A single-crystal lithium-rich manganese-based positive electrode precursor and its preparation method and application

Abstract

The present invention provides a single-crystal lithium-rich manganese-based positive electrode precursor and its preparation method and application. The single-crystal lithium-rich manganese-based positive electrode precursor comprises secondary particles formed by primary particles and satisfies the following relationship: 1.2μm≤D50≤1.8μm, 0.5μm≤D R <6.0μm, 0.5g / cm 3 ≤α≤0.8g / cm 3 , 30m 2 / g≤β≤50m 2 / g, 22≤α·β≤28, 20nm≤N≤45nm, 5≤M / N≤10, wherein D50 is the median particle size of the secondary particles, D R is the particle size of the secondary particles, α is the tap density of the secondary particles, β is the specific surface area of ​​the secondary particles, N is the average thickness of the primary particles, and M is the average length of the primary particles. The median particle size of the secondary particles of the single-crystal-like lithium-rich manganese-based positive electrode precursor provided by the present invention is no more than 1.8 μm, which is significantly lower than the reported particle size of (quasi) single-crystal lithium-rich positive electrode precursors. The precursor can be made into a submicron-level single-crystal-like lithium-rich manganese-based positive electrode material with excellent dispersibility.

Description

Technical Field

[0001] The present invention relates to the field of battery materials, and in particular to a single-crystal-like lithium-rich manganese-based positive electrode precursor, and a preparation method and application thereof. Background Art

[0002] The current mainstream lithium-rich manganese-based cathode materials are composed of micron-sized secondary spherical particles agglomerated from primary particles measuring a few hundred nanometers. These secondary spherical particles exhibit low mechanical strength and robustness. Under high compaction conditions, these secondary spherical particles are easily crushed, exposing the material's internal particles, increasing side reactions and exacerbating metal ion dissolution, leading to reduced electrochemical performance. Furthermore, the primary particles are too fine and contain numerous structural defects, making them prone to structural collapse under high-voltage charge and discharge. Furthermore, the secondary particles struggle to encapsulate these extremely fine particles, making it difficult to suppress interfacial side reactions during high-voltage charge and discharge, leading to structural damage. Furthermore, these secondary spherical particles are prone to safety issues such as flatulence. Compared to traditional secondary spherical particles, single-crystal or quasi-single-crystal lithium-rich manganese-based cathodes have higher compaction and tap density, effectively avoiding particle breakage during electrode sheet rolling. This reduces side reactions between the electrolyte and the material, improving the cycling performance of individual cells and their high-rate performance.

[0003] The structure of the precursor is crucial to the development of single-crystal-like lithium-manganese-based cathodes. The physical and chemical properties of the precursor largely determine key performance indicators such as particle size, capacity, initial coulombic efficiency, and stability. The secondary particles of the precursors used in existing single-crystal-like lithium-manganese-based cathodes have poor particle consistency. The primary particles of the single-crystal-like lithium-manganese-based cathode materials prepared from such precursors are micron-sized (>1μm), which affects the capacity performance and cycling stability of the assembled battery. Summary of the Invention

[0004] The present invention provides a single-crystal-like lithium-manganese-rich positive electrode precursor, which can be used to prepare single-crystal-like lithium-manganese-rich positive electrode materials with submicron-level primary particles, and is expected to further improve the electrochemical performance of single-crystal-like lithium-manganese-rich positive electrode materials.

[0005] The present invention also provides a method for preparing the above-mentioned single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method can prepare the above-mentioned single-crystal lithium-rich manganese-based positive electrode precursor, and the process is simple and the cost is low.

[0006] The present invention also provides a single-crystal-like lithium-rich manganese-based positive electrode material, the primary particles of which are submicron-sized and highly uniform, and can improve the specific capacity and cycle stability of the assembled battery.

[0007] The present invention also provides a positive electrode plate, which includes the above-mentioned single-crystal lithium-rich manganese-based positive electrode material. Therefore, the plate has excellent electrochemical properties.

[0008] In a first aspect, the present invention provides a single-crystal-like lithium-rich manganese-based cathode precursor, comprising secondary particles formed from primary particles, and satisfying the following formulas 1 to 7:

[0009] 1.2μm≤D50≤1.8μm Formula 1,

[0010] 0.5μm≤D R <6.0μm Formula 2,

[0011] 0.5g / cm 3 ≤α≤0.8g / cm 3 Formula 3,

[0012] 30m 2 / g≤β≤50m 2 / g Formula 4,

[0013] 22≤α•β≤28 Formula 5,

[0014] 20nm≤N≤45nm Formula 6,

[0015] 5≤M / N≤10 Formula 7,

[0016] Wherein, D50 is the median particle size of the secondary particles, D R is the particle size of the secondary particles, α is the tap density of the secondary particles, β is the specific surface area of ​​the secondary particles, N is the average thickness of the primary particles, and M is the average length of the primary particles.

[0017] In a preferred embodiment, the number of primary particles on the outer surface of the secondary particles is 12 to 20 per μm. 2 .

[0018] In a preferred embodiment, the chemical formula is Ni x Co y Mn 1-x-y (OH) 2-z F z , where 0.3≤x≤0.38, 0≤y≤0.1, 0≤z≤0.02.

[0019] In a preferred embodiment, 2.7≤(1-y) / x≤3.0.

[0020] In a preferred embodiment, 0.30≤x≤0.33, 0.05≤y≤0.1, 0 <z≤0.02。

[0021] In a second aspect, the present invention provides a method for preparing the above-mentioned single-crystal lithium-rich manganese-based positive electrode precursor, comprising the following steps:

[0022] At 50-70° C., a metal source solution and a precipitant are introduced into a reaction base liquid having a pH of 10.8-11.2, and the mixture is stirred at a speed of 600-800 rpm. After particles appear, the pH of the system is adjusted to 10.4-10.79 and a complexing agent is added until the particle size meets a preset value, and the reaction is stopped to obtain the quasi-single crystal lithium-rich manganese-based positive electrode precursor.

[0023] In the reaction system, the concentration of the complexing agent is 0.02-0.2 g / L, and the total concentration of the metal ions is 1.0-2.0 mol / L.

[0024] In a preferred embodiment, the D50 of the secondary particles of the particles is in the range of 0.6-1.0 μm.

[0025] In a third aspect, the present invention provides a quasi-single-crystal lithium-rich manganese-based positive electrode material, comprising quasi-single-crystal particles formed by primary particles having a particle size of 300 nm to 800 nm, wherein the quasi-single-crystal particles satisfy at least one of Formulas 8 to 11;

[0026] 1.0μm≤D50<5.0μm Formula 8,

[0027] 0.3μm≤Dmin<1.0μm Formula 9,

[0028] 0.5m 2 / g≤α≤2.5m 2 / g Formula 10,

[0029] 8.0μm≤Dmax<18.0μm Formula 11,

[0030] Wherein, D50 is the median particle size of the quasi-single crystal particles, α is the specific surface area of ​​the quasi-single crystal particles, Dmin is the minimum particle size of the quasi-single crystal particles, and Dmax is the maximum particle size of the quasi-single crystal particles.

[0031] In a fourth aspect, the present invention provides a positive electrode plate comprising the above-mentioned single-crystal-like lithium-rich manganese-based positive electrode material.

[0032] The median particle size of the secondary particles of the single-crystal-like lithium-rich manganese-based positive electrode precursor provided by the present invention is not higher than 1.8 μm, which is significantly lower than the reported particle size of (quasi) single-crystal lithium-rich positive electrode precursors. In addition, the present invention defines parameters such as the specific surface area and tap density of such precursors to ensure that they form a submicron-level single-crystal-like lithium-rich manganese-based positive electrode.

[0033] The median particle size of the primary particles of the single-crystal-like lithium-rich manganese-based positive electrode material provided by the present invention is no more than 1 μm. When used in battery pole pieces, it can significantly improve the battery's first efficiency, specific capacity, cycle stability and other performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0035] Figure 1 This is the SEM image of the precursor of Example 1;

[0036] Figure 2 This is the SEM image of the precursor of Comparative Example 1;

[0037] Figure 3 This is the SEM image of the precursor of Comparative Example 2;

[0038] Figure 4 This is an SEM image of a quasi-single-crystal lithium-rich manganese-based cathode material synthesized based on the precursor of Example 1;

[0039] Figure 5 This is an SEM image of a lithium-rich manganese-based cathode material synthesized based on the precursor of Comparative Example 1;

[0040] Figure 6 This is an SEM image of a single-crystal-like lithium-rich manganese-based positive electrode material synthesized based on the precursor of Comparative Example 2. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific embodiments listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts are within the scope of protection of the present invention.

[0042] In a first aspect, the present invention provides a single-crystal-like lithium-rich manganese-based cathode precursor, comprising secondary particles formed from primary particles, and satisfying the following formulas 1 to 7:

[0043] 1.2μm≤D50≤1.8μm Formula 1,

[0044] 0.5μm≤D R <6.0μm Formula 2,

[0045] 0.5g / cm 3 ≤α≤0.8g / cm 3 Formula 3,

[0046] 30m 2 / g≤β≤50m 2 / g Formula 4,

[0047] 22≤α•β≤28 Formula 5,

[0048] 20nm≤N≤45nm Formula 6,

[0049] 5≤M / N≤10 Formula 7,

[0050] Wherein, D50 is the median particle size of the secondary particles, D R is the particle size of the secondary particles, α is the tap density of the secondary particles, β is the specific surface area of ​​the secondary particles, N is the average thickness of the primary particles, and M is the average length of the primary particles.

[0051] The present invention can ensure that the single-crystal-like lithium-rich manganese-based cathode precursor is easily sintered to form a submicron-level single-crystal-like lithium-rich cathode material by limiting various structural parameters thereof. The specific reasons are as follows:

[0052] The precursors that meet Formula 1 and Formula 2 have the characteristics of no serious agglomeration, no micropowder and good sphericity, which is conducive to their full mixing with the lithium source and better sintering effect; the precursors that meet Formula 3 and Formula 4 have a loose structure, wherein a lower tap density allows more air to enter and exhaust waste gas in time, accelerates the sintering process, and makes the primary particles of the positive electrode material easier to form and grow; and a higher specific surface area can increase the contact area between the precursor and the lithium source, increase the reaction active sites, improve the reaction efficiency, reduce the required reaction temperature, and at the same time control the particle size of the primary particles of the positive electrode material to avoid excessive growth; the correlation between the tap density and specific surface area of ​​the precursor varies with the morphology and cross-linking degree of the primary particles of the precursor. Under the same tap density conditions, the thinner the primary sheet, the smaller the specific surface area of ​​the precursor, and the lower the cross-linking degree of the primary sheet. Therefore, the present invention further defines the correlation between the specific surface area and the tap density, that is, Formula 5. The precursor that further satisfies this relationship of Formula 5 can avoid the positive electrode material produced during the sintering process. The primary particles of the material are too coarse and severely agglomerated, or the primary particles are too fine and cannot form a submicron-level single-crystal structure; regarding the primary particles of the precursor, the inventors found during the investigation that a precursor with a loose porous structure formed by staggered primary sheets is more conducive to controlling the formation of the positive electrode material, that is, it conforms to Formula 6 and Formula 7. The inventors also found that if M / N<5 or N<20, the primary particles of the precursor are too small, which is not conducive to the mutual melting of the primary particles to form a single-crystal positive electrode material, or the precursor is a short and thick strip, which easily leads to the primary particle size of the single-crystal positive electrode material exceeding the standard, affecting the material capacity and power characteristics. If M / N>10 or N>45, the pores between the primary sheets are too large or the length of a single primary sheet is too high, which is not conducive to the mutual melting of the primary particles to form a single-crystal positive electrode material, but is more inclined to make the positive electrode material inherit the morphology of the precursor, that is, the primary sheets maintain a long mutually cross-linked secondary ball feature. This secondary spherical positive electrode material has too low density, high specific surface area, low structural strength, and is difficult to be industrially applied.

[0053] It should be noted that, in the present invention, the expression "primary particle" refers to the primary structure of a single particle, and the corresponding "secondary particle" refers to the aggregate of primary particles through physical or chemical bonding between primary particles, that is, the secondary structure; the expression "D50" refers to the particle size corresponding to the secondary particles when the cumulative volume accounts for 50% from the minimum particle size; the expression "0.5μm≤D R "<6.0μm" means that the minimum particle size of the secondary particles is ≥0.5μm and the maximum particle size is <6.0μm; the expression "quasi-single crystal" refers to a structure between single crystal and polycrystalline. A single crystal is a crystal grown from a single grain, and there is no grain boundary inside it. It is a complete and independent grain, while a polycrystalline is an agglomerate formed by many single crystal particles closely connected by multiple grain boundaries.

[0054] According to a specific embodiment of the present invention, the primary particles are hexagonal flakes. It can be understood that M in this case is the average value of the longest diameter of the primary particles of the precursor.

[0055] According to a specific embodiment of the present invention, the number of primary particles contained on the outer surface of the secondary particles is 12 to 20 per μm. 2 This description can also be understood as that the number of primary particles contained on the outer surface of each secondary particle is 12 to 20 per μm. 2 .

[0056] In the above embodiment, by further limiting the number of primary particles contained on the outer surface of the precursor secondary particles, it is possible to ensure the formation of submicron-level single-crystal lithium-rich positive electrode materials, and the size of the primary particles of the positive electrode material is more suitable and the dispersion is better, which in turn helps to improve the electrochemical properties of the positive electrode material, such as capacity and power.

[0057] In addition, the number of primary particles contained in the outer surface can be determined by measuring the radius r of a secondary particle in the SEM image of the precursor and calculating its surface area S = 4πr 2 , read out the sum T of the number of primary particles visible in the SEM image of the secondary particle, and calculate the R value according to the formula R=T / S. R is the number of primary particles contained in a unit area of ​​the outer surface of a secondary particle. Using the same method, measure the R values ​​of at least 20 secondary particles cumulatively and find the average value.

[0058] According to a specific embodiment of the present invention, 20nm≤N≤40nm. The single-crystal-like lithium-rich manganese-based positive electrode material prepared from a precursor that satisfies this relationship has more excellent electrochemical performance.

[0059] According to a specific embodiment of the present invention, the chemical formula is Ni x Co y Mn 1-x-y (OH) 2-z F z , where 0.3≤x≤0.38, 0≤y≤0.1, and 0≤z≤0.02. The precursor that conforms to the above chemical formula can adjust the Ni content to enable the single-crystal lithium-rich manganese-based cathode to have a higher specific capacity and first coulombic efficiency, thereby improving lithium utilization; and the precursor can contain no more than 10 mol% of cobalt, which can improve the kinetics and electronic conductivity of the single-crystal lithium-rich manganese-based cathode, making its capacity and power performance no less than that of secondary spherical lithium-rich manganese-based cathode materials, while providing higher electrochemical stability.

[0060] According to a specific embodiment of the present invention, 2.7 ≤ (1 - y) / x ≤ 3.0. The present invention defines the ratio relationship of nickel, cobalt and manganese, which can endow the lithium-rich manganese-based cathode with more excellent power performance and capacity utilization.

[0061] According to a specific embodiment of the present invention, 0.30 ≤ x ≤ 0.33, 0.05 ≤ y ≤ 0.1, 0 < z ≤ 0.02. The precursor of this embodiment can further improve the comprehensive kinetic performance, capacity utilization and power performance of the single-crystalline-like lithium-rich manganese-based cathode. At the same time, the doping of F can not only improve the structural stability of the single-crystalline-like lithium-rich manganese-based cathode material, but also significantly reduce the primary sintering temperature of the single-crystalline-like lithium-rich manganese-based cathode material due to the solubilizing effect of F, thereby reducing energy consumption. However, the inventors also found that if the concentration of F introduced is too high, it may lead to too large primary particles of the final cathode material and a significant decrease in capacity.

[0062] According to a specific embodiment of the present invention, the single-crystalline-like lithium-rich manganese-based cathode precursor is prepared by a method including the following process:

[0063] At 50 - 70 °C, a metal source solution and a precipitant are introduced into a reaction bottom solution with a pH of 10.8 - 11.2, and stirring treatment is carried out at a rotation speed of 600 - 800 rpm. After particles appear, the pH of the system is adjusted to 10.4 - 10.79 and a complexing agent is added until the particle size meets a preset value, and then the reaction is stopped to obtain the single-crystalline-like lithium-rich manganese-based cathode precursor;

[0064] Wherein, in the reaction system, the concentration of the complexing agent is 0.02 - 0.2 g / L, and the total concentration of metal ions is 1.0 - 2.0 mol / L.

[0065] In a second aspect, the present invention provides a method for preparing the above single-crystalline-like lithium-rich manganese-based cathode precursor, including the following steps:

[0066] At 50 - 70 °C, a metal source solution and a precipitant are introduced into a reaction bottom solution with a pH of 10.8 - 11.2, and stirring treatment is carried out at a rotation speed of 600 - 800 rpm. After particles appear, the pH of the system is adjusted to 10.4 - 10.79 and a complexing agent is added until the particle size meets a preset value, and then the reaction is stopped to obtain the single-crystalline-like lithium-rich manganese-based cathode precursor;

[0067] Wherein, in the reaction system, the concentration of the complexing agent is 0.02 - 0.2 g / L, and the total concentration of metal ions is 1.0 - 2.0 mol / L.

[0068] It should be noted that the preset value refers to the median particle size of the secondary particles, that is, the present invention mainly judges the progress of the reaction by whether the median particle size of the secondary particles meets Equation 1.

[0069] In the present invention, a method of introducing a complexing agent after a certain number of particles appear in the system is adopted. This is because the inventors found through research that adding a complexing agent before the reaction starts will lead to a decrease in the number of nucleations, a larger particle size of the initially formed secondary particles, and an excessive thickness of the primary sheet, which ultimately makes it difficult to sinter the precursor to form a submicron-level single-crystal lithium-rich positive electrode. The complexing agent is only used after a certain number of particles appear. At this time, the complexing agent can effectively improve the consistency of the precursor primary particles, reduce the agglomeration of secondary particles and improve their sphericity.

[0070] Furthermore, the present invention also regulates the synthesis of the precursor by limiting parameters such as the pH of the reaction base liquid, reaction temperature, stirring speed, pH value before adding the complexing agent, concentration of the complexing agent and concentration of metal ions. Among them, limiting the pH of the reaction base liquid can further ensure that the precipitation rate in the initial stage of the reaction system is faster and the salt ion supersaturation is lower, thereby avoiding the formation of a large number of loose, shapeless or too small primary particles. Such loose primary particles are not conducive to sintering and melting. Even if they are melted, the formed positive electrode material primary particles will have more grain boundaries, resulting in a significant decrease in the structural stability of the positive electrode material. The reaction temperature, stirring speed, pH value before adding the complexing agent, concentration of the complexing agent and concentration of metal ions will all affect the microstructure of the precursor. If these conditions are not within the scope of the present invention, even if the median particle size of the secondary particles reaches 1.2~1.8μm, the other parameters of the precursor will be difficult to simultaneously satisfy Equations 2 to 7.

[0071] As for the reaction time, the present invention does not make any specific limitation, and technicians can determine it based on the median particle size of the secondary particles. For example, when the total volume of the space occupied by the liquid in the reaction system is 0.2~50m 3 The reaction time is generally 15~30h.

[0072] Illustratively, aging and cleaning treatments are further included after stopping the reaction; this subsequent treatment can further improve the smoothness of the precursor particles and remove impurity ions on the surface of the precursor.

[0073] In addition, it can be understood that when fluorine needs to be introduced into the positive electrode material, the reaction system also includes a fluorine source, such as sodium fluoride, ammonium fluoride, etc. The fluorine source can be added directly to the reaction base liquid or added at other time points before the introduction of the precipitant.

[0074] Illustratively, the complexing agent is selected from at least one of ammonium sulfate, ammonium nitrate, ammonium acetate, ammonium chloride, glycine, ammonium citrate, sodium citrate, oxalic acid, ammonium oxalate, acetic acid, maleic acid, succinic acid, malonic acid and crown ether, preferably oxalic acid and / or ammonium oxalate; the precipitant is sodium hydroxide and / or potassium hydroxide; and the metal source solution is a solution in which the solute is a sulfate, nitrate, chloride, etc. of the desired metal.

[0075] According to one embodiment of the present invention, the D50 of the secondary particles of the particles is within the range of 0.6-1.0 μm. The inventors have discovered that maintaining the particle size within this range before adding the complexing agent can result in a more suitable precursor particle size, which is more conducive to forming a single-crystal-like lithium-rich manganese-based cathode material with superior electrochemical performance.

[0076] According to a specific embodiment of the present invention, the total concentration of metal ions is 1.2-1.8 mol / L.

[0077] In a third aspect, the present invention provides a quasi-single-crystal lithium-rich manganese-based positive electrode material, comprising quasi-single-crystal particles formed by primary particles having a particle size of 300 nm to 800 nm, wherein the quasi-single-crystal particles satisfy at least one of Formulas 8 to 11;

[0078] 1.0μm≤D50<5.0μm Formula 8,

[0079] 0.3μm≤Dmin<1.0μm Formula 9,

[0080] 0.5m 2 / g≤α≤2.5m 2 / g Formula 10,

[0081] 8.0μm≤Dmax<18.0μm Formula 11,

[0082] Wherein, D50 is the median particle size of the quasi-single crystal particles, α is the specific surface area of ​​the quasi-single crystal particles, Dmin is the minimum particle size of the quasi-single crystal particles, and Dmax is the maximum particle size of the quasi-single crystal particles.

[0083] It should be noted that the particle size of the primary particles is the average particle size of the primary particles, and the single-crystal-like particles are aggregates formed by the aggregation of multiple primary particles.

[0084] The single-crystal-like lithium-rich manganese-based positive electrode material that meets the above parameters has better capacity performance and cycle stability. The primary particle size is submicron-level, which ensures its capacity performance. The D50 of the single-crystal-like particles is 1.0~4.0μm, indicating that the primary particles form a single-crystal-like structure with low agglomeration. Dmin>0.3μm, indicating that although the material has a small size of single-crystal-like particles, there is no significant fine powder, which ensures the interface stability of the material after use in the battery and can effectively inhibit gas production. Specific surface area>0.5m 2 / g, slightly higher than the specific surface area of ​​the ternary single crystal positive electrode, further ensuring its capacity, the specific surface area <2.5m 2 / g, ensuring an acceptable surface area for the material and enabling controllable interfacial side reactions, which helps improve battery stability. Compared to secondary spherical cathodes, single-crystal-like materials have lower surface area, fewer grain boundaries, higher crystallinity, and greater structural stability, helping to improve the stability and service life of battery systems.

[0085] According to a specific embodiment of the present invention, the quasi-single-crystal lithium-rich manganese-based positive electrode material is obtained by calcining the quasi-single-crystal lithium-rich manganese-based positive electrode precursor provided by the first aspect and a lithium source in an oxygen environment.

[0086] Illustratively, the single-crystal-like lithium-rich manganese-based cathode material is obtained by a method comprising the following steps:

[0087] The quasi-single-crystal lithium-rich manganese-based positive electrode precursor is mixed with a lithium salt, placed in an air atmosphere, heated to 950-1050° C. at a rate of 2-5° C. / min, and sintered for 10-15 hours to obtain the quasi-single-crystal lithium-rich manganese-based positive electrode material.

[0088] More preferably, the temperature is raised to 1000-1050° C. at a rate of 2-5° C. / min and sintered for 10-15 hours to obtain the quasi-single-crystal lithium-rich manganese-based positive electrode material.

[0089] In a fourth aspect, the present invention provides a positive electrode plate comprising the above-mentioned single-crystal-like lithium-rich manganese-based positive electrode material.

[0090] The present invention will be further described below with reference to specific embodiments:

[0091] Example 1

[0092] This example provides a quasi-single-crystal lithium-rich manganese-based positive electrode precursor, and its preparation method includes the following steps:

[0093] S1. Prepare a metal salt solution with a total molar ratio of 2.5 mol / L, wherein the molar ratio of nickel, cobalt, and manganese is 0.3:0.1:0.6; prepare a precipitant: a 9.5 mol / L NaOH alkaline solution; prepare a F-containing solution: an aqueous solution containing 1.0 mol / L NaF.

[0094] S2. Fill a 100 L reactor with clean water and set the stirring speed to 800 rpm and the temperature to 55°C. Add a certain amount of precipitant to prepare a reaction base solution with a pH of 10.8, and introduce nitrogen gas. After the reaction system stabilizes, introduce a metal salt solution, a precipitant, and a F-containing solution into the reactor. After reacting for 1 hour, monitor the particle size. After the particle size reaches D50 = 1.0 μm, slowly lower the pH to 10.4, and begin to introduce ammonium oxalate into the reactor to adjust the concentration of the ammonium oxalate complexing agent in the reaction system to 0.1 g / L.

[0095] S3. After 22 hours of reaction, the particle size D50 was detected to be 1.6 μm, and the feeding was stopped, the slurry was aged, and the slurry in the kettle was collected.

[0096] S4, washing, centrifuging, drying and other treatments are performed on the slurry collected in S3 to obtain the precursor Ni 0.3 Co 0.1 Mn 0.6 (OH) 1.99 F 0.01 , and its structural parameters are shown in Table 1.

[0097] Example 2

[0098] This example provides a single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method thereof is different from that of Example 1 in that the molar ratio of nickel, cobalt and manganese in the metal salt solution is adjusted to 0.33:0.08:0.59; the rest remains unchanged; and the single-crystal lithium-rich positive electrode precursor Ni is obtained. 0.33 Co 0.08 Mn 0.59 (OH) 1.99 F 0.01 , and its structural parameters are shown in Table 1.

[0099] Example 3

[0100] This example provides a single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method thereof is different from that of Example 1 in that the molar ratio of nickel, cobalt and manganese in the metal salt solution is adjusted to 0.35:0.05:0.60; the rest remains unchanged; and the single-crystal lithium-rich positive electrode precursor Ni is obtained. 0.35 Co 0.05 Mn 0.60 (OH) 1.99 F 0.01 , and its structural parameters are shown in Table 1.

[0101] Example 4

[0102] This example provides a single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method thereof is different from that of Example 1 in that the molar ratio of nickel, cobalt and manganese in the metal salt solution is adjusted to 0.36:0.02:0.62; the rest remains unchanged; and the single-crystal lithium-rich positive electrode precursor Ni is obtained. 0.36 Co 0.02 Mn 0.62 (OH) 1.99 F 0.01 , and its structural parameters are shown in Table 1.

[0103] Example 5

[0104] This example provides a single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method thereof is different from that of Example 1 in that the molar ratio of nickel, cobalt and manganese in the metal salt solution is adjusted to 0.36:0.00:0.64; the rest remain unchanged; and the single-crystal lithium-rich positive electrode precursor Ni is obtained. 0.36 Mn 0.64 (OH) 1.99 F 0.01 , and its structural parameters are shown in Table 1.

[0105] Example 6

[0106] This example provides a single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method thereof is different from that of Example 1 in that the complexing agent is replaced with oxalic acid so that the total concentration of the oxalic acid input is 0.15 g / L; the rest remain unchanged; and the single-crystal lithium-rich positive electrode precursor Ni is obtained. 0.3 Co 0.1 Mn 0.6 (OH) 1.99 F 0.01 , and its structural parameters are shown in Table 1.

[0107] Example 7

[0108] This example provides a single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method thereof is different from that of Example 1 in that the flow rate of the sodium fluoride solution is doubled, so that the F concentration in the reaction system is doubled; the rest remain unchanged; and the single-crystal lithium-rich positive electrode precursor Ni is obtained. 0.3 Co 0.1 Mn 0.6 (OH) 1.98 F 0.02 The reaction time and product structure parameters are shown in Table 1.

[0109] Example 8

[0110] This example provides a single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method thereof is different from that of Example 1 in that the pH of the reaction bottom liquid is increased to 11 and the pH before the addition of ammonium oxalate is increased to 10.6; the rest remain unchanged; and a single-crystal lithium-rich positive electrode precursor Ni is obtained. 0.3 Co 0.1 Mn 0.6 (OH) 1.99 F 0.01 The reaction time and product structure parameters are shown in Table 1.

[0111] Example 9

[0112] This example provides a single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method thereof is different from that of Example 1 in that the amount of complexing agent is increased to make the complexing agent concentration in the reaction system 0.2 g / L; the rest remain unchanged; and the single-crystal lithium-rich positive electrode precursor Ni is obtained.0.3 Co 0.1 Mn 0.6 (OH) 1.99 F 0.01 The reaction time and product structure parameters are shown in Table 1.

[0113] Example 10

[0114] This example provides a single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method thereof is different from that of Example 1 in that the pH is lowered after the particle size of step S1 reaches 0.6 μm, the reaction is stopped in step S2 until the particle size of the finished product reaches D50=1.5 μm, and the rest remain unchanged; the single-crystal lithium-rich positive electrode precursor Ni is obtained. 0.3 Co 0.1 Mn 0.6 (OH) 1.99 F 0.01 The reaction time and product structure parameters are shown in Table 1.

[0115] Example 11

[0116] This example provides a single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method thereof is different from that of Example 1 in that the NaF solution is not introduced; the rest remains unchanged; the lithium-rich positive electrode precursor Ni 0.3 Co 0.1 Mn 0.6 (OH)2, the reaction time and product structure parameters are shown in Table 1.

[0117] Example 12

[0118] This example provides a single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method thereof is different from that of Example 1 in that the molar ratio of nickel, cobalt and manganese in the salt solution is adjusted to 0.29:0.1:0.61; the rest remains unchanged; and the single-crystal lithium-rich positive electrode precursor Ni is obtained. 0.29 Co 0.10 Mn 0.61 (OH) 1.99 F 0.01 The reaction time and product structure parameters are shown in Table 1.

[0119] Example 13

[0120] This example provides a single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method thereof is different from that of Example 1 in that the molar ratio of nickel, cobalt and manganese in the salt solution is adjusted to 0.33:0:0.67; the rest remains unchanged; and the single-crystal lithium-rich positive electrode precursor Ni is obtained. 0.33 Mn 0.67 (OH) 1.99 F 0.01 The reaction time and product structure parameters are shown in Table 1.

[0121] Example 14

[0122] This example provides a single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method thereof is different from that of Example 1 in that the molar ratio of nickel, cobalt and manganese in the salt solution is adjusted to 0.38:0:0.62; the rest remains unchanged; and the single-crystal lithium-rich positive electrode precursor Ni is obtained. 0.38 Mn 0.62 (OH) 1.99 F 0.01 The reaction time and product structure parameters are shown in Table 1.

[0123] Comparative Example 1

[0124] This example provides a single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method thereof is different from that of Example 1 in that the complexing agent is added when the metal salt solution is introduced, and the other reaction parameters remain unchanged to obtain the lithium-rich positive electrode precursor Ni 0.3 Co 0.1 Mn 0.6 (OH) 1.99 F 0.01 The reaction time and structural parameters are shown in Table 1.

[0125] Comparative Example 2

[0126] This example provides a single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method thereof is different from that of Example 1 in that no complexing agent is used in the whole process, and the rest remains unchanged to obtain a lithium-rich positive electrode precursor Ni 0.3 Co 0.1 Mn 0.6 (OH) 1.99 F 0.01 The reaction time and product structure parameters are shown in Table 1.

[0127] Comparative Example 3

[0128] This example provides a single-crystal lithium-rich manganese-based cathode precursor. The preparation method thereof is different from that of Example 1 in that the total metal ion concentration of the reaction system is regulated to be 0.8 mol / L, and the other reaction parameters remain unchanged to obtain a lithium-rich cathode precursor Ni 0.3 Co 0.1 Mn 0.6 (OH) 1.99 F 0.01 The reaction time and product structure parameters are shown in Table 1.

[0129] Comparative Example 4

[0130] This example provides a single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method thereof is different from that of Example 1 in that the stirring speed is 500 rpm and the rest remain unchanged to obtain a lithium-rich positive electrode precursor Ni 0.3 Co0.1 Mn 0.6 (OH) 1.99 F 0.01 The reaction time and product structure parameters are shown in Table 1.

[0131] Comparative Example 5

[0132] This example provides a single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method thereof is different from that of Example 1 in that the pH of the reaction bottom liquid is increased to 11.5 and the pH before the addition of ammonium oxalate is increased to 11.0; the rest remain unchanged; and the lithium-rich positive electrode precursor Ni is obtained. 0.3 Co 0.1 Mn 0.6 (OH) 1.99 F 0.01 The reaction time and product structure parameters are shown in Table 1.

[0133] Comparative Example 6

[0134] This example provides a single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method thereof is different from that of Example 1 in that the pH of the reaction bottom liquid is lowered to 10.5 and the pH before the addition of ammonium oxalate is lowered to 10.0; the rest remain unchanged; and the lithium-rich positive electrode precursor Ni is obtained. 0.3 Co 0.1 Mn 0.6 (OH) 1.99 F 0.01 The reaction time and product structure parameters are shown in Table 1.

[0135] Comparative Example 7

[0136] This example provides a single-crystal lithium-rich manganese-based positive electrode precursor. The preparation method thereof is different from that of Example 1 in that the amount of the complexing agent is increased to 0.3 g / L; the rest remains unchanged; and the lithium-rich positive electrode precursor Ni is obtained. 0.3 Co 0.1 Mn 0.6 (OH) 1.99 F 0.01 The reaction time and product structure parameters are shown in Table 1.

[0137] Application Examples

[0138] A series of quasi-single-crystal lithium-rich manganese-based positive electrode materials are provided. The preparation method thereof comprises: thoroughly mixing the precursors prepared in Examples 1 to 14 and Comparative Examples 1 to 7 above with lithium carbonate in a certain stoichiometric ratio, wherein the molar ratio of lithium salt to precursor is [1.0 + (molar ratio of manganese in the precursor - molar ratio of nickel in the precursor)]: 1.0; then placing the mixture in an air atmosphere, heating it to 1020°C at a rate of 2°C / min, sintering it for 10 hours, and then naturally cooling it to room temperature to obtain a series of quasi-single-crystal lithium-rich manganese-based positive electrode materials. The reaction time and product structure parameters are shown in Table 2.

[0139] Related performance tests:

[0140] Morphology test: The morphology of the single-crystal lithium-rich manganese-based positive electrode precursors obtained in Example 1 and Comparative Examples 1-2 was observed using a scanning electron microscope (SEM). Figure 1-3 ; And observe the morphology of the single-crystal lithium-rich manganese-based cathode material obtained by the precursor system of Example 1 and Comparative Example 1-2, and the SEM picture thereof is shown Figure 4-6 ;

[0141] Electrical performance test: A series of single-crystal lithium-rich manganese-based cathode materials prepared in the above application examples were slurried with a mass ratio of 92:4:4 for cathode active material: PVDF: SP, and coated to obtain a surface loading of 10 mg / cm 2 The positive electrode sheet uses a PE / PP composite separator, the negative electrode uses metallic lithium, and an appropriate amount of electrolyte is added dropwise. The electrolyte composition is 1M LiPF6 dissolved in an organic mixture of EC:VC:EMC with a volume ratio of 1:1:1. The LR2430 lithium button battery is assembled and the capacity and rate performance of the lithium button battery are tested.

[0142] The test process includes: 2.5~4.55V, 250mAhg -1 For the nominal capacity, the first cycle is charged to 4.55V at a constant current of 0.1C, then charged to 0.02C at a constant voltage, discharged to 2.5V at a constant current of 0.1C, and charged and discharged for 1 cycle; then charged to 4.55V at a constant current of 2.0C, then charged to 0.02C at a constant voltage, discharged to 2.5V at a constant current of 2.0C, and charged and discharged for 1 cycle; then charged to 4.55V at a constant current of 1.0C, then charged to 0.02C at a constant voltage, discharged to 2.5V at a constant current of 1.0C, and cycled 100 times. The test results are shown in Table 3.

[0143] Table 1:

[0144]

[0145] Note: R is the number of primary particles on the outer surface of secondary particles, unit: pieces / μm 2 ; α is the tap density of the secondary particles, β is the specific surface area of ​​the secondary particles, N is the average thickness of the primary particles, and M is the average length of the primary particles; time is the reaction time of step S3.

[0146] Table 2:

[0147]

[0148] Note: D50 is the median particle size of the single-crystal-like particles, Dmin is the minimum particle size of the single-crystal-like particles, and Dmax is the maximum particle size of the single-crystal-like particles.

[0149] Table 3:

[0150]

[0151] As shown in Table 1, the nickel, cobalt, manganese and fluorine contents of the precursors prepared in each embodiment and comparative example are basically consistent with the designed values, indicating that the anions and cations are well precipitated during the reaction process and no precipitation occurs. The physical and chemical indicators of the precursors obtained in Examples 1 to 14 are all consistent with the formulas 1 to 7 defined in the present invention, while the physical and chemical indicators of Comparative Examples 1 to 7 cannot simultaneously meet the requirements of Formulas 1 to 7 due to differences from the preparation method proposed in the present invention. Figure 1 It can be seen that the precursor prepared in Example 1 includes spherical secondary particles composed of primary sheets, the secondary particles have no significant agglomeration and no fine powder, D50 is between 1.5 and 2.0 μm, the thickness of the primary sheet is thin and the consistency is high, and the overall structure is relatively loose; combined with Figure 2 It can be seen that the precursor prepared in Comparative Example 1 includes spherical secondary particles composed of primary sheets, the secondary particles have no significant agglomeration, D50 is about 2.96 μm, the primary sheet is thicker, the overall density is higher, and it is not easy to prepare a submicron-level single-crystal lithium-rich manganese-based positive electrode; combined Figure 3 It can be seen that the precursor prepared in Comparative Example 2 has significantly agglomerated secondary particles and contains too much fine powder, and the overall dispersibility is poor, which makes it difficult to prepare a submicron-level single-crystal lithium-rich manganese-based positive electrode with good dispersibility.

[0152] As can be seen from Table 2, the single-crystal-like lithium-rich manganese-based cathode materials synthesized from the precursors of each embodiment have relatively high primary particle dispersibility and high primary particle uniformity, and the size of the primary particles is between 300 and 800 nm; while in each comparative example, since the structural parameters of the precursor particle size cannot reach the optimal range, the lithium-rich manganese-based cathode materials synthesized based on the precursors cannot form the submicron-like single-crystal lithium-rich manganese-based cathode materials of the present invention. Figure 4 It can be seen that the submicron-scale single-crystal lithium-rich manganese-based cathode material synthesized based on the precursor of Example 1 has relatively high primary particle dispersion and high primary particle uniformity, and the size of its primary particles is between 350 and 550 nm; combined with Figure 5 It can be seen that since the precursor particle size of Comparative Example 1 is too large and the thickness of the primary particles is relatively thick, the overall structure density is relatively high, resulting in the lithium-rich manganese-based positive electrode material synthesized based on the precursor being unable to form a single crystal morphology; combined with Figure 6 It can be seen that due to the significant agglomeration of the secondary particles of the precursor of Comparative Example 2 and the presence of excessive fine powder, the overall dispersibility is poor. The primary particles of the submicron-level single-crystal lithium-rich manganese-based positive electrode material synthesized based on this precursor are too small, and the particles are severely adhered and difficult to disperse. Its use in battery production will easily lead to poor batch stability and low electrode compaction density.

[0153] It can be seen from Table 3 that the single-crystal-like lithium-rich manganese-based positive electrode materials prepared based on the precursors of Examples 1 to 14 all have excellent electrochemical properties, while the first efficiency, 2.0C / 0.1C capacity retention rate and cycle performance of the single-crystal-like lithium-rich manganese-based positive electrode materials prepared based on the precursors of Comparative Examples 1 to 7 are significantly lower than those of the Examples.

[0154] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A single-crystal lithium-rich manganese-based cathode precursor, characterized in that: It contains secondary particles formed from primary particles and satisfies the following formulas 1 to 7: 1.2μm≤D50≤1.8μm Formula 1, 0.5μm≤D R <6.0μm Formula 2, 0.5g / cm 3 ≤α≤0.8g / cm 3 Formula 3, 30m 2 / g≤β≤50m 2 / g Formula 4, 22≤α•β≤28 Formula 5, 20nm≤N≤45nm Equation 6, 5≤M / N≤10 Formula 7, Wherein, D50 is the median particle size of the secondary particles, D R is the particle size of the secondary particles, α is the tap density of the secondary particles, β is the specific surface area of ​​the secondary particles, N is the average thickness of the primary particles, and M is the average length of the primary particles.

2. The single-crystal-like lithium-rich manganese-based cathode precursor according to claim 1, characterized in that: The number of primary particles on the outer surface of the secondary particles is 12 to 20 per μm. 2 .

3. The single-crystal-like lithium-rich manganese-based cathode precursor according to claim 1, characterized in that: Its chemical formula is Ni x Co y Mn 1-x-y (OH) 2-z F z , where 0.3≤x≤0.38, 0≤y≤0.1, 0≤z≤0.

02.

4. The single-crystal-like lithium-rich manganese-based cathode precursor according to claim 3, characterized in that: 2.7≤(1-y) / x≤3.

0.

5. The single-crystal-like lithium-rich manganese-based cathode precursor according to claim 3, characterized in that: 0.30≤x≤0.33,0.05≤y≤0.1,0 <z≤0.02。 6. A method for preparing a quasi-single-crystal lithium-manganese-based positive electrode precursor according to any one of claims 1 to 5, characterized in that: The following steps are involved: At 50-70° C., a metal source solution and a precipitant are introduced into a reaction base liquid having a pH of 10.8-11.2, and a fluorine source is introduced or not introduced depending on the product composition. The mixture is stirred at a speed of 600-800 rpm. After particles appear, the pH of the system is adjusted to 10.4-10.79 and a complexing agent is added until the particle size meets a preset value. The reaction is stopped to obtain the quasi-single crystal lithium-rich manganese-based positive electrode precursor. In the reaction system, the concentration of the complexing agent is 0.02-0.2 g / L, and the total concentration of the metal ions is 1.0-2.0 mol / L.

7. The preparation method according to claim 6, characterized in that When the D50 of the secondary particles of the particles is 0.6~1.0μm, the pH of the system is adjusted to 10.4~10.

79.

8. A single-crystal lithium-rich manganese-based positive electrode material, characterized in that: The quasi-single-crystal lithium-rich manganese-based positive electrode material is obtained by calcining a reaction system comprising the quasi-single-crystal lithium-rich manganese-based positive electrode precursor according to any one of claims 1 to 5, and the quasi-single-crystal lithium-rich manganese-based positive electrode material comprises quasi-single-crystal particles formed by primary particles having a particle size of 300 nm to 800 nm, and the quasi-single-crystal particles satisfy at least one of Formulas 8 to 11; 1.0μm≤D50<5.0μm Formula 8, 0.3μm≤Dmin<1.0μm Formula 9, 0.5m 2 / g≤α≤2.5m 2 / g Formula 10, 8.0μm≤Dmax<18.0μm Formula 11, Wherein, D50 is the median particle size of the quasi-single crystal particles, α is the specific surface area of ​​the quasi-single crystal particles, Dmin is the minimum particle size of the quasi-single crystal particles, and Dmax is the maximum particle size of the quasi-single crystal particles.

9. A positive electrode plate, characterized in that: Including the single-crystal-like lithium-rich manganese-based positive electrode material as described in claim 8.

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