Secondary-sphere positive electrode active material and preparation method therefor, positive electrode, and battery

Abstract

The present application belongs to the technical field of battery materials. Disclosed are a secondary-sphere positive electrode active material and a preparation method therefor, a positive electrode, and a battery. Primary particles of the secondary-sphere positive electrode active material are doped with Sb and S.

Description

Secondary spherical positive electrode active materials and their preparation methods, positive electrode and battery

[0001] Related applications

[0002] This application claims priority to Chinese Patent Application No. 2025101150771, filed on January 24, 2025, entitled "A Secondary Spherical Positive Electrode Active Material and Its Preparation Method Thereof", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application belongs to the field of battery materials technology, and particularly relates to secondary spherical positive electrode active materials and their preparation methods, positive electrodes and batteries. Background Technology

[0004] With the rapid development of new energy vehicles, battery performance has made great progress, but battery development is far from over. Further development to improve material performance is still underway. Cathode materials, as key materials, are also facing new requirements, such as better capacity, first-time efficiency, cycle life, and lower impedance. Progress is being made in all aspects.

[0005] Improving the first-cycle coulombic efficiency of the material is also an important aspect. For cathode materials, the first-cycle coulombic efficiency is not 100%. Improving the first-cycle coulombic efficiency of the cathode material can increase the amount of active lithium in the battery, thereby further improving the energy density of the battery.

[0006] There are many ways to improve the initial coulombic efficiency of cathode materials. For example, Chinese patent application CN106025257A improves the initial efficiency by reducing the average particle size of the material by 0.7μm-1.5μm. However, materials with such small particle sizes are rarely used in practice, making widespread application difficult. Chinese patent application CN 115986108A reduces the particle size and improves the initial efficiency by doping with F, S, and Cl, but the improvement cannot exceed 93%, which is insufficient for higher initial efficiency requirements. Furthermore, these elements are applied to the material surface through pretreatment of the precursor material, increasing processing costs. Chinese patent application CN 117352672A improves the initial coulombic efficiency by controlling the ratio of lithium carbonate to lithium hydroxide and the total residual lithium. However, controlling the total residual lithium is not suitable for many types of materials, such as high-nickel and waterless washing materials, limiting its application. Therefore, developing a universal, commercially viable, effective, and stable method to improve the initial coulombic efficiency is crucial for improving battery performance. Summary of the Invention

[0007] The technical problem to be solved by this application is to overcome the deficiencies and defects mentioned in the background art above, and to provide a secondary spherical positive electrode active material that can be applied to general commercial products and improve the first coulombic efficiency, as well as its preparation method, positive electrode and battery.

[0008] To solve the above-mentioned technical problems, the technical solution proposed in this application is as follows:

[0009] A secondary spherical positive electrode active material, wherein the primary particles of the secondary spherical positive electrode active material are doped with Sb and S, and the chemical formula of the secondary spherical positive electrode active material is Li. a Ni b Co c M1 d M2 e M3 f Sb g S h O i The element M1 includes at least one of Mn and Al, the element M2 includes at least one of Zr, Sr, Nb, Ba, Y, Mg, B, W, Mo, Ta and Ti, and the element M3 includes at least one of B, Al, Zr, Ce and Co. The following conditions apply: 0.98≤a≤1.12, 0.8≤b≤0.99, 0.01≤c≤0.5, 0.005≤d≤0.5, 0.005≤e≤0.03, 0.005≤f≤0.03, 0.0001≤g≤0.04, 0.001≤h≤0.1, and 1.9≤i≤2.5.

[0010] In some embodiments, the average particle size of the equivalent diameter of the primary particles on the surface of the secondary spherical positive electrode active material is ≤0.28 μm. Optionally, the average particle size of the equivalent diameter of the primary particles on the surface of the secondary spherical positive electrode active material is 0.2 μm to 0.28 μm. It is understood that the average particle size of the equivalent diameter of the primary particles on the surface includes, but is not limited to, 0.2 μm, 0.21 μm, 0.22 μm, 0.23 μm, 0.24 μm, 0.25 μm, 0.26 μm, 0.27 μm, and 0.28 μm. In some examples, it can be any two of these point values ​​as end values ​​within a range, the same below. Optionally, the average particle size of the equivalent diameter of the primary particles on the surface of the secondary spherical positive electrode active material is 0.22 μm to 0.25 μm.

[0011] In some of these embodiments, in the above-mentioned secondary spherical cathode active material, the average value of the aspect ratio of the particle size of the primary particles on the surface of the secondary spherical cathode active material is less than 3.0:1. Optionally, the average value of the aspect ratio of the particle size of the primary particles on the surface of the secondary spherical cathode active material is 2.0 to 3.0:1. It can be understood that the average value of the aspect ratio of the particle size of the primary particles on the surface includes but is not limited to 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3.0:1. Optionally, the average value of the aspect ratio of the particle size of the primary particles on the surface of the secondary spherical cathode active material is 2.5 to 2.9:1.

[0012] In some of these embodiments, in the above-mentioned secondary spherical cathode active material, the Span value of the particle size distribution coefficient of the primary particles on the surface of the secondary spherical cathode active material meets the following conditions: 0.7 < Span < 1.0. Optionally, 0.75 ≤ Span ≤ 0.95. It can be understood that the average value of the aspect ratio of the particle size of the primary particles on the surface includes but is not limited to 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95. Optionally, 0.77 ≤ Span ≤ 0.92.

[0013] Based on a general inventive concept, the present application also provides a method for preparing a secondary spherical cathode active material, including the following steps:

[0014] (1) Mix a precursor containing Ni, Co, and M1 with a sulfur-containing compound, an antimony-containing compound, a compound containing M2, and a lithium source, and perform a first sintering under a protective atmosphere to obtain a first sintered product;

[0015] (2) After washing and drying the first sintered product obtained in step (1), mix it with a compound containing M3, and perform a second sintering in an oxygen-containing atmosphere to obtain a secondary spherical cathode active material.

[0016] In some of these embodiments, in the above-mentioned method for preparing a secondary spherical cathode active material, in step (1), the conditions for the first sintering are as follows: first sinter at 400°C - 600°C for 1h - 5h, then raise the temperature to 680°C - 780°C and sinter for 8h - 15h, and the heating rate is 1°C / min - 5°C / min. The protective atmosphere is nitrogen.

[0017] In some embodiments, in the preparation method of the above-mentioned secondary spherical positive electrode active material, in step (2), the solid-liquid mass ratio of the water washing is 0.5-3:1, the water washing temperature is 5℃-30℃, and the water washing time is 1min-30min.

[0018] In some embodiments, in the preparation method of the above-mentioned secondary spherical positive electrode active material, in step (2), the temperature of the second sintering is 300℃-700℃ and the sintering time is 1h-10h.

[0019] In some embodiments, in the preparation method of the above-mentioned secondary spherical positive electrode active material, the S-containing compound includes at least one of lithium sulfate, zirconium sulfate, aluminum sulfate, magnesium sulfate, strontium sulfate, manganese sulfate, cobalt sulfate, cobalt(II) sulfate, and nickel sulfate.

[0020] In some embodiments, in the preparation method of the above-mentioned secondary spherical positive electrode active material, the Sb-containing compound includes at least one of antimony trioxide, antimony trioxide pentoxide, antimony tetroxide, antimony sulfate, antimony chloride, antimony acetate, and antimony carbonate.

[0021] In some embodiments, the lithium source in the preparation method of the above-mentioned secondary spherical positive electrode active material includes at least one of lithium carbonate and lithium hydroxide.

[0022] This application also provides a positive electrode, comprising the above-described secondary spherical positive electrode active material or the secondary spherical positive electrode active material prepared by the above-described method for preparing the secondary spherical positive electrode active material.

[0023] This application also provides a battery comprising the above-mentioned secondary spherical positive electrode active material, the secondary spherical positive electrode active material prepared by the above-mentioned method for preparing the secondary spherical positive electrode active material, or the above-mentioned positive electrode.

[0024] Compared with the prior art, the beneficial effects of this application are as follows:

[0025] (1) The ionic radius of Sb ions is larger than that of transition metals. After doping, the lithium ion channel can be widened, which is beneficial to the insertion and extraction of lithium ions. In addition, Sb oxide has the effect of storing lithium ions and its specific capacity is also very high. These are all beneficial to the insertion and extraction of lithium ions. The combined effect of S and Sb compounds can further improve the initial coulombic efficiency of the material. In the actual test, it can also be seen that the combined doping of the two has a significantly better effect on the initial coulombic efficiency than the single doping.

[0026] (2) Doping with Sb compounds can increase the lattice volume and increase the diffusion channels of lithium ions. Co-doping with S compounds and Sb-containing compounds can reduce the size of the primary particles of the secondary spheres and improve the uniformity of the primary particles, which is beneficial to reduce migration resistance and improve the cycle performance of the material.

[0027] (3) Adding the S compound and the Sb compound simultaneously during the primary mixing process can effectively control the size of the primary particles. The simultaneous addition of the two elements can make the primary particles smaller and closer to spherical particles. At the same time, the uniformity of the primary particles is also very good, with the average particle size of the primary particles ≤ 0.28 μm, the average aspect ratio of the particle size of the surface primary particles less than 3.0∶1, and the particle size distribution coefficient of the primary particles being 0.7 < Span < 1.0. When synthesizing the secondary spherical cathode active material, the size, uniformity, and morphology of the primary particles can directly affect the initial Coulombic efficiency of the material. The co-doping of S and Sb elements can make the primary particles smaller and more spherical in morphology, which is beneficial to reducing the lithium insertion kinetics characteristics of the material during charge and discharge, thereby improving the initial Coulombic efficiency of the material.

[0028] (4) Adding the relevant elements directly during the primary mixing process, mixing them evenly, sintering, and then performing the water washing process and the second sintering process. The preparation process is conventional and simple, suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for description in the embodiments or the prior art. Obviously, the following-described drawings are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 is the FE-SEM (A) and the model recognition graph (B) of Example 1; (3) Adding the S compound and the Sb compound simultaneously during the primary mixing process can effectively control the size of the primary particles. The simultaneous addition of the two elements can make the primary particles smaller and closer to spherical particles. At the same time, the uniformity of the primary particles is also very good, with the average particle size of the primary particles ≤ 0.28 μm, the average aspect ratio of the particle size of the surface primary particles less than 3.0∶1, and the particle size distribution coefficient of the primary particles being 0.7 < Span < 1.0. When synthesizing the secondary spherical cathode active material, the size, uniformity, and morphology of the primary particles can directly affect the initial Coulombic efficiency of the material. The co-doping of S and Sb elements can make the primary particles smaller and more spherical in morphology, which is beneficial to reducing the lithium insertion kinetics characteristics of the material during charge and discharge, thereby improving the initial Coulombic efficiency of the material.

[0031] Figure 2 is the FE-SEM (A) and the model recognition graph (B) of Example 2; <000^178>

[0032] Figure 3 is the FE-SEM (A) and the model recognition graph (B) of Example 3;

[0033] Figure 4 is the FE-SEM (A) and the model recognition graph (B) of Example 4; <00001^2>

[0034] Figure 5 is the FE-SEM (A) and the model recognition graph (B) of Example 5;

[0035] Figure 6 is the FE-SEM (A) and the model recognition graph (B) of Comparative Example 1;

[0036] Figure 7 is the FE-SEM (A) and the model recognition graph (B) of Comparative Example 4;

[0037] Figure 8 is the FE-SEM (A) and the model recognition graph (B) of Comparative Example 7. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] To facilitate understanding of this application, the following description will be more comprehensive and detailed in conjunction with the accompanying drawings and preferred embodiments, but the scope of protection of this application is not limited to the following specific embodiments.

[0039] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of this application.

[0040] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application are available on the market or can be prepared by existing methods.

[0041] In the following examples and comparative examples, the average particle size of the primary particles, the average aspect ratio of the primary particles, and the particle size distribution coefficient Span of the primary particles were obtained by testing and calculation using the following methods: Field emission electron microscopy (FEM) was performed on the sintered secondary spherical particles at 50,000x magnification to identify the outline of the primary particles. The area of ​​each primary particle was equivalent to the area of ​​a circle of the same size, and the diameter of the circle was calculated to be equivalent to the diameter of the primary particle. The length and width of the identified primary particles were compared to obtain the aspect ratio and the length-to-diameter ratio. The particle size distribution coefficient Span was calculated as follows: Span = (D90 - D10) / D50, where D10 is the particle size corresponding to a cumulative distribution ratio of 10% in the system, D50 is the particle size corresponding to a cumulative distribution ratio of 50% in the system, and D90 is the particle size corresponding to a cumulative distribution ratio of 90% in the system.

[0042] Example 1:

[0043] The preparation method of the secondary spherical positive electrode active material of this application includes the following steps:

[0044] S1. Ni cobalt aluminum hydroxide with a D50 of 12.8 μm 0.925 Co 0.055 Al 0.02 (OH)₂, lithium-containing compound LiOH·H₂O, 0.15% mol ZrO₂, 0.05% mol Sb₂O₃, and 0.2% mol Li₂SO₄ were mixed in a high-speed mixer, wherein the molar ratio of LiOH·H₂O to nickel-cobalt-aluminum hydroxide was 1.05:1. The mixture was then placed in an oxygen atmosphere furnace and sintered at 450℃ for 3 hours, followed by sintering at 650℃ for 10 hours. After natural cooling, the matrix material Li was obtained. 1.05 Ni 0.925 Co 0.055 Al 0.02 Zr 0.0015 Sb0.001 S 0.002 O2, wherein the heating rate is 4℃ / min;

[0045] S2. Manually sieve the matrix material from step S1, wash it for 15 minutes according to the mass ratio of matrix material to deionized water = 1:1, filter it, and then place it in a vacuum drying oven to dry for 8 hours.

[0046] S3. The washed material was mixed with Co(OH)2 at a molar ratio of 1:0.05 and sintered in an oxygen furnace at 650°C for 7 hours. After cooling, the mixture was sieved to dissociate the material and obtain Li. 1.05 Ni 0.92 Co 0.06 Al 0.02 Zr 0.0015 Sb 0.001 S 0.002 The positive electrode active material of O2 has an average particle size of 0.25 μm, an aspect ratio of 2.5, and a span of 0.92.

[0047] As shown in Figure 1, the particles are uniform and tend to be spherical.

[0048] Example 2:

[0049] The preparation method of the secondary spherical positive electrode active material of this application includes the following steps:

[0050] Compared with Example 1, the precursor, lithium source, and preparation process are the same as in Example 1. The difference is that the additives are 0.15% mol ZrO2, 0.1% mol TiO2, 0.08% mol Sb2O3, and 0.2% mol Li2SO4 mixed and sintered to finally obtain Li 1.05 Ni 0.92 Co 0.06 Al 0.02 Zr 0.0015 Ti 0.001 Sb 0.0016 S 0.002 The positive electrode active material of O2 has an average particle size of 0.24 μm, an aspect ratio of 2.6, and a span of 0.84.

[0051] As shown in Figure 2, the particles are uniform and tend to be spherical.

[0052] Example 3:

[0053] The preparation method of the secondary spherical positive electrode active material of this application includes the following steps:

[0054] S1. Ni cobalt manganese hydroxide with a D50 of 13.2 μm 0.88 Co 0.09 Mn0.03 (OH)2, lithium-containing compound LiOH·H2O, 0.3% mol ZrO2, 0.05% mol Sb2O3, and 0.6% mol Li2SO4 were mixed in a high-speed mixing device, wherein the molar ratio of LiOH·H2O to nickel cobalt manganese hydroxide was 1.03:1. The mixture was then placed in an oxygen atmosphere furnace and sintered at 500℃ for 4 hours, and then heated to 745℃ for 8 hours. The matrix material was obtained by natural cooling. The heating rate was 4℃ / min.

[0055] S2. Manually sieve the matrix material from step S1, wash it for 20 minutes according to the mass ratio of matrix material to deionized water = 1:1.2, filter it, and then place it in a vacuum drying oven to dry for 12 hours.

[0056] S3. The washed material was mixed with boric acid at a molar ratio of 1:0.009 and sintered in an oxygen furnace at 350°C for 8 hours. After cooling, the mixture was sieved to dissociate the compounds and obtain Li. 1.03 Ni 0.88 Co 0.09 Mn 0.03 Zr 0.003 Sb 0.001 S 0.006 B 0.009 The positive electrode active material of O2 has an average particle size of 0.23 μm, an aspect ratio of 2.5, and a span of 0.77.

[0057] As shown in Figure 3, the particles are uniform and tend to be spherical.

[0058] Example 4:

[0059] The preparation method of the secondary spherical positive electrode active material of this application includes the following steps:

[0060] Compared with Example 3, the precursor, lithium source, and preparation process are the same as in Example 3. The difference is that the additives are 0.3% mol Zr(SO4)2, 0.15% mol Y2O3, and 0.05% mol Sb2O3 mixed and sintered to finally obtain Li. 1.03 Ni 0.88 Co 0.09 Mn 0.03 Zr 0.003 Y 0.003 Sb 0.001 S 0.006 B 0.009 The positive electrode active material of O2 has an average particle size of 0.22 μm, an aspect ratio of 2.6, and a span of 0.82.

[0061] As shown in Figure 4, the particles are uniform and tend to be spherical.

[0062] Example 5:

[0063] The preparation method of the secondary spherical positive electrode active material of this application includes the following steps:

[0064] Compared with Example 3, the precursor, lithium source, and preparation process are the same as in Example 3. The difference is that the additives are 0.3% mol Zr(SO4)2, 0.15% mol Y2O3, 0.1% mol TiO2, and 0.05% Sb2O3 mixed and sintered to finally obtain Li. 1.03 Ni 0.88 Co 0.09 Mn 0.03 Zr 0.003 Y 0.003 Ti 0.001 Sb 0.001 S 0.006 B 0.009 The positive electrode active material of O2 has an average particle size of 0.24 μm, an aspect ratio of 2.9, and a span of 0.90.

[0065] As shown in Figure 5, the particles are uniform and tend to be spherical.

[0066] Comparative Example 1:

[0067] The preparation method of a secondary spherical positive electrode active material is as follows:

[0068] Compared with Example 1, the precursor, lithium source, and preparation process are the same as in Example 1, except that the additive is 0.15% mol ZrO2, and it does not contain Sb or S compounds. The mixture is then sintered to finally obtain Li. 1.05 Ni 0.92 Co 0.06 Al 0.02 Zr 0.0015 The positive electrode active material of O2 has an average particle size of 0.33 μm, an aspect ratio of 3.2, and a span of 1.06.

[0069] Compared to Figure 1, the primary particles in Figure 6 have poor uniformity, and some of the primary particles are more rounded and some are more elongated.

[0070] Comparative Example 2:

[0071] The preparation method of a secondary spherical positive electrode active material is as follows:

[0072] Compared with Example 1, the precursor, lithium source, and preparation process are the same as in Example 1, except that the additives are 0.15% mol ZrO2 and 0.04% mol Sb2O3, and no sulfur compounds are present. The mixture is then sintered to finally obtain Li. 1.05Ni 0.92 Co 0.06 Al 0.02 Zr 0.0015 Sb 0.0008 The positive electrode active material of O2 has an average particle size of 0.31 μm, an aspect ratio of 3.2, and a span of 1.05.

[0073] Comparative Example 3:

[0074] The preparation method of a secondary spherical positive electrode active material is as follows:

[0075] Compared with Example 1, the precursor, lithium source, and preparation process are the same as in Example 1, except that the additives are 0.15% mol ZrO2 and 0.3% mol Li2SO4, and Sb compounds are not present. The mixture is then sintered to finally obtain Li. 1.05 Ni 0.92 Co 0.6 Al 0.2 Zr 0.0015 S 0.003 The positive electrode active material of O2 has an average particle size of 0.33 μm, an aspect ratio of 3.2, and a span of 0.88.

[0076] Comparative Example 4:

[0077] The preparation method of a secondary spherical positive electrode active material is as follows:

[0078] Compared with Example 3, the precursor, lithium source, and preparation process are the same as in Example 3, except that the additives are 0.3% mol ZrO2 and 0.05% mol Sb2O3, and no sulfur compounds are present. The mixture is then sintered to finally obtain Li. 1.03 Ni 0.88 Co 0.09 Mn 0.03 Zr 0.003 Sb 0.001 B 0.009 The positive electrode active material of O2 has an average particle size of 0.36 μm, an aspect ratio of 3.1, and a span of 1.01.

[0079] Compared to Figure 3, the particles in Figure 7 are significantly longer and larger.

[0080] Comparative Example 5:

[0081] The preparation method of a secondary spherical positive electrode active material is as follows:

[0082] Compared with Example 3, the precursor, lithium source, and preparation process are the same as in Example 3, except that the additives are 0.3% mol Zr(SO4)2, 0.15% mol ZrO2, and 0.01% mol WO3, and Sb compounds are not included. The mixture is then sintered to finally obtain Li. 1.03 Ni 0.88 Co 0.09 Mn 0.03 Zr 0.003 W 0.0001 S 0.006 B 0.009 The positive electrode active material of O2 has an average particle size of 0.32 μm, an aspect ratio of 3.6, and a span of 1.03.

[0083] Comparative Example 6:

[0084] The preparation method of a secondary spherical positive electrode active material is as follows:

[0085] Compared with Example 3, the precursor, lithium source, and preparation process are the same as in Example 3, except that the additives are 0.3% mol ZrO2 and 0.3% mol Li2SO4, and Sb compounds are not present. The mixture is then sintered to finally obtain Li. 1.03 Ni 0.88 Co 0.09 Mn 0.03 Zr 0.003 S 0.003 B 0.009 The positive electrode active material of O2 has an average particle size of 0.30 μm, an aspect ratio of 3.4, and a span of 1.02.

[0086] Comparative Example 7:

[0087] The preparation method of a secondary spherical positive electrode active material is as follows:

[0088] Compared with Example 3, the precursor, lithium source, and preparation process are the same as in Example 3. The difference is that the primary sintering additive in step S1 is 0.3% mol ZrO2, and the secondary sintering additives in step S2 are 0.05% mol Sb2O3, 0.6% mol Li2SO4, and 0.9% boric acid, which are mixed and sintered to finally obtain Li. 1.03 Ni 0.88 Co 0.09 Mn 0.03 Zr 0.003 Sb 0.001 S 0.006 B 0.009 The positive electrode active material of O2 has an average particle size of 0.39 μm, an aspect ratio of 3.4, and a span of 1.00.

[0089] Compared to Figure 3, the particles in Figure 8 are clearly elongated and larger.

[0090] The experimental methods in this application are as follows:

[0091] (1) Primary particle characterization of positive electrode active material

[0092] Field emission scanning electron microscopes were used to take images at 50,000x magnification. The images were then imported into a trained deep learning model to obtain the features and statistical information of the particles.

[0093] (2) Lithium carbonate and lithium hydroxide content test

[0094] The lithium carbonate and lithium hydroxide content on the surface of the cathode materials prepared in the examples and comparative examples was tested by potentiometric titration.

[0095] (3) Assembly and performance testing of lithium batteries

[0096] The positive electrode active material obtained in the examples and comparative examples was mixed with conductive carbon black (SP), polyvinylidene fluoride (PVDF) in a mass ratio of 92.5:5:2.5 and then dispersed with solvent NMP. This mixture was coated onto an aluminum foil substrate and rolled to obtain a positive electrode sheet. Evaluation tests were conducted on coin cells with lithium metal sheets as the negative electrode. The cells were charged at 0.1C and discharged at 0.1C under normal temperature and a voltage range of 3.0–4.3V. Cycle retention was tested at room temperature (25°C) for 50 cycles of 1C charging and 1C discharging, or at a high temperature (45°C) for 50 cycles of 0.5C charging and 0.5C discharging. The initial coulombic efficiency (%) was calculated as: initial discharge capacity (mAh / g) / initial charge capacity (mAh / g) × 100. The physicochemical properties and coin cell results are shown in Table 1 below.

[0097] Table 1: Physicochemical property test results and tethering results of each embodiment and comparative example

[0098] Through the comparison of experimental test data, the average particle size, aspect ratio, and Span value of primary particles will affect the electrical properties of the material, but have little impact on properties such as residual lithium. The average particle size of the equivalent diameter of primary particles in the examples is ≤0.28 μm, the average value of the aspect ratio is less than 3.0, and the particle size distribution coefficient of primary particles is 0.7 < Span < 1.0, but the comparative examples are not within this range. By directly observing the SEM images, it can also be found that the uniformity of primary particles in the comparative examples is inferior to that of primary particles in the examples, and the particle size is also larger than that in the examples. Comparative Example 2 and Comparative Example 3 added Sb element and S element respectively compared with Comparative Example 1, and the first efficiency and the first discharge capacity were improved, but the improvement amplitude was significantly worse compared with Examples 1-5. The first efficiency of Examples 1-5 can all reach more than 93%. Compared with Comparative Examples 1-3, Examples 1 and 2 added Sb element and S element at the same time, and the first discharge capacity and the first efficiency were significantly improved, and the cycle performance was also improved. Compared with Comparative Examples 4-6, Examples 3-5 also had significantly higher first discharge capacity and first efficiency, and the cycle performance had a small improvement. The rule is the same as the previous rule, indicating that adding Sb element and S element at the same time can significantly improve the first discharge capacity and the first efficiency. Comparing Example 3 with Comparative Example 7, it can be seen that the effect of adding a dopant in the coating stage is significantly worse, and there is no improvement effect on the first efficiency.

[0099] The technical features of the above-mentioned examples can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above-mentioned examples are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0100] The above-mentioned examples only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A secondary spherical positive electrode active material, wherein the primary particles of the secondary spherical positive electrode active material are doped with Sb and S, and the chemical formula of the secondary spherical positive electrode active material is Li. a Ni b Co c M1 d M2 e M3 f Sb g S h O i The element M1 includes at least one of Mn and Al, the element M2 includes at least one of Zr, Sr, Nb, Ba, Y, Mg, B, W, Mo, Ta and Ti, and the element M3 includes at least one of B, Al, Zr, Ce and Co. The following conditions apply: 0.98≤a≤1.12, 0.8≤b≤0.99, 0.01≤c≤0.5, 0.005≤d≤0.5, 0.005≤e≤0.03, 0.005≤f≤0.03, 0.0001≤g≤0.04, 0.001≤h≤0.1, and 1.9≤i≤2.

5.

2. The secondary spherical positive electrode active material according to claim 1, wherein, The average diameter of the primary particles on the surface of the secondary spherical positive electrode active material is ≤0.28μm, and the average aspect ratio of the primary particles on the surface is less than 3.0∶1.

3. The secondary spherical positive electrode active material according to claim 2, wherein, The average particle size of the primary particles on the surface of the secondary spherical positive electrode active material is 0.2 μm to 0.28 μm.

4. The secondary spherical positive electrode active material according to any one of claims 2-3, wherein, The average particle size of the primary particles on the surface of the secondary spherical positive electrode active material is 0.22 μm to 0.25 μm.

5. The secondary spherical positive electrode active material according to any one of claims 2-4, wherein, The average aspect ratio of the primary particles on the surface of the secondary spherical positive electrode active material is 2.0 to 3.0:

1.

6. The secondary spherical positive electrode active material according to any one of claims 2-5, wherein, The average aspect ratio of the primary particles on the surface of the secondary spherical positive electrode active material is 2.5 to 2.9:

1.

7. The secondary spherical positive electrode active material according to any one of claims 1-6, wherein, The particle size distribution coefficient (Span) of the primary particles on the surface of the secondary spherical positive electrode active material meets the following condition: 0.7 <Span<1.0。 8. The secondary spherical positive electrode active material according to claim 7, wherein, 0.75≤Span≤0.

95.

9. The secondary spherical positive electrode active material according to any one of claims 7-8, wherein, 0.77≤Span≤0.

92.

10. A method for preparing a secondary spherical positive electrode active material as described in any one of claims 1-9, comprising the following steps: (1) A precursor containing Ni, Co and M1 is mixed with a compound containing S, a compound containing Sb, a compound containing M2 and a lithium source, and the mixture is sintered for the first time under a protective atmosphere to obtain a first sintered product. (2) After washing and drying the first sintering product obtained in step (1), it is mixed with the M3-containing compound and sintered a second time in an oxygen-containing atmosphere to obtain the secondary spherical positive electrode active material.

11. The method for preparing the secondary spherical positive electrode active material according to claim 10, wherein, In step (1), the conditions for the first sintering are as follows: first sinter at 400℃-600℃ for 1h-5h, then sinter at 680℃-780℃ for 8h-15h, with a heating rate of 1℃ / min-5℃ / min.

12. The method for preparing the secondary spherical positive electrode active material according to any one of claims 10-11, wherein, In step (1), the protective atmosphere is nitrogen.

13. The method for preparing the secondary spherical positive electrode active material according to any one of claims 10-12, wherein, In step (2), the solid-liquid mass ratio used for water washing is 0.5-3:1, the water washing temperature is 5℃-30℃, and the water washing time is 1min-30min.

14. The method for preparing the secondary spherical positive electrode active material according to any one of claims 10-13, wherein, In step (2), the temperature of the second sintering is 300℃-700℃ and the sintering time is 1h-10h.

15. The method for preparing the secondary spherical positive electrode active material according to any one of claims 10-14, wherein, The S-containing compound includes at least one of lithium sulfate, zirconium sulfate, aluminum sulfate, magnesium sulfate, strontium sulfate, manganese sulfate, cobalt sulfate, cobalt(II) sulfate, and nickel sulfate.

16. The method for preparing the secondary spherical positive electrode active material according to any one of claims 10-15, wherein, The Sb-containing compound includes at least one of antimony trioxide, antimony trioxide, antimony tetroxide, antimony sulfate, antimony chloride, antimony acetate, and antimony carbonate.

17. The method for preparing the secondary spherical positive electrode active material according to any one of claims 10-16, wherein, The lithium source includes at least one of lithium carbonate and lithium hydroxide.

18. A positive electrode, comprising a secondary spherical positive electrode active material as described in any one of claims 1-9 or a secondary spherical positive electrode active material prepared by any one of claims 10-17.

19. A battery comprising a secondary spherical positive electrode active material as described in any one of claims 1-9, a secondary spherical positive electrode active material prepared by the method for preparing the secondary spherical positive electrode active material as described in any one of claims 10-17, or a positive electrode as described in claim 18.

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