Cathode material precursor, single-crystal cathode material and preparation method, and lithium ion battery

Abstract

The application relates to a positive electrode material precursor, a single-crystal positive electrode material and a preparation method and a lithium ion battery. a Co b Mn c N d O e , wherein 0.50<=a<=0.98, 0 The positive electrode material precursor has a chemical general formula of Ni The application also relates to a single-crystal positive electrode material and a preparation method and a lithium ion battery.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202311331910.3, filed on October 13, 2023, entitled “Cathode Material Precursor, Single Crystal Cathode Material and Preparation Method Thereof, Lithium-ion Battery”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of cathode material technology, and in particular to cathode material precursors, single-crystal cathode materials and their preparation methods, and lithium-ion batteries. Background Technology

[0004] Lithium-ion cathode materials are mainly divided into lithium iron phosphate and ternary materials. Lithium iron phosphate is suitable for commercial vehicles, low-to-mid-range passenger vehicles, and energy storage due to its superior cost, cycle life, and thermal stability compared to ternary materials. Ternary materials have high energy density and good low-temperature performance, making them suitable for mid-to-high-end passenger vehicles.

[0005] Traditional polycrystalline ternary cathode materials consist of primary particles (hundreds of nanometers) tightly aggregated into spherical secondary particles (typically >10 μm in diameter). During charge and discharge, as the crystal lattice contracts, localized stress easily forms along grain boundaries, causing structural collapse and microcracks, leading to rapid capacity decay. Single-crystalization is one method to improve the cycle performance of ternary materials. Single-crystal ternary materials consist of dispersed primary particles (typically a few micrometers in diameter, with the vast majority being single grains with the same orientation), without the presence of secondary spherical particles. Eliminating grain boundaries suppresses cracking during charge and discharge, exhibiting excellent stability. However, single-crystal ternary materials also face other challenges. The long diffusion path of Li in single-crystal ternary materials results in slow Li transport, manifesting as high DC internal resistance (DCR) and poor rate performance. Furthermore, although single-crystal particles can suppress particle cracking, crystal slip and dislocation still occur during cycling, further generating microcracks.

[0006] Ternary single-crystal cathode materials are generally prepared by high-temperature sintering of precursor compounds containing Ni / Co / Mn and lithium salts. During sintering, the formation of the cathode material is typically slow and the growth rate is uneven, leading to stress concentration within the formed cathode material. Furthermore, due to limitations in ion diffusion, the elemental distribution within the ternary material exhibits concentration differences, resulting in a mismatch in the internal lattice parameters. This hinders lithium-ion transport, increasing the impedance of the cathode material and reducing its rate performance. On the other hand, the internal lattice micro-stress causes the cathode material to crack and pulverize during cycling, further reducing its cycle performance.

[0007] Therefore, how to improve the rate performance, reduce impedance, and further improve the cycle performance of single-crystal cathode materials are still technical problems that need to be solved. Summary of the Invention

[0008] The purpose of this application is to provide a cathode material precursor, a single-crystal cathode material and its preparation method, and a lithium-ion battery. The single-crystal cathode material provided by this application has a low lattice strain, which can reduce the diffusion barrier of lithium ions between microcrystals and increase the Li ion diffusion coefficient, thereby making the single-crystal cathode material exhibit a lower DCR and better rate performance. It can also reduce the occurrence of crystal plane slip, dislocation and other phenomena, thereby suppressing the generation of microcracks, improving the structural stability of the single-crystal cathode material, and thus improving the cycle performance of the single-crystal cathode material.

[0009] In a first aspect, embodiments of this application provide a single-crystal cathode material, wherein the general chemical formula of the single-crystal cathode material is Li. x Ni a Co b Mn c N d O2, wherein 0.98≤x≤1.1, 0.50≤a≤0.98, 0<b≤0.20, 0<c≤0.30, 0≤d≤0.10, a+b+c+d=1, and N includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Ca, Nb, W, Sb, Ta, Sn and Y;

[0010] When observing the single-crystal cathode material with a scanning electron microscope, at a magnification of 3K, 10 points were randomly selected on the single-crystal cathode material for EDS point scanning to test the content of Ni, Co, and Mn. In the EDS spectrum results of the single-crystal cathode material, the standard deviation of the mass content of each element Ni, Co, and Mn in the single-crystal cathode material was ≤0.03.

[0011] The lattice strain of the single-crystal cathode material is ε, and ε < 0.2%.

[0012] In some embodiments, the single-crystal cathode material includes SO4. 2- SO4 2- The content of is δ, where 0ppm≤δ≤800ppm.

[0013] In some embodiments, the single-crystal cathode material contains at least one single grain with the same orientation, wherein the average grain size of the single grain is 1 μm to 5 μm.

[0014] In some embodiments, the grain size of the single-crystal cathode material is D, where 150nm < D < 250nm.

[0015] In some embodiments, the average particle size D of the single-crystal cathode material 50 The size ranges from 1.5μm to 5μm.

[0016] In some embodiments, the Batter tap density of the single-crystal cathode material is >1.5 g / cm³. 3 .

[0017] In some embodiments, the range of mass content of each element Ni, Co, and Mn in the single-crystal cathode material is ≤0.08.

[0018] Secondly, embodiments of this application provide a cathode material precursor, wherein the general chemical formula of the cathode material precursor is Ni. a Co b Mn c N d O e Wherein, 0.50≤a≤0.98, 0<b≤0.20, 0<c≤0.30, 0≤d≤0.10, a+b+c+d=1, 1≤e≤1.15, and N includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Ca, Nb, W, Sb, Ta, Sn and Y;

[0019] The surface area weighted average particle size D[3,2] of the cathode material precursor is less than 2.0 μm, and the standard deviation of the mass content of each element Ni, Co and Mn in the cathode material precursor is less than 0.05.

[0020] In some embodiments, the range of mass content of each element Ni, Co and Mn in the cathode material precursor is ≤0.12.

[0021] In some embodiments, the cathode material precursor includes secondary particles, which comprise a plurality of aggregated primary particles.

[0022] In some embodiments, the cathode material precursor includes secondary particles, which comprise a plurality of aggregated primary particles, the primary particles being spherical.

[0023] In some embodiments, the cathode material precursor includes secondary particles, which in turn include a plurality of aggregated primary particles, the primary particles having a particle size of 20 nm to 1000 nm.

[0024] In some embodiments, the average particle size D of the cathode material precursor 50 <3.5μm.

[0025] In some embodiments, the specific surface area of ​​the cathode material precursor is >5m². 2 / g.

[0026] In some embodiments, the Batter tap density of the cathode material precursor is >1 g / cm³. 3 .

[0027] Thirdly, embodiments of this application provide a method for preparing a single-crystal cathode material, comprising the following steps:

[0028] A mixed solution containing nickel, cobalt, and manganese salts is atomized and then thermally decomposed to obtain a cathode material precursor. The surface area weighted average particle size D[3,2] of the cathode material precursor is <2.0 μm, and the standard deviation of the mass content of each element Ni, Co, and Mn in the cathode material precursor is ≤0.05. The cathode material precursor is mixed with a lithium source and sintered in an oxygen-containing atmosphere to obtain a single-crystal cathode material. The standard deviation of the mass content of each element Ni, Co, and Mn in the single-crystal cathode material is ≤0.03. The lattice strain of the single-crystal cathode material is ε, and ε <0.2%.

[0029] In some embodiments, the cathode material precursor includes SO4. 2- The SO4 2- The content of is η, where 0ppm≤η≤1800ppm.

[0030] In some embodiments, the nickel salt includes at least one of nickel chloride, nickel sulfate, nickel nitrate, nickel carbonate, nickel oxalate, and nickel acetate.

[0031] In some embodiments, the cobalt salt includes at least one of cobalt chloride, cobalt oxalate, cobalt carbonate, cobalt sulfate, cobalt nitrate, and cobalt acetate.

[0032] In some embodiments, the manganese salt includes at least one of manganese chloride, manganese carbonate, manganese sulfate, manganese oxalate, manganese nitrate, and manganese acetate.

[0033] In some embodiments, the molar ratio of Ni, Co and Mn in the mixed solution is (50-98):(0-20):(0-30), and the content of Co and Mn in the mixed solution is not 0.

[0034] In some embodiments, the total metal concentration in the mixed solution is 200 g / L to 500 g / L.

[0035] In some embodiments, the mixed solution further includes a dopant containing N, where N includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Ca, Nb, W, Sb, Ta, Sn, and Y.

[0036] In some embodiments, the general chemical formula of the cathode material precursor is Ni. a Cob Mn c N d O e Wherein, 0.50≤a≤0.98, 0<b≤0.20, 0<c≤0.30, 0≤d≤0.10, a+b+c+d=1, 1≤e≤1.15, and N includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Ca, Nb, W, Sb, Ta, Sn and Y.

[0037] In some embodiments, the range of mass content of each element Ni, Co and Mn in the cathode material precursor is ≤0.12.

[0038] In some embodiments, the flow rate of the mixed solution is 100 L / h to 900 L / h.

[0039] In some embodiments, the pressure of the atomization process is 0.4 MPa to 0.8 MPa.

[0040] In some embodiments, the temperature of the first sintering is 500°C to 850°C.

[0041] In some embodiments, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium sulfate, lithium chloride, lithium nitrate, and lithium oxalate.

[0042] In some embodiments, the molar ratio of lithium in the lithium source to the total of nickel, cobalt and manganese in the cathode material precursor is 0.98 to 1.10.

[0043] In some embodiments, the sintering temperature is 750°C to 950°C.

[0044] In some embodiments, the sintering time is 10h to 30h.

[0045] Fourthly, embodiments of this application provide a lithium-ion battery, the lithium-ion battery comprising the single-crystal cathode material described in the first aspect or the single-crystal cathode material prepared by the preparation method of the single-crystal cathode material described in the third aspect.

[0046] Compared with the prior art, the technical solution of this application has at least the following beneficial effects:

[0047] The single-crystal cathode material provided in this application underwent EDS point scanning tests on 10 randomly selected points to determine the Ni, Co, and Mn content. The EDS spectra of the single-crystal cathode material showed that the standard deviation of the mass content of each element (Ni, Co, and Mn) was ≤0.03, indicating good uniformity of Ni, Co, and Mn distribution within the single-crystal cathode material. This is beneficial for reducing crystal structure defects in the single-crystal cathode material. The lattice strain ε of the single-crystal cathode material was <0.2%, which lowers the diffusion barrier between lithium ions and increases the Li ion diffusion coefficient, resulting in good rate performance and low DCR. Simultaneously, the low lattice strain can also suppress the generation of microcracks within the single-crystal cathode material, thereby improving its cycle performance.

[0048] The cathode material precursor provided in this application has a surface area weighted average particle size D[3,2] < 2.0 μm, exhibiting high reactivity, which is beneficial for improving the reaction efficiency and mass transfer efficiency in the subsequent preparation of cathode materials from the cathode material precursor. Simultaneously, the standard deviation of the mass content of each element Ni, Co, and Mn in the cathode material precursor obtained by the above preparation method is ≤ 0.05, indicating that the distribution uniformity of Ni, Co, and Mn elements in the cathode material precursor is good. Using this cathode material precursor to prepare cathode materials can improve the distribution uniformity of Ni, Co, and Mn elements in the cathode material, resulting in fewer crystal structure defects and lower lattice stress in the cathode material prepared from this cathode material precursor.

[0049] The method for preparing single-crystal cathode material provided in this application involves atomizing a mixed solution containing nickel salt, cobalt salt, and manganese salt, followed by thermal decomposition to obtain a cathode material precursor. The surface area-weighted average particle size D[3,2] of this cathode material precursor is <2.0 μm, exhibiting high reactivity, which is beneficial for improving the reaction efficiency and mass transfer efficiency between the cathode material precursor and the lithium source during subsequent high-temperature sintering. Simultaneously, the standard deviation of the mass content of each element Ni, Co, and Mn in the cathode material precursor obtained by the above preparation method is ≤0.05, indicating good uniformity of Ni, Co, and Mn distribution in the cathode material precursor. Furthermore, the single-crystal cathode material prepared by sintering the above cathode material precursor with a lithium source exhibits high uniformity of Ni, Co, and Mn content. The standard deviation of the mass content of each element is ≤0.03, indicating good uniformity of Ni, Co, and Mn element distribution within the single-crystal cathode material. This helps reduce crystal structure defects in the single-crystal cathode material. Furthermore, the single-crystal cathode material has a low lattice strain, ε<0.2%, which can reduce the diffusion barrier of lithium ions between microcrystals and increase the Li ion diffusion coefficient, resulting in good rate performance and low DCR. At the same time, the low lattice strain can also suppress the generation of microcracks within the single-crystal cathode material, thereby improving the cycle performance of the single-crystal cathode material. Attached Figure Description

[0050] The present application will be further described below with reference to the accompanying drawings and embodiments.

[0051] Figure 1 This is a SEM image of the cathode material precursor prepared in Example 1 of this application;

[0052] Figure 2 This is another SEM image of the cathode material precursor prepared in Example 1 of this application;

[0053] Figure 3 The above are the EDS spectra of the cathode material precursor prepared in Example 1 of this application;

[0054] Figure 4 The Williamson-Hall analysis fitting curve is shown for the single-crystal cathode material prepared in Example 1 of this application. Detailed Implementation

[0055] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0056] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0057] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0058] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0059] In a first aspect, embodiments of this application provide a single-crystal cathode material, wherein the general chemical formula of the single-crystal cathode material is Li. x Ni a Co b Mn c N dO2, wherein 0.98≤x≤1.1, 0.50≤a≤0.98, 0<b≤0.20, 0<c≤0.30, 0≤d≤0.10, a+b+c+d=1, and N includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Ca, Nb, W, Sb, Ta, Sn and Y;

[0060] When observing the single-crystal cathode material with a scanning electron microscope, at a magnification of 3K, 10 points were randomly selected on the single-crystal cathode material for EDS point scanning to test the content of Ni, Co, and Mn. In the EDS spectrum results of the single-crystal cathode material, the standard deviation of the mass content of each element Ni, Co, and Mn in the single-crystal cathode material was ≤0.03.

[0061] The lattice strain of the single-crystal cathode material is ε, and ε < 0.2%.

[0062] The single-crystal cathode material provided in this application underwent EDS point scanning tests on 10 randomly selected points to determine the Ni, Co, and Mn content. The EDS spectra of the single-crystal cathode material showed that the standard deviation of the mass content of each element (Ni, Co, and Mn) was ≤0.03, indicating good uniformity of Ni, Co, and Mn distribution within the single-crystal cathode material. This is beneficial for reducing crystal structure defects in the single-crystal cathode material. The lattice strain ε of the single-crystal cathode material was <0.2%, which lowers the diffusion barrier between lithium ions and increases the Li ion diffusion coefficient, resulting in good rate performance and low DCR. Simultaneously, the low lattice strain can also suppress the generation of microcracks within the single-crystal cathode material, thereby improving its cycle performance.

[0063] Specifically, the value of x can be 0.98, 0.99, 1.0, 1.01, 1.03, 1.05, 1.08, 1.09 or 1.1, etc., without any restrictions.

[0064] The specific values ​​of 'a' can be 0.50, 0.55, 0.60, 0.63, 0.70, 0.75, 0.80, 0.85, 0.88, 0.90, 0.95, or 0.98, etc.; the values ​​of 'b' can be 0.01, 0.05, 0.08, 0.10, 0.11, 0.13, 0.15, 0.18, or 0.20, etc.; the values ​​of 'c' can be 0.01, 0.05, 0.10, 0.15, 0.18, 0.20, 0.23, 0.27, or 0.30, etc.; and the values ​​of 'd' can be 0, 0.01, 0.03, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.10, etc., without any restrictions here.

[0065] Specifically, the standard deviation of the mass content of each element Ni, Co and Mn in the single-crystal cathode material can be 0.01, 0.015, 0.02, 0.025, 0.026, 0.028 or 0.03, etc., and is not limited here.

[0066] In some embodiments, the range of mass content of each element Ni, Co and Mn in the single-crystal cathode material is ≤0.08, specifically 0.01, 0.02, 0.028, 0.03, 0.05, 0.057, 0.06, 0.07, 0.075 or 0.08, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0067] Understandably, the lower the standard deviation and range of the mass content of each element Ni, Co, and Mn in a single-crystal cathode material, the higher the uniformity of the distribution of Ni, Co, and Mn elements in the single-crystal cathode material. In this application, the standard deviation and range of the mass content of each element Ni, Co, and Mn in the single-crystal cathode material are within the above range, indicating that the distribution of Ni, Co, and Mn elements in the single-crystal cathode material of this application is uniform. This is beneficial for reducing lattice defects in the single-crystal cathode material, lowering lattice stress, and improving the cycle performance and rate performance of the single-crystal cathode material.

[0068] The lattice strain of a single-crystal cathode material can be 0.01%, 0.03%, 0.05%, 0.08%, 0.10%, 0.11%, 0.12%, 0.15%, 0.18%, or 0.19%, etc., and is not limited here.

[0069] In some embodiments, the single-crystal cathode material further includes a coating layer comprising a metal oxide or a lithium-ion conductor, wherein the metal oxide comprises at least one of Al, Ti, Zr, Y, Nb, Mg, W, B, Ce, Co, and Mn. The coating layer can reduce the direct contact between the single-crystal cathode material and the electrolyte, reduce the occurrence of side reactions between the material and the electrolyte, and further improve the electrochemical performance of the single-crystal cathode material.

[0070] In some embodiments, the SO4 free on the surface of the single-crystal cathode material 2- The SO4 content is less than or equal to 1000 ppm, preferably ≤800 ppm. (SO4 content in single-crystal cathode materials) 2- The specific concentration can be 0 ppm, 5 ppm, 10 ppm, 50 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, or 1000 ppm, etc. When free SO4... 2-When the content is within the above range, the cathode material exhibits better rate capability and cycle performance. Traditional ternary precursor materials, due to the use of NiSO4, CoSO4, and MnSO4 as raw materials in their preparation, often retain a high content of sulfate ions in the co-precipitated precursor. Sulfate ions are difficult to decompose, resulting in a high sulfate ion content (typically >1000 ppm) on the surface of the subsequently sintered cathode material. Free sulfate ions negatively impact the electrochemical performance of the cathode material. When free SO42- on the surface... 2- When the content is high, SO4 2- It binds to Li ions, trapping some Li ions and causing a deterioration in the material's capacity and rate capability; in addition, free SO4 on the surface 2- It can also affect the stability of the SEI membrane.

[0071] SO42-free surface of single-crystal cathode material 2- The content of SO42- on the surface of the cathode material precursor is related to its content. 2- The content exhibits strong inheritance; SO4 content in cathode material precursors... 2- The higher the content, the more free SO4 on the surface of the single-crystal cathode material. 2- The higher the content, the better. The free SO4 on the surface of the cathode material precursor provided in this application... 2- A content of ≤1000ppm is more conducive to the preparation of surface-free SO4. 2- The cathode material has a content of ≤800ppm.

[0072] In order to reduce SO4 content in the precursor of single-crystal cathode material 2- In some embodiments, the Ni, Mn, Co, and N salts each independently include at least one of chloride, nitrate, oxalate, and acetate. The nitrates, chlorides, oxalates, and acetates of nickel, cobalt, and manganese decompose readily at high temperatures, leaving no significant residue, and therefore have virtually no impact on the performance of the cathode material. This is achieved by controlling the SO4 content in the metal salt mixed solution. 2- The content is so high that it can even be used to prepare SO4. 2- The cathode material precursor has a content close to zero. However, this requires high purity of raw materials, which increases the cost of raw materials. Using a precursor containing SO4... 2- The Ni, Co, Mn, and N sources in the ternary recycled material containing impurities are used as metal sources, and SO4 in the metal sources is controlled. 2- It is more economical to prepare cathode material precursors by adjusting the content of certain substances.

[0073] In some embodiments, in the metal salt mixed solution, based on the total mass of Ni, Co, and Mn elements, SO4 2- The content of SO42- is ≤800ppm, which makes it easier to prepare surface-free SO42-.2- The lower content of single-crystal cathode material further improves the capacity and rate performance of single-crystal cathode material.

[0074] In some embodiments, the single-crystal cathode material contains at least one single grain with the same orientation, wherein the average grain size of the single grain is 1μm to 5μm, such as 1μm, 2μm, 3μm, 4μm, 5μm, etc.

[0075] The cathode material single-crystal particles of this application contain at least one single grain with the same orientation, and the average particle size of a single particle meeting the above conditions is 1-5 μm as measured under EBSD testing. It can stably achieve its own high packing density while preventing cracks from appearing due to compression or other reasons after the particles reach their densest packing. The identical orientation of the particles can alleviate stress and strain during charge-discharge cycles, significantly reducing cracking during cycling and thus greatly improving the structural stability of the cathode particles.

[0076] It should be noted that the grain orientation of the cathode material can be tested by electron backscatter diffraction (EBSD) at least. 100 individual grains with the same orientation are randomly selected, and the grain size of each grain is measured. The arithmetic mean is then taken as the average grain size of the individual grains.

[0077] The difference between single-crystal cathode materials and polycrystalline ternary cathode materials (i.e., polycrystalline secondary particles) lies in the fact that the smallest particle in polycrystalline secondary particles is a secondary particle formed by the agglomeration of primary particles. In contrast, the smallest particle in single-crystal cathode materials is typically a micrometer-sized single primary particle. Generally, in addition to EBSD testing, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) can be used to determine whether the obtained cathode product is a single-crystal material. For conventional single-crystal cathode materials, SEM is also an important and reliable characterization method. Single-crystal particles generally exhibit a regular or irregular polyhedral shape and show no significant particle agglomeration. TEM is an auxiliary secondary characterization method, observing whether the crystal plane orientation of the obtained product is consistent, and further characterizing it in conjunction with selected area electron diffraction (SAED). All of the above methods can be used to determine whether it is a single-crystal cathode material. For ease of understanding, the single-crystal cathode material of this application can be understood as a cathode material particle containing at least one single grain with the same orientation, and the average particle size of the aforementioned single grain is 1μm-5μm.

[0078] Understandably, a single grain in this application can be a single particle composed of a primary particle. The aforementioned single-crystal cathode material may also contain a small number of "quasi-secondary particles" formed by the adhesion of several single particles. "Primary particle" refers to the smallest particle unit identified when observing cathode active materials using a scanning electron microscope. "Secondary particle" refers to a secondary structure formed by the aggregation of multiple primary particles, exhibiting a relatively rounded spherical morphology. "Quasi-secondary particles" are formed by the adhesion of several single particles. Typically, the particle size of a single particle in these quasi-secondary particles is between 1µm and 5µm, and generally, the roundness of "quasi-secondary particles" is lower than that of conventional "secondary particles."

[0079] It is important to clarify that the "single-crystal cathode material" known to those skilled in the art is not a "single crystal" in the strict sense. In crystallography, an ideal single crystal is a crystal with completely identical arrangement and orientation. However, due to limitations imposed by impurities, strain, and crystal defects, ideal single crystals are extremely rare and difficult to produce in a laboratory. Therefore, the single-crystal cathode materials known in the art are actually more accurately described as "single-crystal morphology" cathode materials, exhibiting only a large particle size similar to single crystals, distinguishing them from polycrystalline materials composed of numerous small primary particles.

[0080] In some embodiments, the grain size of the single-crystal cathode material is D, where 150nm < D < 250nm. The specific grain size of the single-crystal cathode material can be 151nm, 155nm, 160nm, 170nm, 185nm, 190nm, 200nm, 205nm, 230nm, or 245nm, etc., and is not limited here. If the grain size of the single-crystal cathode material is less than 150nm, the cycle stability of the single-crystal cathode material is poor; if the grain size of the single-crystal cathode material is greater than 250nm, the capacity and rate performance of the single-crystal cathode material are poor. Controlling the grain size of the single-crystal cathode material within the above range is beneficial to improving the electrochemical performance of the single-crystal cathode material.

[0081] It should be noted that grain size is generally calculated using the Scherrer formula based on the full width at half maximum (FWHM). This method assumes that the lattice stress is zero, and the broadening of the diffraction peaks is entirely due to grain size. However, in reality, the lattice stress within single-crystal cathode materials cannot be completely ignored. Many factors cause stress concentration within single-crystal cathode materials, thus the grain size calculated using the Scherrer formula has inherent limitations. This application uses the Williamson-Hall method to separate the diffraction peak broadening caused by crystallite size from that caused by lattice stress. Therefore, the calculated grain size can better reflect the electrochemical performance of the material.

[0082] In some embodiments, the average particle size D of the single-crystal cathode material 50 The particle size is between 1.5 μm and 5 μm, specifically 1.5 μm, 1.8 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm, or other values ​​within the above range, which are not limited here. Controlling the particle size of the single-crystal cathode material within the above range is beneficial to improving the structural stability, thermal stability, and long-cycle stability of the single-crystal cathode material.

[0083] In some embodiments, the Batter tap density of the single-crystal cathode material is >1.5 g / cm³. 3 Specifically, it can be 1.55 g / cm³. 3 1.58g / cm 3 1.62g / cm 3 1.63g / cm 3 1.65g / cm 3 1.70g / cm 3 Or 1.75g / cm 3 Of course, other values ​​within the above range are also possible and are not limited here. When the tap density of the single-crystal cathode material is controlled within the above range, it is beneficial to improve the energy density of the battery made from the single-crystal cathode material.

[0084] In some embodiments, the compaction density of the single-crystal cathode material is >3.0 g / cm³. 3 Specifically, it could be 3.1 g / cm³. 3 3.2g / cm 3 3.3g / cm 3 3.5g / cm 3 3.7g / cm 3 3.9g / cm 3 Or 4.1g / cm 3 "etc." can also be other values ​​within the above range, and no restrictions are imposed here.

[0085] Secondly, embodiments of this application provide a cathode material precursor, wherein the general chemical formula of the cathode material precursor is Ni. a Co b Mn c N d O e Wherein, 0.50≤a≤0.98, 0<b≤0.20, 0<c≤0.30, 0≤d≤0.10, a+b+c+d=1, 1≤e≤1.15, and N includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Ca, Nb, W, Sb, Ta, Sn and Y;

[0086] The surface area weighted average particle size D[3,2] of the cathode material precursor is less than 2.0 μm, and the standard deviation of the mass content of each element Ni, Co and Mn in the cathode material precursor is less than 0.05.

[0087] In existing technologies, the reaction between the cathode material precursor and lithium salt is limited by ion diffusion rate and temperature gradient, resulting in differences in crystal growth rate and cell parameters among the various microregions within the material. This leads to the accumulation of lattice stress within the material. Lattice stress increases the diffusion barrier of Li ions between crystal planes / grain boundaries, reduces the Li ion diffusion coefficient, and ultimately increases the material's diffusion coefficient (DCR). The morphology and structural characteristics of the cathode material precursor are highly inherited by the cathode material itself; therefore, the composition and structure of the cathode material precursor directly affect the performance of the final cathode material. The cathode material precursor provided in this application has a surface area weighted average particle size D[3,2] < 2.0 μm, exhibiting high reactivity, which is beneficial for improving the reaction efficiency and mass transfer efficiency in the subsequent preparation of cathode materials from the cathode material precursor. Simultaneously, the standard deviation of the mass content of each element Ni, Co, and Mn in the cathode material precursor obtained by the above preparation method is ≤ 0.05, indicating that the distribution uniformity of Ni, Co, and Mn elements in the cathode material precursor is good. Using this cathode material precursor to prepare cathode materials can improve the distribution uniformity of Ni, Co, and Mn elements in the cathode material, resulting in fewer crystal structure defects and lower lattice stress in the cathode material prepared from this cathode material precursor.

[0088] In some embodiments, the cathode material precursor includes SO4. 2- The SO4 2- The content of is η, where 0ppm≤η≤1800ppm.

[0089] Understandable, SO4 on the surface of the precursor 2- It is difficult to decompose and difficult to incorporate into the interior of the cathode material, therefore the free SO4 on the surface of the cathode material is difficult to decompose. 2- Content and free SO4 in precursor 2- The content may have a certain degree of inheritance; SO4 in the precursor 2- The higher the content, the more free SO4 on the surface of the ternary cathode material. 2- The higher the content, the better. The free SO4 on the surface of the cathode material precursor provided in this application... 2- A content of ≤1800ppm is more conducive to the preparation of surface-free SO4. 2- The cathode material contains ≤800ppm SO42-. This is to reduce the SO42- content in the cathode material precursor. 2-In some embodiments, the Ni, Mn, Co, and N salts each independently include at least one of chloride, nitrate, oxalate, and acetate, avoiding the use of nickel sulfate, cobalt sulfate, and manganese sulfate. Nitrates, chlorides, oxalates, and acetates of nickel, cobalt, and manganese decompose readily at high temperatures, leaving no significant residue, thus having virtually no impact on the performance of the cathode material. This is achieved by controlling the SO4 content in the metal salt mixture solution. 2- The content is so high that it can even be used to prepare SO4. 2- The cathode material precursor has a content close to zero. However, this requires high purity of raw materials, leading to increased raw material costs. Using a precursor containing SO4... 2- The Ni, Co, Mn, and N sources in the ternary recycled material containing impurities are used as metal sources, and SO4 in the metal sources is controlled. 2- It is more economical to prepare cathode material precursors by adjusting the content of certain substances.

[0090] In some embodiments, in the metal salt mixed solution, based on the total mass of Ni, Co, and Mn elements, SO4 2- The content is ≤1800ppm. Specifically, it can be 500ppm, 800ppm, 1200ppm, 1600ppm, 1700ppm or 1800ppm, etc., without any limit.

[0091] In industry, the average particle size D is generally used. 50 The particle size of the cathode material precursor is used to characterize the particle size. However, the reaction between the cathode material precursor and lithium salt is a process related to the contact area. Therefore, the Sauter average particle size, i.e., the surface area-weighted average particle size D[3,2], is actually more suitable for characterizing the particle size of the cathode material precursor. The larger D[3,2] is, the lower the surface activity of the cathode material precursor and the slower the reaction rate with lithium salt.

[0092] It should be noted that the surface area-weighted average particle size D[3,2] of the cathode material precursor in this application can be directly measured using a Malvern 3000 laser particle size analyzer. Specifically, it can be obtained using the following formula: D[3,2]=(∑y 3 N d ) / (∑y 2 N d The calculation yields the result, where y is the particle size; N is the particle size. d y represents the number of particles with a particle size of y.

[0093] Specifically, the surface area weighted average particle size D[3,2] of the cathode material precursor can be 1.98 μm, 1.95 μm, 1.8 μm, 1.75 μm, 1.64 μm, 1.5 μm, 1.3 μm, 1.2 μm, 1.1 μm, 0.8 μm, 0.9 μm, or 0.5 μm, etc., and is not limited here. When the surface area weighted average particle size D[3,2] of the cathode material precursor is controlled within the above range, the cathode material precursor has high reactivity, which is beneficial to improving the reaction efficiency and mass transfer efficiency of the cathode material precursor in the subsequent sintering process with the lithium source.

[0094] The standard deviation of the mass content of each element Ni, Co and Mn in the cathode material precursor can be 0.001, 0.005, 0.009, 0.01, 0.013, 0.02, 0.025, 0.03, 0.036, 0.04, 0.044, 0.045, 0.047 or 0.049, etc., and is not limited here.

[0095] In some embodiments, the range of mass content of each element Ni, Co, and Mn in the cathode material precursor is ≤0.12, specifically 0.01, 0.015, 0.018, 0.02, 0.029, 0.03, 0.035, 0.048, 0.059, 0.06, 0.08, 0.097, 0.10, 0.105, 0.11, 0.112, 0.115, or 0.119, etc., or other values ​​within the above range, which are not limited here.

[0096] Understandably, the standard deviation and range of the mass content of each of the elements Ni, Co, and Mn in the cathode material can reflect the uniformity of the distribution of Ni, Co, and Mn elements in the cathode material precursor. The lower the standard deviation and range of the mass content of each of the elements Ni, Co, and Mn, the more uniform the distribution of Ni, Co, and Mn elements in the cathode material precursor. At the same time, there is a good inheritance between the uniformity of the distribution of Ni, Co, and Mn elements in the cathode material precursor and the uniformity of the distribution of Ni, Co, and Mn elements in the single-crystal cathode material. The more uniform the distribution of Ni, Co, and Mn elements in the cathode material precursor, the more uniform the distribution of Ni, Co, and Mn elements in the single-crystal cathode material made from the cathode material precursor will be.

[0097] Therefore, controlling the standard deviation and range of the mass content of each element Ni, Co and Mn in the cathode material precursor within the above range is beneficial to improving the uniformity of the distribution of Ni, Co and Mn elements in the single-crystal cathode material, resulting in good uniformity of the distribution of Ni, Co and Mn elements in the single-crystal cathode material, fewer crystal structure defects in the single-crystal cathode material, and low lattice strain.

[0098] In some embodiments, the cathode material precursor includes secondary particles, which comprise a plurality of aggregated primary particles.

[0099] In some embodiments, the cathode material precursor includes secondary particles, which comprise a plurality of aggregated primary particles, the primary particles being spherical.

[0100] In some embodiments, the cathode material precursor includes secondary particles, which in turn include multiple aggregated primary particles. The particle size of the primary particles is 20 nm to 1000 nm, specifically 20 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 500 nm, 800 nm, or 1000 nm, but is not limited to the listed values; other unlisted values ​​within this range also apply. When the particle size of the primary particles is greater than 1000 nm, the surface reactivity of the cathode material precursor is poor, resulting in a large lattice strain in the prepared single-crystal cathode material, and poor cycle performance and rate performance. When the primary particles are smaller than 20 nm, the tap density of the cathode material precursor is low, leading to a low tap density in the prepared single-crystal cathode material. Controlling the particle size of the primary particles within the above-mentioned range is beneficial for improving the cycle performance and rate performance of the single-crystal cathode material made from this cathode material precursor.

[0101] In some embodiments, the average particle size D of the cathode material precursor 50 <3.5μm, specifically it can be 0.5μm, 0.8μm, 1.2μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.2μm, or 3.5μm, etc., and of course, it can also be other values ​​within the above range, which are not limited here. The particle size D of the cathode material precursor. 50 When controlled within the above range, it is beneficial to improve the reactivity of the cathode material precursor.

[0102] In some embodiments, the specific surface area of ​​the cathode material precursor is ≥5m². 2 / g, specifically 5m 2 / g、6m 2 / g、8m 2 / g, 10m 2 / g、12m 2 / g, 15m 2 / g、20m 2 / g、25m 2 / g, 50m 2 / g or 100m 2 / g, etc., can also be other values ​​within the above range, and are not limited here. The larger the specific surface area of ​​the cathode material precursor, the higher the reactivity of the cathode material precursor, which is beneficial to the reaction between the lithium source and the cathode material precursor, and can reduce the lattice defects of the single crystal cathode material prepared from the cathode material precursor.

[0103] In some embodiments, the Batter tap density of the cathode material precursor is >1 g / cm³. 3 Specifically, it could be 1.1 g / cm³. 3 1.2g / cm 3 1.3g / cm 3 1.8g / cm 3 2.3g / cm 3 2.5g / cm 3 Or 3g / cm 3 Of course, other values ​​within the above range are also possible and are not limited here. When the tap density of the cathode material precursor is controlled within the above range, it is beneficial to improve the tap density of the prepared single-crystal cathode material, thereby improving the energy density of the battery.

[0104] Thirdly, embodiments of this application provide a method for preparing a single-crystal cathode material, comprising the following steps:

[0105] Step S100: After atomizing the mixed solution containing nickel salt, cobalt salt and manganese salt, thermal decomposition is performed to obtain a cathode material precursor. The surface area weighted average particle size D[3,2] of the cathode material precursor is <2.0μm, and the standard deviation of the mass content of each element Ni, Co and Mn in the cathode material precursor is ≤0.05.

[0106] In step S200, the cathode material precursor is mixed with a lithium source and then sintered in an oxygen-containing atmosphere to obtain a cathode material. The standard deviation of the mass content of each element Ni, Co and Mn in the single-crystal cathode material is ≤0.03. The lattice strain of the single-crystal cathode material is ε, and ε < 0.2%.

[0107] The method for preparing single-crystal cathode material provided in this application involves atomizing a mixed solution containing nickel salt, cobalt salt, and manganese salt, followed by thermal decomposition to obtain a cathode material precursor. The surface area-weighted average particle size D[3,2] of this cathode material precursor is <2.0 μm, exhibiting high reactivity, which is beneficial for improving the reaction efficiency and mass transfer efficiency between the cathode material precursor and the lithium source during subsequent high-temperature sintering. Simultaneously, the standard deviation of the mass content of each element Ni, Co, and Mn in the cathode material precursor obtained by the above preparation method is ≤0.05, indicating good uniformity of Ni, Co, and Mn distribution in the cathode material precursor. Furthermore, the single-crystal cathode material prepared by sintering the above cathode material precursor with a lithium source exhibits high uniformity of Ni, Co, and Mn content. The standard deviation of the mass content of each element is ≤0.03, indicating good uniformity of Ni, Co, and Mn element distribution within the single-crystal cathode material. This helps reduce crystal structure defects in the single-crystal cathode material. Furthermore, the single-crystal cathode material has a low lattice strain, ε<0.2%, which can reduce the diffusion barrier of lithium ions between microcrystals and increase the Li ion diffusion coefficient, resulting in good rate performance and low DCR. At the same time, the low lattice strain can also suppress the generation of microcracks within the single-crystal cathode material, thereby improving the cycle performance of the single-crystal cathode material.

[0108] Step S100: After atomizing the mixed solution containing nickel salt, cobalt salt and manganese salt, thermal decomposition is performed to obtain a cathode material precursor. The surface area weighted average particle size D[3,2] of the cathode material precursor is <2.0μm, and the standard deviation of the mass content of each element Ni, Co and Mn in the cathode material precursor is ≤0.05.

[0109] Specifically, the surface area weighted average particle size D[3,2] of the cathode material precursor can be 1.98 μm, 1.95 μm, 1.8 μm, 1.75 μm, 1.64 μm, 1.5 μm, 1.3 μm, 1.2 μm, 1.1 μm, 0.8 μm, 0.9 μm, or 0.5 μm, etc., and is not limited here. When the surface area weighted average particle size D[3,2] of the cathode material precursor is controlled within the above range, the cathode material precursor has high reactivity, which is beneficial to improving the reaction efficiency and mass transfer efficiency of the cathode material precursor in the subsequent sintering process with the lithium source. The surface area weighted average particle size D[3,2] of the precursor is mainly related to the pyrolysis temperature. As the pyrolysis temperature increases, the surface area weighted average particle size D[3,2] increases, and the reactivity of the precursor decreases.

[0110] The standard deviation of the mass content of each element Ni, Co and Mn in the cathode material precursor can be 0.001, 0.005, 0.009, 0.01, 0.013, 0.02, 0.025, 0.03, 0.036, 0.01, 0.044, 0.045, 0.047 or 0.049, etc., and is not limited here.

[0111] In some embodiments, the nickel salt includes at least one of nickel chloride, nickel sulfate, nickel nitrate, nickel carbonate, nickel oxalate, and nickel acetate.

[0112] In some embodiments, the cobalt salt includes at least one of cobalt chloride, cobalt oxalate, cobalt carbonate, cobalt sulfate, cobalt nitrate, and cobalt acetate.

[0113] In some embodiments, the manganese salt includes at least one of manganese chloride, manganese carbonate, manganese sulfate, manganese oxalate, manganese nitrate, and manganese acetate.

[0114] In some embodiments, the molar ratio of Ni, Co, and Mn in the mixed solution is (50–98):(0–20):(0–30), and the content of Co and Mn in the mixed solution is not zero. Specifically, the molar ratio of Ni, Co, and Mn in the mixed solution can be 50:0.1:0.1, 60:10:30, 65:15:20, 65:5:30, 70:5:25, 70:10:20, 80:5:15, 85:10:5, or 98:1:1, etc., and is not limited here.

[0115] In some embodiments, the total metal concentration in the mixed solution is 200 g / L to 500 g / L, specifically 200 g / L, 220 g / L, 260 g / L, 300 g / L, 350 g / L, 400 g / L, 450 g / L, 480 g / L, or 500 g / L, etc., and of course, other values ​​within the above range are also possible, and are not limited here. The applicant has found that the metal concentration in the mixed solution can affect the preparation efficiency of the precursor and the degree of thermal decomposition reaction. When the metal concentration of the mixed liquid is too high, the precursor reaction may be incomplete, which will not only lead to structural instability, but also make the uniformity of particle element distribution unsatisfactory. When the metal concentration of the mixed liquid is too low, not only is the preparation efficiency low, but when the mixed liquid evaporates rapidly at high temperature, it is easy to produce more hollow spherical particles and breakage, which will lead to unsatisfactory particle size distribution. In addition, a large number of micro powder particles that affect the performance of the material will also be produced, while a small number of large particles will be produced. Large particles are more likely to cause uneven element distribution and affect the surface area weighted average particle size D of the single crystal cathode material precursor [3, 2].

[0116] In some embodiments, the mixed solution further includes a dopant containing N, where N includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Ca, Nb, W, Sb, Ta, Sn, and Y.

[0117] In some embodiments, the mixture is further subjected to an ultrasonic stirring step before atomization treatment. The ultrasonic stirring includes heating and ultrasonic stirring the mixture in a reaction vessel equipped with ultrasonic stirring function.

[0118] In some embodiments, the ultrasonic stirring temperature is 50°C to 70°C.

[0119] In some embodiments, the ultrasonic stirring frequency is 30KHz-50KHz, and the ultrasonic stirring time is 0.5h-2h.

[0120] Heating and ultrasonic stirring before atomization can further mix the chemical elements in the mixture, and quickly obtain more uniform droplets. This results in a more uniform distribution of elements on the surface of the precursor particles during thermal decomposition, and a smaller standard deviation of mass content.

[0121] In some embodiments, a surfactant, including polyethylene glycol, is added to the mixture before atomization.

[0122] Understandably, when polyethylene glycol dissolves in water to a certain concentration, it reduces the surface tension of the system, resulting in a smaller overall particle size of the cathode material precursor particles, a more uniform element distribution, and a reduction in the surface area weighted average particle size D of the single-crystal cathode material precursor [3, 2].

[0123] In some embodiments, the surfactant accounts for 0.5%-5% of the total mass of the mixture. Within this range, the surfactant can stably produce precursor particles with smooth, uniform morphology and good dispersibility. If the concentration is too low, the surfactant's effect is not significant; if it is too high, it will not only affect the overall concentration of the mixture but also lead to the precipitation of Ni, Co, and Mn metal ions.

[0124] In some embodiments, the mixture is further subjected to an ultrasonic stirring step before atomization. The mixture is placed in a reactor equipped with ultrasonic stirring and heated to 50°C–70°C. Simultaneously, the ultrasonic stirring frequency is adjusted to 30–50 kHz. After ultrasonic stirring in the reactor for 0.5–2 hours, the heating function is turned off, and 0.5%–5% (by mass) of polyethylene glycol is added to the mixture. The mixture is then ultrasonically stirred again for 0.5–1 hour. In some embodiments, the general chemical formula of the cathode material precursor is Ni. a Co b Mn c N d O eWherein, 0.50≤a≤0.98, 0<b≤0.20, 0<c≤0.30, 0≤d≤0.10, a+b+c+d=1, 1≤e≤1.15, and N includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Ca, Nb, W, Sb, Ta, Sn and Y.

[0125] In some embodiments, the range of mass content of each element Ni, Co, and Mn in the cathode material precursor is ≤0.12, specifically 0.01, 0.015, 0.018, 0.02, 0.029, 0.03, 0.035, 0.048, 0.059, 0.06, 0.08, 0.097, 0.10, 0.105, 0.11, 0.112, 0.115, or 0.119, etc., or other values ​​within the above range, which are not limited here.

[0126] Understandably, the standard deviation and range of the mass content of each of the elements Ni, Co, and Mn in the cathode material can reflect the uniformity of the distribution of Ni, Co, and Mn elements in the cathode material precursor. The lower the standard deviation and range of the mass content of each of the elements Ni, Co, and Mn, the more uniform the distribution of Ni, Co, and Mn elements in the cathode material precursor. At the same time, there is a good inheritance between the uniformity of the distribution of Ni, Co, and Mn elements in the cathode material precursor and the uniformity of the distribution of Ni, Co, and Mn elements in the single-crystal cathode material. The more uniform the distribution of Ni, Co, and Mn elements in the cathode material precursor, the more uniform the distribution of Ni, Co, and Mn elements in the single-crystal cathode material made from the cathode material precursor will be.

[0127] Controlling the standard deviation and range of the mass content of each element Ni, Co and Mn in the cathode material precursor within the above range is beneficial to improving the uniformity of the distribution of Ni, Co and Mn elements in the single-crystal cathode material, resulting in good uniformity of the distribution of Ni, Co and Mn elements in the single-crystal cathode material, fewer crystal structure defects in the single-crystal cathode material, and low lattice strain.

[0128] In some embodiments, the flow rate of the mixed solution is 100 L / h to 900 L / h, specifically 100 L / h, 200 L / h, 300 L / h, 400 L / h, 500 L / h, 600 L / h, 700 L / h, 800 L / h, or 900 L / h, etc., and is not limited thereto. A higher flow rate of the mixed solution results in a faster precursor synthesis rate, but also a worse uniformity in the Ni / Co / Mn distribution. A flow rate below 100 L / h leads to low precursor synthesis efficiency and high preparation costs. When the flow rate of the mixed solution exceeds 900 L / h, the standard deviation and variance of the mass content of each element (Ni, Co, and Mn) in the precursor increase significantly, resulting in a decrease in the uniformity of the Ni, Co, and Mn element distribution in the prepared single-crystal cathode material and an increase in lattice strain.

[0129] In some embodiments, the pressure of the atomization treatment is 0.4MPa to 0.8MPa, specifically 0.4MPa, 0.5MPa, 0.6MPa, 0.7MPa, 0.75MPa or 0.8MPa, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0130] In some embodiments, the thermal decomposition temperature is 500℃~850℃, specifically 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, or 800℃, but not limited to the listed values; other unlisted values ​​within this range also apply. As the thermal decomposition temperature increases, the surface area weighted average particle size D[3,2] of the cathode material precursor decreases, resulting in a reduction in precursor activity. When the pyrolysis temperature is higher than 850℃, the surface area weighted average particle size D[3,2] of the cathode material precursor is greater than 2.0 μm; at this point, the cathode material precursor has poor reactivity, leading to more defects in the subsequently prepared single-crystal cathode material, with a lattice strain ε exceeding 0.2%, resulting in poor rate performance, high DCR, and low cycle performance in the single-crystal cathode material. Therefore, appropriately lowering the thermal decomposition temperature of the precursor is beneficial to improving the precursor's reactivity and improving the rate performance and DCR of the cathode material. However, when the pyrolysis temperature is below 500℃, the metal salts of Ni, Co, and Mn do not decompose completely, resulting in incomplete decomposition of the precursor Cl. - NO3 - CO3 2- If the anion content is too high, these residual anions will inhibit the formation of single crystals and corrode the sintering furnace during the subsequent preparation of cathode materials.

[0131] In step S200, the cathode material precursor is mixed with a lithium source and then sintered in an oxygen-containing atmosphere to obtain a cathode material. The standard deviation of the mass content of each element Ni, Co and Mn in the single-crystal cathode material is ≤0.03. The lattice strain of the single-crystal cathode material is ε, and ε < 0.2%.

[0132] In some embodiments, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium sulfate, lithium chloride, lithium nitrate, and lithium oxalate.

[0133] In some embodiments, the molar ratio of lithium in the lithium source to the total of nickel, cobalt and manganese in the cathode material precursor is 0.98 to 1.10, specifically 0.98, 0.99, 1.01, 1.03, 1.05, 1.06, 1.08, 1.09 or 1.10, etc. Of course, other values ​​within the above range are also possible, and are not limited here.

[0134] In some embodiments, the sintering reaction temperature is 750℃ to 950℃, specifically 750℃, 760℃, 780℃, 800℃, 850℃, 900℃, 920℃, or 950℃, etc., and of course, other values ​​within the above range are also possible, without limitation. The sintering temperature is closely related to the Ni content; the higher the Ni content, the lower the sintering temperature. In addition, a suitable sintering temperature is beneficial for reducing crystal structure defects and lattice strain, thereby improving the electrochemical performance of the single-crystal cathode material.

[0135] In some embodiments, the sintering reaction time is 10h to 30h, specifically 10h, 12h, 15h, 16h, 18h, 20h, 24h, 28h or 30h, etc., and of course other values ​​within the above range are also possible, which are not limited here.

[0136] Fourthly, embodiments of this application provide a lithium-ion battery comprising a cathode material prepared by the method described in the first aspect or the method described in the third aspect for preparing a single-crystal cathode material.

[0137] The beneficial effects of this application will be further illustrated below with reference to embodiments and comparative examples.

[0138] Example 1

[0139] (1) Mass ratio (n) Ni :n Co :n Mn=0.67:0.05:0.28) Weigh nickel chloride, cobalt chloride, and manganese chloride and add them to water to prepare a mixed solution. Control the total metal concentration in the mixed solution to be 300 g / L. Place the mixed solution in a reactor with ultrasonic stirring function and heat it to 60°C. Simultaneously adjust the ultrasonic stirring frequency to 33 kHz. After ultrasonic stirring in the reactor for 1 hour, turn off the heating function and add 1% polyethylene glycol of the total mass of the mixed solution. Then ultrasonically stir for another 0.5 hours. Based on the total mass of Ni, Co, and Mn elements, SO4 2- The content was 900 ppm.

[0140] (2) After the above mixed solution is atomized into droplets, it is placed in an air atmosphere and thermally decomposed at 650°C in a calcining furnace; the flow rate of the mixed solution is controlled at 200L / h and the atomization pressure is 0.6MPa.

[0141] (3) The thermal decomposition products are subjected to air jet milling to obtain the cathode material precursor (Ni). 0.67 Co 0.05 Mn 0.28 O).

[0142] (4) Mass ratio (n) Ni+Co+Mn :n Li =1:1) Weigh out the cathode material precursor and mix it evenly with lithium carbonate, then place it in an oxygen atmosphere and heat it to 920℃ for 20h to obtain single crystal cathode material.

[0143] The single-crystal cathode material prepared in this embodiment has the general chemical formula LiNi. 0.67 Co 0.05 Mn 0.28 O2, average particle size D of single-crystal cathode material 50 The thickness is 3.8 μm, and the Baxter tap density is 1.95 g / cm³. 3 .

[0144] Figure 1 This is a SEM image of the cathode material precursor prepared in Example 1 of this application. Figure 2 Here is another SEM image of the cathode material precursor prepared in Example 1 of this application, as shown below. Figure 1 and Figure 2 As shown, the cathode material precursor includes secondary particles, which in turn include multiple aggregated primary particles.

[0145] When observing the cathode material precursor prepared in Example 1 of this application using a scanning electron microscope, at a magnification of 3K, 10 points were randomly selected for EDS point scanning to test the Ni, Co, and Mn contents. The EDS spectrum results of the cathode material precursor are as follows: Figure 3As shown, the range of Ni content in the cathode material precursor is 0.095, and the standard deviation is 0.036; the range of Co content is 0.029, and the standard deviation is 0.009; the range of Mn content is 0.081, and the standard deviation is 0.030. This indicates that the cathode material precursor prepared in Example 1 has good uniformity of Ni, Co, and Mn distribution. Furthermore, ion chromatography detection revealed free SO42- on the precursor surface. 2- The content was 504 ppm.

[0146] Figure 4 The Williamson-Hall analysis fitting curve for the single-crystal cathode material prepared in Example 1 of this application is shown below. Figure 4 As shown, by analyzing Figure 4 Analysis and calculation of the data yielded a lattice strain of 0.11% for the single-crystal cathode material. Other performance parameters of the cathode material precursor and the single-crystal cathode material are detailed in Tables 1 and 2.

[0147] Example 2

[0148] Unlike Example 1, (2) after the above mixed solution was atomized into droplets, it was placed in an air atmosphere and thermally decomposed in a calcining furnace at 750°C; the flow rate of the mixed solution was controlled at 200 L / h and the atomization pressure was 0.6 MPa.

[0149] The single-crystal cathode material prepared in this embodiment has the general chemical formula LiNi. 0.67 Co 0.05 Mn 0.28 The O2 single-crystal cathode material has an average particle size D50 of 3.7 μm and a tap density of 1.85 g / cm³. 3 .

[0150] Other performance parameters of the cathode material precursor and single-crystal cathode material are detailed in Tables 1 and 2.

[0151] Example 3

[0152] Unlike Example 1, (2) after the above mixed solution was atomized into droplets, it was placed in an air atmosphere and thermally decomposed in a calcining furnace at 650°C; the flow rate of the mixed solution was controlled at 100L / h and the atomization pressure was 0.6MPa.

[0153] The single-crystal cathode material prepared in this embodiment has the general chemical formula LiNi. 0.67 Co 0.05 Mn 0.28 The O2 single-crystal cathode material has an average particle size D50 of 4.0 μm and a tap density of 2.12 g / cm³. 3 .

[0154] Other performance parameters of the cathode material precursor and single-crystal cathode material are detailed in Tables 1 and 2.

[0155] Example 4

[0156] Unlike Example 1, (2) after the above mixed solution was atomized into droplets, it was placed in an air atmosphere and thermally decomposed at 500°C in a calcining furnace; the flow rate of the mixed solution was controlled at 500L / h and the atomization pressure was 0.6MPa.

[0157] The single-crystal cathode material prepared in this embodiment has the general chemical formula LiNi. 0.67 Co 0.05 Mn 0.28 The O2 single-crystal cathode material has an average particle size D50 of 3.8 μm and a tap density of 1.90 g / cm³. 3 .

[0158] Other performance parameters of the cathode material precursor and single-crystal cathode material are detailed in Tables 1 and 2.

[0159] Example 5

[0160] Unlike Example 1, (4) molar ratio (n) Ni+Co+Mn :n Li =1:1) Weigh out the cathode material precursor and mix it evenly with lithium carbonate, then place it in an oxygen atmosphere and heat it to 950℃ for 20h to obtain single crystal cathode material.

[0161] The single-crystal cathode material prepared in this embodiment has the general chemical formula LiNi. 0.67 Co 0.05 Mn 0.28 The O2 single-crystal cathode material has an average particle size D50 of 4.5 μm and a Batter tap density of 2.2 g / cm³. 3 .

[0162] Other performance parameters of the cathode material precursor and single-crystal cathode material are detailed in Tables 1 and 2.

[0163] Example 6

[0164] Unlike Example 1, (4) molar ratio (n) Ni+Co+Mn :n Li =1:1) Weigh out the cathode material precursor and mix it evenly with lithium carbonate, then place it in an oxygen atmosphere and heat it to 900℃ for 20h to obtain single crystal cathode material.

[0165] The single-crystal cathode material prepared in this embodiment has the general chemical formula LiNi. 0.67 Co 0.05 Mn 0.28The O2 single-crystal cathode material has an average particle size D50 of 3.0 μm and a tap density of 1.68 g / cm³. 3 .

[0166] Other performance parameters of the cathode material precursor and single-crystal cathode material are detailed in Tables 1 and 2.

[0167] Example 7

[0168] (1) Mass ratio (n) Ni :n Co :n Mn =0.88:0.06:0.04) Weigh out nickel chloride, cobalt chloride, and manganese chloride and add them to water to prepare a mixed solution. Control the total metal concentration in the mixed solution to be 300 g / L. Based on the total mass of Ni, Co, and Mn elements, SO4 2- The content is ≤1780ppm.

[0169] (2) After the above mixed solution is atomized into droplets, it is placed in an air atmosphere and thermally decomposed at 600°C in a calcining furnace; the flow rate of the mixed solution is controlled at 200L / h and the atomization pressure is 0.6MPa.

[0170] (3) The thermal decomposition products are subjected to air jet milling to obtain the cathode material precursor (Ni). 0.88 Co 0.06 Mn 0.04 O).

[0171] (4) Mass ratio (n) Ni+Co+Mn :n Li =1:1) Weigh out the cathode material precursor and mix it evenly with lithium carbonate, then place it in an oxygen atmosphere and heat it to 850℃ for sintering for 15h to obtain single crystal cathode material.

[0172] The single-crystal cathode material prepared in this embodiment has the general chemical formula LiNi. 0.88 Co 0.06 Mn 0.04 The O2 single-crystal cathode material has an average particle size D50 of 3.2 μm and a tap density of 1.77 g / cm³. 3 .

[0173] Other performance parameters of the cathode material precursor and single-crystal cathode material are detailed in Tables 1 and 2.

[0174] Example 8

[0175] (1) Mass ratio (n) Ni :n Co :n Mn :n Al=0.88:0.06:0.03:0.03) Weigh out nickel chloride, cobalt chloride, manganese chloride and aluminum chloride and add them to water to prepare a mixed solution. Control the total metal concentration in the mixed solution to be 300 g / L.

[0176] (2) After the above mixed solution is atomized into droplets, it is placed in an air atmosphere and thermally decomposed at 600°C in a calcining furnace; the flow rate of the mixed solution is controlled at 200L / h and the atomization pressure is 0.6MPa.

[0177] (3) The thermal decomposition products are subjected to air jet milling to obtain the cathode material precursor (Ni). 0.88 Co 0.06 Mn 0.03 Al 0.03 O).

[0178] (4) Mass ratio (n) Ni+Co+Mn+Al :n Li =1:1) Weigh out the cathode material precursor and mix it evenly with lithium hydroxide, then place it in an oxygen atmosphere and heat it to 850℃ for sintering for 15h to obtain the cathode material.

[0179] The single-crystal cathode material prepared in this embodiment has the general chemical formula LiNi. 0.88 Co 0.06 Mn 0.03 Al 0.03 The O2 single-crystal cathode material has an average particle size D50 of 3.2 μm and a tap density of 1.78 g / cm³. 3 .

[0180] Other performance parameters of the cathode material precursor and single-crystal cathode material are detailed in Tables 1 and 2.

[0181] Example 9

[0182] Unlike Example 1, (1) based on the total mass of Ni, Co, and Mn elements, SO4 2- The content was 200 ppm. Ion chromatography analysis showed that the free SO42- on the surface of the precursor prepared in this example... 2- The content of [missing information] is 100 ppm. The single-crystal cathode material prepared in this embodiment has the general chemical formula LiNi. 0.67 Co 0.05 Mn 0.28 O2, average particle size D of single-crystal cathode material 50 The thickness is 3.8 μm, and the Baxter tap density is 1.95 g / cm³. 3 Other performance parameters of the cathode material precursor and single-crystal cathode material are detailed in Tables 1 and 2.

[0183] Example 10

[0184] Unlike Example 1, (1) molar ratio (n) Ni :n Co :n Mn =0.67:0.05:0.28) Weigh out nickel chloride, cobalt chloride, and manganese chloride and add them to water to prepare a mixed solution. Control the total metal concentration in the mixed solution to be 500 g / L, and add 5% polyethylene glycol by mass of the total mass of the mixed solution; based on the total mass of Ni, Co, and Mn elements, SO4 2- The content was 900 ppm.

[0185] The single-crystal cathode material prepared in this embodiment has the general chemical formula LiNi. 0.67 Co 0.05 Mn 0.28 The O2 single-crystal cathode material has an average particle size D50 of 3.8 μm and a tap density of 1.83 g / cm³. 3 Other performance parameters of the cathode material precursor and single-crystal cathode material are detailed in Tables 1 and 2.

[0186] Example 11

[0187] Unlike Example 1, (1) molar ratio (n) Ni :n Co :n Mn =0.67:0.05:0.28) Weigh nickel chloride, cobalt chloride, and manganese chloride and add them to water to prepare a mixed solution. Control the total metal concentration in the mixed solution to be 200 g / L. Place the mixed solution in a reaction vessel with ultrasonic stirring function and heat it to 60℃. At the same time, adjust the ultrasonic stirring frequency to 33 kHz and ultrasonically stir in the reaction vessel for 1 hour. Based on the total mass of Ni, Co, and Mn elements, SO4 2- The content was 900 ppm.

[0188] The single-crystal cathode material prepared in this embodiment has the general chemical formula LiNi. 0.67 Co 0.05 Mn 0.28 The O2 single-crystal cathode material has an average particle size D50 of 4.1 μm and a tap density of 1.82 g / cm³. 3 Other performance parameters of the cathode material precursor and single-crystal cathode material are detailed in Tables 1 and 2.

[0189] Comparative Example 1

[0190] Unlike Example 1, (2) after the above mixed solution was atomized into droplets, it was placed in an air atmosphere and thermally decomposed in a calcining furnace at 880°C; the flow rate of the mixed solution was controlled at 200L / h and the atomization pressure was 0.6MPa.

[0191] The single-crystal cathode material prepared in this comparative example has the general chemical formula LiNi. 0.67 Co 0.05 Mn 0.28 The O2 cathode material has an average particle size D50 of 3.82 μm and a Baxter tap density of 1.86 g / cm³. 3 .

[0192] Other performance parameters of the cathode material precursor and single-crystal cathode material are detailed in Tables 1 and 2.

[0193] Comparative Example 2

[0194] Unlike Example 1, (2) after the above mixed solution was atomized into droplets, it was placed in an air atmosphere and thermally decomposed in a calcining furnace at 650°C; the flow rate of the mixed solution was controlled at 1000L / h and the atomization pressure was 0.6MPa.

[0195] The single-crystal cathode material prepared in this comparative example has the general chemical formula LiNi. 0.67 Co 0.05 Mn 0.28 The O2 single-crystal cathode material has an average particle size D50 of 3.72 μm and a tap density of 1.90 g / cm³. 3 .

[0196] Other performance parameters of the cathode material precursor and single-crystal cathode material are detailed in Tables 1 and 2.

[0197] Comparative Example 3

[0198] Unlike Example 1, (4) molar ratio (n) Ni+Co+Mn :n Li =1:1) Weigh out the cathode material precursor and mix it evenly with lithium carbonate, then place it in an oxygen atmosphere and heat it to 700℃ for 20h to obtain the cathode material.

[0199] The cathode material prepared in this comparative example is a polycrystalline cathode material with the general chemical formula LiNi. 0.67 Co 0.05 Mn 0.28 The O2 polycrystalline cathode material has an average particle size D50 of 3.2 μm and a tap density of 1.8 g / cm³. 3 .

[0200] Other performance parameters of the cathode material precursor and single-crystal cathode material are detailed in Tables 1 and 2.

[0201] Comparative Example 4

[0202] Ni was prepared according to Example 2 of CN113488642A. 0.88 Co 0.06 Mn 0.03 Al0.03 (OH)2 quaternary precursor and corresponding cathode material.

[0203] (1) Preparation of the first solution: Weigh nickel sulfate hexahydrate, manganese sulfate monohydrate, and cobalt sulfate heptahydrate according to the molar ratio of nickel:cobalt:manganese = 0.88:0.06:0.03, dissolve them in deionized water, and prepare a transition metal salt solution with a mass concentration of 2 mol / L, which is called the first solution;

[0204] (2) Preparation of the second solution: Weigh aluminum nitrate nonahydrate and dissolve it in deionized water. Then, add concentrated ammonia solution with a mass concentration of 25% dropwise to the aluminum salt solution while stirring continuously. Stop adding concentrated ammonia solution when the pH is 8-9. Finally, make up the volume to a concentration of aluminum hydroxide of 0.11 mol / L, which is called the second solution.

[0205] (3) Preparation of quaternary transition metal hydroxide precursor: Ammonia solution was added to the reactor beforehand, the reaction system temperature was controlled at 55℃, and the stirring speed was adjusted to 1000 rpm. The first solution was added to the reactor at a rate of 35 L / h using metering pump No. 1, the second solution was added to the reactor at a rate of 20 L / h using metering pump No. 2, and ammonia solution was added using metering pump No. 3 to maintain the ammonia concentration in the system at 0.5 mol / L. Sodium hydroxide solution was added using metering pump No. 4 to control the pH of the reaction system at 10.0 ± 0.5. The reaction was continued for 17 h, and then aged for 10 h. The final precipitate was filtered and washed, dried in an oven at 110℃ for 12 h, crushed and sieved to obtain Ni. 0.88 Co 0.06 Mn 0.03 Al 0.03 (OH)2 hydroxide precursor.

[0206] (4) The hydroxide precursor and lithium hydroxide were mixed evenly at a molar ratio of 1:1.05, and sintered at 500℃ for 3 h and 850℃ for 15 h under an oxygen atmosphere. After cooling, the product was pulverized and sieved until the D50 was 12 μm to obtain the single crystal cathode material LiNi. 0.88 Co 0.06 Mn 0.03 Al 0.03 O2.

[0207] Other performance parameters of the cathode material precursor and single-crystal cathode material are detailed in Tables 1 and 2.

[0208] Comparative Example 5

[0209] Ni preparation according to CN116230922A 0.8 Co 0.1 Mn 0.1 (OH)2 precursor and corresponding cathode materials.

[0210] (1) Mix NiSO4, CoSO4 and MnSO4 in a Ni / Co / Mn molar ratio of 0.8:0.1:0.1 to prepare a solution.

[0211] (2) The solution was added to a reactor at 55°C, and NaOH and NH3·H2O were used as precipitating and chelating agents respectively to carry out a co-precipitation reaction for 36 hours to obtain Ni. 0.8 Co 0.1 Mn0.1(OH)2 precursor.

[0212] (3) The precursor is dried at 80°C for 12 hours and then dried again at 110°C for 12 hours.

[0213] (4) Add the precursor and lithium hydroxide to a dry high-speed mixer at a molar ratio of 1:1.05 and mix for 5 minutes.

[0214] (5) The temperature was increased to 950℃ at a rate of 2℃ / min and held at 950℃ for 5 hours, then naturally cooled to 900℃ and held for 5 hours. Oxygen was continuously purged at a flow rate of 10 mL / min during the heating and holding periods. After calcination, the mixture was naturally cooled to room temperature and then pulverized and graded to prepare LiNi. 0.8 Co 0.1 Mn 0.1 O2 single-crystal cathode material.

[0215] Other performance parameters of the cathode material precursor and single-crystal cathode material are detailed in Tables 1 and 2.

[0216] Comparative Example 6

[0217] Unlike Example 1, (1) based on the total mass of Ni, Co, and Mn elements, SO4 2- The content is 2000ppm.

[0218] The precursor prepared in this embodiment contains free SO4 on its surface. 2- The content of [unspecified substance] is 1200 ppm. The single-crystal cathode material prepared in this embodiment has the general chemical formula LiNi. 0.67 Co 0.05 Mn 0.28 O2, average particle size D of single-crystal cathode material 50 The thickness is 3.8 μm, and the Baxter tap density is 1.95 g / cm³. 3 Other performance parameters of the cathode material precursor and single-crystal cathode material are detailed in Tables 1 and 2.

[0219] Test method:

[0220] (1) At a magnification of 3K, the energy dispersive X-ray spectrometer (EDS) attached to the scanning electron microscope was used to randomly select 10 points on the surface of the untreated cathode material precursor or single crystal cathode material for scanning and testing the Ni, Co and Mn content of the cathode material precursor or single crystal cathode material. The standard deviation and range of the mass content of each element Ni, Co and Mn were counted to characterize the uniformity of the distribution of Ni, Co and Mn elements.

[0221] (2) The surface area weighted average particle size D of the cathode material precursor was obtained by using a Malvern 3000 laser particle size analyzer [3, 2].

[0222] (3) The lattice strain and grain size of the single-crystal cathode material were calculated from the XRD data using Williamson-Hall analysis:

[0223] The specific procedure was as follows: Measurements were taken using a Rigaku X-ray diffractometer (Japan), under the following conditions: 0.75 degrees / minute, step size 0.02, continuous scanning within the 2θ range from 10 to 90 degrees. The result was plotted using 4sinθ. hkl Let β be the x-axis. hkl cosθ hkl Using the vertical axis as the ordinate, a curve is plotted and linearly fitted. The strain ε and grain size D can be calculated using the slope and intercept. It is worth noting that the full width at half maximum (FWHM) β used for fitting... hkl The influence of the instrument needs to be eliminated, i.e., β. hkl =β 总 -β 仪器 , where β 总 β is the actual measured full width at half maximum (FWHM). 仪器 The half-peak width broadening caused by the instrument can be calculated using XRD on a standard silicon wafer. The β value of the testing equipment used in this application... 仪器 The value is 0.000103. In addition, the data of seven strong diffraction peaks (003), (101), (102), (104), (015), (107), and (113) were selected for fitting to improve the linear fitting degree and reduce the experimental error.

[0224]

[0225] Where β is the full width at half maximum (FWHM), θ is the diffraction angle (in radians), k is a constant of 0.89, λ is the X-ray wavelength of 0.154 nm, D is the grain size (in nm), and ε is the lattice strain, which is dimensionless.

[0226] (4) Using Baxter vibration, a certain amount of sample was weighed and vibrated 3000 times at 300 times / min to test the compaction density.

[0227] (5) Electrochemical performance testing:

[0228] The electrochemical performance of the materials was evaluated using coin cell half-cells. The specific procedure was as follows: Single-crystal positive electrode material, conductive carbon black, and PVDF were weighed in a mass ratio of 93:5:2. N-methyl-2-pyrrolidone (NMP) was added at a solid content of 50%, and the mixture was stirred into a viscous slurry using a high-speed disperser. This slurry was then evenly coated onto aluminum foil using a scraper, dried in an oven at 80°C, rolled, and cut into positive electrode sheets with a diameter of 14 mm. A 16 mm lithium foil was used as the negative electrode, a Celgard polypropylene membrane as the separator, and a 1 mol / L LiPF6 carbonate solution as the electrolyte. The cells were assembled in an argon-filled glove box to obtain coin cell half-cells. Capacity and cycle performance tests were conducted using a LAND battery testing system at 25°C and 3.0–4.3 V. The nominal capacity at 1C was set to 200 mAh / g. In addition, the voltage UA at the beginning of each discharge cycle and the voltage data UB at 60 seconds are recorded. The discharge current IDis is calculated using the formula DCR = (U... A -U B ) / I Dis .

[0229] (6) SO4 2- Content testing:

[0230] Dissolve 0.5 g in 50 ml of water, sonicate for 5 min, filter, and measure SO4 in the filtrate using ion chromatography (Thermo Fisher Scientific ICS 6000HPIC). 2- Ion content.

[0231] (7) Electron backscatter diffraction (EBSD) test:

[0232] The cathode material sample was first embedded in a carbon varnish (PELCO) graphite block, and then the cross-section of the block was polished using an argon ion beam. Electron backscatter diffraction (EBSD) imaging was performed using a JEOL JSM-7000F scanning electron microscope. The EBSD image step size was set to 250 nm (each pixel is 250 nm × 250 nm).

[0233] The test results are detailed in Tables 1 to 3.

[0234] Table 1. Performance parameters of the cathode material precursors prepared in each embodiment and comparative example.

[0235]

[0236]

[0237] Table 2 shows the performance parameters of the single-crystal cathode materials prepared in each embodiment and comparative example.

[0238]

[0239] Table 3. Electrochemical performance test results of the single-crystal cathode materials prepared in each example and comparative example.

[0240]

[0241]

[0242] According to the test data in Tables 1-3, the standard deviation of the mass content of each element Ni, Co, and Mn in the single-crystal cathode materials prepared in Examples 1-8 is ≤0.03, and the range of the mass content of each element Ni, Co, and Mn is ≤0.08. This indicates that the distribution of Ni, Co, and Mn elements inside the single-crystal cathode material is relatively uniform, which is beneficial to reducing crystal structure defects in the single-crystal cathode material. The lattice strain ε of the single-crystal cathode material is <0.2%, which can reduce the diffusion barrier of lithium ions between microcrystals, increase the Li ion diffusion coefficient, and make the single-crystal cathode material exhibit good rate performance and low DCR. At the same time, the low lattice strain can also suppress the generation of microcracks in the single-crystal cathode material, thereby improving the cycle performance of the single-crystal cathode material.

[0243] According to the data in Tables 1 and 2, there is a good inheritance between the uniformity of Ni, Co, and Mn distribution in the cathode material precursor and the uniformity of Ni, Co, and Mn distribution in the single-crystal cathode material. The smaller the range and standard deviation of the mass content of each element Ni, Co, and Mn in the cathode material precursor, the smaller the range and standard deviation of the mass content of each element Ni, Co, and Mn in the single-crystal cathode material. In addition, the range and standard deviation of Ni, Co, and Mn content in the single-crystal cathode material are always smaller than those in the precursor. This is because the preparation of single-crystal cathode material requires high-temperature sintering, which allows metal ions to diffuse further, thereby improving the uniformity of Ni, Co, and Mn distribution.

[0244] According to the test data in Tables 1-3, the single-crystal cathode material prepared in Example 1 has the best overall performance.

[0245] Comparing Examples 1 and 2, the single-crystal cathode material of Example 1 exhibits better rate performance, lower impedance, and higher cycle performance. This is because the temperature at which the atomized mixed solution undergoes thermal decomposition during the preparation of the cathode material precursor in Example 1 is suitable, resulting in a low surface area-weighted average particle size D[3,2] of the cathode material precursor, high reactivity of the cathode material precursor, reduced crystal structure defects in the single-crystal cathode material, and low lattice strain in the single-crystal cathode material. Therefore, the single-crystal cathode material prepared in Example 1 exhibits better rate performance, lower impedance, and better cycle performance.

[0246] Compared to Example 1, Example 5 involved an increased sintering temperature during the sintering of the cathode material precursor and the lithium source. This resulted in lower ranges and standard deviations of the mass content of each element (Ni, Co, and Mn) in the single-crystal cathode material, and a decrease in the lattice strain ε, thus improving cycle performance. However, due to the significantly larger grain size of the single-crystal cathode material and the longer Li ion diffusion path, the rate performance of the single-crystal cathode material prepared in Example 5 was lower than that in Example 1.

[0247] Compared with Example 1, in Example 6, the sintering temperature was lowered during the sintering process of the cathode material precursor and the lithium source, resulting in a smaller grain size of the single-crystal cathode material and an increase in the lattice strain ε. Therefore, the cycle stability of the single-crystal cathode material in Example 6 was lower than that of the single-crystal cathode material in Example 1.

[0248] Compared to Example 1, the free SO4 in the precursor and cathode material of Example 9 2- The reduced content results in better rate capability and cycle performance.

[0249] Compared with Example 1, Example 10 did not perform ultrasonic stirring before atomization of the single-crystal cathode material precursor mixture. The range and standard deviation of the mass content of each element Ni, Co and Mn in the single-crystal cathode precursor were higher, which affected its cycle life and internal resistance.

[0250] Compared with Example 1, Example 11 did not add polyethylene glycol for ultrasonic stirring before atomizing the single crystal cathode material precursor mixture. The surface area weighted average particle size D[3,2] of the single crystal cathode material was larger, which may lead to the formation of large agglomerates. In addition, the range and standard deviation of the mass content of each element Ni, Co and Mn in the single crystal cathode precursor were higher, which affected its cycle life and internal resistance.

[0251] Compared to Example 1, the free SO4 in the cathode material of Comparative Example 6 2- Exceeding 1000 ppm. Excessive SO4. 2- This leads to a deterioration in material capacity, rate capability, and cycle performance.

[0252] Compared with Example 1, Comparative Example 1 increased the thermal decomposition temperature during the preparation of the cathode material precursor, thereby making the surface area weighted average particle size D[3,2] of the cathode material precursor greater than 2.0 μm; the cathode material precursor had poor reactivity, resulting in more defects in the subsequently prepared single-crystal cathode material, with lattice strain ε exceeding 0.2%, which caused the single-crystal cathode material to exhibit poor rate performance, high DCR and low cycle performance.

[0253] Compared with Example 1, the cathode material of Comparative Example 2 had an increased atomization flow rate during the preparation of the precursor. The standard deviation and variance of the mass content of each element Ni, Co and Mn in the prepared cathode material precursor were significantly increased, resulting in a decrease in the uniformity of the distribution of Ni, Co and Mn elements in the prepared single crystal cathode material and an increase in lattice strain ε exceeding 0.2%. Therefore, the rate performance and cycle performance of the single crystal cathode material prepared in Comparative Example 2 both decreased.

[0254] Compared to Example 1, the cathode material in Comparative Example 3 was sintered at too low a temperature during the sintering process of the precursor and lithium source, resulting in a polycrystalline structure. This cathode material has a grain size of less than 150 nm and exhibits good rate performance; however, its lattice strain exceeds 0.2%, making it prone to cracking and pulverization during cycling, reducing the structural stability of the cathode material and causing a significant decrease in its cycle capacity.

[0255] Compared with Example 1, the standard deviation and variance of the mass content of each element Ni, Co and Mn in the cathode material precursor of Comparative Example 4 are significantly greater than those in Example 1. Therefore, the lattice strain of the prepared single-crystal cathode material is significantly increased, exceeding 0.2%, which leads to a significant decrease in the rate performance and cycle performance of the single-crystal cathode material.

[0256] Similarly, in the single-crystal cathode material prepared in Comparative Example 5, the surface area weighted average particle size D[3,2] of the cathode material precursor is too large, and the standard deviation and variance of the mass content of each element Ni, Co and Mn in the cathode material precursor are significantly greater than those in Example 1. Therefore, the lattice strain of the prepared single-crystal cathode material is significantly increased, and the lattice strain exceeds 0.2%, which leads to a significant decrease in the rate performance and cycle performance of the cathode material.

[0257] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A cathode material precursor, characterized in that, The general chemical formula of the cathode material precursor is Ni. a Co b Mn c N d O e Wherein, 0.50≤a≤0.98, 0<b≤0.20, 0<c≤0.30, 0≤d≤0.10, a+b+c+d=1, 1≤e≤1.15, and N includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Ca, Nb, W, Sb, Ta, Sn and Y; The surface area weighted average particle size D[3,2] of the cathode material precursor, measured by a Malvern 3000 laser particle size analyzer, is <2.0 μm. When observing the cathode material precursor with a scanning electron microscope, at a magnification of 3K, 10 points were randomly selected on the cathode material precursor for EDS point scanning to test the Ni, Co, and Mn contents. In the EDS spectrum results of the cathode material precursor, the standard deviation of the mass content of each element Ni, Co, and Mn in the cathode material precursor was ≤0.

05.

2. The cathode material precursor according to claim 1, characterized in that, The range of mass content of each element Ni, Co and Mn in the cathode material precursor is ≤0.

12.

3. The cathode material precursor according to claim 1, characterized in that, The cathode material precursor satisfies at least one of the following technical features: (1) The cathode material precursor includes secondary particles, which include a plurality of aggregated primary particles; (2) The cathode material precursor includes secondary particles, which include multiple aggregated primary particles, and the primary particles are spherical. (3) The cathode material precursor includes secondary particles, which include multiple aggregated primary particles, and the particle size of the primary particles is 20nm~1000nm.

4. The cathode material precursor according to claim 1, characterized in that, The cathode material precursor satisfies at least one of the following technical features: (1) The average particle size D of the cathode material precursor 50 <3.5μm; (2) The specific surface area of ​​the cathode material precursor is >5m². 2 / g; (3) The Batter tap density of the cathode material precursor is >1 g / cm³. 3 .

5. The cathode material precursor according to claim 1, characterized in that, The surface area-weighted average particle size D[3,2] of the cathode material precursor satisfies one of the following conditions: (1) The surface area weighted average particle size D[3,2] of the cathode material precursor is 1.98μm, 1.95μm, 1.8μm, 1.75μm, 1.64μm, 1.5μm, 1.3μm, 1.2μm, 1.1μm, 0.8μm, 0.9μm or 0.5μm or within any two of the above values; (2)1.5μm≤D[3,2]≤1.9μm.

6. The cathode material precursor according to claim 1, characterized in that, The standard deviation of the mass content of each element Ni, Co, and Mn in the cathode material precursor satisfies one of the following conditions: (1) The standard deviation of the mass content of each element Ni, Co and Mn in the cathode material precursor is 0.001, 0.005, 0.009, 0.01, 0.013, 0.02, 0.025, 0.03, 0.036, 0.04, 0.044, 0.045, 0.047 or 0.049 or within any two of the above values; (2) The standard deviation of the mass content of each element Ni, Co and Mn in the cathode material precursor is ≤0.040; (3) The standard deviation of the mass content of each element Ni, Co and Mn in the cathode material precursor is ≤0.030; (4) The standard deviation of the mass content of each element Ni, Co and Mn in the cathode material precursor is ≤0.

020.

7. A single-crystal cathode material, wherein the single-crystal cathode material is prepared by mixing the cathode material precursor according to any one of claims 1-6 with a lithium source, characterized in that, The chemical formula of the single-crystal cathode material is Li. x Ni a Co b Mn c N d O2, wherein 0.98≤x≤1.1, 0.50≤a≤0.98, 0<b≤0.20, 0<c≤0.30, 0≤d≤0.10, a+b+c+d=1, and N includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Ca, Nb, W, Sb, Ta, Sn and Y; When observing the single-crystal cathode material with a scanning electron microscope, at a magnification of 3K, 10 points were randomly selected on the single-crystal cathode material for EDS point scanning to test the content of Ni, Co, and Mn. In the EDS spectrum results of the single-crystal cathode material, the standard deviation of the mass content of each element Ni, Co, and Mn in the single-crystal cathode material was ≤0.

03. The lattice strain of the single-crystal cathode material, calculated from XRD data using Williamson-Hall analysis, is ε, and ε < 0.2%.

8. The single-crystal cathode material according to claim 7, characterized in that, The range of mass content of each element Ni, Co and Mn in the single-crystal cathode material is ≤0.

08.

9. The single-crystal cathode material according to claim 7, characterized in that, The single-crystal cathode material satisfies at least one of the following characteristics: (1) The average particle size D of the single-crystal cathode material 50 The thickness ranges from 1.5μm to 5μm. (2) The Batter tap density of the single-crystal cathode material is >1.5 g / cm³. 3 ; (3) The compaction density of the single-crystal cathode material is >3.0 g / cm³. 3 .

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the single-crystal cathode material as described in any one of claims 7 to 9.

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