Positive electrode material precursor with composite structure, preparation method of positive electrode material precursor, positive electrode material, lithium ion battery and electric equipment

Abstract

The invention provides a composite structure positive electrode material precursor and a preparation method thereof, a positive electrode material, a lithium ion battery and electric equipment, and relates to the technical field of new energy. The positive electrode material precursor comprises an inner core, a middle layer and an outer layer; wherein the inner core is dense, uniform pores are distributed in the middle layer, the outer layer is dense, and the radius of the inner core, the thickness of the middle layer and the thickness of the outer layer meet the formula of 1: (0.9-1.4): (0.5-0.8). According to the method, the seed crystal with the compact structure is prepared firstly, and then the theoretical average v. / lg [(pH-1) * 1000] value of each stage is controlled to obtain the section with expected characteristics. The inner core of the precursor can ensure the stability of the whole structure, pores of the middle layer can reduce the diffusion energy barrier of a lithium source, and when the dense outer layer is sintered, crystals in the region can grow and develop more coarsely, crack propagation is inhibited, particles are reinforced, the contact area with an electrolyte is reduced, side reactions are reduced, and the cycle performance of the material is improved.

Description

Technical Field

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

[0002] Lithium-ion batteries made using high-nickel cathode materials have become key components in digital products, small power tools, and electric vehicles due to their high specific energy, high rate capability, and low-temperature resistance. Precursors, as raw materials for high-nickel cathode materials, have physicochemical properties (e.g., particle size, specific surface area, crystallinity), primary particle morphology, and internal structure that profoundly affect the physicochemical properties of the cathode material, lithium-ion intercalation / deintercalation during charge / discharge, and the phase transition of the cathode material. The mainstream preparation process for precursors is co-precipitation, which allows for precise control of the content of each element and achieves thorough and uniform mixing. Ideal precursor materials can be obtained by precisely and rationally controlling parameters such as salt solution concentration, flow rate, temperature, stirring speed, and precipitants and complexing agents. With the rapid development of the market, end customers increasingly favor batteries with high energy density, long cycle life, high power, and excellent high and low temperature performance. However, high-nickel cathode materials have high residual alkali on the surface, are prone to side reactions with the electrolyte, have poor storage performance, and are susceptible to structural degradation and cracking during charge / discharge cycles.

[0003] Therefore, developing precursors with composite structures that reduce the lithium source diffusion barrier, promote lithium-ion conduction on the AB crystal plane, inhibit crack propagation, strengthen particles, and improve capacity and cycle life are crucial for improving the performance of high-nickel cathode materials. Summary of the Invention

[0004] The purpose of this application is to provide a composite structure cathode material precursor and its preparation method, cathode material, lithium-ion battery and related equipment, aiming to solve the problems of particle cracking and rapid capacity decay under high capacity conditions.

[0005] This application first provides a composite structure cathode material precursor, the composite structure cathode material precursor including a core, an intermediate layer covering the core, and an outer layer covering the intermediate layer; The ratio of kernel radius to intermediate layer thickness to outer layer thickness is 1:(0.9~1.4):(0.5~0.8).

[0006] In some embodiments, the porosities of the core, intermediate layer, and outer layer are 0-1%, 5%-20%, and 0.5%-1.5%, respectively; the average porosity of the composite structure cathode material precursor is 5%-12%.

[0007] In some embodiments, the composite structure cathode material precursor includes secondary particles formed by the stacking of primary particles, and the composite structure cathode material precursor satisfies at least one of the following conditions: A. The secondary particles are spherical or near-spherical; B. The primary particles are stacked on the surface of the secondary particles in a plate-like manner.

[0008] In some embodiments, at least one of the following conditions is met: A. The composite structure cathode material precursor D v 50 is in the range of 7~18um; B. The composite structure cathode material precursor Span=(D v 90-D v 10) / D v 50≤0.70; Preferably, the composite structure cathode material precursor Span=(D v 90-D v 10) / D v 50≤0.50; C. The chemical formula of the composite structure cathode material precursor is Ni x Co y Mn 1-x-y (OH)2, where 0.80≤x<1.00, 0.05≤y<0.20, x+y≤1; D. The tap density of the composite structure cathode material precursor is 1.8 g / cm³. 3 ~2.3g / cm 3 ; E. The specific surface area of ​​the composite structure cathode material precursor is 8m². 2 / g~14m 2 / g.

[0009] This application also provides a method for preparing a composite structure cathode material precursor as described above, comprising: The mixed salt, precipitant, and complexing agent are passed into the first reaction substrate to carry out the first coprecipitation reaction until the target particle size I is reached, thus obtaining seed crystals. A mixed salt, precipitant, and complexing agent are introduced into a second reaction substrate containing the seed crystals to carry out a second coprecipitation reaction until the target particle size II is reached, thereby obtaining the composite structure cathode material precursor. The second coprecipitation reaction includes a first stage and a second stage. In the first stage, the particle growth rate υ and the reaction pH satisfy the value of υ / lg[(pH-1)×1000] being between 13 and 58. In the second stage, the particle growth rate υ and the reaction pH satisfy the value of υ / lg[(pH-1)×1000] being between 1 and 13.

[0010] In some embodiments, at least one of the following conditions is met: A. The pH of the first reaction substrate is 11.00~11.80; B. The ammonia concentration in the bottom liquid of the first reaction is 3.0 g / L to 8.0 g / L; C. The temperature of the first reaction substrate is 55~70℃; D. The mixed salt is selected from one or two of the sulfates, chlorides or nitrates of soluble nickel, cobalt and manganese; E. The D of the target granularity I v 50 ranges from 3.0μm to 5.5μm; F. The total molar concentration of metal ions in the mixed salt is 0.8 mol / L to 2.5 mol / L; G. The precipitant is a sodium hydroxide solution or a potassium hydroxide solution, and the concentration of the precipitant is 5 mol / L to 11 mol / L; H. The complexing agent includes at least one of ammonia, ammonium sulfate, and ammonium chloride, wherein if the complexing agent is ammonia, the mass concentration is 10~22 wt.%; I. The flow rate of the mixed salt in the first coprecipitation reaction is 5 L / h to 30 L / h.

[0011] In some embodiments, at least one of the following conditions is met: A. The pH of the second reaction substrate is 10.20~10.85; B. The concentration of ammonia in the bottom liquid of the second reaction is 1.0 g / L to 4.0 g / L; C. The temperature for the second coprecipitation reaction is 50~75℃; D. The target particle size II of D v 50 is 7~18μm; E. The flow rate of the mixed salt in the second coprecipitation reaction is 2% to 10% of the reactor volume per hour. F. The final solid content after the reaction is completed is 250~650g / L; G. The pH of the second coprecipitation reaction is 10.00~11.00.

[0012] This application also provides a cathode material prepared from the above-mentioned composite structure cathode material precursor.

[0013] This application also provides a lithium-ion battery, including the above-described positive electrode material.

[0014] This application also provides an electrical device, including the aforementioned lithium-ion battery.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The composite structure cathode material precursor provided in this application includes a core, an intermediate layer, and an outer layer, with the core radius, intermediate layer thickness, and outer layer thickness satisfying a certain ratio. After this precursor with a special structure is mixed with a lithium source and sintered into a cathode material, the pores in the intermediate layer provide more transport channels for lithium ions. Simultaneously, it reduces the resistance to lithium ion insertion and extraction during charging and discharging, shortens the lithium ion transport distance, and increases the transport rate, effectively enhancing the stability of the cathode material's internal structure. Meanwhile, the denser outer layer can inhibit crack propagation and reinforce particles to ensure structural stability, thus exhibiting superior electrochemical performance.

[0016] The composite cathode material precursor provided in this application is obtained by first preparing seed crystals and then controlling the theoretical average υ / lg[(pH-1)×1000] value of each stage in the co-precipitation reaction to obtain a composite precursor with core, intermediate layer, and outer layer cross-sectional characteristics. When the precursor is mixed with lithium source and sintered, the intermediate layer can fully allow the lithium source to diffuse into the particle interior; the outer layer crystals grow robustly, which can effectively inhibit crack propagation, strengthen the particles, and improve cycle performance. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, 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 this application and should not be regarded as a limitation on the scope of this application.

[0018] Figure 1 This is a cross-sectional schematic diagram of the composite structure cathode material precursor of this application; Figure 2 This is a cross-sectional view of the composite structure cathode material precursor of Example 1; Figure 3 This is a cross-sectional view of the positive electrode material in Example 1; Figure 4 This is a cross-sectional view of the composite structure cathode material precursor of Example 2; Figure 5 This is a cross-sectional view of the composite structure cathode material precursor of Example 3; Figure 6 This is a cross-sectional view of the composite structure cathode material precursor of Example 4; Figure 7 This is a cross-sectional view of the composite structure cathode material precursor of Comparative Example 1; Figure 8 This is a cross-sectional view of the composite structure cathode material precursor in Comparative Example 2; Figure 9 Here is a SEM image of the cathode material in Comparative Example 2; Figure 10This is a cross-sectional view of the cathode material in Comparative Example 2. Detailed Implementation

[0019] This application provides a composite structure cathode material precursor, the cross-sectional structure of which is shown in the schematic diagram below. Figure 1 As shown, the composite structure cathode material precursor includes a core, an intermediate layer covering the core, and an outer layer covering the intermediate layer; the core is dense, the intermediate layer has pores, and the outer layer is dense. The ratio of core radius: intermediate layer thickness: outer layer thickness satisfies 1:(0.9~1.4):(0.55~1), for example, it can be any ratio between 1:0.9:0.55, 1:1.1:0.7, 1:1.0:1, 1:1.4:1 or 1:(0.9~1.4):(0.55~1).

[0020] The precursor with a composite structure, when mixed with lithium source and calcined, provides more transport channels for lithium ions through the pores in the middle layer. At the same time, it reduces the resistance to lithium ion insertion and extraction during charging and discharging, shortens the lithium ion transport distance, and improves the transport rate, which can effectively enhance the stability of the internal structure of the cathode material. The denser outer layer can inhibit crack propagation and reinforce particles to ensure structural stability, thus exhibiting superior electrochemical performance.

[0021] In some embodiments, the porosities of the core, the intermediate layer, and the outer layer are 0-1%, 5%-20%, and 0.5%-1.5%, respectively; the porosity of the core can be, for example, any value between 0, 0.2%, 0.5%, 0.7%, 0.9%, 1%, or 0-1%; the porosity of the intermediate layer can be, for example, any value between 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 15%, 17%, 18%, 20%, or 5%-20%; the porosity of the outer layer can be, for example, any value between 0.5%, 0.7%, 0.9%, 1%, 1.2%, 1.3%, 1.5%, or 0.5%-1.5%.

[0022] In some embodiments, the average porosity of the composite precursor is 5% to 12%, for example, it can be any value between 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12% or 5% to 12%.

[0023] The porosity calculation used image processing software (such as ImageJ, MIPAR, and Avizo). Since the pores are mostly irregular shapes, the maximum diameter (or the maximum diagonal of the irregular shape) was selected as the diameter of the pore.

[0024] In some embodiments, the composite structure cathode material precursor includes secondary particles formed by the stacking of primary particles, wherein the secondary particles are spherical or near-spherical.

[0025] In some embodiments, the primary particles are stacked on the surface of the secondary particles in a plate-like manner.

[0026] In some embodiments, the D of the composite structure cathode material precursor v 50 is 7~18um, for example, it can be 7um, 8um, 10um, 12um, 15um, 18um or any value between 7 and 18um.

[0027] In some embodiments, the particle size distribution of the composite structure cathode material precursor is Span = (D v 90-D v 10) / D v 50 ≤ 0.70, for example, it can be any value of 0.70, 0.65, 0.60, 0.55, 0.50, 0.45, or ≤ 0.70. Optionally, the composite structure cathode material precursor Span = (D v 90-D v 10) / D v 50≤0.50. The particle size and particle size distribution were measured using a Malvern 2000 particle size analyzer.

[0028] In some embodiments, the chemical formula of the composite structure cathode material precursor is Ni. x Co y Mn 1-x-y (OH)2, Where 0.80≤x<1.00, 0.05≤y≤0.20, and x+y≤1.

[0029] The precursor for this composite cathode material can be a nickel-cobalt binary precursor or a nickel-cobalt-manganese ternary precursor.

[0030] In some embodiments, the tap density of the composite structure cathode material precursor is 1.8–2.3 g / cm³. 3 For example, it can be 1.8 g / cm³. 3 1.9g / cm 3 2.0g / cm 3 2.1g / cm 3 2.2g / cm 3 2.3g / cm 3 Or 1.8~2.3g / cm 3 Any value between.

[0031] In some embodiments, the specific surface area of ​​the composite structure cathode material precursor is 8~14m². 2 / g, for example, can be 8m 2 / g、9m 2 / g, 10m2 / g、11m 2 / g、12m 2 / g、13m 2 / g、14m 2 / g or 8~14m 2 Any value between / g.

[0032] This application also provides a method for preparing a composite structure cathode material precursor as described above, comprising: The mixed salt, precipitant, and complexing agent are passed into the first reaction substrate to carry out the first coprecipitation reaction until the target particle size I is reached, thus obtaining seed crystals.

[0033] A mixed salt, precipitant, and complexing agent are introduced into a second reaction substrate containing the seed crystals to carry out a second coprecipitation reaction until the target particle size II is reached, thereby obtaining the composite structure cathode material precursor. The second coprecipitation reaction includes a first stage and a second stage. In the first stage, the particle growth rate υ and the reaction pH satisfy the value of υ / lg[(pH-1)×1000] being between 13 and 58. In the second stage, the particle growth rate υ and the reaction pH satisfy the value of υ / lg[(pH-1)×1000] being between 1 and 13.

[0034] In some embodiments, the particle growth rate υ of the first stage of the second coprecipitation reaction satisfies the reaction pH such that υ / lg[(pH-1)×1000] is between 13 and 58, for example, it can be any value between 13, 14, 15, 16, 17, 18, 19, 20, 21, 25, 30, 35, 40, 45, 50, 55, 58 or 13 to 58.

[0035] In some embodiments, the particle growth rate υ of the second stage of the second coprecipitation reaction satisfies the reaction pH such that υ / lg[(pH-1)×1000] is between 1 and 13, for example, it can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or any value between 1 and 13.

[0036] In some embodiments, the pH of the first reaction substrate is 11.00 to 11.80, for example, it can be any value between 11.00, 11.10, 11.30, 11.50, 11.70, 11.80 or 11.00 to 11.80; the ammonia concentration of the first reaction substrate is 3.0 g / L to 8.0 g / L, for example, it can be any value between 3.0 g / L, 3.5 g / L, 4.0 g / L, 4.5 g / L, 5.0 g / L, 5.5 g / L, 6.0 g / L, 6.5 g / L, 7.0 g / L, 7.5 g / L, 8.0 g / L or 3.0 g / L to 8.0 g / L; the temperature of the first reaction substrate is 55 to 70°C, for example, it can be any value between 55°C, 60°C, 65°C, 70°C or 55 to 70°C.

[0037] In some embodiments, the mixed salt solution is selected from one or two of the sulfates, chlorides, and nitrates of soluble nickel, cobalt, and manganese; the total molar concentration of metal ions in the mixed salt solution is 0.8 mol / L to 2.5 mol / L, for example, it can be any value between 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, 2.0 mol / L, 2.2 mol / L, 2.5 mol / L, or 0.8 mol / L to 2.5 mol / L.

[0038] In some embodiments, the D of the target granularity I v 50 is 3.0μm to 5.5μm, for example, it can be any value between 3.0μm, 3.5μm, 4.0μm, 4.5μm, 5.0μm, 5.5μm or 3.0μm to 5.5μm.

[0039] In some embodiments, the precipitant is a sodium hydroxide solution or a potassium hydroxide solution, and the concentration of the precipitant is 5 mol / L to 11 mol / L, for example, it can be any value between 5 mol / L, 6 mol / L, 8 mol / L, 10 mol / L, 11 mol / L or 5 mol / L to 11 mol / L.

[0040] In some embodiments, the complexing agent includes at least one of ammonia, ammonium sulfate, and ammonium chloride. If the complexing agent is ammonia, the mass concentration is 10 wt.% to 22 wt.%, for example, it can be any value between 10 wt.%, 12 wt.%, 15 wt.%, 18 wt.%, 20 wt.%, 22 wt.%, or 10 wt.% to 22 wt.%.

[0041] In some embodiments, the flow rate of the mixed salt in the first coprecipitation reaction is 5 L / h to 30 L / h, for example, it can be any value between 5 L / h, 10 L / h, 15 L / h, 20 L / h, 25 L / h, 30 L / h or 5 L / h to 30 L / h.

[0042] In some embodiments, the pH of the second reaction substrate is 10.20~10.85, for example, it can be any value between 10.20, 10.25, 10.30, 10.35, 10.40, 10.45, 10.50, 10.55, 10.60, 10.65, 10.70, 10.75, 10.80, 10.85 or 10.20~10.85; the ammonia concentration of the second reaction substrate is 1.0 g / L~4.0 g / L, for example, it can be any value between 1.0 g / L, 2.0 g / L, 3.0 g / L, 4.0 g / L or 1.0 g / L~4.0 g / L; the D of the target particle size II v 50 is 7μm to 18μm, for example, it can be 7μm, 9μm, 10μm, 12μm, 15μm, 16μm, 18μm or any value between 7μm and 18μm.

[0043] In some embodiments, the flow rate of the mixed salt in the second coprecipitation reaction is 2% / h to 10% / h of the reactor volume, for example, it can be any value between 2% / h, 4% / h, 6% / h, 8% / h, 10% / h or 2% / h to 10% / h.

[0044] In some embodiments, the temperature of the second coprecipitation reaction is 50°C to 75°C, for example, it can be any value between 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 50°C to 75°C.

[0045] In some embodiments, the final solid content after the second coprecipitation reaction is 250~650 g / L, for example, it can be any value between 250 g / L, 300 g / L, 350 g / L, 400 g / L, 450 g / L, 500 g / L, 550 g / L, 600 g / L, 650 g / L or 250~650 g / L.

[0046] In some embodiments, the pH of the second coprecipitation reaction is 10.0 to 11.0, for example, it can be any value between 10.0, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 11.0 or 10.0 to 11.0.

[0047] This application also provides a cathode material prepared from the above-mentioned composite structure cathode material precursor.

[0048] This application also provides a lithium-ion battery, including the above-described positive electrode material.

[0049] This application also provides an electrical device, including the aforementioned lithium-ion battery.

[0050] 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.

[0051] Before describing specific embodiments and comparative examples, we will first introduce the specific meanings of some symbols and formulas.

[0052] Solid content calculation formula: W=Q×ρ / ω×T×V(1); In formula (1), W represents the solid content of the precipitate in the system at time T (in g / L), Q is the volume of the mixed salt solution entering the reactor (in L), ρ is the total concentration of metal ions in the mixed salt solution (in g / L), T is the reaction time (in h), V is the volume of the precipitate, and ω is the ratio of the average relative atomic mass of the metal element in the precursor to the relative molecular mass of the precursor (the value is generally between 0.60 and 0.65).

[0053] The growth rate is defined as: υ=(D v 50 m -D v 50 n ) / (mn)×1000(2); In formula (2), υ is the average growth rate of the precipitate over a period of time, and D v 50 represents the median particle size at the volume distribution, m(n) represents the reaction time m(n), and D v 50 m (D v 50 n ) represents the median particle size of the precipitate at time m(n).

[0054] Median granularity D v Estimate 50: (3); In formula (3), A is a coefficient, which is generally taken as 0.8~1.1. If the spherical precipitate has high dispersibility, does not stick together, and has high density, the coefficient is closer to 1. The median particle size of the precipitate at a certain moment as the reaction time increases can be estimated by the solid content and the particle size at the previous moment. For example, if the initial seed particle size is 4.2μm, the particle size at 1h, 2h and other times can be estimated when the amount of water added, the amount of seed added to the reactor and the salt flow rate are known. The appropriate stirring blade linear velocity is matched according to the theoretical particle size at different times to prevent a series of problems such as particle cracking and sticking. The maximum linear velocity v of the blade installed in the reactor is 8~10m / s. As the theoretical particle size Dv50(t) increases, the maximum linear velocity is continuously reduced (5.5→1.2m / s); the value lg(v(t)×Dv50(t)) satisfies 1.2~1.5. After adding seed crystals, pure water and appropriate amounts of ammonia water and sodium hydroxide solution to the reactor. In addition to maintaining the ammonia concentration at 1.0~4.0 g / L, the ideal precursor cross-sectional characteristics were obtained by controlling υ / lg[(pH-1)×1000]. Specific example information is as follows.

[0055] Example 1 A nickel-cobalt binary precursor is prepared by the following steps: Step S1: Based on the molecular formula Ni 0.90 Co 0.10 Prepare a 2 mol / L nickel-cobalt mixed salt solution with (OH)2; prepare a 10.8 mol / L sodium hydroxide solution; prepare a 20.5 wt.% ammonia solution.

[0056] Step S2: Add 200L of pure water, sodium hydroxide solution, and ammonia water to the reaction vessel respectively. The maximum linear velocity of the stirring paddle is 6m / s, and the temperature is always controlled at 55℃ to obtain a base solution with an ammonia concentration of 2.0~2.5g / L and a pH of 11.40~11.45 (Mettler pH meter, displayed at 50℃; this method is used throughout the text and will not be described again).

[0057] Step S3: The first co-precipitation reaction is carried out, while the mixed salt, sodium hydroxide, and ammonia are continuously introduced into the reactor at flow rates of 9 L / h, 3.6 L / h, and 0.38 L / h, respectively, to carry out the seed precipitation reaction. When precipitate D... V When the pH reaches 50 to 1.5~2.0 μm, the pH is reduced to 10.8 within 2 hours by finely adjusting the sodium hydroxide flow rate; when the reaction time reaches 10 hours, the flow rates of the mixed salt, sodium hydroxide, and ammonia are adjusted to 18 L / h, 7.2 L / h, and 0.76 L / h, respectively, until D... V The reaction was stopped when the particle size decreased from 50 μm to 4.5-5.0 μm. During the reaction, the mother liquor was discharged through a concentration device, and the volume of the precipitate in the reactor remained essentially constant. The obtained precipitate was washed, centrifuged, and dehydrated to obtain a seed filter cake.

[0058] Step S4: Perform the second coprecipitation reaction, add 200L of water to the reactor, and add 3.7kg of the seed filter cake obtained in step S3 to the reactor; additionally, add appropriate amounts of ammonia water and sodium hydroxide solution to obtain a new bottom solution with an ammonia concentration of 1.8~2.3g / L and a pH of 10.40~10.55.

[0059] The first stage of the second coprecipitation reaction (0-7h): The mixed salt was continuously fed into the reactor at a flow rate of 12L / h, while sodium hydroxide and ammonia were fed into the reactor at flow rates of 4.4L / h and 0.24L / h, respectively. The pH was maintained at approximately 10.20±0.15, and the average theoretical υ / lg[(pH-1)×1000] was 46.5. The coprecipitation reaction proceeded until the D50 reached 11.02um.

[0060] Second stage of the second coprecipitation reaction (7-30h): (7-15h): The mixed salt is continuously fed into the reactor at a flow rate of 24L / h, while sodium hydroxide and ammonia are fed into the reactor simultaneously at flow rates of 8.8L / h and 0.48L / h, respectively. The pH is maintained at approximately 10.70±0.15, and the average theoretical υ / lg[(pH-1)×1000] is 6.8, allowing the coprecipitation reaction to proceed. (15-30h): The mixed salt is continuously fed into the reactor at a flow rate of 28.8L / h, while sodium hydroxide and ammonia are fed into the reactor simultaneously at flow rates of 10.56L / h and 0.58L / h, respectively. The pH is maintained at approximately 10.85±0.15, and the average theoretical υ3 / lg(pH3) is 5.3, allowing the coprecipitation reaction to proceed.

[0061] Throughout the reaction process, the ammonia concentration remained between 1.8 and 2.3 g / L. When the particle size D... v The reaction was stopped when the precipitate reached 14.5~15.0 μm, with a solids content of 342 g / L at the stop. The mother liquor still needed to be discharged through a concentration device during the reaction process to ensure that the volume of precipitate in the reactor remained essentially constant. The resulting slurry was filtered, washed, dried, and sieved to obtain Ni. 0.90 Co 0.10 (OH)2 precursor, its cross-sectional diagram is as follows Figure 2 As shown, the cross-sectional view of the prepared cathode material is as follows. Figure 3 As shown.

[0062] Example 2 Example 2 uses the seed crystals prepared in steps S1-S3 of Example 1. The difference between Example 2 and Example 1 is: The first stage of the second coprecipitation reaction (0-7h): The mixed salt was continuously fed into the reactor at a flow rate of 12L / h, while sodium hydroxide and ammonia were fed into the reactor at flow rates of 4.4L / h and 0.24L / h, respectively. The pH was maintained at approximately 10.50±0.15, and the average theoretical υ / lg[(pH-1)×1000] was 18.8. The coprecipitation reaction proceeded until the D50 reached 11.88um.

[0063] The second stage of the second coprecipitation reaction (7-34h): The mixed salt was continuously introduced into the reactor at a flow rate of 22.8 L / h, while sodium hydroxide and ammonia were introduced into the reactor at flow rates of 8.4 L / h and 0.91 L / h, respectively. The pH was maintained at approximately 10.10~10.30, and the average theoretical υ / lg[(pH-1)×1000] was 7.7, thus carrying out the coprecipitation reaction.

[0064] Throughout the reaction process, the ammonia concentration remained between 1.8 and 2.3 g / L. When the particle size D... v The reaction was stopped when the precipitate reached 14.41 μm, with a solids content of 308 g / L at the stop. The mother liquor still needed to be discharged through a concentration device during the reaction process to ensure that the volume of precipitate in the reactor remained essentially constant. The resulting slurry was filtered, washed, dried, and sieved to obtain Ni. 0.90 Co 0.10 (OH)2 precursor, its cross-sectional diagram is as follows Figure 4 As shown.

[0065] Example 3 Example 3 uses the seed crystals prepared in steps S1-S3 of Example 1. The difference between Example 3 and Example 1 is: The first stage of the second coprecipitation reaction (0-7h): The mixed salt was continuously fed into the reactor at a flow rate of 9L / h, while sodium hydroxide and ammonia were fed into the reactor at flow rates of 3.3L / h and 0.18L / h, respectively. The pH was maintained at approximately 10.50±0.15, and the average theoretical υ / lg[(pH-1)×1000] was 13.2. The coprecipitation reaction proceeded until the sample reached 11.15µm.

[0066] The second stage of the second coprecipitation reaction (7-34h): The mixed salt was continuously introduced into the reactor at a flow rate of 21L / h, while sodium hydroxide and ammonia were introduced into the reactor at flow rates of 7.7L / h and 0.42L / h, respectively. The pH was maintained at approximately 10.65±0.15, and the average theoretical υ / lg[(pH-1)×1000] was 5.1, thus initiating the coprecipitation reaction.

[0067] Throughout the reaction process, the ammonia concentration remained between 1.8 and 2.3 g / L. When the particle size D... vThe reaction was stopped when the precipitate reached 14.5~15.0 μm, with a solids content of 256 g / L at the stop tank. The mother liquor still needed to be discharged through a concentration device during the reaction process to ensure that the volume of precipitate in the reactor remained essentially constant. The resulting slurry was filtered, washed, dried, and sieved to obtain Ni. 0.90 Co 0.10 (OH)2 precursor, its cross-sectional diagram is as follows Figure 5 As shown.

[0068] Example 4 Example 4 uses the seed crystal fabrication process of steps S1-S3 in Example 1, only based on the molecular formula Ni 0.90 Co 0.06 Mn 0.04 Prepare a 2 mol / L mixed salt solution of nickel, cobalt, and manganese using (OH)₂. Repeat the preparation process of the first coprecipitation reaction, the first stage of the second coprecipitation reaction, and the second stage of the second coprecipitation reaction in Example 1, when the particle size D... v The reaction was stopped when the slurry reached a thickness of 14.5~15.0 μm, with a solids content of 357 g / L at the stop. The resulting slurry was filtered, washed, dried, and sieved to obtain Ni. 0.90 Co 0.06 Mn 0.04 (OH)2 precursor, its cross-sectional diagram is as follows Figure 6 As shown.

[0069] Comparative Example 1 Comparative Example 1 used the seed crystals prepared in steps S1-S3 of Example 1. The same base liquid conditions were used in step S4. The difference between Comparative Example 1 and Example 1 is: The mixed salt was continuously fed into the reactor at a flow rate of 18 L / h, while sodium hydroxide and ammonia were also fed into the reactor simultaneously at flow rates of 6.6 L / h and 0.36 L / h, respectively. The pH was maintained at approximately 10.65 ± 0.15, with an average theoretical υ / lg[(pH-1)×1000] of 10.2. The reaction proceeded until the D50 reached approximately 8.3 μm, after which the pH was adjusted to 10.90 ± 0.05, with an average theoretical υ / lg[(pH-1)×1000] of 5.3, to initiate a co-precipitation reaction. When the particle size D... v The reaction was stopped when the slurry reached a thickness of 14.5~15.0 μm, with a solids content of 425 g / L at the stop. The resulting slurry was then filtered, washed, dried, and sieved to obtain Ni. 0.90 Co 0.10 (OH)2 precursor, its cross-sectional diagram is as follows Figure 7 As shown.

[0070] Comparative Example 2 Comparative Example 2 used the seed crystals prepared in steps S1-S3 of Example 1. The same base liquid conditions were used in step S4. The difference between Comparative Example 2 and Example 1 is: The mixed salt was continuously fed into the reactor at a flow rate of 24 L / h, while sodium hydroxide and ammonia were also fed into the reactor simultaneously at flow rates of 8.8 L / h and 0.48 L / h, respectively. The pH was maintained at approximately 10.50 ± 0.15, with an average theoretical υ / lg[(pH-1)×1000] of 14.1. The reaction proceeded until D50 reached 13 μm, after which the pH was adjusted to 11.00 ± 0.05, with an average theoretical υ / lg[(pH-1)×1000] of 10.5, for co-precipitation. When the particle size D... v The reaction was stopped when the slurry reached a thickness of 14.5~15.0 μm, with a solids content of 511 g / L at the stop. The resulting slurry was then filtered, washed, dried, and sieved to obtain Ni. 0.90 Co 0.10 (OH)2 precursor, its cross-sectional diagram is as follows Figure 8 As shown, the SEM image of the prepared cathode material is as follows. Figure 9 As shown, the cross-sectional view is as follows Figure 10 As shown.

[0071] The testing methods for the precursors of each embodiment and comparative example are as follows: Calculations of porosity and radial ratio require sample pretreatment and imaging under a scanning electron microscope (SEM). Sample pretreatment, for example, can employ argon ion polishing to remove the surface layer of the sample without stress, obtaining an atomically clean surface. Further image processing software (MIPAR, Avizo, etc.) can be used to obtain the dimensional information of each region. The porosity of a single particle cross-section is calculated as (pore area of ​​each region / cross-sectional area of ​​each region × 100%), allowing for the calculation of porosity in different regions; all porosities in this paper are characterized using this method. The radial ratio refers to the ratio of the thickness of the dense intermediate layer to the high-porosity outer shell along the radial direction.

[0072] Primary particle width and length measurement: The width and length of primary particles in a 10000x SEM image were measured using ImageJ software. The rules are as follows: the longest dimension of a single primary particle is considered its length, and the dimension measured perpendicular to the longest dimension is considered its width. A sufficient number of data points were selected, and their average values ​​were calculated as the average width and average length of the primary particles.

[0073] Particle size testing: The Malvern 2000 laser particle size analyzer, a mainstream technology in the industry, was used for testing. The dispersant was purified water and ultrasonically dispersed.

[0074] Tap density: Tested using a Dandong Baite BT-312 / 313 tap density meter.

[0075] Specific surface area: measured using a Bestar specific surface area meter.

[0076] The physicochemical properties of the precursors for each embodiment and comparative example are shown in Table 1.

[0077] Table 1 Physicochemical properties of the ternary precursors in each embodiment and comparative example

[0078] Electrochemical performance testing (1) Preparation of cathode material: The precursors obtained in each example and comparative example were mixed with lithium hydroxide monohydrate at a molar ratio of 1:1.04 in a high-speed mixer at 1000 rpm for 1 h. The uniformly mixed material was spread evenly in a sagger and sintered at high temperature in a box furnace. The temperature of the box furnace was set at 500℃ for the first stage and held for 5 h; the temperature of the second stage was set at 720℃ and held for 15 h, with an oxygen flow rate of 20 L / min; after cooling to room temperature in the furnace, the material was crushed and sieved through a 325 mesh to obtain the corresponding cathode material.

[0079] (2) Button cell fabrication and testing: The positive electrode materials obtained from each example and comparative example were mixed in a ratio of positive electrode material: conductive agent: binder = 90:6:4 with N-methylpyrrolidone as solvent to form a uniform slurry, which was coated on aluminum foil. After drying, rolling and cutting, positive electrode sheets were obtained; lithium metal sheets were used as negative electrode sheets. Then, lithium batteries were prepared in the order of positive electrode shell - positive electrode sheet - separator - negative electrode sheet - stainless steel sheet - spring sheet - negative electrode shell. The electrolyte was 1 mol / L LiPF6 / EC:DMC (volume ratio 1:1) with 10% (volume fraction) fluoroethylene carbonate (FEC). The separator was a polypropylene microporous membrane. Button half-cells of Examples 1-3 and Comparative Examples 1-2 were prepared respectively, and their electrochemical performance was tested at 2.5-4.25V.

[0080] The battery performance of each embodiment and comparative example is shown in Table 2.

[0081] Table 2 Electrochemical performance of each example and comparative example

[0082] 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.

[0083] 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 composite structure cathode material precursor, characterized in that, The composite structure cathode material precursor includes a core, an intermediate layer covering the core, and an outer layer covering the intermediate layer; the core radius: intermediate layer thickness: outer layer thickness is 1:(0.9~1.4):(0.5~0.8).

2. The composite structure cathode material precursor according to claim 1, wherein the porosities of the core, the intermediate layer and the outer layer are 0~1%, 5%~20% and 0.5%~1.5%, respectively; and the average porosity of the composite structure cathode material precursor is 5%~12%.

3. The composite structure cathode material precursor according to claim 1 or 2, characterized in that, The composite structure cathode material precursor includes secondary particles formed by the stacking of primary particles, and the composite structure cathode material precursor satisfies at least one of the following conditions: A. The secondary particles are spherical or near-spherical; B. The primary particles are stacked on the surface of the secondary particles in a plate-like manner.

4. The composite structure cathode material precursor according to claim 3, characterized in that, At least one of the following conditions must be met: A. The secondary particles D of the composite structure cathode material precursor v 50 is 7~18um; B. The secondary particles of the composite structure cathode material precursor, Span=(D v 90-D v 10) / D v 50≤0.70; Preferably, Span=(D v 90-D v 10) / D v 50≤0.50; x Wherein, 0.80≤x<1.00, 0.05≤y≤0.20, x+y≤1; D. The tap density of the composite structure cathode material precursor is 1.8 g / cm³. 3 ~2.3g / cm 3 ; E. The specific surface area of ​​the composite structure cathode material precursor is 8m². 2 / g~14m 2 / g.

5. A method for preparing a composite structure cathode material precursor as described in any one of claims 1 to 4, characterized in that, include: The mixed salt, precipitant, and complexing agent are passed into the first reaction substrate to carry out the first coprecipitation reaction until the target particle size I is reached, thus obtaining seed crystals. A mixed salt, precipitant, and complexing agent are introduced into a second reaction substrate containing the seed crystals to carry out a second coprecipitation reaction until the target particle size II is reached, thereby obtaining the composite structure cathode material precursor. The second coprecipitation reaction includes a first stage and a second stage. In the first stage, the particle growth rate υ and the reaction pH satisfy the value of υ / lg[(pH-1)×1000] being between 13 and 58. In the second stage, the particle growth rate υ and the reaction pH satisfy the value of υ / lg[(pH-1)×1000] being between 1 and 13.

6. The method for preparing the composite structure cathode material precursor according to claim 5, characterized in that, At least one of the following conditions must be met: A. The pH of the first reaction substrate is 11.0~11.80; B. The ammonia concentration of the first reaction substrate is 3.0 g / L to 8.0 g / L; C. The temperature of the first reaction substrate is 55~70℃; D. The mixed salt is selected from one or two of the sulfates, chlorides or nitrates of soluble nickel, cobalt and manganese; E. The D of the target granularity I v 50 ranges from 3.0μm to 5.5μm; F. The total molar concentration of metal ions in the mixed salt is 0.8 mol / L to 2.5 mol / L; G. The precipitant is a sodium hydroxide or potassium hydroxide solution, and the concentration of the precipitant is 5 mol / L to 11 mol / L; H. The complexing agent includes at least one of ammonia, ammonium sulfate, and ammonium chloride, wherein if the complexing agent is ammonia, the mass concentration is 10 wt.% to 22 wt.%. I. The flow rate of the mixed salt in the first coprecipitation reaction is 5 L / h to 30 L / h.

7. The method for preparing the composite structure cathode material precursor according to claim 5, characterized in that, At least one of the following conditions must be met: A. The pH of the second reaction substrate is 10.20~10.85; B. The ammonia concentration in the bottom liquid of the second reaction is 1.0 g / L to 4.0 g / L; C. The temperature for the second coprecipitation reaction is 50~75℃; D. The target particle size II of D v 50 has a thickness of 7μm to 18μm; E. The flow rate of the mixed salt in the second coprecipitation reaction is 2% to 10% of the reactor volume per hour. F. The final solid content after the second coprecipitation reaction is 250~650 g / L; G. The pH of the second coprecipitation reaction is 10.00~11.

00.

8. A positive electrode material, characterized in that, It is prepared from the composite structure cathode material precursor according to any one of claims 1 to 4.

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.

Images