Cathode material precursor, preparation method thereof, cathode material, lithium ion battery and electrical equipment

Abstract

The application provides a positive electrode material precursor, a preparation method of the positive electrode material precursor, a positive electrode material, a lithium ion battery and an electrical equipment. The positive electrode material precursor comprises secondary particles composed of a plurality of primary particles. The secondary particles comprise an inner layer, an intermediate layer and an outer layer from inside to outside. The porosity of the outer layer is greater than that of the inner layer, and the porosity of the inner layer is greater than that of the intermediate layer. The secondary particles of the positive electrode material precursor provided in the embodiments of the application have the structure of the inner layer being disordered, loose and porous, the intermediate layer being dense and having few pores, and the outer layer being loose and porous. The relatively loose inner layer and the outer layer are connected through the dense intermediate layer, the overall structural compression resistance of the secondary particles is improved, the structural stability is higher, and thus the problems of material cracking and pulverization can be avoided, and the cycle stability and safety performance of the positive electrode material are greatly improved.

Description

Technical Field

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

[0002] Lithium-ion batteries, as one of the representatives of clean energy, have many advantages such as high energy density, good safety, long cycle life, environmental friendliness and low cost. They are increasingly widely used in energy storage power systems such as hydropower, thermal power and solar power, as well as in portable electronic devices, electric vehicles, military equipment and aerospace.

[0003] The four main materials of a lithium-ion battery include the positive electrode, negative electrode, separator, and electrolyte. Among them, the positive electrode is the core component that determines its capacity, rate capability, lifespan, and safety. Currently, the main positive electrode materials that have been successfully developed and applied include lithium cobalt oxide (LCO), lithium iron phosphate (LFP), lithium manganese oxide (LMO), ternary materials such as lithium nickel cobalt manganese oxide (NCM), and lithium nickel cobalt aluminum oxide (NCA). Among these, ternary positive electrode materials, as a rising star, have advantages over LCO and LFP, including higher specific capacity, better cycle performance, and lower manufacturing costs.

[0004] Ternary cathode materials can almost completely inherit the internal structural characteristics of the precursor. Currently, with the development of high nickel content in ternary cathode material precursors, the specific capacity of the material has been significantly improved. However, the structural stability of the material is insufficient, and problems such as material cracking and pulverization are prone to occur, affecting the cycle life and safety of the battery. Summary of the Invention

[0005] This application aims to at least improve one of the technical problems existing in the prior art. To this end, this application provides a cathode material precursor and its preparation method, a cathode material, a lithium-ion battery, and an electrical device.

[0006] This application provides a cathode material precursor, comprising secondary particles composed of multiple primary particles. The secondary particles include an inner layer, an intermediate layer, and an outer layer from the inside out, wherein the porosity of the outer layer is greater than that of the inner layer, which in turn is greater than that of the intermediate layer.

[0007] The cathode material precursor provided in this application, through special control of different reaction conditions in three stages, possesses a core-shell structure consisting of an inner layer, an intermediate layer, and an outer layer from the inside out. Because the core-shell structure has significantly tunable physicochemical characteristics, it can strengthen the crystal lattice to a certain extent, control interfacial reactions, and adjust the contact area between the cathode material and the electrolyte, which is beneficial for improving the material's specific capacity, safety, and cycle performance. Specifically, in this application embodiment, the porosity of the inner layer is greater than that of the intermediate layer but less than that of the outer layer. That is, the secondary particles have a structure of disordered, loose, and porous inner layer, dense, less porous intermediate layer, and loose, porous outer layer. The dense intermediate layer connects the relatively loose inner and outer layers, improving the overall structural compressive strength of the secondary particles and resulting in higher structural stability. This avoids problems such as material cracking and pulverization, greatly enhancing the cycle stability and safety performance of the cathode material. Moreover, the porous inner layer can provide a buffer space for the stress generated by the expansion of the particles. When used to prepare lithium-ion batteries, it can prevent the rapid insertion and extraction of lithium ions from damaging the crystal structure, which is beneficial to reducing the diffusion resistance of lithium ions, thereby providing an effective lithium ion diffusion channel and improving the cycle stability and capacity performance of the material.

[0008] In some embodiments of this application, the precursor satisfies at least one of the following ag conditions:

[0009] a. The porosity difference between the inner layer and the intermediate layer is 1%-10%, optionally 2%-5%;

[0010] b. The porosity difference between the outer layer and the middle layer is 5%-20%, preferably 5.5%-15%;

[0011] c. The porosity difference between the outer layer and the inner layer is 2%-20%, optionally 3%-10%;

[0012] d. The porosity of the inner layer is 0.05%-10%, optionally 2.0%-4.5%;

[0013] e. The porosity of the intermediate layer is 0.01%-5%, optionally 0.05%-1.0%;

[0014] f. The porosity of the outer layer is 5.0%-20.0%, optionally 6%-12%;

[0015] g. The cathode material precursor also includes a hollow layer, and the precursor consists of a hollow layer, an inner layer, a middle layer and an outer layer from the inside out.

[0016] In some embodiments of this application, the precursor satisfies at least one of the following conditions:

[0017] h. The radius of the hollow layer is 0.5-1.5 μm;

[0018] i. The thickness of the inner layer is 0.8-1.8 μm;

[0019] j. The thickness of the intermediate layer is 1.3-2.1 μm;

[0020] k. The thickness of the outer layer is 1.2-3.7 μm;

[0021] 1. On the cross-section of the secondary particles, the area ratio S1 of the intermediate layer to the inner layer is 1.3-2.5;

[0022] m. On the cross-section of the secondary particle, the area ratio S2 of the outer layer to the middle layer is 1.0-3.0.

[0023] In some embodiments of this application, the precursor satisfies at least one of the following conditions (1)-(11):

[0024] (1) The secondary particles are spherical or near-spherical, and the primary particles constituting the outer layer are dendritic or elongated; optionally, the average length-to-width ratio of the primary particles constituting the outer layer is 5-11.

[0025] (2) The D50 of the secondary particles is 9.0-14.0 μm;

[0026] (3) The particle size distribution span value of the secondary particles is 0.5-1.0;

[0027] (4) The particle fragmentation of the secondary particles is 10.0%-21.5%;

[0028] (5) The specific surface area of ​​the secondary particles is 7.5-16.5 m². 2 / g;

[0029] (6) The tap density of the secondary particles is 1.7-2.3 g / cm³. 3 ;

[0030] (7) The full width at half maximum (FWHM) α of the characteristic peak of the (001) crystal plane of the precursor is 0.2-0.6°, optionally 0.3-0.55°, optionally 0.40-0.47°;

[0031] (8) The full width at half maximum (FWHM) β of the characteristic peak of the (101) crystal plane of the precursor is 0.2-0.6°, optionally 0.3-0.58°, optionally 0.52-0.56°;

[0032] (9) The ratio of the half-width β of the characteristic peak of the (101) crystal plane of the precursor to the half-width α of the characteristic peak of the (001) crystal plane is β / α = 1.0-1.3, and can be 1.10-1.22.

[0033] (10) The peak intensity ratio I between the characteristic peak of the (001) crystal plane of the precursor and the characteristic peak of the (101) crystal plane of the precursor. 001 / I 101 It is 1.4-1.7;

[0034] (11) The general chemical formula of the precursor is Ni x Co y M 1-x-y (OH)2, where 0.8≤x<1, 0<y≤0.2, and M is at least one of Mn, Al, Zr, Ti, Cr, Mo, W, B, Ba, Nb and Sr.

[0035] In other embodiments of this application, a method for preparing the cathode material precursor is also provided, comprising the following steps:

[0036] Seed crystals are obtained by mixing a metal salt solution with a precipitant and a complexing agent to carry out a first reaction.

[0037] The seed crystals were mixed with a metal salt solution, a precipitant, and a complexing agent to carry out a second reaction, yielding a reaction product with a particle size D50 of 9.0-14.0 μm.

[0038] The reaction products were post-processed to obtain the cathode material precursor.

[0039] In some embodiments of this application, the preparation method satisfies at least one of the following conditions (1)-(4):

[0040] (1) The metal salt includes soluble salts of nickel, cobalt and / or manganese; optionally, the soluble salt includes at least one of sulfate, nitrate, acetate and chloride.

[0041] (2) The total concentration of metal ions in the metal salt solution is 1-5 mol / L;

[0042] (3) The precipitant includes at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide; optionally, the concentration of the precipitant is 2-20 mol / L;

[0043] (4) The complexing agent includes at least one of ammonia, ammonium bicarbonate solution, ammonium carbonate solution, EDTA, ethylenediamine, sodium citrate and urea; optionally, the complexing agent is ammonia with a mass fraction of 15-35%.

[0044] In some embodiments of this application, the preparation method satisfies at least one of the following conditions ①-⑦:

[0045] ① The reaction temperature of the first reaction is 55-85℃; the reaction temperature of the second reaction is 55-85℃;

[0046] ② The reaction temperature of the second reaction is higher than that of the first reaction. Optionally, the endpoint reaction temperature of the second reaction is higher than the initial reaction temperature. Optionally, the endpoint reaction temperature of the second reaction is 10-20°C higher than the initial reaction temperature.

[0047] ③ The pH value of the reaction system for the first reaction and the second reaction is 10.50-12.10;

[0048] ④ The complexing agent includes ammonia water, and the ammonia concentration in the first reaction and the second reaction is 5.0-12.6 g / L;

[0049] ⑤ During the first and second reactions, the feed flow rate of the metal salt solution is 100 L / h - 700 L / h;

[0050] ⑥ During the second reaction process, the feed flow rate of the metal salt solution gradually increases over time;

[0051] ⑦ Both the first and second reactions are carried out under stirring, and the stirring speed is 100-240 r / min.

[0052] In some other embodiments of this application, a cathode material is also provided, which is prepared from the cathode material precursor described above.

[0053] In other embodiments of this application, a lithium-ion battery is also provided, which is prepared from the above-described positive electrode material.

[0054] Other embodiments of this application also provide an electrical device, including the lithium-ion battery described above.

[0055] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0056] To more clearly illustrate the specific embodiments of this application or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0057] Figure 1 SEM image of the precursor prepared in Example 1 of this application;

[0058] Figure 2 The CP diagram of the precursor prepared in Example 1 of this application;

[0059] Figure 3SEM image of the precursor prepared in Example 2 of this application;

[0060] Figure 4 The CP diagram of the precursor prepared in Example 2 of this application;

[0061] Figure 5 SEM image of the precursor prepared in Example 3 of this application;

[0062] Figure 6 The CP diagram of the precursor prepared in Example 3 of this application;

[0063] Figure 7 SEM image of the precursor prepared in Example 4 of this application;

[0064] Figure 8 The CP diagram of the precursor prepared in Example 4 of this application;

[0065] Figure 9 Here is a SEM image of the precursor prepared in Comparative Example 1 of this application;

[0066] Figure 10 Here is the CP diagram of the precursor prepared in Comparative Example 1 of this application;

[0067] Figure 11 Here is a SEM image of the precursor prepared in Comparative Example 2 of this application;

[0068] Figure 12 Here is the CP diagram of the precursor prepared in Comparative Example 2 of this application;

[0069] Figure 13 Here is a SEM image of the precursor prepared in Comparative Example 3 of this application;

[0070] Figure 14 The CP diagram is of the precursor prepared in Comparative Example 3 of this application. Detailed Implementation

[0071] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0072] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0073] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0074] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, optionally sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0075] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0076] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0077] In this application, D50 refers to the particle size corresponding to a cumulative volume distribution percentage of secondary particles in the cathode material precursor reaching 50% or more; D95 refers to the particle size corresponding to a cumulative volume distribution percentage of secondary particles in the cathode material precursor reaching 95% or more; and D5 refers to the particle size corresponding to a cumulative volume distribution percentage of secondary particles in the cathode material precursor reaching 5% or more.

[0078] Pure water generally refers to water with an electrical conductivity of less than or equal to 10 μS / cm, total organic carbon of less than or equal to 20 mg / L, metal ions (Na, K, Ca, Mg, etc.) of less than or equal to 1000 μg / L, and other ions (Cl, NO3-) of less than or equal to 1000 μg / L. - Water with a concentration of less than or equal to 2000 μg / L.

[0079] This application provides a cathode material precursor, including secondary particles composed of multiple primary particles. The secondary particles include an inner layer, an intermediate layer, and an outer layer from the inside out, with the porosity of the outer layer > the porosity of the inner layer > the porosity of the intermediate layer.

[0080] The cathode material precursor provided in this application has a core-shell structure, consisting of an inner layer, a middle layer, and an outer layer from the inside out. Due to the significantly tunable physicochemical characteristics of the core-shell structure, it can strengthen the crystal lattice to a certain extent, control interfacial reactions, and adjust the contact area between the cathode material and the electrolyte, which is beneficial for improving the material's specific capacity, safety, and cycle performance. Specifically, in this application embodiment, the porosity of the inner layer is greater than that of the middle layer but less than that of the outer layer. That is, the secondary particles have a structure of disordered, loose, and porous inner layer, dense, less porous middle layer, and loose, porous outer layer. The dense middle layer connects the relatively loose inner and outer layers, improving the overall structural compressive strength of the secondary particles and increasing structural stability. This avoids problems such as material cracking and pulverization, greatly improving the cycle stability and safety performance of the cathode material. Moreover, the porous inner layer can provide a buffer space for the stress generated by the expansion of the particles. When used to prepare lithium-ion batteries, it can prevent the rapid insertion and extraction of lithium ions from damaging the crystal structure, which is beneficial to reducing the diffusion resistance of lithium ions, thereby providing an effective lithium ion diffusion channel and improving the cycle stability and capacity performance of the material.

[0081] Furthermore, the spherical or near-spherical shape of the secondary particles can effectively avoid the problem of secondary particles easily agglomerating or breaking into micro powder, and can also improve the filling capacity of active materials in the positive electrode, which is beneficial to improving the energy density of the positive electrode material.

[0082] To evaluate the characteristics of porosity, this application uses image analysis software (ImageJ) to directly calculate the pore area and cross-sectional area of ​​the CP image. The porosity of different regions is calculated by "porosity = pore area of ​​each region / cross-sectional area of ​​each region × 100%". The porosity in this paper is characterized by this method. The magnification of the CP image is 8000 to 10000 times.

[0083] It should be noted that, in order to evaluate the characteristics of the inner, intermediate, and outer layers of the secondary particles, this application can divide the secondary particles into multiple rings from the inside out based on the CP diagram. For secondary particles with hollow layers, the midpoint of the longest axis of the hollow layer is taken as the center, and half of the longest axis is taken as the radius to draw a circle. The inner region of the first circle is considered as the hollow layer. Then, the division is carried out from the hollow layer outwards. The thickness between each ring is 0.2 micrometers. The porosity difference Δ between adjacent ring regions is calculated. If Δ ≥ 0.5, the circle at the junction of two adjacent rings is taken as the boundary of different layers. The region between the hollow layer and the inside of this circle is considered as the inner layer. Using this method, the calculation is carried out outwards to find the second Δ ≥ 0.5. The region from the inner layer outwards to the inside of the second boundary circle is considered as the intermediate layer. Then, the region from the largest ring of the intermediate layer to the surface layer is collectively referred to as the outer layer. For secondary particles without hollow layers, the midpoint of the longest axis of the entire secondary particle is taken as the center, and multiple rings are divided from the inside out. The layering method for the inner, middle, and outer layers is the same as described above. This application can divide the CP diagram of secondary particles into inner, middle, and outer layers according to the above method, as shown in the appendix to the specification. Figure 2 , 4 As shown in 6, 8, 10 and 12, 14.

[0084] It should also be noted that, in order to evaluate the characteristics of the cross-sectional structure (CP) of the secondary particles, in the embodiments of this application, when determining the physicochemical properties of the cathode material precursor, the prepared precursor particles were first vacuum-embedded on conductive adhesive, then the particles were cut, and finally the cut precursor powder was photographed by scanning electron microscopy to obtain the final CP image. The CP images in this article are all obtained according to the method described here.

[0085] In some embodiments, the porosity difference between the inner layer and the intermediate layer is 1%-10%, optionally 2%-5%. Optionally, the porosity difference between the inner layer and the intermediate layer can be any value among 1.5%, 3.5%, 5.5%, 7.5%, 9.5%, and 1%-10%.

[0086] In some embodiments, the porosity difference between the outer layer and the intermediate layer is 5%-20%, optionally 5.5%-15%. Optionally, the porosity difference between the outer layer and the intermediate layer can be any value among 6%, 8%, 10%, 12%, 14%, 16%, 18%, and 5%-20%.

[0087] In some embodiments, the porosity difference between the outer layer and the inner layer is 2%-20%, optionally 3%-10%. Optionally, the porosity difference between the outer layer and the inner layer can be any value among 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, and 2%-20%.

[0088] Under at least one of the above-mentioned suitable porosity ranges, the precursor particles can provide sufficient support for the inner and outer layers, improve the strength of the material, and at the same time facilitate the penetration of electrolyte into the interior of the material, thus facilitating the utilization of capacity.

[0089] In some embodiments, the porosity of the inner layer is 0.05%-10%, optionally 2.0%-4.5%. Optionally, the porosity of the inner layer can be any value among 1%, 2%, 3%, 4%, 6%, 6%, 7%, 8%, 9% and 0.05%-10%.

[0090] In some embodiments, the porosity of the intermediate layer is 0.01%-5%, optionally 0.05%-1.0%. Optionally, the porosity of the intermediate layer can be any value among 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.8%, 2%, 3%, 4%, and 0.01%-5%.

[0091] In some embodiments, the porosity of the outer layer is 5.0%-20.0%, optionally 6%-12%. Optionally, the porosity of the outer layer can be any value among 7%, 8%, 9%, 10%, 14%, 15%, 16%, 17%, 19%, and 5.0%-20.0%.

[0092] Under at least one of the above-mentioned suitable porosity ranges, the precursor particles are not prone to cracking, have high compressive strength, and can improve the cycle stability and safety performance of the material while maintaining high specific capacity.

[0093] In some embodiments, the cathode material precursor further includes a hollow layer, and the precursor consists of a hollow layer, an inner layer, a middle layer, and an outer layer from the inside out. This increases the contact area between the particle and the electrolyte, and provides a buffer space for the corresponding cathode material to undergo volume changes during charging and discharging, thereby ensuring the structural stability of the cathode material and facilitating a balance between rate performance and cycle performance.

[0094] In some embodiments, the radius of the hollow layer is 0.5-1.5 μm.

[0095] In some embodiments, the thickness of the inner layer is 0.8-1.8 μm; the thickness of the middle layer is 1.3-2.1 μm; and the thickness of the outer layer is 1.2-3.7 μm.

[0096] By controlling the radius of the hollow layer of the hollow structure to be 0.5-1.5μm, and the thickness of the inner, middle and outer layers to be within the above range, the hollow structure can provide abundant and favorable channels for the rapid extraction and insertion of lithium ions, thereby increasing the contact area with the electrolyte. At the same time, it can also provide a buffer space when volume changes occur during charging and discharging, providing a better platform for high-current charging and discharging.

[0097] It should be noted that since the secondary particles of the precursor are not necessarily regular spheres, when determining the radius of the hollow layer, it is necessary to first convert the hollow layer into a quasi-spherical body with equal area, that is, the actual area of ​​the hollow layer is equal to the area of ​​the sphere, and then calculate the diameter of the sphere to obtain the diameter of the hollow layer.

[0098] To achieve a balanced relationship between the hollow layer, inner layer, intermediate layer, and outer layer, thus facilitating the acquisition of structurally stable secondary particles, in some embodiments, the area ratio S1 between the intermediate layer and the inner layer is controlled to be 1.3-2.5, and the area ratio S2 between the outer layer and the intermediate layer is controlled to be 1.0-3.0 in the cross-section of the secondary particle. It should be understood that the cross-section of the secondary particle can be any cross-section, optionally passing through the center of the secondary particle. The area ratios S1 and S2 can further regulate the thickness relationship of each layer, which is beneficial for further improving the overall structural stability of the secondary particle and thus enhancing the cycle performance of the cathode material.

[0099] In some embodiments, the secondary particles are spherical or near-spherical, and the primary particles constituting the outer layer are dendritic or elongated. The primary particles constituting the outer layer are elongated, thicker in the middle and thinner at both ends, growing radially on the surface of the secondary particles and intersecting in a dendritic pattern. This allows the primary particles to support each other, resulting in better compressive strength and higher structural stability of the secondary particles. It can effectively avoid problems such as surface cracking and breakage of the secondary particles and improve circulation performance.

[0100] In some embodiments, the average aspect ratio (length to width ratio) of the primary particles constituting the outer layer is 5-11. This is beneficial for further enhancing the overall compressive strength of the secondary particles, while providing short-range channels for lithium-ion insertion, thereby improving the electrochemical performance of the cathode material, such as rate performance and cycle performance.

[0101] It should be noted that, to evaluate the aspect ratio of primary particles, Nano Measurer software was used to measure the length and width of primary particles on the surface of secondary particles in SEM images at magnifications of 10000–5000x. The longest axis of a single primary particle was considered its length, and the minor axis measured perpendicular to the midpoint of the longest axis was considered its width. At least 10 sets of data for a single primary particle were collected, and the average value was calculated to obtain the average width and average length of the primary particles, and then the average aspect ratio was calculated. This can be done by taking data from several SEM images (e.g., 5 images) and then averaging them. The length and width of primary particles in this paper were obtained using this method.

[0102] In some embodiments, the particle size distribution span of the secondary particles is 0.7-1.0, where span = (D95-D5) / D50. Within this particle size distribution range in this embodiment, the compressive strength of the precursor particles can be further improved, thereby enhancing the cycle performance of the cathode material.

[0103] In some embodiments, the particle fragmentation degree of the secondary particles is 10.0%-21.5%; wherein, the particle fragmentation degree is measured using the "particle size distribution change rate under 2.5 MPa pressure" method. Within the particle fragmentation degree range of this embodiment, the structural strength of the corresponding precursor is enhanced, and the compressive strength of the particles is improved, thereby reducing the probability of side reactions during the charging and discharging process caused by particle breakage and effectively improving battery safety performance.

[0104] The particle fragmentation test method in this application is as follows: Accurately weigh 2.0g of the sample to be tested and load it into the thickness gauge mold. Set the pressure gauge to 2.5MPa, tighten the pressure control knob, hold the brake lever for 30s, slowly remove the sample, redisperse it, and measure the volumetric particle size and compacted density. Simultaneously, detect the uncompacted particle size and compacted density. Combine the particle size volume distribution and compacted density before and after compaction to calculate the particle size distribution change rate. In other words, the particle's compressive strength is indirectly reflected by the particle size distribution change rate. Generally, the smaller the particle size distribution change rate, the smaller the particle fragmentation, and the higher the particle strength.

[0105] Furthermore, adjusting the specific surface area and tap density of the secondary particles can also improve the performance of the precursor. In some embodiments, the specific surface area (BET) of the secondary particles is 7.5-16.5 m². 2 / g; By controlling the specific surface area within a suitable range, the secondary particles are less likely to undergo side reactions with the electrolyte. In some embodiments, the tap density (TD) of the secondary particles is 1.7-2.3 g / cm³. 3 By controlling the tap density within a suitable range, it is beneficial to improve the energy density of the cathode material.

[0106] In some embodiments, the full width at half maximum (FWHM) α of the characteristic peak of the (001) crystal plane of the precursor is 0.2-0.6°, optionally 0.30-0.55°, optionally 0.40-0.47°; the FWHM β of the characteristic peak of the (101) crystal plane of the precursor is 0.2-0.6°, optionally 0.30-0.58°, optionally 0.52-0.56°; the ratio of the FWHM β of the characteristic peak of the (101) crystal plane of the precursor to the FWHM α of the characteristic peak of the (001) crystal plane, β / α, is 1.0-1.3, optionally 1.1-1.22. The peak intensity ratio I of the characteristic peak of the (001) crystal plane of the precursor to the characteristic peak of the (101) crystal plane of the precursor is... 001 / I 101 It is 1.4-1.7.

[0107] The full width at half maximum (FWHM) of the (001) and (101) crystal planes of the precursor are within the above range, and the peak intensity ratio I 001 / I 101 The value is 1.4-1.7, indicating that the (001) crystal plane has a high diffraction intensity. The precursor grows preferentially on the (001) crystal plane, has good crystallinity, and the cathode material has better cycle stability.

[0108] In some embodiments, the precursor has the general chemical formula Ni x Co y M 1-x-y (OH)₂, where 0.8 ≤ x < 1, 0 < y ≤ 0.15, and M is at least one of Mn, Al, Zr, Ti, Cr, Mo, W, B, Ba, Nb, and Sr. The precursor provided in this embodiment is a high-nickel product, and the corresponding cathode material has advantages such as good cycle performance, high energy density, stability, and safety performance.

[0109] Another embodiment of this application provides a method for preparing a cathode material precursor, comprising the following steps: mixing a metal salt solution with a precipitant and a complexing agent to carry out a first reaction to obtain seed crystals; mixing the seed crystals with a metal salt solution, a precipitant and a complexing agent to carry out a second reaction to obtain a reaction product with a particle size D50 of 9.0-14.0 μm; and post-processing the reaction product to obtain a cathode material precursor.

[0110] According to the preparation method provided in the embodiments of this application, a cathode material precursor is prepared by co-precipitation under the specific steps and conditions described above. The obtained cathode material precursor includes secondary particles composed of multiple primary particles. The secondary particles are spherical or near-spherical and include an inner layer, a middle layer, and an outer layer from the inside out. The porosity of the inner layer is greater than that of the middle layer and less than that of the outer layer. That is, the obtained precursor particles have a structure of disordered, loose, and porous inner layer, dense and less porous middle layer, and loose and porous outer layer. This is beneficial to improving the overall structural compressive strength of the precursor particles and the structural stability. The corresponding cathode material has good cycle stability, safety performance, specific capacity, and other properties.

[0111] In some embodiments, the metal salt includes soluble salts of nickel, cobalt, and / or manganese; optionally, the soluble salt includes at least one of sulfates, nitrates, acetates, and chlorides. For example, a nickel-cobalt-manganese ternary cathode material precursor can be prepared using metal salts containing nickel, cobalt, and manganese.

[0112] In some embodiments, the total concentration of metal ions in the metal salt solution is 1-5 mol / L; the precipitant includes at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide; optionally, the concentration of the precipitant is 2-20 mol / L; the complexing agent includes at least one of ammonia, ammonium bicarbonate solution, ammonium carbonate solution, EDTA, ethylenediamine, sodium citrate, and urea; optionally, the complexing agent is ammonia with a mass fraction of 15-35%.

[0113] In some embodiments, the reaction temperature of the first reaction is 55-85°C; the reaction temperature of the second reaction is 55-85°C;

[0114] In some embodiments, the reaction temperature of the second reaction is higher than that of the first reaction. Optionally, the endpoint reaction temperature of the second reaction is higher than the initial reaction temperature, and optionally, the endpoint reaction temperature of the second reaction is 10-20°C higher than the initial reaction temperature. More preferably, the reaction temperature of the second reaction varies with a time gradient, for example, the heating rate can be maintained at about 1°C / 10min. By designing a reaction temperature gradient change and increasing the reaction temperature and other conditions of the outer layer of the precursor, the growth arrangement of the primary particles in the outer layer can be adjusted to achieve a cross-distribution of primary particles, forming a porous structure while strengthening the compressive strength of the outer layer. This helps to solve the problem of large particles being brittle and prone to cracking in medium-high nickel ternary precursors and improves the rate performance of the cathode material.

[0115] In some embodiments, the pH value of the reaction system for the first and second reactions is 10.50-12.10; the complexing agent includes ammonia water, and the ammonia concentration in the first and second reactions is 5.0-12.6 g / L. By controlling the pH value and ammonia concentration of the reaction system within the above-mentioned suitable ranges, it is beneficial to prepare precursor particles with a disordered, loose, and porous inner layer, a dense, low-porosity middle layer, and a loose, porous outer layer.

[0116] In some embodiments, during the first and second reactions, the feed flow rate of the metal salt solution is 300 L / h to 700 L / h; optionally, during the second reaction, the feed flow rate of the metal salt solution gradually increases over time; more preferably, the feed flow rate of the metal salt solution varies with a time gradient. By controlling the flow rate of the metal salt solution within the above-mentioned suitable range, it is beneficial to prepare a cathode material precursor that meets the target requirements.

[0117] In some embodiments, both the first and second reactions are carried out under stirring conditions, and the stirring speed is 100-240 r / min, which is beneficial for preparing a cathode material precursor that meets the target requirements.

[0118] In some embodiments, the average particle size D50 of the seed crystals obtained in the first reaction is 3-4 μm. In this case, after obtaining the seed crystals through the first reaction, changing the reaction conditions to carry out the second reaction is beneficial to obtaining a cathode material precursor with disordered and loose porous inner layer, dense and less porous middle layer, and loose and porous outer layer.

[0119] According to another embodiment of this application, a cathode material is provided, which is made using the above-described cathode material precursor. For example, the cathode material precursor in the above embodiment can be mixed with a lithium salt and then sintered to prepare the cathode material. The resulting cathode material can be directly used to prepare lithium-ion batteries and electrical devices.

[0120] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all reagents and raw materials used in the embodiments are commercially available or synthesized by conventional methods, and the instruments used in the embodiments are also commercially available.

[0121] Example 1

[0122] This embodiment provides a method for preparing a cathode material precursor, including the following steps:

[0123] (1) Raw material preparation:

[0124] Metal salt solution: Select raw materials NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O, and prepare a metal salt solution with a total metal ion concentration of 2 mol / L according to the molar ratio of nickel, cobalt and manganese of 0.89:0.07:0.04.

[0125] Precipitant: 10.8 mol / L sodium hydroxide aqueous solution is selected.

[0126] Complexing agent: Use a 20% (w / w) ammonia solution.

[0127] (2) First reaction:

[0128] Under nitrogen protection, start stirring and add 5.0 m³ of [unspecified substance] to reactor (I). 3 Pure water was used, and a precipitant and complexing agent were added to adjust the ammonia concentration to 10.8 g / L and the pH to 11.90. The reaction temperature in the reactor (I) was raised to 60°C, and the stirring speed was controlled at 240 r / min. After the conditions were met, the metal salt solution, precipitant, and complexing agent were simultaneously introduced to carry out the first reaction. At the beginning of the reaction, the flow rate of the metal salt solution was controlled at 300 L / h, and the flow rates of the precipitant and complexing agent were adjusted accordingly to maintain the pH at 11.90. After maintaining this for a certain period of time, the flow rates of the precipitant and complexing agent were adjusted to lower the pH to the final pH of 10.95, resulting in seed crystals with a particle size D50 of 3.2 μm. The obtained seed crystals included the inner layer of the precursor.

[0129] (3) Second reaction:

[0130] Under nitrogen protection, start stirring and add 5m of [unclear] into reactor (II). 3 Pure water was added quantitatively to 140 kg of the dehydrated dry base material of the above-mentioned seed crystals. Under stirring conditions of 240 r / min, precipitant and complexing agent were added to adjust the ammonia concentration to 8.3 g / L and the pH value to 10.85. The reaction temperature in the reactor (II) was raised to 60℃, and the metal salt solution, precipitant and complexing agent were introduced to carry out the second reaction. During the second reaction, the pH value was maintained at 10.85 throughout the reaction by adjusting the flow rate of precipitant and complexing agent. The metal salt solution was fed at a flow rate of 100 L / h. When the temperature of the reaction system T1 = 60℃, an intermediate was obtained, which included the inner layer and intermediate layer of the precursor. Then the flow rate of the metal salt solution was increased to the final flow rate of 700 L / h, and the temperature of the reaction system was increased to T2 = 75℃ at a heating rate of 1℃ / 10 min until the reaction product with a particle size D50 of 10.5 μm was obtained. The reaction product included the inner layer, intermediate layer and outer layer of the precursor.

[0131] (4) Post-processing: The reaction product obtained from the second reaction is centrifuged, washed, dried, sieved, and demagnetized to obtain the chemical formula Ni. 0.89 Co0.07 Mn 0.04 The ternary cathode material precursor of (OH)₂, with a span of 0.81, is shown in Table 1 for XRD diffraction results and microstructure as follows. Figure 1 and Figure 2 As shown, the secondary particles of the obtained cathode material precursor are spherical or near-spherical, and the outer primary particles grow in a strip-like or dendritic pattern on the surface of the secondary particles.

[0132] Example 2

[0133] This embodiment provides a method for preparing a cathode material precursor, including the following steps:

[0134] (1) Raw material preparation:

[0135] Metal salt solution: Select raw materials NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O, and prepare a metal salt solution with a total metal ion concentration of 2 mol / L according to the molar ratio of nickel, cobalt and manganese of 0.85:0.10:0.05.

[0136] Precipitant: 10.8 mol / L sodium hydroxide aqueous solution is selected.

[0137] Complexing agent: Use a 20% (w / w) ammonia solution.

[0138] (2) First reaction:

[0139] Under nitrogen protection, start stirring and add 5.0 m³ of [unspecified substance] to reactor (I). 3 Pure water was used, and a precipitant and complexing agent were added to adjust the ammonia concentration to 12.5 g / L and the pH to 12.0. The reaction temperature in the reactor (I) was raised to 60°C, and the stirring speed was controlled at 240 r / min. After the conditions were met, the metal salt solution, precipitant, and complexing agent were simultaneously introduced to carry out the first reaction. At the beginning of the reaction, the flow rate of the metal salt solution was controlled at 300 L / h, and the flow rates of the precipitant and complexing agent were adjusted accordingly to maintain the pH at 12.0. After maintaining this for a certain period of time, the flow rates of the precipitant and complexing agent were adjusted to lower the pH to the final pH of 11.25. The reaction system temperature was maintained at T1 = 60°C to obtain seed crystals with a particle size D50 of 3.8 μm. The obtained seed crystals included the inner layer of the precursor.

[0140] (3) Second reaction (continuous with the first reaction):

[0141] Based on the first reaction, after obtaining the seed crystals, the process was adjusted, and the flow rate of the metal salt solution was adjusted to 400 L / h to initiate the second reaction. During the second reaction, the pH value was maintained at 10.80 throughout the reaction by adjusting the flow rates of the precipitant and complexing agent, and the flow rate of the metal salt solution was gradually increased to the final flow rate of 700 L / h. At the same time, the temperature of the reaction system was increased at a rate of 1℃ / 10min until the final temperature of T2 = 75℃ was reached, until a reaction product with a particle size D50 of 10.8 μm was obtained. The obtained reaction product includes the inner, middle, and outer layers of the precursor.

[0142] (4) Post-processing: The reaction product obtained from the second reaction is centrifuged, washed, dried, sieved, and demagnetized to obtain the chemical formula Ni. 0.85 Co 0.10 Mn 0.05 The ternary cathode material precursor of (OH)₂ has a span of 0.86. The XRD diffraction results are shown in Table 1, and the microstructure is as follows: Figure 3 and Figure 4 As shown, the secondary particles of the obtained cathode material precursor are spherical or near-spherical, and the outer primary particles grow in a strip-like or dendritic pattern on the surface of the secondary particles.

[0143] Example 3

[0144] This embodiment provides a method for preparing a cathode material precursor, including the following steps:

[0145] (1) Raw material preparation:

[0146] Metal salt solution: Select raw materials NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O, and prepare a metal salt solution with a total metal ion concentration of 2 mol / L according to the molar ratio of nickel, cobalt and manganese of 0.86:0.08:0.06.

[0147] Precipitant: 10.8 mol / L sodium hydroxide aqueous solution is selected.

[0148] Complexing agent: Use a 20% (w / w) ammonia solution.

[0149] (2) First reaction:

[0150] Under nitrogen protection, start stirring and add 5.0 m³ of [unspecified substance] to reactor (I). 3Pure water was used, and a precipitant and complexing agent were added to adjust the ammonia concentration to 5.5 g / L and the pH to 12.0. The reaction temperature in the reactor (I) was raised to 60°C, and the stirring speed was controlled at 240 r / min. After the conditions were met, the metal salt solution, precipitant, and complexing agent were simultaneously introduced to carry out the first reaction. At the beginning of the reaction, the flow rate of the metal salt solution was controlled at 100 L / h. During the reaction, the flow rate of the metal salt solution was gradually increased to 400 L / h at the end of the reaction. Correspondingly, the flow rates of the precipitant and complexing agent were also gradually increased until the pH value at the end of the reaction was 11.20, resulting in seed crystals with a particle size D50 of 3.6 μm, which included the inner layer of the precursor.

[0151] (3) Second reaction:

[0152] Under nitrogen protection, start stirring and add 5m of [unclear] into reactor (II). 3 Pure water was added in a measured amount of 120 kg of the dehydrated dry base material of the above-mentioned seed crystals. Under stirring conditions of 240 r / min, precipitant and complexing agent were added to adjust the ammonia concentration to 8.0 g / L and the pH value to 10.85. The reaction temperature in the reactor (II) was raised to T1 = 60℃, and the metal salt solution, precipitant and complexing agent were introduced to carry out the second reaction. In the second reaction process, the pH value was maintained at 10.85 throughout the reaction by adjusting the flow rates of the precipitant and complexing agent. The metal salt solution was fed at a flow rate of 100 L / h. After the pH value of the reaction system stabilized (at which point the inner and middle layers of the precursor were obtained), the flow rate of the metal salt solution was increased to 200 L / h. At the same time, the temperature of the reaction system was increased to T2 = 75℃ at a heating rate of 1℃ / 10min. Subsequently, the flow rate of the metal salt solution was gradually increased over time until the flow rate of the metal salt solution reached 600 L / h at the end of the reaction, resulting in a reaction product with a particle size D50 of 10.3 μm. The obtained reaction product included the inner, middle and outer layers of the precursor.

[0153] (4) Post-processing: The reaction product obtained from the second reaction is centrifuged, washed, dried, sieved, and demagnetized to obtain the chemical formula Ni. 0.86 Co 0.08 Mn 0.06 The ternary cathode material precursor of (OH)₂, with a span of 0.88, is shown in Table 1 for XRD diffraction results and microstructure as follows. Figure 5 and Figure 6 As shown, the secondary particles of the obtained cathode material precursor are spherical or near-spherical, and the outer primary particles grow in a strip-like or dendritic pattern on the surface of the secondary particles.

[0154] Example 4

[0155] This embodiment provides a method for preparing a nickel-cobalt-manganese ternary cathode material precursor, including the following steps:

[0156] (1) Raw material preparation:

[0157] Metal salt solution: Select raw materials NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O, and prepare a metal salt solution with a total metal ion concentration of 2 mol / L according to the molar ratio of nickel, cobalt and manganese of 0.88:0.07:0.05.

[0158] Precipitant: 10.8 mol / L sodium hydroxide aqueous solution is selected.

[0159] Complexing agent: Use a 20% (w / w) ammonia solution.

[0160] (2) First reaction:

[0161] Under nitrogen protection, start stirring and add 5.0 m³ of [unspecified substance] to reactor (I). 3 Pure water was used, and a precipitant and complexing agent were added to adjust the ammonia concentration to 6.5 g / L and the pH to 12.05. The reaction temperature in the reactor (I) was raised to 60℃, and the stirring speed was controlled at 240 r / min. After the conditions were met, the metal salt solution, precipitant, and complexing agent were simultaneously introduced to carry out the first reaction. At the beginning of the reaction, the flow rate of the metal salt solution was controlled at 100 L / h. During the reaction, the flow rate of the metal salt solution was gradually increased to 300 L / h at the end of the reaction. Correspondingly, the flow rates of the precipitant and complexing agent were also gradually increased until the pH value at the end of the reaction was 11.50, resulting in seed crystals with a particle size D50 of 3.0 μm, which included the inner layer of the precursor.

[0162] (3) Second reaction:

[0163] Under nitrogen protection, start stirring and add 5m of [unclear] into reactor (II). 3 Pure water was added in a measured amount of 90 kg of the dehydrated dry base material of the above-mentioned seed crystals. Under stirring conditions of 240 r / min, precipitant and complexing agent were added to adjust the ammonia concentration to 8.5 g / L and the pH value to 10.55. The reaction temperature in the reactor (II) was raised to T1 = 60℃, and the metal salt solution, precipitant and complexing agent were introduced to carry out the second reaction. In the second reaction process, the pH value was maintained at 10.65 throughout the reaction by adjusting the flow rates of the precipitant and complexing agent. The metal salt solution was fed at a flow rate of 100 L / h. After the pH value of the reaction system stabilized (at which point the inner and middle layers of the precursor were obtained), the flow rate of the metal salt solution was increased to 200 L / h. At the same time, the temperature of the reaction system was increased to T2 = 75℃ at a heating rate of 1℃ / 10min. Subsequently, the flow rate of the metal salt solution was gradually increased over time until the flow rate of the metal salt solution reached 600 L / h at the end of the reaction, and a reaction product with a particle size D50 of 10.8 μm was obtained. The obtained reaction product included the inner, middle and outer layers of the precursor.

[0164] (4) Post-processing: The reaction product obtained from the second reaction is centrifuged, washed, dried, sieved, and demagnetized to obtain the chemical formula Ni. 0.88 Co 0.07 Mn 0.05 The ternary cathode material precursor of (OH)₂ has a span of 0.92. The XRD diffraction results are shown in Table 1, and the microstructure is as follows: Figure 7 and Figure 8 As shown, the secondary particles of the obtained cathode material precursor are spherical or near-spherical, and the outer primary particles grow in a strip-like or dendritic pattern on the surface of the secondary particles.

[0165] Comparative Example 1

[0166] The difference from Example 1 lies in the reaction conditions of the second reaction process. The second reaction in this comparative example specifically includes the following steps:

[0167] Under nitrogen protection, start stirring and add 5m of [unclear] into reactor (II). 3 Pure water was added in a measured amount of 140 kg of the dehydrated dry substrate containing the above-mentioned seed crystals. Under stirring at 240 r / min, a precipitant and a complexing agent were added to adjust the ammonia concentration to 8.0 g / L and the pH to 10.85. A metal salt solution, precipitant, and complexing agent were then introduced to initiate the second reaction. During the second reaction, the pH was maintained at 10.70 throughout the reaction by adjusting the flow rates of the precipitant and complexing agent. The reaction temperature was maintained at 55℃. The metal salt solution was fed at a flow rate of 100 L / h. After the pH of the reaction system stabilized, the flow rate of the metal salt solution was increased to 200 L / h, and then gradually increased over time until the final flow rate reached 700 L / h, until a reaction product with a particle size D50 of 10.5 μm was obtained.

[0168] The reaction product obtained from the second reaction was centrifuged, washed, dried, sieved, and demagnetized to obtain a product with the chemical formula Ni. 0.89 Co 0.07 Mn 0.04 The ternary cathode material precursor of (OH)₂ has a span of 0.93. The XRD diffraction results are shown in Table 1, and the microstructure is as follows: Figure 9 and Figure 10 As shown, the secondary particles of the obtained cathode material precursor are spherical or near-spherical, and the outer primary particles are distributed in a relatively coarse strip shape on the surface of the secondary particles.

[0169] Comparative Example 2

[0170] The difference from Example 2 lies in the reaction conditions of the first and second reactions. The first and second reactions specifically include the following steps:

[0171] Under nitrogen protection, start stirring and add 5.0 m³ of [unspecified substance] to reactor (I). 3 Pure water was used, and a precipitant and complexing agent were added to adjust the ammonia concentration to 5.5 g / L and the pH to 11.60. The reaction temperature in reactor (I) was raised to 60°C, and the stirring speed was controlled at 240 r / min. After the conditions were met, the metal salt solution, precipitant, and complexing agent were simultaneously introduced to carry out the first reaction. The flow rate of the metal salt solution was gradually increased over time. After the pH of the reaction system stabilized, the flow rate of the metal salt solution was increased to 500 L / h, and the temperature of the reaction system was maintained at T2 = 60°C. The pH of the reaction system was controlled at 10.75 throughout the process until a reaction product with a particle size D50 of 10.5 μm was obtained.

[0172] (4) Post-processing: The reaction product obtained from the second reaction is centrifuged, washed, dried, sieved, and demagnetized to obtain the chemical formula Ni. 0.85 Co 0.10 Mn 0.05 The ternary cathode material precursor was obtained with a span of 0.89. The XRD diffraction results are shown in Table 1, and the microstructure is as follows: Figure 11 and Figure 12 As shown, the secondary particles of the obtained cathode material precursor are spherical or near-spherical, and the outer primary particles grow in a relatively coarse, elongated shape on the surface of the secondary particles.

[0173] Comparative Example 3

[0174] The difference from Example 1 lies in the reaction conditions of the second reaction, which specifically includes the following steps:

[0175] Under nitrogen protection, start stirring and add 8m³ of nitrogen gas to reactor (II). 3 Pure water was added in a measured amount of 140 kg of the dehydrated dry base material of the above-mentioned seed crystals. Under stirring conditions of 240 r / min, precipitant and complexing agent were added to adjust the ammonia concentration to 8.5 g / L and the pH value to 10.85. The reaction temperature in the reactor (II) was raised to 60℃, and the metal salt solution, precipitant and complexing agent were introduced to carry out the second reaction. During the second reaction, the pH value was maintained at 10.85 throughout the reaction by adjusting the flow rate of precipitant and complexing agent, the reaction system temperature was maintained at 60℃, and the metal salt solution was fed at a flow rate of 100 L / h. After the pH value of the reaction system stabilized, the flow rate of the metal salt solution was increased to 200 L / h, and then gradually increased over time until the final flow rate was 700 L / h, until the reaction product with a particle size D50 of 10.5 μm was obtained.

[0176] The reaction product obtained from the second reaction was centrifuged, washed, dried, sieved, and demagnetized to obtain a product with the chemical formula Ni. 0.89 Co 0.07 Mn 0.04The ternary cathode material precursor of (OH)₂ has a span of 0.89. The XRD diffraction results are shown in Table 1, and the microstructure is as follows: Figure 13 and Figure 14 As shown, the secondary particles of the obtained cathode material precursor are spherical or near-spherical, and the outer primary particles grow in a relatively coarse, elongated shape on the surface of the secondary particles.

[0177] Table 1. Comparison of XRD diffraction data of cathode material precursors obtained in each embodiment and comparative example.

[0178]

[0179] As shown in Table 1, X-ray diffraction (XRD) analysis reveals that, compared to Comparative Examples 1-3, the nickel-cobalt-manganese ternary cathode material precursors prepared in Examples 1-4 exhibit a half-width α (FWHM) of 0.40-0.47° at a diffraction angle of 19.2±1° and a FWHM β (FWHM) of 0.52-0.56° at a diffraction angle of 38.5±1°, with β / α = 1.10-1.22. These values ​​indicate suitable FWHMs. Furthermore, the precursor I in these examples... 001 / I 101 The peak intensity is 1.4-1.7, indicating a high peak intensity. It also indicates a high diffraction intensity on the (001) crystal plane, which means that the precursor structure preferentially grows on the (001) crystal plane. This shows that the precursor obtained in the example has good crystallinity and better cycle stability.

[0180] Table 2. Structural parameters of the cathode material precursors obtained in each embodiment and comparative example.

[0181]

[0182]

[0183] According to the attached figures and the data in Table 2, the precursors prepared in Examples 1-4 and Comparative Examples 1-3 all consist of an inner layer, a middle layer, and an outer layer from the inside out. The inner layers of Examples 1 and 2 exhibit a hollow structure. In Examples 1-4, the overall porosity from the inside out is: outer layer > inner layer > middle layer. From the CP cross-sectional view, the primary particles in the outer layer are relatively thin and elongated, and are distributed along the cross-section of the secondary particles in the precursor. However, the porosity of each layer in the comparative examples differs from that in the examples, and the primary particles in the outer layer are relatively coarse and elongated.

[0184] The main reason for the differences in porosity relationships and particle shapes between the layers is that in the precursor preparation process of this application, a high-temperature reaction is used starting from the formation of the outer layer. By refining the morphology of the primary particles in the outer layer, the porosity of the inner layer is increased, and the arrangement of the primary particles is adjusted, resulting in a porous outer layer with dendritic cross-growth of the primary particles, thereby strengthening the overall support capacity of the secondary particles. Due to the differences in the preparation process, the corresponding particle strength is as follows: Example 2 > Example 1 > Example 3 > Example 4, and Examples 1-4 are greater than Comparative Examples 1-3.

[0185] Electrochemical performance testing

[0186] (1) The cathode material precursors obtained in Examples 1-4 and Comparative Examples 1-3 were mixed with LiOH in a high-speed mixer at a molar ratio of 1.06:1. The mixture was sintered in an air environment using a box furnace at a sintering temperature of 650°C and a holding time of 9 hours. After cooling to room temperature, the mixture was crushed and sieved to obtain the ternary cathode material.

[0187] (2) Electrochemical performance testing using a button cell: The above-mentioned positive electrode material, conductive carbon black, and binder PVDF (polyvinylidene fluoride) were mixed in a ratio of 8:1:1 to form a slurry, which was then uniformly coated onto an aluminum foil with dimensions of 1*2cm to form a positive electrode sheet. The negative electrode sheet was a lithium metal sheet, and the electrolyte was 1mol / L LiPF6 EC:DMC:EMC = 1:1:1 (volume ratio). The battery case, positive and negative electrode sheets, separator (PE double-layer ceramic separator), spring sheet, and gasket were assembled into a button cell in a vacuum glove box. Electrochemical performance testing was conducted using the Blue Electric CT3002A testing system. The initial coulombic efficiency, 0.1C / 1C 50-cycle retention rate (1C = 210mAh g-1), and 2C / 0.1C rate performance tests were performed under conditions of 3.0-4.3V. The measurement temperature was 25℃±1℃, and the humidity was <40%. The results are shown in Table 3.

[0188] Table 3. Electrochemical performance test results

[0189]

[0190] According to the attached figures and the data in Tables 1-3, the precursors prepared in Examples 1-4 have the structural characteristics of high porosity in the inner and outer layers and relatively dense, low-pore middle layer to provide support. This can provide an effective channel for lithium-ion transport in the cathode material during charging and discharging. Under the same conditions of 50 cycles at 0.1C / 1C, the cycle performance of Examples 1-4 is 98.2%, 97.9%, 97.6%, and 97.7%, respectively, which are all better than those of Comparative Examples 1-3. The corresponding initial DC resistance (DCR) is also significantly lower than that of Comparative Examples 1-3. Furthermore, compared to Examples 3 and 4, the precursors prepared in Examples 1 and 2 have an inner hollow structure with a diameter of 0.5-1.5 μm. After being mixed and sintered with lithium salt, the hollow structure is retained, which can provide a wider contact area for the electrolyte and a buffer space for the gas expansion inside the cathode material, thereby effectively slowing down the collapse and deterioration of the internal structure. Moreover, the outer porosity is moderate. Accordingly, the rate performance and cycle performance of Examples 1 and 2 are better than those of Examples 3 and 4, and the rate performance of Examples 1-4 is significantly better than that of Comparative Examples 1-3.

[0191] The cathode material precursors provided in Examples 1-4 of this application have an inner layer that is porous or contains a hollow structure. This hollow structure can be formed by shrinkage after high-temperature sintering, and then combined with the dense structure of the intermediate layer. The intermediate layer with lower porosity can reduce the residue of lithium ions in the transport path, reduce the occurrence of side reactions, and to a certain extent improve the resistance to cracking caused by volume changes inside the material, thereby improving the cycle performance of the material. The outer layer has relatively high porosity and particle strength. The higher porosity increases the contact area with the electrolyte, provides a fast lithium ion channel, shortens the lithium ion movement path, improves capacity, and also ensures the cycle performance of the cathode material.

[0192] As can be seen, according to the precursor preparation method provided in this application, by controlling the reaction conditions such as reaction temperature and flow rate during the preparation process, the structural characteristics such as the inner layer growth mode and layer thickness can be adjusted, thereby regulating the diameter of the inner hollow structure, the porosity range between the inner and outer layers, and the particle fragmentation (particle strength). The prepared precursor with the above-mentioned special porosity distribution structure has excellent cycle performance and structural strength, lower initial internal resistance, and higher capacity retention. Moreover, when the inner layer contains a hollow structure, it can mitigate the expansion pressure that occurs during charging and discharging, reduce the collapse and deterioration of the material's interior, and thus improve the battery's safety performance, showing good application prospects.

[0193] The technical features described above can be combined arbitrarily. Although not all possible combinations of these technical features are described, any combination of these technical features should be considered to be covered by this specification, provided that such combination does not contain contradictions.

[0194] 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.

Claims

1. A cathode material precursor, characterized in that, The secondary particles comprise multiple primary particles, each comprising an inner layer, a middle layer, and an outer layer from the inside out. The porosity of the outer layer is greater than that of the inner layer, which in turn is greater than that of the middle layer. In the cross-section of the secondary particles, the area ratio S1 between the middle layer and the inner layer is 1.3-2.

5. In the cross-section of the secondary particles, the area ratio S2 between the outer layer and the middle layer is 1.0-3.

0. The secondary particles are spherical or near-spherical, and the primary particles constituting the outer layer are dendritic.

2. The cathode material precursor according to claim 1, characterized in that, The precursor satisfies at least one of the following conditions: a. The porosity difference between the inner layer and the intermediate layer is 1%-10%; b. The porosity difference between the outer layer and the middle layer is 5%-20%; c. The porosity difference between the outer and inner layers is 2%-20%; d. The porosity of the inner layer is 0.05%-10%; e. The porosity of the intermediate layer is 0.01%-5%; f. The porosity of the outer layer is 5.0%-20.0%; g. The cathode material precursor also includes a hollow layer, and the precursor consists of a hollow layer, an inner layer, a middle layer and an outer layer from the inside out.

3. The cathode material precursor according to claim 2, characterized in that, The precursor satisfies at least one of the following conditions: The porosity difference between the inner layer and the middle layer is 2%-5%; The porosity difference between the outer layer and the middle layer is 5.5%-15%; The porosity difference between the outer and inner layers is 3%-10%; The porosity of the inner layer is 2.0%-4.5%; The porosity of the intermediate layer is 0.05%-1.0%; The porosity of the outer layer is 6%-12%.

4. The cathode material precursor according to any one of claims 1-3, characterized in that, The precursor satisfies at least one of the following conditions: h. The radius of the hollow layer is 0.5-1.5 μm; i. The thickness of the inner layer is 0.8-1.8 μm; j. The thickness of the intermediate layer is 1.3-2.1 μm; k. The thickness of the outer layer is 1.2-3.7 μm.

5. The cathode material precursor according to any one of claims 1-3, characterized in that, The precursor satisfies at least one of the following conditions (1)-(11): (1) The average aspect ratio of the primary particles constituting the outer layer is 5-11; (2) The D50 of the secondary particles is 9.0-14.0 μm; (3) The particle size distribution span value of the secondary particles is 0.5-1.0; (4) The particle fragmentation of the secondary particles is 10.0%-21.5%; (5) The specific surface area of ​​the secondary particles is 7.5-16.5 m². 2 / g; (6) The tap density of the secondary particles is 1.7-2.3 g / cm³. 3 ; (7) The full width at half maximum (FWHM) α of the characteristic peak of the (001) crystal plane of the precursor is 0.2-0.6°; (8) The full width at half maximum (FWHM) β of the characteristic peak of the (101) crystal plane of the precursor is 0.2-0.6°; (9) The ratio of the full width at half maximum (FWHM) β of the characteristic peak of the (101) crystal plane of the precursor to the FWHM α of the characteristic peak of the (001) crystal plane is β / α = 1.0-1.3; (10) The peak intensity ratio I between the characteristic peak of the (001) crystal plane of the precursor and the characteristic peak of the (101) crystal plane of the precursor. 001 / I 101 It is 1.4-1.7; (11) The general chemical formula of the precursor is Ni x Co y M 1-x-y (OH)2, where 0.8≤x<1, 0<y≤0.2, and M is at least one of Mn, Al, Zr, Ti, Cr, Mo, W, B, Ba, Nb and Sr.

6. The cathode material precursor according to claim 5, characterized in that, The precursor satisfies at least one of the following conditions: The full width at half maximum (FWHM) α of the characteristic peak of the (001) crystal plane of the precursor is 0.30-0.55°; The full width at half maximum (FWHM) β of the characteristic peak of the (101) crystal plane of the precursor is 0.30-0.58°; The ratio of the full width at half maximum (FWHM) β of the characteristic peak of the (101) crystal plane of the precursor to the FWHM α of the characteristic peak of the (001) crystal plane is β / α = 1.1-1.

22.

7. The cathode material precursor according to claim 6, characterized in that, The full width at half maximum (FWHM) α of the characteristic peak of the (001) crystal plane of the precursor is 0.40-0.47°; and / or, The half-peak width β of the characteristic peak of the (101) crystal plane of the precursor is 0.52-0.56°.

8. A method for preparing a cathode material precursor as described in any one of claims 1-7, characterized in that, Includes the following steps: Seed crystals are obtained by mixing a metal salt solution with a precipitant and a complexing agent to carry out a first reaction. The seed crystals are mixed with a metal salt solution, a precipitant, and a complexing agent to carry out a second reaction to obtain the reaction product; The reaction products were post-processed to obtain a cathode material precursor. The reaction temperature of the first reaction is 55-85℃; the reaction temperature of the second reaction is 55-85℃; the endpoint reaction temperature of the second reaction is higher than the initial reaction temperature; and the pH value of the reaction system of the first and second reactions is 10.50-12.

10.

9. The method for preparing the cathode material precursor according to claim 8, characterized in that, The preparation method satisfies at least one of the following conditions (1)-(4): (1) The metal salt includes soluble salts of nickel, cobalt and / or manganese; (2) The total concentration of metal ions in the metal salt solution is 1-5 mol / L; (3) The precipitant includes at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide; (4) The complexing agent includes at least one of ammonia, ammonium bicarbonate solution, ammonium carbonate solution, EDTA, ethylenediamine, sodium citrate and urea.

10. The method for preparing the cathode material precursor according to claim 9, characterized in that, The preparation method satisfies at least one of the following conditions: The soluble salt includes at least one of sulfate, nitrate, acetate and chloride. The concentration of the precipitant is 2-20 mol / L; The complexing agent is ammonia water with a mass fraction of 15-35%.

11. The method for preparing the cathode material precursor according to any one of claims 8-10, characterized in that, The preparation method satisfies at least one of the following conditions ①-⑤: ① The reaction temperature of the second reaction is higher than that of the first reaction; ②The complexing agent includes ammonia water, and the ammonia concentration in the first reaction and the second reaction is 5.0-12.6 g / L; ③ During the first and second reactions, the feed flow rate of the metal salt solution is 100 L / h - 700 L / h; ④ During the second reaction process, the feed flow rate of the metal salt solution gradually increases over time; ⑤ Both the first reaction and the second reaction are carried out under stirring, and the stirring speed is 100-240 r / min.

12. The method for preparing the cathode material precursor according to any one of claims 8-10, characterized in that, The endpoint temperature of the second reaction is 10-20°C higher than the initial reaction temperature.

13. A positive electrode material, characterized in that, It is prepared from the cathode material precursor according to any one of claims 1 to 7.

14. A lithium-ion battery, characterized in that, It is prepared from the cathode material described in claim 13.

15. An electrical-related device, characterized in that, Including the lithium-ion battery of claim 14.

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