Preparation method of ternary positive electrode material, ternary positive electrode material and electrochemical device thereof

Abstract

The application provides a preparation method of a ternary positive electrode material, the ternary positive electrode material and an electrochemical device thereof. The preparation method comprises the following steps: performing a co-precipitation reaction on a ternary positive electrode material precursor and a W source and a Zr source respectively to obtain a first precursor doped with W and a second precursor doped with Zr, wherein the median particle size D50 of the first precursor is D1, the median particle size D50 of the second precursor is D2, and the following condition is met: 1.2≤D2 / D1≤1.8; mixing the first precursor and the second precursor to obtain a mixed precursor; mixing the mixed precursor and a lithium source and performing sintering to make the first precursor form single-crystal first particles and make the second precursor form single-crystal second particles, thereby obtaining a base material; and mixing the base material and a coating material and performing sintering, thereby obtaining the ternary positive electrode material. The above preparation method can improve the structural stability of the positive electrode material, and make the material have good cycle performance and rate performance on the basis of high tap density.

Description

Technical Field

[0001] This application relates to the field of battery materials technology, and in particular to a method for preparing a ternary cathode material, the ternary cathode material and its electrochemical device. Background Technology

[0002] With the increasing demand for range in the new energy vehicle market, increasing the compaction density of cathode materials has become an important way to increase battery capacity, given the limitations of battery pack size and weight.

[0003] Currently, in pursuit of high energy density, the industry typically uses single-crystal cathode materials to improve compaction density. However, the calcination temperature of single-crystal nickel ternary cathode materials during high-temperature lithiation is about 100°C higher than that of polycrystalline materials. This causes severe Li / O loss, generating more oxygen vacancy defects. These defects affect the crystal structure and electrochemical performance of the material, thus adversely impacting the improvement of compaction density. It also reduces the material's stability and cycle performance. Furthermore, in pursuit of high energy density, battery manufacturers may over-pressure the electrodes. Over-pressure causes large-area breakage of the spherical ternary material, forming fine particles. These small particles may locally deteriorate the electrode's conductivity, increase the specific surface area, increase side reactions, and reduce electrode porosity, making it difficult for electrolyte to penetrate the electrode interior. This leads to poorer specific capacity, greater polarization during battery cycling, faster degradation, and a significant increase in internal resistance.

[0004] Therefore, there is an urgent need for a new type of ternary cathode material and its preparation method, which can improve the material's structural stability while increasing the material's compaction density, thereby solving the technical problem of the deterioration of the cycle stability and rate performance of existing ternary cathode materials under high pressure. Summary of the Invention

[0005] In view of this, in order to solve at least one of the above technical problems, this application provides a method for preparing a ternary cathode material and a ternary cathode material.

[0006] In addition, this application also provides an electrochemical device using the aforementioned ternary cathode material.

[0007] In a first aspect, embodiments of this application provide a method for preparing a ternary cathode material, comprising: co-precipitating a ternary cathode material precursor with a W source and a Zr source respectively to obtain a W-doped first precursor and a Zr-doped second precursor, wherein the median particle size D50 of the first precursor is D1 and the median particle size D50 of the second precursor is D2, satisfying: 1.2≤D2 / D1≤1.8; mixing the first precursor and the second precursor to obtain a mixed precursor, wherein the median particle size D50 of the mixed precursor is D3, satisfying: 3.7μm≤D3≤4.2μm; mixing the mixed precursor with a lithium source and sintering it to form a first single-crystal particle of the first precursor and a second single-crystal particle of the second precursor, thereby obtaining a matrix material; and mixing the matrix material with a coating material and sintering it to obtain the ternary cathode material.

[0008] Based on the first aspect, in some embodiments of this application, when preparing the first precursor, the doping amount of W element accounts for 0.1wt% to 0.5wt% of the total metal ion mass of the first precursor; and / or, when preparing the second precursor, the doping amount of Zr element accounts for 0.1wt% to 0.3wt% of the total metal ion mass of the second precursor.

[0009] Based on the first aspect, in some embodiments of this application, the mass ratio of the first precursor to the second precursor is (1~2):1.

[0010] Based on the first aspect, in some embodiments of this application, D1 is 3.0μm~3.5μm and D2 is 4.5μm~5.0μm.

[0011] Based on the first aspect, in some embodiments of this application, the W source includes at least one of tungstic acid, ammonium tungstate, sodium tungstate, and tungsten trioxide; and / or, the Zr source includes at least one of zirconium hydroxide, zirconium oxide, and zirconium oxychloride.

[0012] Based on the first aspect, in some embodiments of this application, the general chemical formula of the ternary cathode material precursor is LiNi. x Co y Mn 1-x-y (OH)2, wherein 0.5≤x≤0.7, 0<y≤0.1; and / or the molar ratio of the number of lithium moles in the lithium source to the total number of nickel, cobalt and manganese moles in the mixed precursor is (1.02~1.3):1.

[0013] Based on the first aspect, in some embodiments of this application, in the step of sintering the mixed precursor with the lithium source, the sintering temperature is 900℃~1000℃ and the sintering time is 8h~15h; and / or the step of mixing the matrix material with the coating material and sintering it includes: mixing the matrix material with the Ti source and sintering it to form a first coating layer on the surface of the matrix material; and mixing the matrix material coated with the first coating layer with the Al source and sintering it to form a second coating layer on the surface of the first coating layer.

[0014] Based on the first aspect, in some embodiments of this application, the sintering temperature for forming the first coating layer is 700°C to 800°C, and the sintering time is 8h to 15h; and / or, the sintering temperature for forming the second coating layer is 400°C to 500°C, and the sintering time is 8h to 15h.

[0015] Secondly, this application provides a ternary cathode material prepared by the aforementioned method for preparing ternary cathode materials, wherein the ternary cathode material includes the matrix material, and the matrix material includes the first particle and the second particle.

[0016] Thirdly, this application provides an electrochemical device, including a positive electrode, a negative electrode, and an electrolyte located between the positive electrode and the negative electrode, wherein the positive electrode is made of the aforementioned ternary positive electrode material.

[0017] The method for preparing ternary cathode materials disclosed in this application involves forming a W-doped first precursor and a Zr-doped second precursor, respectively. The particle sizes of the two precursors can be controlled, ensuring that the median particle size ratio D2 / D1 is between 1.2 and 1.8. Simultaneously, by adjusting the overall average particle size D3 of the mixed precursor to within the range of 3.7 μm to 4.2 μm, an optimized particle size distribution structure is formed within the ternary cathode material. This particle size distribution structure allows the smaller first-stage particles to effectively fill the voids formed by the accumulation of larger second-stage particles, improving the overall porosity of the material and thus effectively increasing the compaction density. Furthermore, the separate doping of W and Zr elements helps stabilize the lattice structure of the single-crystal particles, improving the structural stability of the material. This allows the ternary cathode material to achieve both high compaction density and good cycle performance and rate performance. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the preparation method of the ternary cathode material provided in the embodiments of this application.

[0019] Figure 2 This is a SEM image of the W-doped first precursor in Embodiment 1 of this application.

[0020] Figure 3 The image shows the SEM morphology of the Zr-doped second precursor in Example 1.

[0021] Figure 4 The image shows the SEM morphology of the mixed precursor obtained by mixing the first and second precursors in Example 1.

[0022] Figure 5 The image shows the SEM morphology of the ternary cathode material prepared in Example 1.

[0023] Figure 6 The image shows the laser particle size distribution of the first precursor, the second precursor, and the mixed precursor prepared in Example 1.

[0024] Figure 7 The compaction density curves of the ternary cathode materials prepared in Examples 1 to 11 and Comparative Example 1 are shown.

[0025] Figure 8 The graph shows the capacity retention rate of the coin cells prepared in Examples 1 to 11 and Comparative Example 1 after 100 cycles at 45°C.

[0026] Figure 9 The graph shows a comparison of the first charge and discharge capacities of the coin cells prepared in Examples 1 to 11 and Comparative Example 1. Detailed Implementation

[0027] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of this application pertain. The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0028] The terms "first" and "second" appearing in this application are used solely for descriptive convenience to distinguish different components with the same name and do not indicate a sequential or primary / secondary relationship. For example, "first particle" and "second particle" simply refer to two different doped particles, and "first coating layer" and "second coating layer" simply refer to two different coating layers; they do not in themselves impose any restrictions on a specific order or importance.

[0029] The following describes some embodiments of this application in detail. Unless otherwise specified, the embodiments and features described below can be combined with each other.

[0030] With the increasing demand for range in the new energy vehicle market, increasing the compaction density of cathode materials has become an important way to increase battery capacity, given the limitations of battery pack size and weight.

[0031] Currently, in pursuit of high energy density, the industry typically uses single-crystal cathode materials to improve compaction density. However, the calcination temperature of single-crystal nickel ternary cathode materials during high-temperature lithiation is about 100°C higher than that of polycrystalline materials. This causes severe Li / O loss, generating more oxygen vacancy defects. These defects affect the crystal structure and electrochemical performance of the material, thus adversely impacting the improvement of compaction density. It also reduces the material's stability and cycle performance. Furthermore, in pursuit of high energy density, battery manufacturers may over-pressure the electrodes. Over-pressure causes large-area breakage of the spherical ternary material, forming fine particles. These small particles may locally deteriorate the electrode's conductivity, increase the specific surface area, increase side reactions, and reduce electrode porosity, making it difficult for electrolyte to penetrate the electrode interior. This leads to poorer specific capacity, greater polarization during battery cycling, faster degradation, and a significant increase in internal resistance.

[0032] Therefore, this application provides a novel ternary cathode material and its preparation method, which can improve the material's structural stability while increasing the material's compaction density, thereby improving the ternary cathode material's cycle stability and rate performance under high pressure.

[0033] Please see Figure 1 As shown in the figure, this application provides a method for preparing a ternary cathode material, including the following steps: Step S1: The ternary cathode material precursor is co-precipitated with W source and Zr source respectively to obtain W-doped first precursor and Zr-doped second precursor respectively.

[0034] By introducing W and Zr sources respectively during the co-precipitation stage, the growth of precursor particles can be differentiated and controlled, resulting in particles with significant size differences between the first and second precursors during the reaction. This lays the foundation for the subsequent construction of a particle size distribution structure. W exists in the reaction system as tungstate or other oxygen-containing anions during co-precipitation. Its large ionic radius and high charge make it easily adsorbed onto specific crystal faces of the growing nuclei. Furthermore, W, as a refractory element with extremely slow diffusion, has a diffusion coefficient much lower than that of matrix atoms (such as Li, Ni, Co, Mn, O, and metal atoms). This characteristic not only inhibits the directional growth of nuclei through steric hindrance but also slows down the mass transport rate during crystal growth, thus suppressing the directional growth and aggregation of nuclei, resulting in smaller primary and secondary spherical particles. Therefore, with increasing W doping (within a suitable range), the particle size of the obtained first precursor tends to decrease. Zr exists as zirconium ions (Zr ions) during co-precipitation. 4+ Zr exists in the form of colloids or zirconium hydroxide. Its hydrolysis and precipitation behavior differs from that of Ni, Co, and Mn. It can serve as a nucleation center or a "bridge" to promote grain growth, reducing the interfacial energy for nucleation and promoting the growth and aggregation of nuclei, resulting in larger secondary spherical particles. Therefore, with the increase of Zr doping (within a suitable range), the particle size of the obtained second precursor tends to increase.

[0035] The median particle size D50 of the first precursor is D1, and the median particle size D50 of the second precursor is D2, satisfying: 1.2 ≤ D2 / D1 ≤ 1.8. By using different doping elements to dope the two precursors, the particle size ratio can be controlled within the above range, enabling them to form an optimized particle size distribution structure after mixing. When the D2 / D1 ratio is too low, the particle size difference between the first and second precursors is insufficient, and the small-sized first precursor cannot effectively fill the voids formed by the large-sized second precursor, resulting in limited improvement in the packing density of the mixed precursor. When the D2 / D1 ratio is too high, the particle size difference is too large, and there are too many or too fine small-sized precursors, which may lead to an increase in interparticle contact points and porosity, which is not conducive to the formation of a uniform and dense matrix material during subsequent sintering. By controlling the D2 / D1 ratio within the aforementioned range, the small-particle-size first precursor can be fully filled into the voids formed by the accumulation of the large-particle-size second precursor, achieving close packing of the mixed precursors. This results in the matrix material obtained after the first sintering having optimized particle size distribution and high compaction density. At the same time, this particle size ratio range works synergistically with the lattice stabilizing effect of W and Zr doping, which is beneficial for the matrix material to achieve both high compaction density and good structural stability and electrochemical performance.

[0036] For example, the values ​​of D2 / D1 can be 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, or any value within the range of any two of the above values.

[0037] In some embodiments, D1 is 3.0 μm to 3.5 μm, and D2 is 4.5 μm to 5.0 μm. By controlling the particle sizes of the first precursor and the second precursor within the aforementioned ranges, a suitable particle size difference can be formed between them in the mixed precursor. This ensures that the smaller-sized first precursor particles can effectively fill the voids formed by the accumulation of larger-sized second precursor particles, achieving close packing of the mixed precursor. This lays the foundation for forming an optimized particle size distribution structure during subsequent sintering. Furthermore, controlling the particle sizes of the first and second precursors within the aforementioned range facilitates their growth into single-crystal particles with corresponding size differences during the first sintering process. This ultimately leads to an optimized particle size distribution structure within the matrix material, improving the particle packing density and porosity distribution. Consequently, it effectively enhances the compaction density without relying on excessively high rolling pressure. Simultaneously, this particle size range helps the first and second precursors maintain good single-crystal morphology and structural integrity during sintering, synergistically improving the structural stability and electrochemical performance of the material in conjunction with the lattice stabilizing effects of W and Zr doping. The exemplary values ​​of D1 can be 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, or any value within the range of any two of the aforementioned values. The exemplary values ​​of D2 can be 4.5 μm, 4.6 μm, 4.7 μm, 4.8 μm, 4.9 μm, 5.0 μm, or any value within the range of any two of the aforementioned values.

[0038] The aforementioned particle size range is matched with the regulatory effect of W and Zr doping: under appropriate W and Zr doping conditions, precursors within the above particle size range can be stably obtained, avoiding the influence of excessively fine or coarse precursor particle size due to excessively high or low doping levels, which would affect the gradation effect.

[0039] In some embodiments, when preparing the first precursor, the doping amount of W element accounts for 0.1 wt% to 0.5 wt% of the total metal ion mass of the first precursor. Controlling the doping amount within the above range is beneficial for effectively controlling the particle size during the growth of the first precursor, resulting in a suitable small particle size distribution. Simultaneously, an appropriate amount of W doping can stabilize the crystal structure and reduce defect formation during subsequent sintering, thus ensuring the structural stability and electrochemical performance of the ternary cathode material. The exemplary doping amount of W element in preparing the first precursor can be 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, or any value within the range of any two of the above values.

[0040] It is understandable that the total metal ions of the first precursor refer to the mass corresponding to the total molar amount of the three metal elements nickel, cobalt and manganese in the first precursor, and the doping amount of W element refers to the percentage of the mass of added W element to the total metal ion mass.

[0041] In some embodiments, the W source includes at least one of tungstic acid, ammonium tungstate, sodium tungstate, tungsten trioxide, etc.

[0042] In some embodiments, when preparing the second precursor, the Zr doping amount accounts for 0.1 wt% to 0.3 wt% of the total metal ion mass of the second precursor. Controlling the doping amount within the above range is beneficial for effectively controlling the particle size during the growth of the second precursor, resulting in a suitable large particle size distribution. Simultaneously, an appropriate amount of Zr doping can enhance lattice stability during subsequent sintering, suppress structural degradation during cycling, and improve the long-cycle performance of the material. The exemplary Zr doping amount in preparing the second precursor can be 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, or any value within the range of any two of the above values.

[0043] It is understandable that the total metal ions of the second precursor refer to the mass corresponding to the total molar amount of the three metal elements nickel, cobalt, and manganese in the second precursor, and the doping amount of Zr element refers to the percentage of the mass of the added Zr element to the total metal ion mass.

[0044] In some embodiments, the Zr source includes at least one of zirconium hydroxide, zirconium oxide, zirconium oxychloride, etc.

[0045] The general formula for ternary cathode material precursors is Ni. x Co y Mn 1-x-y (OH)₂, 0.5≤x≤0.7, 0<y≤0.1. Controlling the molar ratio of each metal element in the precursor within the above range is beneficial for forming a ternary cathode material with a good layered structure during subsequent sintering, thereby achieving higher discharge capacity and cycle performance while ensuring the stability of the material structure. The value of x can be, for example, 0.5, 0.55, 0.6, 0.65, 0.7, or any value within the range of any two of the above values; the value of y can be, for example, 0.02, 0.04, 0.06, 0.08, 0.1, or any value within the range of any two of the above values.

[0046] Step S2: Mix the first precursor with the second precursor to obtain a mixed precursor. The median particle size D50 of the mixed precursor is D3, and 3.7μm≤D3≤4.2μm.

[0047] By controlling the D2 / D1 ratio within the range of 1.2 to 1.8, the average particle size D3 of the mixed precursor can be adjusted from 3.7 μm to 4.2 μm. By mixing first and second precursors of different particle sizes, a preliminary particle size distribution structure can be formed before sintering. Smaller first precursor particles fill the voids formed by the accumulation of larger second precursor particles, resulting in a densely packed mixed precursor with a more uniform particle distribution and reduced porosity. This preliminary particle size distribution structure lays the foundation for forming a single-crystal matrix material with optimized particle size distribution during the subsequent first sintering process, which is beneficial for ultimately obtaining a ternary cathode material with high compaction density and good structural stability.

[0048] In some embodiments, a high-speed mixer is used to mix the first and second precursors. The mixing process includes sequential low-speed mixing and high-speed mixing. The low-speed mixing frequency is 500 rpm to 700 rpm, and the mixing time is 2 min to 10 min. The high-speed mixing frequency is 1000 rpm to 1400 rpm, and the mixing time is 8 min to 15 min. By controlling the rotation speed and time of the low-speed and high-speed mixing within the above ranges, it is beneficial to achieve uniform dispersion and thorough mixing of the first and second precursors while avoiding breakage of precursor particles due to collision. This results in an optimized spatial distribution structure of particles of different sizes within the mixed precursors, laying the foundation for a uniform particle size distribution during subsequent sintering. The mixing frequency for low-speed mixing can, for example, be 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, or any value within the range of any two of the above values; the low-speed mixing time can, for example, be 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, or any value within the range of any two of the above values. The mixing frequency for high-speed mixing can, for example, be 1000 rpm, 1050 rpm, 1100 rpm, 1150 rpm, 1200 rpm, 1250 rpm, 1300 rpm, 1350 rpm, 1400 rpm, or any value within the range of any two of the above values. The high-speed mixing time can, for example, be 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, or any value within the range of any two of the above values. In some embodiments, the mixing mass ratio of the first precursor to the second precursor is (1~2):1. Controlling the mixing ratio within the aforementioned values ​​is beneficial for achieving a superior particle size distribution in the matrix material. This allows smaller particles to fully fill the voids created by the accumulation of larger particles, ensuring both increased compaction density and good particle distribution uniformity. Examples of this mass ratio could be 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, or any value within the range of any two of the aforementioned values.

[0049] Step S3: First, add half of the mixed precursor, then add half of the lithium salt, followed by the other half of the mixed precursor, and finally add the remaining lithium salt. Set the mixing parameters to low speed 700 r / min for 10 minutes, then high speed 1400 r / min for 10 minutes to ensure uniform mixing. Then, perform a sintering process to transform the first precursor into the first single-crystal particle and the second precursor into the second single-crystal particle, thereby obtaining the matrix material.

[0050] Specifically, the mixed precursor and lithium source can be sintered in an oxygen-containing atmosphere. During the sintering process, precursor particles of different sizes grow into single-crystal particles with corresponding size differences, ultimately forming an optimized particle size distribution structure inside the matrix material, which is beneficial to improving the particle packing density and compaction performance of the material.

[0051] In some embodiments, the molar ratio of lithium in the lithium source to the total molar ratio of nickel, cobalt, and manganese in the mixed precursor (two precursors) is (1.02–1.3):1. This molar ratio can be, for example, 1.02:1, 1.05:1, 1.08:1, 1.10:1, 1.12:1, 1.15:1, 1.18:1, 1.20:1, 1.22:1, 1.25:1, 1.28:1, 1.30:1, or any value within the range of any two of the above values.

[0052] In some embodiments, the sintering temperature is 900°C to 1000°C, and the sintering time is 8 hours to 15 hours. Controlling the sintering temperature and time within these ranges facilitates the complete reaction of each precursor with the lithium source to form well-crystallized single-crystal particles, while avoiding problems such as lithium and oxygen loss and increased lattice defects caused by excessively high temperatures or excessively long times. The sintering temperature for the first sintering can, for example, be 900°C, 920°C, 940°C, 950°C, 960°C, 980°C, 1000°C, or any value within the range of any two of the above values; the sintering time can, for example, be 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, or any value within the range of any two of the above values.

[0053] Step S4: Mix the matrix material and the coating material and sinter them to obtain the ternary cathode material.

[0054] Specifically, the coating process can be divided into two steps: the first coating process and the second coating process.

[0055] First coating process: The matrix material is mixed with a Ti source and sintered a second time in an oxygen-containing atmosphere to form a first coating layer on the surface of the matrix material.

[0056] By forming a Ti-containing first coating layer on the surface of the substrate material, an interface layer with good lithium-ion conductivity can be constructed on the material surface. This coating layer can serve as a fast channel for lithium-ion transport, reduce interface impedance, and thus improve the rate performance and capacity utilization of the material. At the same time, the coating layer has a certain mechanical strength, which can provide physical protection for the substrate material and buffer volume changes during cycling.

[0057] In some embodiments, the Ti element coating amount is 0.03 wt% to 0.1 wt% of the total mass of the matrix material. Controlling the coating amount within the above range is beneficial for forming a uniform and continuous first coating layer on the surface of the matrix material, ensuring both the integrity and coverage of the coating layer, and avoiding the problem of increased lithium-ion transport resistance caused by an excessively thick coating layer. The exemplary coating amount of Ti element in the first coating layer can be 0.03 wt%, 0.04 wt%, 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, 0.10 wt%, or any value within the range of any two of the above values.

[0058] In some embodiments, the Ti source includes at least one of titanium dioxide and lithium titanate.

[0059] In some embodiments, the secondary sintering temperature is 700°C to 800°C, and the sintering time is 8 hours to 15 hours. Controlling the temperature and duration of the secondary sintering within these ranges facilitates the uniform spreading of the Ti-containing source on the surface of the matrix material and the formation of a stable coating layer, while avoiding excessive temperature that could lead to over-reaction or crystal transformation between the coating layer and the matrix. The exemplary temperatures for the second sintering can be 700°C, 720°C, 740°C, 750°C, 760°C, 780°C, 800°C, or any value within the range of any two of the above values; the exemplary sintering times can be 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, or any value within the range of any two of the above values.

[0060] The second coating process involves mixing the matrix material coated with the first coating layer with an Al source and then performing a third sintering under an oxygen-containing atmosphere to form a second coating layer on the surface of the first coating layer.

[0061] By further forming a second coating layer containing Al on the surface of the first coating layer, a double-layer composite coating structure is constructed. The second coating layer can form a dense protective layer, effectively blocking the direct contact between the matrix material and the electrolyte, inhibiting side reactions and metal dissolution, thereby improving the cycle stability and capacity retention of the material. In synergy with the first coating layer, it can enhance interface stability while improving rate performance.

[0062] In some embodiments, the Al coating amount is 0.02 wt% to 0.1 wt% of the total mass of the matrix material. Controlling the Al coating amount within this range facilitates the formation of a dense protective layer on the material surface, effectively preventing direct contact between the electrolyte and the matrix material, suppressing side reactions and metal dissolution, thereby significantly improving the material's cycle stability. Simultaneously, this coating amount range avoids the problem of excessive capacity loss due to an excessively thick coating layer, balancing improved cycle performance with good energy density. The exemplary Al coating amount in the second coating layer can be 0.02 wt%, 0.03 wt%, 0.04 wt%, 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, 0.10 wt%, or any value within the range of any two of the above values.

[0063] In some embodiments, the Al source includes at least one of aluminum phosphate, lithium aluminate, and aluminum oxide.

[0064] In some embodiments, the temperature for the third sintering is 400°C to 500°C, and the sintering time is 8 hours to 15 hours. Controlling the temperature and duration of the third sintering within these ranges facilitates the uniform spreading of the Al-containing source on the surface of the first coating layer and the formation of a dense coating layer, while avoiding excessively high temperatures that could lead to crystal transformation of the coating layer or adverse reactions with the inner layer. The exemplary temperatures for the third sintering can be 400°C, 420°C, 440°C, 450°C, 460°C, 480°C, 500°C, or any value within the range of any two of the above values; the exemplary sintering times can be 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, or any value within the range of any two of the above values.

[0065] This application also provides a ternary cathode material prepared by the aforementioned method for preparing ternary cathode materials. The ternary cathode material includes a matrix material, which includes a first particle and a second particle.

[0066] This ternary cathode material incorporates W and Zr elements into single-crystal particles for doping. On one hand, the different influences of the doping elements on particle growth allow the first and second particles to form single-crystal morphologies with different particle sizes, thereby constructing an optimized particle size distribution structure within the matrix material. On the other hand, the doping of W and Zr elements effectively suppresses lattice distortion and structural degradation during cycling, improves the structural and interfacial stability of the material, reduces metal dissolution and side reactions, and thus enhances the cycle life and capacity retention of the material.

[0067] Based on the above structural design, this ternary cathode material optimizes the packing of particles of different sizes, allowing the smaller first-particle size to effectively fill the voids formed by the larger second-particle size, thus improving the overall particle packing density and pore distribution. This achieves an effective increase in compaction density without relying on excessively high rolling pressure, avoiding electrochemical performance degradation caused by particle breakage due to overpressure. Simultaneously, the doping of W and Zr effectively suppresses lattice distortion and structural degradation during cycling, improving the material's structural and interfacial stability, reducing metal dissolution and side reactions, thereby enhancing the material's cycle life and capacity retention. Furthermore, this structural design achieves high compaction density without sacrificing rate performance, allowing the material to maintain good lithium-ion insertion / extraction capability at high current densities, balancing high energy density and high power output, and comprehensively improving the electrochemical performance of the ternary cathode material.

[0068] Compared with the prior art, the ternary cathode material and preparation method provided in this application have the following beneficial effects: 1. This ternary cathode material incorporates W and Zr elements into single-crystal particles for doping. On one hand, the different influences of the doping elements on particle growth allow the first and second particles to form single-crystal morphologies with different particle sizes, thereby constructing an optimized particle size distribution structure within the matrix material. On the other hand, the doping of W and Zr elements effectively suppresses lattice distortion and structural degradation during cycling, improves the structural and interfacial stability of the material, reduces metal dissolution and side reactions, and thus enhances the cycle life and capacity retention of the material. Based on the above structural design, this ternary cathode material optimizes the packing of particles of different sizes, allowing the smaller first-particle size to effectively fill the voids formed by the larger second-particle size, thus improving the overall particle packing density and pore distribution. This achieves an effective increase in compaction density without relying on excessively high rolling pressure, avoiding electrochemical performance degradation caused by particle breakage due to overpressure. Simultaneously, the doping of W and Zr effectively suppresses lattice distortion and structural degradation during cycling, improving the material's structural and interfacial stability, reducing metal dissolution and side reactions, thereby enhancing the material's cycle life and capacity retention. Furthermore, this structural design achieves high compaction density without sacrificing rate performance, allowing the material to maintain good lithium-ion insertion / extraction capability at high current densities, balancing high energy density and high power output, and comprehensively improving the electrochemical performance of the ternary cathode material.

[0069] 2. The preparation method provided in this application introduces W and Zr sources for doping during the precursor co-precipitation stage, respectively. Utilizing the differentiated control of particle growth by different doping elements, a first and second precursor with different particle sizes are prepared. After mixing the two precursors and performing a first sintering with a lithium source, single-crystal particles of different sizes can be grown under the same sintering conditions, thereby forming an optimized particle size distribution structure within the matrix material. This preparation method achieves particle size distribution construction through doping control in the precursor stage, eliminating the need for complex sieving or multiple sintering processes. It simplifies the production process and reduces preparation costs while improving compaction density.

[0070] 3. The preparation method provided in this application also includes a two-stage coating process of sequentially coating the substrate material with Ti-based and Al-based coatings. A first coating layer containing Ti is formed through a second sintering, which constructs an interface layer with good lithium-ion conductivity on the material surface, improving the rate performance and capacity utilization of the material. A second coating layer containing Al is formed through a third sintering, which forms a dense protective layer on the outermost layer, effectively preventing direct contact between the electrolyte and the substrate material, suppressing side reactions and metal dissolution, and improving the cycle stability and capacity retention of the material. This two-stage coating process, through stepwise sintering, ensures that both the inner and outer coating layers form uniform and stable structures, avoiding interface compatibility issues that may occur with single-stage co-coating. In summary, the preparation method provided in this application, through the synergistic process design of "doping gradation + two-stage coating," produces a ternary cathode material that achieves high high solid density while also considering excellent cycle performance and rate performance, comprehensively improving the electrochemical performance of the material. Furthermore, the process is highly controllable and easily scalable for mass production.

[0071] This application also provides a positive electrode sheet comprising the ternary positive electrode material described in any of the foregoing embodiments. Compared to the prior art, this positive electrode sheet, due to the use of the aforementioned ternary positive electrode material with optimized particle size distribution and double-layer composite coating, can achieve a higher electrode compaction density under the same rolling conditions, thereby increasing the active material loading per unit volume. Simultaneously, thanks to the excellent structural and interfacial stability of the material itself, this positive electrode sheet can maintain an intact electrode structure during long-term cycling, reducing side reactions and effectively improving the cycle life and rate performance of the battery.

[0072] This application also provides an electrochemical device, including a positive electrode, a negative electrode, and an electrolyte layer located between the positive and negative electrodes. The positive electrode is prepared from the aforementioned ternary positive electrode material or by the aforementioned method for preparing ternary positive electrode material. Because this electrochemical device uses a ternary positive electrode material with high compaction density, excellent cycle performance, and rate performance, it achieves high energy density while maintaining good cycle stability and power output capability, thus meeting the comprehensive requirements of power batteries for long lifespan and extended range.

[0073] The following specific examples further illustrate the aforementioned battery cathode material, its preparation method, and its application.

[0074] Example 1 Step S1, Preparation of precursor: Step S1.1: Mix aqueous solutions of nickel nitrate, cobalt nitrate, and manganese nitrate in a molar ratio of Ni:Co:Mn = 66:6:28, stir until homogeneous, add tungstic acid, and calculate the added W content as 0.3 wt% of the total metal ion mass of the precursor. Then, perform a co-precipitation reaction to obtain a ternary hydroxide precipitate. After filtering, washing, and drying the precipitate, obtain the W-doped first precursor.

[0075] Step S1.2: Mix aqueous solutions of nickel nitrate, cobalt nitrate, and manganese nitrate in a molar ratio of Ni:Co:Mn = 66:6:28, stir until homogeneous, and then add zirconium hydroxide. The Zr content added is calculated as 0.2 wt% of the total metal ions in the precursor. Then, a co-precipitation reaction is carried out to obtain a ternary hydroxide precipitate. After filtering, washing, and drying the precipitate, a Zr-doped second precursor is obtained.

[0076] Step S2, Preparation of the mixed precursor: The W-doped first precursor and the Zr-doped second precursor are put into a high-speed mixer at a certain ratio of 1:1 and mixed evenly to obtain a mixed precursor with particle size distribution.

[0077] Step S3, Preparation of matrix material: Step S3.1: The above-mentioned mixed precursor and lithium hydroxide are added to a mixing device and mixed at a low speed of 700 rpm for 5 minutes, followed by a high speed of 1400 rpm for 10 minutes to ensure uniform mixing and prepare a mixed powder. The molar ratio of lithium to the total metal ions of nickel, cobalt, and manganese in the mixed precursor is 1.04:1. Step S3.2: The mixed powder is sintered for the first time in a pure oxygen atmosphere. After pulverization, a ternary cathode material matrix is ​​obtained. The first sintering temperature is 950℃, and the sintering time is 15 hours. The matrix material includes W-doped first particles formed by sintering the first precursor and Zr-doped second particles formed by sintering the second precursor.

[0078] Step S4, Preparation of the first coating layer: Step S4.1: The above ternary cathode material matrix and titanium dioxide are put into a high-speed mixer and mixed evenly. The amount of titanium dioxide added is calculated as 0.05 wt% of the total mass of the matrix material containing Ti element.

[0079] Step S4.2: The mixed sample is sintered for the second time in a pure oxygen atmosphere at a sintering temperature of 730℃ for 10 hours. After crushing, a single-crystal ternary material with a uniform first coating layer on the surface is obtained.

[0080] Step S5, Preparation of the second coating layer: Step S5.1: The above-mentioned single-crystal ternary material with the first coating layer and aluminum phosphate are put into a high-speed mixer and mixed evenly. The amount of aluminum phosphate added is calculated as 0.05 wt% of the total mass of the matrix material in which Al element accounts for 0.05 wt%.

[0081] Step S5.2: The mixed sample is sintered for the third time in a pure air atmosphere, and after crushing, a single-crystal ternary cathode material with a uniform double-layer coating is obtained. The third sintering temperature is 450℃ and the sintering time is 10h.

[0082] Example 2: The difference between this embodiment and Embodiment 1 is that: in step S1.1, the added W content is calculated as 0.1 wt% of the total metal ion mass of the first precursor; and in step S2, except for the different mass ratio of the first precursor and the second precursor, the other steps are the same as in Embodiment 1.

[0083] Example 3: The difference between this embodiment and Embodiment 1 is that: in step S1.1, the added W content is calculated as 0.5wt% of the total metal ion mass of the first precursor; and in step S2, except for the different mass ratio of the first precursor and the second precursor, the other steps are the same as in Embodiment 1.

[0084] Example 4: The difference between this embodiment and Embodiment 1 is that in step S4.1, the amount of titanium dioxide added is calculated based on the Ti element accounting for 0.1 wt% of the total mass of the matrix material, while the remaining steps are the same as in Embodiment 1.

[0085] Example 5: The difference between this embodiment and Embodiment 1 is that in step S5.1, the amount of aluminum phosphate added is calculated based on the proportion of Al element to the total mass of the matrix material being 0.1 wt%, while the remaining steps are the same as in Embodiment 1.

[0086] Example 6: The difference between this embodiment and Embodiment 1 is that: in step S1.1, the added W content is calculated as 0.7wt% of the total metal ion mass of the first precursor, and in step S2, except for the different mass ratio of the first precursor and the second precursor, the other steps are the same as in Embodiment 1.

[0087] Example 7: The difference between this embodiment and Embodiment 1 is that in step S4.1, the amount of titanium dioxide added is calculated based on the Ti element accounting for 0.02 wt% of the total mass of the matrix material, while the remaining steps are the same as in Embodiment 1.

[0088] Example 8: The difference between this comparative example and Example 1 is that in step S5.1, the amount of aluminum phosphate added is calculated based on the fact that the Al element accounts for 0.2 wt% of the total mass of the matrix material. The remaining steps are the same as in Example 1.

[0089] Example 9: The difference between this comparative example and Example 1 is that titanium dioxide is not added for coating in step S4, that is, steps S4.1 and S4.2 are omitted, and the remaining steps are the same as in Example 1.

[0090] Example 10: The difference between this comparative example and Example 1 is that aluminum phosphate is not added for coating in step S5, that is, steps S5.1 and S5.2 are omitted, and the remaining steps are the same as in Example 1.

[0091] Comparative Example 1: The difference between this comparative example and Example 1 is that no dopant is added during the precursor preparation process, that is, no tungstic acid is added in step S1.1 and no zirconium hydroxide is added in step S1.2. The remaining steps (including the coating treatment) are the same as those in Example 1.

[0092] Comparative Example 2 The difference between this comparative example and Example 1 is that the coating process is not performed, that is, steps S4 and S5 are omitted, while the remaining steps are the same as in Example 1.

[0093] The differences between Examples 1 to 10 and Comparative Examples 1 to 2 are shown in Table 1 below.

[0094] Table 1 Note: In Table 1, M1 represents the mass of the first precursor and M2 represents the mass of the second precursor. In Table 2, M1:M2 represents the mixing mass ratio of the first and second precursors in step S2.

[0095] Preparation of coin cells: The ternary cathode materials prepared in Examples 1 to 11 and Comparative Examples 1 to 3 were respectively made into cathode sheets, and coin cells were assembled using lithium metal as the anode material.

[0096] Test method: The electrochemical performance of the coin cells prepared above was tested within a voltage range of 2.8V to 4.35V as follows: (1) High temperature cycle performance test: At 45℃, charge and discharge cycle test was performed at a current density of 1C within the voltage range of 2.8V to 4.35V, and the capacity retention rate and cycle life of the battery were recorded.

[0097] (2) Compaction density test: The ternary cathode materials prepared in Examples 1 to 11 and Comparative Examples 1 to 3 were tested using an energy analyzer to obtain compaction density data under different pressures.

[0098] (3) Particle size test: The particle size distribution of the first precursor, the second precursor and the mixed precursor was tested using a laser particle size analyzer to obtain the corresponding particle size distribution map. The particle size distribution map includes the volumetric particle size distribution Dv and the number particle size distribution Dn.

[0099] (4) Initial charge-discharge capacity: The prepared ternary cathode material, conductive carbon, and binder polyvinylidene fluoride were mixed uniformly at a mass ratio of 90:5:5 to form a coin cell. Constant current charge-discharge tests were conducted using a LAND battery testing system. During the test, the working voltage range for the initial discharge capacity test was 2.8V~4.35V, the charge-discharge rate was +1C / -1C, and the CV cutoff current was 0.01C; the working voltage range for the 45℃ cycle test was 2.8V~4.35V, the charge-discharge rate was +1C / 1C, and the CV cutoff current was 0.01C.

[0100] (5) SEM test: Take a small amount of the prepared ternary cathode material onto the electrode sheet, spread it flat and blow it, place it in the instrument, test it under vacuum, and obtain the SEM morphology of the sample at different magnifications.

[0101] The test results of Examples 1 to 10 and Comparative Examples 1 to 3 are shown in Table 2 below.

[0102] Table 2 Note: In Table 2, D1 represents the median particle size of the first precursor; D2 represents the median particle size of the second precursor; and D3 represents the median particle size of the mixed precursor.

[0103] The scanning electron microscope (SEM) images of the precursor and the finally prepared ternary cathode material in Example 1 are shown below. Figures 2 to 5 .

[0104] Results analysis: Combining Figures 2 to 9 As shown in Table 2, the SEM morphology of the first precursor (W-doped) in the ternary cathode material prepared in Example 1 is as follows: Figure 2 As shown in the figure, SEM results indicate that W doping does not alter the secondary spherical structure of the precursor (a secondary spherical structure refers to a spherical body formed by the aggregation of many small particles), but the overall particle size of the first precursor is smaller. Figure 2 The particle size of the first precursor is approximately 1 μm to 2 μm; the SEM morphology of the second precursor (Zr-doped) is as follows. Figure 3 As shown in the figure, SEM results indicate that Zr doping does not change the secondary spherical structure of the precursor, but the overall particle size of the second precursor is larger. Figure 3 The particle size of the second precursor in the mixture is approximately 4 μm to 5 μm; the mixed precursor obtained after mixing the two is as follows: Figure 4 As shown, the precursor exhibits a distinct particle size distribution structure after mixing; the ternary cathode material obtained after the first sintering is as follows: Figure 5 As shown, the sample consists of particles ranging from 1 μm to 10 μm, exhibiting a single-crystal morphology, good particle roundness, polarized particle size distribution, and a relatively wide particle size distribution. Furthermore, Figure 6 The laser particle size distribution map further verified the particle size distribution characteristics of the first precursor, the second precursor, and the mixed precursor. The mixed precursor showed a clear bimodal distribution in terms of quantity distribution. It can be seen that by introducing W and Zr elements for doping in the precursor co-precipitation stage, the growth of precursor particles can be differentiated, resulting in a significant particle size difference between the first and second precursors. After mixing the two, a particle size distribution structure can be constructed in the precursor stage. After the first sintering, this distribution structure is retained and transformed into single crystal particles with corresponding particle size differences, ultimately forming an optimized particle size distribution morphology inside the matrix material.

[0105] Depend on Figure 7 The compaction density curve, combined with the data in Table 2, shows that the compaction density of the ternary cathode material prepared in Example 1 can reach 3.46 g / cm³ under a pressure of 200 MPa. 3 The above is significantly higher than the compaction density level of conventional ternary cathode materials (3.3 g / cm³). 3 (Left and right). As can be seen, this application achieves differentiated control of particle growth by introducing W and Zr elements for doping in the precursor stage, thereby constructing an optimized particle size distribution structure inside the matrix material, effectively improving particle packing density and pore distribution, and thus achieving an increase in compaction density without relying on excessively high rolling pressure.

[0106] Depend on Figure 8The high-temperature cycling performance comparison chart, combined with the data in Table 2, shows that the coin cell prepared in Example 1 exhibits high capacity retention after 100 cycles at 45°C, demonstrating good cycling stability. This demonstrates that the doping of W and Zr elements stabilizes the lattice structure of the single-crystal particles, suppressing lattice distortion and structural degradation during cycling. Simultaneously, through the synergistic effect of Ti-based and Al-based double-layer coating, a composite coating layer with both lithium-ion conductivity and interface protection functions is constructed on the material surface, effectively blocking direct contact between the electrolyte and the substrate material, reducing metal dissolution and side reactions, thereby improving the cycle life and capacity retention of the material.

[0107] Depend on Figure 9 The comparison chart of the initial charge-discharge capacity, combined with the data in Table 2, shows that Example 1 exhibits an initial discharge capacity of 191.34 mAh / g within a voltage range of 2.8V to 4.35V and a current density of 0.1C, demonstrating high capacity performance. This indicates that this application achieves high energy density and excellent cycle stability without sacrificing the material's capacity performance, resulting in a ternary cathode material that combines high energy density, long cycle life, and good rate performance in its overall electrochemical properties.

[0108] Based on the data from Examples 1, 2, 3, and 6, it can be seen that the W doping amount in the first precursor has a regulatory effect on the particle size of the first particle, thereby affecting the particle size distribution and compaction density of the matrix material. When the W doping amount is 0.1 wt%, the particle size of the first particle is relatively large, the number of small particles is small, the distribution effect is limited, and the increase in compaction density is small. When the W doping amount increases to 0.3 wt%, the particle size of the first particle is moderate, the number of small particles is appropriate, and it can effectively fill the gaps formed by the accumulation of large particles, obtaining a better distribution effect and a higher compaction density. When the W doping amount further increases to 0.5 wt%, the particle size of the first particle continues to decrease, the number of small particles increases, but too many fine particles lead to an increase in the gaps between particles, and the compaction density decreases compared to Example 1. When the W doping amount reaches 0.7 wt%, the particle size of the first particle is too small, the number of small particles is too large, the gaps between particles increase significantly, and the compaction density decreases significantly compared to Example 1. Therefore, controlling the W doping amount within an appropriate range (such as 0.1wt% to 0.5wt%) is beneficial to forming an optimized particle size distribution structure, thereby achieving a better compaction density improvement effect.

[0109] Based on the data from Examples 1, 4, 7, and 9, it is evident that the Ti coating layer plays a positive role in the rate performance and capacity of the material. Specifically, Example 9 (without Ti coating) exhibits lower rate performance than Example 1 due to the lack of a Ti coating layer. Example 1 (0.05 wt% Ti coating) maintains a high compaction density while achieving good rate performance and cycle stability. Example 4 (0.1 wt% Ti coating) shows limited improvement in rate performance. This demonstrates that the presence of an appropriate Ti coating layer helps construct fast lithium-ion transport channels on the material surface, reducing interfacial impedance and improving rate performance. Furthermore, based on the data from Examples 1, 4, 7, 9, and Comparative Example 1, although W / Zr doping can effectively improve the compaction density of the matrix material by constructing a particle size distribution structure, the rate performance and interfacial stability are still somewhat affected without the assistance of a Ti coating layer. The introduction of an appropriate Ti coating layer can further optimize the overall electrochemical performance of the material without sacrificing compaction density. However, the Ti coating amount also needs to be controlled within an appropriate range (such as 0.02wt% to 0.1wt%). If the coating amount is too low, the improvement effect will be limited, and if the coating amount is too high, it may increase production costs and reduce the marginal benefit of performance improvement.

[0110] The difference between Example 5 and Example 1 is that the Al content in the second coating layer is adjusted to 0.1 wt%. (Combined with...) Figure 8 , Figure 9 As shown in Table 2, the high-temperature cycling performance of the material is further improved after the Al coating amount is increased, and the capacity retention rate is higher than that of Example 1. This is because the dense Al coating layer can effectively block electrolyte corrosion and inhibit metal dissolution.

[0111] The difference between Example 8 and Example 1 is that the Al content in the second coating layer is adjusted to 0.2 wt%. Figure 8 , Figure 9 As shown in Table 2, excessive Al coating leads to an excessively thick coating layer, while Li... + Increased transmission resistance led to a decrease in initial discharge capacity to 189.15 mAh / g, lower than in Examples 1 and 5. Although cycle stability was further improved, capacity loss was significant.

[0112] The difference between Example 10 and Example 1 is that Example 10 does not include aluminum phosphate for coating (no Al coating). Combined with Figure 8 , Figure 9 As shown in Table 2, the high-temperature cycling performance of the material is significantly reduced and the capacity retention rate is lower than that of Example 1 when the Al coating layer is missing.

[0113] Based on the data from Examples 5, 8, and 10, it can be seen that the Al coating layer improves the high-temperature cycling stability of the material, but the coating amount needs to be controlled within a suitable range to balance capacity performance. In Example 10 (no Al coating), due to the lack of Al coating protection, the material surface is directly exposed to the electrolyte, leading to increased side reactions, intensified metal dissolution, a significant decrease in high-temperature cycling performance, and a lower capacity retention rate than Example 1. Example 5 (0.1 wt% Al coating) forms a relatively dense protective layer on the surface of the substrate material, effectively preventing direct contact between the electrolyte and the substrate material, suppressing side reactions and metal dissolution, resulting in better high-temperature cycling performance than Example 1 and further improved capacity retention. Although Example 8 (0.2 wt% Al coating) further improves cycling stability, the excessively thick coating layer leads to Li... + The transmission resistance increased significantly, and the initial discharge capacity dropped to 189.15 mAh / g, indicating a noticeable capacity loss. This demonstrates that an appropriate amount of Al coating can form an effective protective layer on the material surface, improving high-temperature cycling performance while keeping capacity loss within an acceptable range. Too little coating results in insufficient protection, while too much coating leads to excessive capacity loss. Therefore, controlling the Al coating amount within a suitable range (e.g., 0.02 wt% to 0.1 wt%) is crucial for achieving a balance between cycle stability and capacity performance.

[0114] The difference between Comparative Example 1 and Example 1 is that no dopants (no W, no Zr) were added during the preparation of the precursor in Comparative Example 1. Figures 2 to 9 As shown in Table 2, in Comparative Example 1, due to the lack of particle size control effect of doping elements, the first precursor and the second precursor cannot form a significant particle size difference. After mixing, it is difficult to construct an effective particle size distribution structure, and the compaction density of the matrix material is low. At the same time, due to the lack of lattice stabilization effect of W and Zr elements, the structural stability of the material is poor. Although subsequent coating treatment was carried out, its rate performance and cycle capacity retention rate are still significantly worse than those of Example 1.

[0115] The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 does not undergo any coating treatment. (Combined with...) Figure 8 , Figure 9 As shown in Table 2, although the matrix material in Comparative Example 2 has a particle size distribution structure and a high compaction density, the lack of a coating layer means that the material surface is in direct contact with the electrolyte, leading to increased side reactions, intensified metal dissolution, and a sharp deterioration in high-temperature cycling performance. The capacity retention rate and rate performance are significantly lower than those in Example 1.

[0116] In summary, this application achieves particle size distribution through W / Zr doping control, which can improve the material's compaction density while enhancing its structural stability, thereby improving the ternary cathode material's cycle stability and rate performance under high pressure.

[0117] The above description describes some specific embodiments of this application, but in actual applications, the application should not be limited to these embodiments. For those skilled in the art, other modifications and alterations made based on the technical concept of this application should fall within the protection scope of this application.

Claims

1. A method for preparing a ternary cathode material, characterized in that, include: The ternary cathode material precursor was co-precipitated with W source and Zr source respectively to obtain W-doped first precursor and Zr-doped second precursor respectively. The median particle size D50 of the first precursor was D1 and the median particle size D50 of the second precursor was D2, satisfying: 1.2≤D2 / D1≤1.

8. The first precursor and the second precursor are mixed to obtain a mixed precursor. The median particle size D50 of the mixed precursor is D3, which satisfies the following condition: 3.7μm≤D3≤4.2μm. The mixed precursor is mixed with a lithium source and sintered to form a first single crystal particle from the first precursor and a second single crystal particle from the second precursor, thereby obtaining a matrix material. as well as The matrix material and the coating material are mixed and sintered to obtain the ternary cathode material.

2. The method for preparing the ternary cathode material according to claim 1, characterized in that, In preparing the first precursor, the doping amount of W element accounts for 0.1wt% to 0.5wt% of the total metal ion mass of the first precursor; and / or, When preparing the second precursor, the amount of Zr doping accounts for 0.1wt% to 0.3wt% of the total metal ion mass of the second precursor.

3. The method for preparing the ternary cathode material according to claim 1, characterized in that, The mass ratio of the first precursor to the second precursor is (1~2):

1.

4. The method for preparing the ternary cathode material according to claim 1, characterized in that, D1 is 3.0μm~3.5μm, and D2 is 4.5μm~5.0μm.

5. The method for preparing the ternary cathode material according to claim 1, characterized in that, The W source includes at least one of tungstic acid, ammonium tungstate, sodium tungstate, and tungsten trioxide; and / or, the Zr source includes at least one of zirconium hydroxide, zirconium oxide, and zirconium oxychloride.

6. The method for preparing the ternary cathode material according to claim 1, characterized in that, The general chemical formula of the ternary cathode material precursor is LiNi. x Co y Mn 1-x-y (OH)₂, where 0.5 ≤ x ≤ 0.7, 0 < y ≤ 0.1; and / or The molar ratio of lithium in the lithium source to the total molar ratio of nickel, cobalt and manganese in the mixed precursor is (1.02~1.3):

1.

7. The method for preparing the ternary cathode material according to claim 1, characterized in that, In the step of sintering the mixed precursor with the lithium source, the sintering temperature is 900℃~1000℃, and the sintering time is 8h~15h; and / or The step of mixing the matrix material and the coating material and then sintering them includes: The matrix material is mixed with a Ti source and sintered to form a first coating layer on the surface of the matrix material; and The matrix material coated with the first coating layer is mixed with an Al source and sintered to form a second coating layer on the surface of the first coating layer.

8. The method for preparing the ternary cathode material according to claim 7, characterized in that, The sintering temperature for forming the first coating layer is 700℃~800℃, and the sintering time is 8h~15h; and / or, The sintering temperature for forming the second coating layer is 400℃~500℃, and the sintering time is 8h~15h.

9. A ternary cathode material prepared by the method for preparing a ternary cathode material as described in any one of claims 1 to 8, characterized in that, The ternary cathode material includes the matrix material, which includes the first particle and the second particle.

10. An electrochemical device, characterized in that, It includes a positive electrode, a negative electrode, and an electrolyte located between the positive electrode and the negative electrode, wherein the positive electrode is made of the ternary positive electrode material as described in claim 9.

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