porosity of the core, intermediate layer, and shell gradually decreases, enhancing the overall structural strength of the particle and effectively resisting mechanical failure during cycling.

[0018] The core of this application has a high porosity. On the one hand, the high porosity of the core provides a buffer space for the volume change of the material during the charging and discharging process, reducing internal stress; on the other hand, the core has a continuous pore structure, which provides a shorter path for lithium ion diffusion in the subsequent lithiation process, which is beneficial to improving the structural stability of the material.

[0019] The intermediate layer in this application is designed in conjunction with the core structure. The nitrogen (M) element is enriched in the stress concentration region, achieving a synergistic effect of internal buffering and interface strengthening. The intermediate layer not only stabilizes the core with its high porosity but also acts as a functional load-bearing ring, combining with the core's buffering effect to jointly resist cyclic stress, suppress particle breakage and microcrack propagation, and prevent core disintegration. Furthermore, by selecting different M elements (such as Al for lattice stability and Zr for interface strengthening), different ternary material systems can be specifically optimized, thereby improving the material's cycle life and thermal stability. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0021] Figure 1 This is a cross-sectional SEM image of the hollow seed crystal obtained in step S1 of Example 1; Figure 2 This is a cross-sectional SEM image of the precursor product from Example 1; Figure 3 The image shown is a CP-SEM image of the hollow seed crystals obtained in step S1 of Example 2. Figure 4 Here is a CP-SEM image of the precursor product from Example 2; Figure 5 Here is the CP-SEM image of the hollow seed crystals obtained in step S1 of Comparative Example 1; Figure 6 Here is a CP-SEM image of the precursor product obtained in Comparative Example 1; Figure 7 The image shown is a CP-SEM image of the precursor product in Comparative Example 2. Detailed Implementation

[0022] As used in this article: "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0023] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0024] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0025] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0026] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0027] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0028] A ternary cathode material precursor includes secondary particles, wherein the secondary particles comprise, from the inside out, a core, an intermediate layer and a shell. The porosity of the core is higher than that of the intermediate layer, and the porosity of the intermediate layer is higher than that of the shell. Both the core and the intermediate layer contain element M; the molar percentage of element M in the total metal elements of the intermediate layer is higher than the molar percentage of element M in the total metal elements of the core; M includes at least one of Al, Ti, Zr, Mg, W, and Nb.

[0029] In this application, the porosity of the core, intermediate layer and shell gradually decreases, which can effectively improve the structural stability of secondary particles and thus improve the mechanical strength of the ternary cathode material precursor.

[0030] In some embodiments, M is preferably Al or Zr. Al can effectively stabilize the crystal structure, while Zr can form a more robust interfacial protective layer on the particle surface.

[0031] In some embodiments, the kernel comprises filamentary units, and a plurality of filamentary units constitute the kernel.

[0032] According to embodiments of this application, the porosity of the core is 60%~85%, the porosity of the intermediate layer is 20%~40%, and the porosity of the shell layer is 5%~15%. For example, the porosity of the core is 60%, 65%, 70%, 75%, 80%, 85%, or any value between 60% and 85%; the porosity of the intermediate layer is 20%, 25%, 30%, 35%, 40%, or any value between 20% and 40%; and the porosity of the shell is 5%, 10%, 15%, or any value between 5% and 15%.

[0033] The core has a D50 particle size of 1.0 μm to 5.0 μm, the intermediate layer has a thickness of 0.5 μm to 2.0 μm, and the shell has a thickness of 5.0 μm to 15.0 μm.

[0034] For example, the D50 particle size of the core can be 1.0μm, 2.0μm, 3.0μm, 4.0μm, 5.0μm or any value between 1.0μm and 5.0μm; the thickness of the intermediate layer can be 0.5μm, 1.0μm, 1.5μm, 2.0μm or any value between 0.5μm and 2.0μm; and the thickness of the shell can be 5.0μm, 10.0μm, 15.0μm or any value between 5.0μm and 15.0μm.

[0035] According to an embodiment of this application, the chemical formula of the core is Ni. x1 Co y1 Mn z1 M a1 (OH)2, where 0.50≤x1<1, 0<y1≤0.20, 0<z1≤0.30, 0.01≤a1≤0.08, x1 + y1 + z1 + a1 = 1; For example, x1 can be 0.50, 0.60, 0.70, 0.80, 0.90, 0.93, 0.95, 0.98 or any value between 0.50 and 1; y1 can be 0.01, 0.03, 0.037, 0.04, 0.05, 0.08, 0.10, 0.13, 0.15, 0.18, 0.20 or any value between 0 and 0.20; z1 can be 0.0097, 0.01, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30 or any value between 0 and 0.30; a1 can be 0.01, 0.02, 0.0233, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08 or any value between 0.01 and 0.08.

[0036] In some embodiments, the core has the chemical formula Ni. 0.93 Co 0.037 Mn 0.0097 M 0.0233 (OH)2.

[0037] The chemical formula of the intermediate layer is Ni. x2 Co y2 Mn z2 M a2 (OH)2, 0.50≤x2<1, 0<y2≤0.20, 0<z2≤0.30, 0.015≤a2≤0.035, x2 + y2 + z2 + a2 = 1, a2>a1; For example, x2 can be 0.50, 0.60, 0.70, 0.80, 0.90, 0.92, 0.95, 0.98 or any value between 0.50 and 1; y2 can be 0.01, 0.03, 0.038, 0.04, 0.05, 0.08, 0.10, 0.13, 0.15, 0.18, 0.20 or any value between 0 and 0.20; z2 can be 0.01, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30 or any value between 0 and 0.30; a2 can be 0.015, 0.02, 0.025, 0.03, 0.032, 0.035 or any value between 0.015 and 0.035.

[0038] In some embodiments, the chemical formula of the intermediate layer is Ni. 0.92 Co 0.038 Mn 0.01 M 0.032 (OH)2.

[0039] The chemical formula of the shell is Ni. x3 Co y3 Mn z3 (OH)2, 0.50≤x3<1, 0<y3≤0.20, 0<z3≤0.30, x3 + y3 + z3 = 1.

[0040] For example, x3 can be 0.50, 0.60, 0.70, 0.80, 0.90, 0.93, 0.95, 0.96, 0.98 or any value between 0.50 and 1; y3 can be 0.01, 0.03, 0.037, 0.04, 0.05, 0.08, 0.10, 0.13, 0.15, 0.18, 0.20 or any value between 0 and 0.20; z3 can be 0.003, 0.0097, 0.01, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30 or any value between 0 and 0.30.

[0041] In some embodiments, the chemical formula of the shell is Ni 0.96 Co 0.037 Mn 0.003 (OH)2.

[0042] This application also provides a method for preparing the ternary cathode material precursor described above, including: The mixed metal salt solution is mixed with M salt solution, precipitant and complexing agent in the first reaction vessel to carry out the first coprecipitation reaction to obtain seed slurry. The mixed metal salt solution includes nickel salt, cobalt salt and manganese salt. The seed slurry is subjected to a second coprecipitation reaction with a mixed metal salt solution, an M salt solution, a precipitant, and a complexing agent in a second reactor to obtain an intermediate. Stop the flow of M salt solution, and carry out a third coprecipitation reaction with the intermediate, mixed metal salt solution, precipitant, and complexing agent to obtain the ternary cathode material precursor.

[0043] According to an embodiment of this application, in the first coprecipitation reaction, the total concentration of metal ions in the mixed metal salt solution is 1.0-1.8 mol / L; For example, in the first coprecipitation reaction, the total concentration of metal ions in the mixed metal salt solution is any value between 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, or 1.0-1.8 mol / L.

[0044] The precipitant includes a sodium hydroxide solution; The concentration of the precipitant is 4.0-6.0 mol / L; for example, the concentration of the precipitant is 4.0 mol / L, 4.5 mol / L, 5.0 mol / L, 5.5 mol / L, 6.0 mol / L or any value between 4.0-6.0 mol / L.

[0045] The complexing agent includes an aqueous ammonia solution; The concentration of the complexing agent is 4.0-8.0 g / L; for example, the concentration of the complexing agent is 4.0 g / L, 5.0 g / L, 6.0 g / L, 7.0 g / L, 8.0 g / L or any value between 4.0 and 8.0 g / L.

[0046] The first coprecipitation reaction includes adding a base liquid to a first reaction vessel, and then adding a mixed metal salt solution and an M salt solution, a precipitant, and a complexing agent to the base liquid to carry out the first coprecipitation reaction; The base solution includes a complexing agent and a precipitating agent, the ammonia concentration of the base solution is 2.0-5.0 g / L, and the pH value of the base solution is 11.5-11.8; for example, the ammonia concentration of the base solution is 2.0 g / L, 3.0 g / L, 4.0 g / L, 5.0 g / L, or any value between 2.0-5.0 g / L; the pH value of the base solution is 11.5, 11.6, 11.7, 11.8, or any value between 11.5 and 11.8.

[0047] The temperature of the first coprecipitation reaction is 50-60°C; for example, the temperature of the first coprecipitation reaction is 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C or any value between 50-60°C.

[0048] The stirring speed for the first coprecipitation reaction is 300-500 rpm; for example, the stirring speed for the first coprecipitation reaction is any value between 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, or 300-500 rpm.

[0049] The pH value of the first coprecipitation reaction is 10.2-11.6; for example, the pH value of the first coprecipitation reaction is 10.2, 10.5, 11, 11.3, 11.6 or any value between 10.2 and 11.6.

[0050] The method further includes: when the particle size of the seed slurry is detected to be 2.2-4.2 μm (e.g., 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4 μm, 4.1 μm, 4.2 μm or any value between 2.2-4.2 μm), the first coprecipitation reaction ends; The time for the first coprecipitation reaction is 8-18 hours; for example, the time for the first coprecipitation reaction is any value between 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours or between 8 and 18 hours.

[0051] In the first coprecipitation reaction, the molar amount of M accounts for 2% to 5% of the total molar amount of all metal elements in the feed liquid (e.g., 2%, 3%, 4%, 5% or any value between 2% and 5%).

[0052] When the molar amount of M is within the above range, one-dimensional crystal growth can be induced, avoiding the problem of uncontrollable reaction kinetics caused by excessive M.

[0053] According to an embodiment of this application, the second coprecipitation reaction includes: transferring the seed slurry to a second reaction vessel, adding water to a solid content of 100-180 g / L (e.g., 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L, 150 g / L, 160 g / L, 170 g / L, 180 g / L or any value between 100-180 g / L), and then adding a mixed metal salt solution, an M salt solution, a precipitant, and a complexing agent to carry out the second coprecipitation reaction; By adding water to the seed slurry to a solid content of 100-180 g / L, the reaction system can be guaranteed to have suitable rheological properties, which is conducive to mass transfer and heat exchange.

[0054] When carrying out the second coprecipitation reaction, the concentration of ammonia in the system is 4.0-7.0 g / L; for example, the concentration of ammonia in the system when carrying out the second coprecipitation reaction is 4.0 g / L, 5.0 g / L, 6.0 g / L, 7.0 g / L or any value between 4.0 and 7.0 g / L.

[0055] The stirring speed for the second coprecipitation reaction is 200-400 rpm; for example, the stirring speed for the second coprecipitation reaction is any value between 200 rpm, 300 rpm, 400 rpm, or 200-400 rpm.

[0056] The temperature of the second coprecipitation reaction is 50-58°C; for example, the temperature of the second coprecipitation reaction is any value between 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C or 50-58°C.

[0057] The pH value of the second coprecipitation reaction is 10.2-11.6; for example, the pH value of the second coprecipitation reaction is 10.2, 10.5, 10.8, 11.0, 11.3, 11.6 or any value between 10.2 and 11.6.

[0058] The method further includes: when the particle size of the intermediate is detected to be 4.2-8.2 μm (e.g., 4.2 μm, 4.5 μm, 5.0 μm, 5.5 μm, 6.0 μm, 6.5 μm, 7.0 μm, 7.5 μm, 8.0 μm, 8.2 μm or any value between 4.2-8.2 μm), the second coprecipitation reaction ends; The second coprecipitation reaction takes 2-5 hours; for example, the second coprecipitation reaction takes 2 hours, 3 hours, 4 hours, 5 hours or any value between 2 and 5 hours.

[0059] In the second coprecipitation reaction, the molar amount of M accounts for 1.5% to 3.5% of the total molar amount of all metal elements in the feed solution. For example, the molar amount of M in the second coprecipitation reaction can be any value between 1.5%, 2.0%, 2.5%, 3.0%, 3.5% or 1.5% to 3.5% of the total molar amount of all metal elements in the feed solution.

[0060] When the molar amount of M is within the above range, the enrichment of element M is ensured, while the problem of uneven precipitation caused by excessively high local concentration of element M is avoided.

[0061] According to an embodiment of this application, the pH value of the third coprecipitation reaction is 10.4-11.0; for example, the pH value of the third coprecipitation reaction is 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 11.0 or any value between 10.4 and 11.0.

[0062] When carrying out the third coprecipitation reaction, the concentration of ammonia in the system is 4.0-7.0 g / L; for example, the concentration of ammonia in the system during the third coprecipitation reaction can be 4.0 g / L, 5.0 g / L, 6.0 g / L, 7.0 g / L, or any value between 4.0 and 7.0 g / L.

[0063] The stirring speed for the third coprecipitation reaction is 200-400 rpm; for example, the stirring speed for the third coprecipitation reaction is any value between 200 rpm, 300 rpm, 400 rpm, or 200-400 rpm.

[0064] The temperature of the third coprecipitation reaction is 50-58°C; for example, the temperature of the third coprecipitation reaction is any value between 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, or 50-58°C.

[0065] The method further includes: when the particle size is detected to be 15.2-39.2 μm (e.g., 15.2 μm, 20 μm, 25 μm, 30 μm, 35 μm, 39.2 μm or any value between 15.2-39.2 μm), the third coprecipitation reaction ends; The time for the third coprecipitation reaction is 20-35 hours; for example, the time for the third coprecipitation reaction is any value between 20 hours, 25 hours, 30 hours, 35 hours or 20-35 hours.

[0066] The method further includes: after the third coprecipitation reaction is completed, aging, washing and drying are performed sequentially to obtain the ternary cathode material precursor; The aging temperature is 50-60℃, and the aging time is 4-10 hours; for example, the aging temperature is any value between 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, 56℃, 57℃, 58℃, 59℃, 60℃, or 50-60℃, and the aging time is any value between 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, or 4-10 hours.

[0067] The washing process includes: washing with hot water at 40-50℃ (e.g., 40℃, 41℃, 42℃, 43℃, 44℃, 45℃, 46℃, 47℃, 48℃, 49℃, 50℃ or any value between 40-50℃) by centrifugation or pressure filtration until the conductivity of the filtrate is <50 μS / cm; using hot water can improve washing efficiency and effectively remove impurities such as sulfate ions.

[0068] The drying process includes drying the washed filter cake at a temperature of 100-120°C (e.g., 100°C, 105°C, 110°C, 115°C, 120°C, or any value between 100-120°C) for 10-15 hours (e.g., 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, or any value between 10-15 hours). After drying, the moisture content of the final product is <1.0%.

[0069] This application also provides a cathode material, which is made by lithiation sintering of a ternary cathode material precursor. The ternary cathode material precursor is the ternary cathode material precursor described above or the ternary cathode material precursor prepared by the preparation method described above.

[0070] This application also provides a lithium-ion battery, including the positive electrode material described above.

[0071] This application also provides an electrical device, including the lithium-ion battery described above.

[0072] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0073] Example 1 Example 1 provides a ternary cathode material precursor, comprising secondary particles. The secondary particles, from the inside out, consist of a core, an intermediate layer, and a shell. The core has the chemical formula Ni. 0.93 Co 0.037 Mn 0.0097 Al 0.0233 (OH)₂, the chemical formula of the intermediate layer is Ni 0.92 Co 0.038 Mn 0.01 Al 0.032 (OH)₂, the chemical formula of the shell is Ni 0.96 Co 0.037 Mn 0.003(OH)2. The porosity of the core is 70%, the porosity of the middle layer is 25%, and the porosity of the shell is 5%; the D50 particle size of the core is 3.7 μm, the thickness of the middle layer is 1.1 μm, and the thickness of the shell is 9.2 μm.

[0074] The preparation methods of ternary cathode material precursors include: S1-Synthetic Kernel: S1-1. Solution preparation: Prepare a mixed aqueous solution of nickel sulfate, cobalt sulfate, and manganese sulfate, wherein the molar ratio of nickel, cobalt, and manganese is consistent with the ratio in the core chemical formula, i.e., Ni:Co:Mn = 0.93:0.037:0.0097, and the total concentration of metal ions is controlled at 1.3 mol / L.

[0075] Prepare a 5.2 mol / L sodium hydroxide solution as a precipitant.

[0076] Prepare an ammonia solution with a concentration of 6.7 g / L as a complexing agent.

[0077] Premix the aluminum sulfate solution with the above mixed salt solution to ensure that Al 3+ The molar percentage of ions in the total metal ions is 2.33% (consistent with the Al content a1=0.0233 in the core chemical formula).

[0078] S1-2. Coprecipitation reaction: In the first reaction vessel (seed crystal synthesis vessel), the base liquid is added, and the initial ammonia concentration is controlled at 4.0 g / L. The initial amount of alkali is also controlled to make the pH reach 11.65.

[0079] Start the stirrer and control the stirring speed at 500 rpm. Maintain the temperature of the reactor at 55℃.

[0080] The mixed salt solution, sodium hydroxide solution, and supplemental ammonia were added in a parallel flow. The addition rate of sodium hydroxide solution was monitored and controlled online using a precision pH meter to stabilize the pH of the reaction system at 10.45.

[0081] The reaction continued until the target particle size was detected to be 3.8 μm (requiring 15 hours), at which point the first coprecipitation reaction ended. The cross-sectional SEM image of the hollow seed crystals obtained in step S1 of Example 1 is shown below. Figure 1 As shown.

[0082] S2 - Building the intermediate layer: S2-1. System Transfer and Preparation: The seed slurry obtained from S1 is transferred to the second reactor (growth reactor).

[0083] Add deionized water to precisely adjust the solid content of the system to 150 g / L.

[0084] Add ammonia water to control the initial ammonia concentration of the system to 5.0 g / L.

[0085] Maintain the stirring speed at 400 rpm and the temperature at 55℃.

[0086] S2-2. Enriched layer deposition: Preparation of enrichment solution: In this mixed salt solution, the molar ratio of nickel, cobalt and manganese is consistent with the ratio in the intermediate layer chemical formula, that is, Ni:Co:Mn = 0.92:0.038:0.01, and the molar percentage of Al element is maintained at 3.2% (consistent with the Al content a2=0.032 in the intermediate layer chemical formula).

[0087] The enrichment solution, conventional mixed salt solution, sodium hydroxide solution, and ammonia solution were added in parallel.

[0088] By adjusting the feeding rate and stirring speed to 300 rpm, the pH of the reaction system was stabilized at 10.5, the ammonia concentration was 5.0 g / L, and the reaction temperature was 55℃. When the target particle size was detected to be 6.2 μm (requiring 4 hours), an intermediate layer of the target thickness was formed, and the second coprecipitation reaction ended.

[0089] Step 3 - Growth Shell: S3-1. Switching between feeding and growth: Once the internal reinforcement layer is constructed, immediately stop adding the enrichment solution.

[0090] A conventional nickel-cobalt-manganese mixed salt solution, sodium hydroxide solution, and ammonia water without Al were added in parallel. The molar ratio of nickel, cobalt, and manganese in the conventional nickel-cobalt-manganese mixed salt solution was consistent with the ratio of the shell chemical formula, i.e., Ni:Co:Mn = 0.96:0.037:0.003.

[0091] The reaction temperature was maintained at 55℃, the ammonia concentration in the reaction system was 5.0 g / L, the pH value was 10.45, the stirring speed was 200 rpm, and the reaction was carried out for 25 hours until the target particle size grew to 24.8 μm.

[0092] S4 - Aging, washing, and drying: S4-1. Aging: The reacted precursor slurry is aged at 50°C for 4 hours.

[0093] S4-2. Washing: Wash with hot water at 40℃ using centrifugation or pressure filtration until the conductivity of the filtrate is <30μS / cm.

[0094] S4-3. Drying: The washed filter cake is dried in a drying device (such as a rotary kiln or vacuum dryer) at 120°C for 15 hours. The final product has a moisture content of 0.5%, and the precursor product is obtained.

[0095] Cross-sectional SEM image of the precursor product in Example 1 is shown below. Figure 2 As shown.

[0096] Example 2 Example 2 provides a ternary cathode material precursor, comprising secondary particles. The secondary particles, from the inside out, consist of a core, an intermediate layer, and a shell. The core has the chemical formula Ni. 0.93 Co 0.037 Mn 0.0097 Zr 0.0233 (OH)₂, the chemical formula of the intermediate layer is Ni 0.92 Co 0.038 Mn 0.01 Zr 0.032 (OH)₂, the chemical formula of the shell is Ni 0.96 Co 0.037 Mn 0.003 (OH)2. The porosity of the core is 63%, the porosity of the intermediate layer is 28%, and the porosity of the shell is 9%; the D50 particle size of the core is 3.63 μm, the thickness of the intermediate layer is 1.37 μm, and the thickness of the shell is 9.1 μm.

[0097] The difference between Example 2 and Example 1 is that zirconium oxychloride solution is used instead of aluminum sulfate solution in Example 1. Everything else is the same as in Example 1.

[0098] The CP-SEM image of the hollow seed crystal obtained in step S1 of Example 2 is shown below. Figure 3 As shown, the CP-SEM image of the precursor product in Example 2 is as follows. Figure 4 As shown.

[0099] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that aluminum sulfate solution was not added to Comparative Example 1. Everything else is the same as Example 1.

[0100] The CP-SEM image of the hollow seed crystal obtained in step S1 of Comparative Example 1 is shown below. Figure 5 As shown, the CP-SEM image of the precursor product obtained in Comparative Example 1 is as follows. Figure 6 As shown.

[0101] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 omits step S3 and proceeds directly to step S4 after step S2 is completed. The rest is the same as Example 1.

[0102] Comparative Example 2: Precursor finished product CP-SEM image as shown below Figure 7 As shown.

[0103] I. Preparation of cathode materials The precursors obtained in Examples 1-2 and Comparative Examples 1-2 were prepared into ternary cathode materials under exactly the same conditions, specifically including: Ingredients and Mixing: The precursor powder prepared in the examples or comparative examples and the lithium source (lithium hydroxide LiOH·H2O) were accurately weighed at a total molar ratio of lithium to transition metal of 1.04:1. The two were then thoroughly mixed in a mixer for 3 hours to ensure homogeneity.

[0104] High-temperature sintering: The uniformly mixed material is placed in a box furnace or roller kiln under an oxygen or air atmosphere. Sintering procedure: The temperature is increased to 500°C at a rate of 5°C / min and held for 5 hours for pre-firing to decompose hydroxides and perform preliminary lithiation; then the temperature is increased to 750°C at the same rate and held for 15 hours under an oxygen atmosphere to allow the crystals to grow fully and form a good layered structure. After sintering, the furnace is cooled to room temperature.

[0105] Post-processing: The sintered block material is crushed and ground. It is then sieved using a standard sieve (400 mesh, pore size approximately 38 μm) to obtain cathode material powder with uniform particle size distribution. The obtained cathode material powder is dried in a vacuum oven at 120°C for 4 hours to remove moisture, and then transferred to an argon-filled glove box for storage until later use.

[0106] II. Assembling Lithium-ion Batteries The cathode material prepared above was assembled into a coin cell (CR2032 type) under the same conditions. The specific steps included: Electrode preparation: Slurry preparation: Mix the positive electrode active material, conductive agent (Super P), and binder (polyvinylidene fluoride, PVDF) in an appropriate amount of solvent (N-methylpyrrolidone, NMP) at a mass ratio of 92:4:4, and grind until a uniform slurry with suitable viscosity is formed.

[0107] Coating and drying: Use a coater to evenly coat the slurry onto the aluminum foil current collector, place it in a 110°C forced-air oven for initial drying for 30 minutes, and then transfer it to a 120°C vacuum oven for thorough drying for 12 hours to completely remove solvent and moisture.

[0108] Rolling and cutting: The dried electrode sheets are rolled to the set compaction density using a double roller press under a specific pressure (10MPa), and then cut into round positive electrode sheets with a diameter of 12mm using a punching machine.

[0109] Battery assembly: Assembly was carried out in an argon atmosphere glove box with water and oxygen content both below 0.1 ppm.

[0110] Assembly sequence (from bottom to top): Battery negative electrode shell → Lithium metal sheet (counter electrode / reference electrode) → Electrolyte (add appropriate amount) → Polypropylene porous membrane (Celgard 2400) → Positive electrode sheet → Gasket → Spring sheet → Battery positive electrode shell.

[0111] Use a sealing machine to seal under constant pressure.

[0112] Electrolyte: A 1.0 mol / L LiPF6 EC / EMC / DMC (volume ratio 1:1:1) solution was used, with 2 wt% VC (ethylene carbonate) added as a film-forming additive.

[0113] III. Testing the Electrochemical Performance of the Battery After all the assembled button cells were left to stand in a constant temperature environment of 25±1℃ for 12 hours, their performance was tested on the Newway Battery Testing System using the same method. (1) Capacity and efficiency test: Under the voltage window of 3.0~4.3V, charge and discharge at a rate of 0.1C / 0.1C, record the specific capacity and coulombic efficiency of the first charge and discharge, and record the specific capacity of the second charge.

[0114] (2) DC internal resistance test: At a voltage of 3.0~4.25V, the DC internal resistance (DCR) of the battery at 100% SOC, 90% SOC, 50% SOC and 10% SOC is tested using the 18-second pulse discharge method.

[0115] (3) High-temperature cycle stability test: In an environment of 45℃, charge and discharge cycles were performed at a rate of 0.5C within a voltage range of 3.0~4.3V. The discharge specific capacity at 0.5C was recorded, and the capacity retention rate of the 10th and 20th cycles relative to the first discharge capacity was calculated.

[0116] The electrochemical performance data of Examples 1-2 and Comparative Examples 1-2 are shown in Table 1.

[0117] Table 1. Comparison of electrochemical performance between Examples 1-2 and Comparative Examples 1-2

[0118] Compared with Comparative Examples 1-2, Examples 1-2 simultaneously exhibit higher initial coulombic efficiency, lower DC internal resistance, excellent high-temperature cycle retention, and lower high-temperature capacity decay rate, indicating that the ternary cathode material precursor of this application is beneficial to improving the structural stability of the battery, thereby enhancing the overall electrochemical performance of the battery.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0120] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A ternary cathode material precursor, characterized in that, It includes secondary particles, which, from the inside out, consist of a core, an intermediate layer, and a shell. The porosity of the core is higher than that of the intermediate layer, and the porosity of the intermediate layer is higher than that of the shell. Both the core and the intermediate layer contain element M; the molar percentage of element M in the total metal elements of the intermediate layer is higher than the molar percentage of element M in the total metal elements of the core; M includes at least one of Al, Ti, Zr, Mg, W, and Nb.

2. The ternary cathode material precursor according to claim 1, characterized in that, The porosity of the core is 60-85%, the porosity of the intermediate layer is 20-40%, and the porosity of the shell layer is 5-15%. And / or, the D50 particle size of the core is 1.0 μm to 5.0 μm, the thickness of the intermediate layer is 0.5 μm to 2.0 μm, and the thickness of the shell layer is 5.0 μm to 15.0 μm.

3. The ternary cathode material precursor according to claim 1 or 2, characterized in that, The chemical formula of the core is Ni. x1 Co y1 Mn z1 M a1 (OH)₂, where 0.50≤x₁<1, 0<y₁≤0.20, 0<z₁≤0.30, 0.01≤a₁≤0.08, x₁ + y₁ + z₁ + a₁ = 1. And / or, the chemical formula of the intermediate layer is Ni x2 Co y2 Mn z2 M a2 (OH)2, 0.50≤x2<1, 0<y2≤0.20, 0<z2≤0.30, 0.015≤a2≤0.035, x2 + y2 + z2 + a2 = 1, a2>a1; And / or, the chemical formula of the shell is Ni x3 Co y3 Mn z3 (OH)2, 0.50≤x3<1, 0<y3≤0.20, 0<z3≤0.30, x3 + y3 + z3 = 1.

4. A method for preparing a ternary cathode material precursor as described in any one of claims 1-3, characterized in that, include: The mixed metal salt solution is mixed with M salt solution, precipitant and complexing agent in the first reaction vessel to carry out the first coprecipitation reaction to obtain seed slurry. The mixed metal salt solution includes nickel salt, cobalt salt and manganese salt. The seed slurry is subjected to a second coprecipitation reaction with a mixed metal salt solution, an M salt solution, a precipitant, and a complexing agent in a second reactor to obtain an intermediate. Stop the flow of M salt solution, and carry out a third coprecipitation reaction with the intermediate, mixed metal salt solution, precipitant, and complexing agent to obtain the ternary cathode material precursor.

5. The method for preparing the ternary cathode material precursor according to claim 4, characterized in that, In the first coprecipitation reaction, the total concentration of metal ions in the mixed metal salt solution is 1.0-1.8 mol / L; And / or, the precipitant includes a sodium hydroxide solution; And / or, the concentration of the precipitant is 4.0-6.0 mol / L; And / or, the complexing agent comprises an aqueous ammonia solution; And / or, the concentration of the complexing agent is 4.0-8.0 g / L; And / or, the first coprecipitation reaction includes adding a base liquid to a first reaction vessel, and then adding a mixed metal salt solution and an M salt solution, a precipitant, and a complexing agent to the base liquid to carry out the first coprecipitation reaction; And / or, the base solution includes a complexing agent and a precipitating agent, the ammonia concentration of the base solution is 2.0-5.0 g / L, and the pH value of the base solution is 11.5-11.8; And / or, the temperature of the first coprecipitation reaction is 50-60°C; And / or, the stirring speed for the first coprecipitation reaction is 300-500 rpm; And / or, the pH value of the first coprecipitation reaction is 10.2-11.6; And / or, the method further includes: when the particle size of the seed slurry is detected to be 2.2-4.2 μm, the first coprecipitation reaction ends; And / or, the time for the first coprecipitation reaction is 8-18 hours; And / or, in the first coprecipitation reaction, the molar amount of M accounts for 2% to 5% of the total molar amount of all metal elements in the feed liquid.

6. The method for preparing the ternary cathode material precursor according to claim 4, characterized in that, The second coprecipitation reaction includes: transferring the seed slurry to a second reaction vessel, adding water until the solid content reaches 100-180 g / L, and then adding a mixed metal salt solution, an M salt solution, a precipitant, and a complexing agent to carry out the second coprecipitation reaction; And / or, during the second coprecipitation reaction, the concentration of ammonia in the system is 4.0-7.0 g / L; And / or, the stirring speed for the second coprecipitation reaction is 200-400 rpm; And / or, the temperature of the second coprecipitation reaction is 50-58°C; And / or, the pH value of the second coprecipitation reaction is 10.2-11.6; And / or, the method further includes: when the particle size of the intermediate is detected to be 4.2-8.2 μm, the second coprecipitation reaction ends; And / or, the second coprecipitation reaction takes 2-5 hours; And / or, in the second coprecipitation reaction, the molar amount of M accounts for 1.5% to 3.5% of the total molar amount of all metal elements in the feed liquid.

7. The method for preparing the ternary cathode material precursor according to any one of claims 4-6, characterized in that, The pH value of the third coprecipitation reaction is 10.4-11.0; And / or, during the third coprecipitation reaction, the concentration of ammonia in the system is 4.0-7.0 g / L; And / or, the stirring speed for the third coprecipitation reaction is 200-400 rpm; And / or, the temperature of the third coprecipitation reaction is 50-58°C; And / or, the method further includes: when the particle size is detected to be 15.2-39.2 μm, the third coprecipitation reaction ends; And / or, the time for the third coprecipitation reaction is 20-35 hours; And / or, the method further includes: after the third coprecipitation reaction is completed, aging, washing and drying are performed sequentially to obtain a ternary cathode material precursor; And / or, the aging temperature is 50-60°C, and the aging time is 4-10 hours; And / or, the washing includes: washing with hot water at 40-50°C by centrifugation or pressure filtration until the conductivity of the filtrate is <50 μS / cm; And / or, the drying includes: drying the washed filter cake at a temperature of 100-120°C for 10-15 hours.

8. A positive electrode material, characterized in that, The cathode material is made by lithiation sintering of a ternary cathode material precursor, wherein the ternary cathode material precursor is the ternary cathode material precursor as described in any one of claims 1-3 or the ternary cathode material precursor prepared by the preparation method described in any one of claims 4-7.

9. A lithium-ion battery, characterized in that, Includes the cathode material as described in claim 8.

10. An electrical-related device, characterized in that, Including the lithium-ion battery as described in claim 9.

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