A lithium-rich high-nickel porous positive electrode material, a preparation method and application thereof

Abstract

The application discloses a lithium-rich high-nickel porous positive electrode material and a preparation method and application thereof. The positive electrode material is composed of Li, Ni, M, M', M'' and O elements. The molar ratio of the Ni element to the Li element is above 0.64. The ratio of the total molar number of the Ni, M, M' and M'' elements to the molar number of the Li element is n, and 0.7 < n < 1. M is selected from at least one of the 3rd to 6th period metal elements. M' is selected from at least one of the 2nd to 5th period metal elements. M'' is selected from at least one of metal or non-metal elements, and is different from M and M'. In the X-ray diffraction spectrum of the positive electrode material under CuKa radiation, at least one characteristic peak appears at 20° to 35°. The positive electrode material has a pore structure, and the pore structure includes closed pores and open pores. The battery prepared by using the positive electrode material has a 0.1C reversible specific capacity of above 249 mAh / g.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a lithium-rich high-nickel porous positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] In recent years, with the continuous progress of green energy technology and the deep-rooted concept of carbon neutralization, the electric trend has gradually expanded from the traditional automobile industry to large transportation tools such as aircraft and ships. Since 2023, many enterprises have proposed the strategic goal of increasing the energy density of lithium batteries to 500Wh / kg to meet the demand for high-energy storage of these large tools. As a key component of lithium batteries, the performance of the positive electrode material directly determines the energy density of the battery. Therefore, developing lithium battery positive electrode materials with higher specific energy has become a hot research topic.

[0003] Transition metal oxides, such as lithium cobaltate, lithium nickelate, lithium manganate, and their derivatives, are considered as strong candidates for high-energy density positive electrode materials to achieve the strategic goal of 500Wh / kg lithium batteries due to their high theoretical working voltage and specific capacity. However, in practical applications, the positive electrode material is affected by multiple factors such as electrode-electrolyte side reactions, electron / ion transport barriers, and physical deformation stress, making it difficult to fully realize its theoretical energy density.

[0004] To address these challenges, researchers have optimized existing positive electrode materials and proposed lithium-rich manganese-based positive electrode materials and high-nickel positive electrode materials. Although the lithium-rich manganese-based positive electrode materials disclosed in patent documents CN116856058A, CN115124089A, and CN116375110A have high capacity, their working voltage window is high, and high-voltage triggering of lattice oxygen reversible oxidation and reduction is required, so the upper limit of their working voltage reaches 4.6-4.8V, which exceeds the voltage tolerance window of existing commercial electrolyte systems. In addition, as the contribution of capacity gradually shifts from oxygen to transition metals, lithium-rich manganese-based positive electrode materials also have the problem of voltage decay.

[0005] The high-nickel positive electrode materials disclosed in patent documents CN116581280A, CN116799181A, and CN116588987A have a theoretical specific capacity of about 274mAh / g, and the actual capacity is closely related to the proportion of nickel and cobalt elements in the material, which is significantly lower than the theoretical specific capacity. And under the existing commercial electrolyte voltage tolerance window (4.3-4.45V), the performance of high-nickel positive electrode materials still faces many challenges. For example, although the increase in nickel content can bring higher actual capacity, due to the problems faced by positive electrode materials, how to obtain a high-nickel positive electrode material with a specific capacity greater than 243mAh / g is still a key problem that needs to be solved.

[0006] To break this bottleneck, various strategies have been proposed in existing high-nickel technologies, however, these strategies still have many deficiencies in practical application. For example, the patent document CN116119737A adopts the method of improving the particle size distribution of the precursor to improve the material performance, but its specific capacity is 236 mAh / g, which is significantly less than the target specific capacity; the patent document CN114914440A proposes to limit the half-peak width of the characteristic crystal face diffraction peak of the high-nickel positive electrode material to reduce the proportion of non-stoichiometric product, so that the specific capacity of the high-nickel positive electrode material obtained at 0.1C discharge is about 236 mAh / g; the patent document CN114551835A reduces the degree of nickel-nickel mixing by limiting the ratio between the characteristic peaks of the high-nickel positive electrode material, and the specific capacity of the high-nickel positive electrode material obtained under the condition of 0.1C current density is 235 mAh / g. Therefore, the specific capacity of the high-nickel positive electrode material in the existing technology is still at a low level.

[0007] In summary, it is still a great challenge and a broad development space to realize the further development of the capacity of the high-nickel positive electrode material and at the same time improve the cycle performance of the material, especially the high-nickel positive electrode material that meets the strategic goal of 500 Wh / kg lithium battery. SUMMARY

[0008] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application proposes a lithium-rich high-nickel positive electrode material, which has a high specific capacity.

[0009] The present application also proposes a preparation method of the above-mentioned positive electrode material.

[0010] The present application also proposes an application of the above-mentioned positive electrode material.

[0011] The positive electrode material according to the first aspect of the present application is composed of Li, Ni, M, M', M" and O elements; wherein the molar ratio of Ni element to Li element is above 0.64; the ratio of the total number of moles of Ni, M, M', M" elements to the number of moles of Li element is n, and 0.7 < n < 1;

[0012] M is selected from at least one of the metal elements in the 3rd to 6th period;

[0013] M' is selected from at least one of the metal elements in the 2nd to 5th period;

[0014] M" is selected from at least one of the metal or non-metal elements in the 2nd to 6th period, and is different from M and M';

[0015] The positive electrode material has at least one characteristic peak in the X-ray diffraction pattern (XRD) obtained under CuKa radiation, 2θ is 20°-35°;

[0016] The positive electrode material has a pore structure, and the pore structure includes closed pores and open pores.

[0017] The positive electrode material according to the embodiment of the present application has at least the following beneficial effects: the battery prepared by using the positive electrode material has a reversible specific capacity of 249 mAh / g or more under the condition of a 0.1C current density and in a voltage range of 2.5-4.35 V. The lithium-rich high-nickel porous positive electrode material of the present application realizes the ordered arrangement of lithium ions in the non-lithium metal layer through the strategy of replacing part of the non-lithium metal cations with lithium ions, and forms a unique lithium-rich phase layered crystal structure. In this structure, part of the lithium atoms not only replace part of the positions of the non-lithium metal atoms, but also form an ordered and non-random arrangement with the non-lithium metal atoms. These lithium atoms located in the transition metal layer are also electrochemically active, which not only contributes to the capacity, but also provides additional support for the lithium atoms in the lithium layer, limiting the escape of lattice oxygen. In addition, the doping of multiple characteristic elements in the composition further enhances the stability of the crystal structure and effectively anchors the lattice oxygen.

[0018] In the positive electrode material of the present application, due to the periodic characteristics of the superlattice structure, one or more obvious diffraction characteristic peaks will appear in the X-ray diffraction pattern (XRD) in the region with a 2θ angle ranging from 20° to 35°. The presence of these diffraction characteristic peaks not only verifies that the positive electrode material designed in the present application has a unique crystal structure, but also provides strong evidence for its excellent electrochemical performance.

[0019] The pore structure in the present application provides more transmission channels for lithium ions in the electrolyte, shortening the diffusion path of ions inside the material. This design helps to accelerate the embedding and de-embedding speed of lithium ions, thereby improving the charge and discharge rate and rate performance of the battery. At the same time, the pore structure helps to improve the thermal conductivity of the material, so that the heat generated during the charge and discharge process of the battery can be dissipated faster. This is of great significance to prevent the battery from overheating and improve the thermal stability and safety of the battery. The material morphology of the present application innovatively combines closed pores and open pores. The open pore structure greatly promotes the overall infiltration of the electrolyte, which can penetrate into the primary particle interior, effectively reducing the ion migration distance (lambda). According to the formula of ion transmission time (tau) tau = lambda2 / Di (Di represents the ion migration rate), it can be clearly seen that the shortening of the migration distance can greatly reduce the ion transmission time, thereby significantly improving the rate performance of the material. At the same time, the carefully designed part of the closed pore structure in the material plays a key role, which can effectively alleviate the deformation stress experienced by the particles during the charge and discharge process of the battery, thereby enhancing the structural stability of the material. Therefore, the combined design of open pores and closed pores not only ensures the reversible change of the crystal structure, but also effectively releases the stress, which helps to maintain the stability of the material morphology.

[0020] According to some embodiments of the present application, in the XRD pattern of the positive electrode material, the ratio of the peak intensity of the strongest peak in the characteristic peaks in the 20°-35° region to the peak intensity of the (003) crystal plane is 0

[0021] According to some embodiments of the present application, 0.0001≤A / B≤0.05.

[0022] According to some embodiments of the present application, 0.0001≤A / B≤0.02.

[0023] According to some embodiments of the present application, 0.0001≤A / B≤0.01.

[0024] According to some embodiments of the present application, 0.004≤A / B≤0.01.

[0025] According to some embodiments of the present application, the positive electrode material comprises a plurality of secondary particles composed of primary particles.

[0026] According to some embodiments of the present application, the closed pores are mainly distributed (more than 50%) inside the secondary particles.

[0027] According to some embodiments of the present application, the closed pores are irregular in shape.

[0028] According to some embodiments of the present application, the secondary particles have a maximum cross-sectional porosity of 1%-15%. The porosity in this range can to some extent alleviate the stress caused by volume change during charging and discharging, helping to maintain the structural integrity of the positive electrode material. This is crucial for prolonging the cycle life of the battery and improving safety performance. In addition, the porosity in the range of the present application is conducive to the uniform penetration of electrolyte in the positive electrode material, which helps to reduce the retention and drying of electrolyte inside the material, thereby improving the cycle stability and consistency of the battery.

[0029] According to some embodiments of the present application, the secondary particles have a maximum cross-sectional porosity of 5% to 10%.

[0030] According to some embodiments of the present application, the single secondary particles of the positive electrode material comprise two or more crystallites, and there is a pore structure between adjacent crystallites.

[0031] According to some embodiments of the present application, M and M' can be the same or different.

[0032] According to some embodiments of the present application, M is selected from at least one of Co, Mn, Al, Zr, W, Nb, Sn, Sb, Ta, Sr, Y, Mg, Ti, La, Mo, Mg.

[0033] According to some embodiments of the present application, M is selected from at least one of Co, Mn, Mg, Sb, Mo, Nb, Al, Ti, Zr or W. According to some embodiments of the present application, M' is selected from at least one of Al, Nb, Co, W, Mg, Li, Sn, Zr, Ti.

[0034] According to some embodiments of the present application, M' is selected from at least one of Nb, Co, W, Li, Sn, Zr, Al or Ti. According to some embodiments of the present application, M" is selected from at least one of Ti, Nb, P, Co, B, W, Li or Al. According to some embodiments of the present application, the ratio of Ni / Li in the positive material is above 0.7, such as above 0.75, above 0.8, above 0.85, above 0.9, above 0.95, above 0.97, above 0.98, etc.

[0035] According to some embodiments of the present application, 0.75≤n≤0.99.

[0036] According to some embodiments of the present application, 0.8≤n≤0.99.

[0037] According to some embodiments of the present application, 0.9≤n≤0.99.

[0038] According to some embodiments of the present application, the positive electrode material has the chemical formula Li 1+x (Ni a M b M' c M" d ) 1-x O 2+α ; wherein 0

[0039] The positive electrode material of the scheme is a nickel-rich high-nickel material. By appropriately increasing the content of lithium element and optimizing the utilization efficiency of non-lithium metal ions, a part of lithium ions can be retained in the lithium layer lattice of the material, which plays a crucial role in maintaining the stability of the crystal structure. In addition, the present application also innovatively introduces a variety of doping elements, which can effectively anchor lattice oxygen, further enhancing the stability of the lattice oxygen skeleton. Under the combined action of these comprehensive strategies, the cycle life of the positive electrode material of the scheme is significantly improved. The lithium-rich content ratio combined with the unique open and closed pore joint design further improves the actual reversible specific capacity of the high-nickel positive electrode material. The multi-level and multi-type pore distribution not only accelerates the transmission speed of lithium ions, but also effectively reduces the electrochemical polarization phenomenon, significantly improving the rate performance of the material. In the button lithium battery test, the material exhibits a reversible specific capacity of more than 239 mAh / g at a current density of 0.3C and a voltage range of 2.8-4.3V, reaching 98% of the specific capacity at a current density of 0.1C. In addition, when the voltage range is further widened to 2.5-4.35V and tested at a current density of 0.1C, the reversible specific capacity can reach more than 249 mAh / g. This performance surpasses the traditional high-nickel layered positive electrode material, making an important contribution to improving the energy density of lithium batteries and promoting the development process of 500Wh / kg high-energy-density lithium batteries.

[0040] The high-nickel positive electrode material component (Li 1+x (Ni a M b M’ c M” d ) 1-x O 2+α ), wherein the value of x is directly related to the number of available lithium ions in the component and is a key factor in achieving high capacity. Specifically, the larger the value of x, the more lithium ions available in the material. In traditional high-nickel positive electrode materials, the molar ratio of lithium to non-lithium cations is usually 1:1, and lithium ions in excess of this ratio are attached to the surface of the positive electrode material in the form of lithium carbonate, lithium hydroxide, and other lithium-containing impurities. In contrast, the present application innovatively designs a component with a lithium to transition metal ratio greater than 1, wherein the excess lithium ions not only exist inside the crystal lattice of the positive electrode material but also contribute to capacity and support the crystal structure. Specifically, the lithium-rich high-nickel positive electrode material in the present application has a value of x in the range of 0 < x ≤ 0.17, ensuring that the number of available lithium ions in its component is increased compared to traditional materials.

[0041] In the process of pursuing high lithium ion utilization rate, the traditional high-nickel layered positive electrode material often faces the problem of insufficient crystal structure support caused by limited lithium content, which easily leads to crystal structure collapse and reduces the cycle life. In view of this challenge, the present application effectively solves the problems existing in traditional materials through ingenious structural design. The traditional high-nickel positive electrode material adopts an α-NaFeO2 type crystal structure, in which lithium and non-lithium cations (such as Ni, Co, Mn, etc. transition metals) occupy 3b sites to form a lithium layer and 3a sites to form a transition metal layer in a 1:1 molar ratio; however, the site exchange between trace lithium atoms and nickel atoms may lead to disordered lithium / nickel mixing, which adversely affects the performance of the material. In the present application, part of the lithium atoms replace the positions of non-lithium metal atoms and form a unique structure of ordered arrangement of lithium and transition metals. Specifically, at the 3a position of the α-NaFeO2 type layered positive electrode material, lithium atoms and non-lithium metal atoms exhibit a periodic arrangement, which breaks the traditional lithium-nickel mixing phenomenon and forms a structure with superlattice characteristics.

[0042] According to some embodiments of the present application, 0.01≤x≤0.1. Such as 0.02, 0.05, 0.07, 0.08, 0.1, etc.

[0043] According to some embodiments of the present application, 0.98≤a≤1.

[0044] According to some embodiments of the present application, 0.97≤a<0.995.

[0045] According to some embodiments of the present application, 0.001≤b≤0.015. Such as 0.002, 0.005, 0.007, 0.008, 0.01, 0.012, etc.

[0046] According to some embodiments of the present application, 0.001≤c≤0.01. Such as 0.002, 0.005, 0.007, 0.008, 0.01, 0.012, etc.

[0047] According to some embodiments of the present application, 0.001≤d≤0.008. Such as 0.002, 0.005, 0.007, etc.

[0048] According to the preparation method of the second aspect of the present application, the following steps are included:

[0049] S1, a mixture I containing a precursor and a lithium source is subjected to a first heat treatment in an oxygen-containing atmosphere to form a first sintered sample; wherein the precursor includes a Ni precursor material and a M element precursor material;

[0050] S2, mixing the primary sintered sample with an M' element precursor material to obtain a mixture II, and performing a secondary heat treatment on the mixture II in an oxygen-containing atmosphere to form a secondary sintered sample;

[0051] S3, mixing the secondary sintered sample with an M" element precursor material to obtain a mixture III, and performing a secondary heat treatment on the mixture III in an oxygen-containing atmosphere to obtain a positive electrode material;

[0052] The Ni precursor material has a filamentous whisker morphology and a BET of 10m 2 / g or more; the oxygen intake in step S1 and step S2 independently satisfies the following relationship: 100≤(C / D)*T≤800; where C is the oxygen ventilation volume (m 3 / h), D is the weight of the heat treatment object (kg), and T is the heat treatment temperature (°C); the volume concentration of oxygen in the oxygen-containing atmosphere in steps S1, S2 and S3 is independently selected from 98% to 100%.

[0053] The preparation method according to an embodiment of the present invention has at least the following beneficial effects: The preparation process of the present invention, through step-by-step heat treatment and the gradual introduction of different elemental precursors, enables precise control and optimization of the cathode material's crystal structure, element distribution, performance, and structural stability. This helps improve the battery's electrochemical performance, cycle life, and safety, providing a strong foundation for the production of high-performance, long-life batteries. The preparation process of the present invention cleverly creates a closed-pore and open-pore morphology in the cathode material. The closed pores within the crystal help buffer the volume strain generated by the material during lithium ion insertion and extraction, improving the material's structural stability. The open pores on the crystal surface facilitate electrolyte penetration through the pores, shortening the ion transport path and improving the material's rate performance. According to crystal growth principles and techniques, the actual composition of the crystal components is related to the chemical reaction temperature and the component activation energy, which in turn has a complex structure-activity relationship with the chemical potential and component concentration of the chemical reaction raw materials. The present invention unexpectedly discovered that when the oxygen inlet meets the above conditions, a lithium-rich, high-nickel porous cathode material with a superlattice can be obtained. The present invention innovatively uses a spherical nickel-containing precursor material with a high specific surface area. According to Wullf's theorem, crystal growth shows a trend of decreasing surface energy. Therefore, for the lithium-rich high-nickel porous positive electrode material in the present invention, a spherical nickel-containing precursor material with a high specific surface area is innovatively used. The spherical nickel-containing precursor material has a large specific surface area and high surface energy, which helps to form a morphological structure that combines closed pores and open pores.

[0054] According to some embodiments of the present invention, the Ni precursor material has at least one of the following characteristics: 1) BET range is 15-50m 2 / g; 2) the diameter of the whisker preferably ranges from 5 to 50 nm; 3) the particle size Dv50 of the Ni precursor material ranges from 2 to 5 μm; 4) the Ni precursor material is selected from Ni(OH)2, Ni 0.97 Co 0.03 (OH)2 or Ni 0.98 Mn 0.01 Co 0.01 (OH)2 or Ni 2 (OH)2 or Ni(OH)2.

[0055] The Ni-containing precursor material according to the present application has a BET range of 15-50 m 0.97 / g, which reduces the production cost, and better ensures the sphericity and volumetric energy density. The whisker microcrystal with a diameter of less than 50 nm is selected, and based on the capillary effect, h=(2σcosθ) / (ρgr), wherein h represents the height of the capillary liquid surface, σ represents the surface tension, θ represents the contact angle, ρ represents the liquid density, g represents the gravitational acceleration, and r represents the radius of the capillary tube, therefore, compared with the traditional precursor material, the capillary effect of the precursor material with the structural characteristics is stronger, so that the lithium-containing precursor material after liquefaction can be fully attached to the Ni-containing and M-containing precursor material, which helps the lithiumization reaction of the material to be more uniform, and helps the formation of the lithium-rich structure.

[0056] According to some embodiments of the present application, the lithium source has at least one of the following characteristics: 1) the composition is selected from at least one of LiOH or LiOH·H2O; 2) the particle size Dv50 ranges from 3 to 15 μm.

[0057] According to some embodiments of the present application, the Ni precursor material comprises Ni 0.97 Mn 0.005 Co 0.025 (OH)2, Ni 0.98 Mn 0.01 Co 0.01 (OH)2 or Ni(OH)2.

[0058] According to some embodiments of the present application, at least one of the M element precursor material, the M' element precursor material, and the M" element precursor material contains an anion group; the anion group is selected from: O 2- , OH - , WO4 2- , AlO2 - , ZrO3 2- , Ti5O 12 4- , PO4 3- , C6H5O7 3- , C 36 H 70O4 2- , CH3COO - , HC2O4 - , NbO3 2- , at least one of H2WO4, Nb(HC2O4)5, Li3PO4, LiAlO2, C

[0059] According to some embodiments of the present application, the M element precursor material is selected from at least one of ZrO2, Li2ZrO3, SrO, H2WO4, Nb(HC2O4)5, Li3PO4, LiAlO2, C 10 H5NbO 20 , MoO3·2H2O, WO3, SrCO3, SnO2.

[0060] According to some embodiments of the present application, the M' element precursor material is selected from at least one of CoOOH, Al(OH)3, Nb2O5·nH2O, MoO3·2H2O, H2WO4, Al2O3, LiOH, TiO2.

[0061] According to some embodiments of the present application, the M" element precursor material is selected from at least one of Li3NbO3, Al2O3, Li2WO4, TiO2, LiOH, LiOH·H2O, B2O3, H3BO3, Li3PO4, H3PO4.

[0062] According to some embodiments of the present application, the highest temperature section of the first heat treatment is 300-500℃; and / or, the highest temperature section processing time is 5-15 hours.

[0063] According to some embodiments of the present application, the total time of the first heat treatment is 10-20h.

[0064] According to some embodiments of the present application, the highest temperature section of the second heat treatment is 500-720℃; and / or, the highest temperature section processing time is 10-25 hours.

[0065] According to some embodiments of the present application, the total time of the second heat treatment is 15-30h.

[0066] According to some embodiments of the present application, the highest temperature section of the third heat treatment is 280-600℃; and / or, the highest temperature section processing time is 5-20 hours.

[0067] According to some embodiments of the present application, the total time of the third heat treatment is 10-20h.

[0068] According to the application of the third aspect embodiment, a lithium ion battery comprises the above positive electrode material or the positive electrode material prepared by the above preparation method.

[0069] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0071] Figure 1 Schematic diagram of the crystal structure of the particles constituting the positive electrode material according to an embodiment of the present invention.

[0072] Figure 2 Schematic cross-sectional view of the positive electrode material particles according to an embodiment of the present invention.

[0073] Figure 3 This is a scanning electron microscope morphology image of the positive electrode material obtained in Example 1 of the present invention, magnified 20,000 times.

[0074] Figure 4 This is a scanning electron microscope morphology image of the positive electrode material obtained in Example 1 of the present invention at a magnification of 10,000 times (the scale length in the figure is 5 μm).

[0075] Figure 5 This is a scanning electron microscope morphology image of the cross-section of the positive electrode material particles obtained in Example 2 of the present invention, magnified 25,000 times.

[0076] Figure 6 This is a scanning electron microscope morphology image of the cross section of the positive electrode material particles obtained in Example 2 of the present invention, magnified 10,000 times.

[0077] Figure 7 This is the X-ray diffraction pattern of the positive electrode material particles obtained in Example 2 of the present invention.

[0078] Figure 8 for Figure 7 X-ray diffraction Figure 2 Partial magnification at an angle of 18-50°.

[0079] Figure 9 This is a scanning electron microscope morphology image of the positive electrode material prepared in Comparative Example 1 of the present invention, magnified 20,000 times (the scale length in the figure is 2 μm).

[0080] Figure 10 This is a scanning electron microscope morphology image of the positive electrode material prepared in Comparative Example 1 of the present invention, magnified 3000 times.

[0081] Figure 11 This is a charge-discharge specific capacity diagram of the positive electrode material prepared in Example 1 of the present invention at a rate of 0.1C and a voltage range of 2.8-4.3V.

[0082] Figure 12The charge-discharge specific capacity graph of the positive electrode material prepared for the example 1 of the present application under the condition of 0.1C rate and 2.5-4.35V voltage range.

[0083] Figure 13 The charge-discharge specific capacity graph of the positive electrode material prepared for the example 1 of the present application under the condition of 0.3C rate and 2.8-4.3V voltage range.

[0084] Figure 14 The cycle curve graph of the positive electrode material of the example 1 and the comparative example 1 of the present application.

[0085] Figure 15 The enlarged production graph of the positive electrode material prepared for the example 3 of the present application.

[0086] Explanation of reference signs: 1, negative ion; 2, lithium ion (Li + ); 3, other cation; 4, closed pore structure; 5, open pore structure. DETAILED DESCRIPTION

[0087] The concept and the technical effects of the present application will be described clearly and completely in combination with the examples, so as to fully understand the purpose, features and effects of the present application. Obviously, the described examples are only a part of the examples of the present application, but not all the examples, and other examples obtained by the person skilled in the art without creative labor based on the examples of the present application all belong to the protection scope of the present application. The test methods used in the examples are conventional methods without special instructions, and the materials, reagents, etc. used are commercially available reagents and materials without special instructions. The same parameter values are the same in each example without special instructions. The examples described below are exemplary and are used to explain the present application, and cannot be understood as limiting the present application.

[0088] In the description of the present application, the description of the terms "some embodiments" and the like means that the specific features, structures, materials or characteristics described in combination with the embodiments or examples are contained in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily mean the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0089] In the description of the present application, if there is a description of first, second, etc., it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the sequence of indicated technical features.

[0090] The equipment information used for the characterization of the positive electrode material prepared in the examples and comparative examples of the present application is as follows:

[0091] The high-nickel layered cathode material for lithium ion batteries was characterized by scanning electron microscopy (Hitachi SU8000).

[0092] The crystal structure of the high-nickel layered cathode material was analyzed by a powder X-ray diffractometer (Japan Rigaku smartlab3KW).

[0093] The oxygen volume concentration in the oxygen-containing atmosphere in the following examples was 99% (98%-100%).

[0094] Example 1

[0095] In this example, a cathode material was prepared, which was composed of Li, Ni, M, M', M" and O elements, wherein M was Sr, Nb and Zr, M' was Co and Nb, and M" was B, Ti and Nb.

[0096] The specific preparation process was as follows:

[0097] (1) The lithium hydroxide monohydrate, the precursor (nickel-containing precursor material (Ni 0.97 Mn 0.005 Co 0.025 (OH)2) and M precursor material (strontium oxide, niobium oxalate, zirconium oxide) used as lithium source for lithium batteries were mixed uniformly by using a high-speed mixer to form a uniform mixture, wherein the lithium hydroxide monohydrate and the precursor were matched in a molar ratio of 1.02, wherein the molar amount of Li was concerned for the lithium salt, and the molar amount of transition metal (hereinafter referred to as T M ) was concerned for the precursor, so the above ratio can be expressed as: Li / T M = 1.02, and the strontium oxide, niobium oxalate and zirconium oxide were fed according to the concentration ratio of cations in the cathode material. In this experiment, the concentrations of Sr, Nb and Zr were 1000 ppm, 3000 ppm and 4000 ppm, respectively. The particle sizes (Dv50) of the nickel-containing precursor material and the lithium hydroxide monohydrate were 3.5 and 11.6 μm, respectively, and the specific surface area of the nickel-containing precursor material was 25.2 m 2 / g, and the average diameter of the surface whiskers was in the range of 30.5 nm (Note: The whisker diameter value was obtained by using the software image to collect 100 values and taking the average value).

[0098] (2) The mixture obtained in step (1) was subjected to a first heat treatment in an oxygen-containing atmosphere furnace, and the heat treatment conditions were as follows: the heating rate was 3°C / min, the total heat treatment time was 15 h, the highest temperature was 500°C, and the highest temperature treatment time was 10 h. The weight of the heat treatment material was 20 kg, and the air flow rate was 20 m 3 / h.

[0099] (3) Form a uniform mixture of the once sintered sample of step 2 and a precursor material containing M', the mixing method being the same as step 1, wherein the precursor material containing M' is a mixture of CoOOH, Nb2O5·nH2O, and the concentrations of Co and Nb are 6000 ppm and 2000 ppm, respectively.

[0100] (4) The mixture in step (3) is heat treated under an oxygen-containing atmosphere to form a twice sintered sample. The heat treatment conditions are: a heating rate of 5 ℃ / min, a total heat treatment time of 16 h, a maximum temperature of 720 ℃, a heating rate of 5 ℃ / min, and a maximum temperature treatment time of 11 h. The weight of the heat treated material is 20 kg, and the air flow rate is 10 m 3 / h.

[0101] (5) The twice sintered sample in step (4) is mixed with a precursor material containing M" to form a uniform mixture. The mixing method is the same as step 1, wherein the precursor material containing M" is a mixture of H3BO3, TiO2, and Al2O3, and the concentrations of B, Ti, and Al are 1000 ppm, 1500 ppm, and 1500 ppm, respectively.

[0102] (6) The mixture in step (5) is heat treated under an oxygen-containing atmosphere to form a thrice sintered sample, i.e., a lithium-rich high-nickel positive electrode material. The heat treatment conditions are: a heating rate of 5 ℃ / min, a total heat treatment time of 10 h, a maximum temperature of 400 ℃, a maximum temperature treatment time of 8 h, and a heating rate of 5 ℃ / min. The weight of the heat treated material is 20 kg, and the air flow rate is 45 m 3 / h.

[0103] The schematic diagram of the crystal structure of the composition particles of the material is shown in Figure 1 . Figure 1 The negative ion 1 (O 2- ) in the composition crystal structure occupies the 6c position; the lithium ion 2 (Li + ) in the composition crystal structure mainly occupies the 3b position and partially occupies the 3a position; the other cation 3 (such as Ni 2+ / Ni 3+ , Co 3+ , Mn 4+ , etc.) occupies the 3a position and a small part occupies the 3b position. That is, in the crystal structure of the composition particles of the material, the lithium ion occupies the 3a position in the layered crystal structure, and forms an ordered arrangement with the non-lithium cation in the 3a position, forming a partial superlattice crystal structure.

[0104] The schematic diagram of the cross section of the composition particles of the material is shown in Figure 2 . From Figure 2As can be seen from the drawings, the granular material of the present application has multiple pore characteristics, and both closed pores 4 and open pores 5 exist, wherein the closed pores 4 exist in the interior of the granular material and are not communicated with the outer surface and cannot be penetrated by electrolyte; and the open pores 5 are communicated with the outside and can be directly contacted by electrolyte.

[0105] The SEM characterization results are shown in Figures 3-4 As can be seen from the drawings, the material prepared in the present application has a porous structure. The XRD detection results show that the intensity of the strongest peak in the characteristic peak appearing at 20°-35° is represented as A, the intensity of the (003) crystal face peak is represented as B, the value of A / B is 0.0045, the maximum cross-section porosity distribution of the granular material is 8.2%, the molar ratio of Ni element to Li element is 0.951, and the molar ratio of the total amount of Ni, M, M', M" elements to the molar amount of Li element is 0.984.

[0106] Example 2

[0107] In this example, a positive electrode material was prepared, and the preparation process was basically the same as that of Example 1, except that the Ni precursor material was Ni(OH)2, the concentration of Co in step (3) was 10000 ppm, the temperature of the highest temperature section in step (4) was 665°C, the treatment time of the highest temperature section was 15 h, and the total time of the secondary heat treatment was 20 h. The positive electrode material prepared by the above operation was subjected to SEM characterization, and the SEM image of the cross-section of the granular material is shown in Figures 5-6 As can be seen from the drawings, the material of the present application has a closed pore structure in the interior and an open pore structure on the surface. The maximum cross-section porosity distribution of the granular material is 6.4%.

[0108] The XRD detection results are shown in Figures 7-8 As can be seen from the drawings, the intensity of the strongest peak in the characteristic peak appearing at 20°-35° is represented as A, the intensity of the (003) crystal face peak is represented as B, and the value of A / B is 0.0056. The molar ratio of Ni element to Li element is 0.980, and the molar ratio of the total amount of Ni, M, M', M" elements to the molar amount of Li element is 0.985.

[0109] Example 3

[0110] The example prepared a positive electrode material, its preparation process is basically same with example 1, the difference is: in step (1) the lithium salt uses LiOH, and the niobium oxalate is replaced by WO3, and the concentration is unchanged. The strontium oxide is replaced by LiAlO2, and the concentration is unchanged. In step (5), Al2O3 is replaced by LiPO3, and LiOH is added, and the concentration of Li is 1000ppm. The XRD detection shows that the strongest peak in the characteristic peak appearing at 20°-35° is represented by A, the peak intensity of (003) crystal plane is represented by B, and the value of A / B is 0.0051. The maximum cross-sectional porosity distribution of the particle is 7.1%. The molar ratio of Ni element to Li element is 0.948, and the molar ratio of the total number of Ni, M, M', M" elements to the molar number of Li element is 0.981.

[0111] Example 4

[0112] The example prepared a positive electrode material, its preparation process is basically same with example 1, the difference is: in step (2), the highest temperature of heat treatment is 300℃, the total treatment time of the highest temperature is 14h, and the total time of one heat treatment is 19h. The highest temperature of heat treatment in step (4) is 500℃, the total treatment time of the highest temperature is 23h, and the total time of two heat treatments is 28h. The highest temperature of heat treatment in step (6) is 700℃, the total treatment time of the highest temperature is 13h, and the total time of three heat treatments is 18h. The XRD detection shows that the strongest peak in the characteristic peak appearing at 20°-35° is represented by A, the peak intensity of (003) crystal plane is represented by B, and the value of A / B is 0.0053. The maximum cross-sectional porosity distribution of the particle is 6.8%. The molar ratio of Ni element to Li element is 0.951, and the molar ratio of the total number of Ni, M, M', M" elements to the molar number of Li element is 0.984.

[0113] Example 5

[0114] The example prepared a positive electrode material, its preparation process is basically same with example 1, the difference is: Li / T M =1.05, and the M precursor material is composed of H2WO4, Sb2O3, ZrO2, and Nb2O5, wherein the concentrations of W, Sb, Zr, and Nb are 2000ppm, 2000ppm, 3500ppm, and 1000ppm respectively. The XRD detection shows that the strongest peak in the characteristic peak appearing at 20°-35° is represented by A, the peak intensity of (003) crystal plane is represented by B, and the value of A / B is 0.0063. The maximum cross-sectional porosity distribution of the particle is 6.6%. The molar ratio of Ni element to Li element is 0.924, and the molar ratio of the total number of Ni, M, M', M" elements to the molar number of Li element is 0.956.

[0115] Example 6

[0116] In this example, a positive electrode material was prepared. The preparation process was basically the same as that in Example 1, except that the Ni precursor material was replaced by Ni 0.98 Mn 0.01 Co 0.01 (OH)2, lithium salt is replaced by LiOH, the Li / T M =1.1, the lithium salt particle size Dv50 is 6.3μm, and the M material is composed of MoO3·2H2O, Sb2O3, ZrO2, and Al2O3, with Mo, Sb, Zr, and Al concentrations of 8000ppm, 2000ppm, 3500ppm, and 500ppm, respectively. XRD analysis shows that the strongest peak among the characteristic peaks appearing at 20° to 35° is represented by A, and the peak intensity representing the (003) crystal plane is represented by B. The A / B value is 0.0081, and the maximum cross-sectional porosity distribution of the particles is 5.9%. The molar ratio of Ni to Li is 0.891, and the ratio of the total molar number of Ni, M, M', and M" elements to the molar number of Li is 0.913.

[0117] Example 7

[0118] This example prepares a positive electrode material, and its preparation process is basically the same as that of Example 1, except that: Li / T M =1.03, the M material is composed of WO3 and ZrO2, wherein the concentrations of W and Zr are 3000ppm and 2000ppm, respectively; the Co in M' is increased to 12000ppm, and LiOH is added, wherein the concentration of lithium is 500ppm. The total treatment time in step (4) is 20h. XRD detection shows that the strongest peak among the characteristic peaks appearing at 20° to 35° is represented by the peak intensity A, the peak intensity representing the (003) crystal plane is represented by the peak intensity B, and the A / B value is 0.0058. The maximum cross-sectional porosity distribution of the particles is 7.8%, wherein the molar ratio of Ni to Li is 0.950, and the ratio of the total molar number of Ni, M, M', and M" elements to the molar number of Li is 0.984.

[0119] Example 8

[0120] This example prepares a positive electrode material, and its preparation process is basically the same as that of Example 1, except that: Li / T M= 1.07, M material consists of MoO3-2H2O, Sb2O3, ZrO2, SrCO3, wherein the concentration of Mo, Sb, Zr, Sr is respectively: 3000 ppm, 2000 ppm, 3500 ppm, 500 ppm. M" increases Li2WO4, wherein the concentration of W is 1000 ppm. The strongest peak in the characteristic peak appearing at 20°-35° is detected by XRD, the peak intensity is represented by A, the peak intensity of (003) crystal plane is represented by B, the value of A / B is 0.0075, the maximum cross-section porosity distribution of the particle is 6.3%, wherein the mole of Ni element to Li element is 0.904, the ratio of the total mole of Ni, M, M', M" elements to the mole of Li element is 0.940.

[0121] Example 9

[0122] In this example, a positive electrode material is prepared, and the preparation process is basically the same as that of Example 1, except that: the weight of the material for heat treatment in step (2) is 10 kg, the air flow rate is 6 m 3 / h, the weight of the material for heat treatment in step (4) is 5 kg, the air flow rate is 5 m 3 / h. The strongest peak in the characteristic peak appearing at 20°-35° is detected by XRD, the peak intensity is represented by A, the peak intensity of (003) crystal plane is represented by B, the value of A / B is 0.0048, the maximum cross-section porosity distribution of the particle is 7.6%. Wherein the mole of Ni element to Li element is 0.951, the ratio of the total mole of Ni, M, M', M" elements to the mole of Li element is 0.984.

[0123] Example 10

[0124] In this example, a positive electrode material is prepared, and the preparation process is basically the same as that of Example 1, except that: Li / TM = 1.1, the precursor is replaced by Ni(OH)2, the weight of the material for heat treatment in step (2) is 10 kg, the air flow rate is 5 m 3 / h, the temperature of the highest temperature section is 420°C, the total treatment time of the highest temperature section is 15 h, and the total time of the first heat treatment is 20 h. The weight of the material for heat treatment in step (4) is 5 kg, the air flow rate is 6 m 3 / h, the temperature of the highest temperature section is 650°C, the total treatment time of the highest temperature section is 18 h, and the total time of the second heat treatment is 23 h. The strongest peak in the characteristic peak appearing at 20°-35° is detected by XRD, the peak intensity is represented by A, the peak intensity of (003) crystal plane is represented by B, the value of A / B is 0.0083, the maximum cross-section porosity distribution of the particle is 9.1%. Wherein the mole of Ni element to Li element is 0.909, the ratio of the total mole of Ni, M, M', M" elements to the mole of Li element is 0.913.

[0125] Comparative Example 1

[0126] In this example, a cathode material was prepared by the same method as in Example 1, except that the precursor particles were tightly packed, and the specific surface area of the precursor was 5 m 2 / g, to obtain a comparative cathode material.

[0127] The SEM image of the prepared material is shown in Figure 1, and it can be seen from the figure that there are no obvious holes on the surface. In addition, it can be seen from the cross-sectional view that there are no obvious pores inside. The X-ray diffraction pattern (XRD) of the cathode material obtained under CuKa radiation shows that there are no characteristic peaks at 20°-35°. The molar ratio of Ni element to Li element is 0.951, and the ratio of the total number of moles of Ni, M, M', M" elements to the number of moles of Li element is 0.984. Figures 9-10

[0128] Comparative Example 2

[0129] In this example, a cathode material was prepared by the same method as in Example 1, except that in step (2), the mixture obtained in step (1) was subjected to a first heat treatment in an oxygen-containing atmosphere furnace, and the heat treatment conditions were as follows: the temperature of the highest temperature section was 720°C, and the treatment time at the highest temperature section was 10 h. The weight of the heat-treated material was 20 kg, and the air flow rate was 1 m 3 / h. The XRD diffraction pattern of the obtained cathode material obtained under CuKa radiation shows that there are no obvious peaks at 20°-35°. The molar ratio of Ni element to Li element is 0.951, and the ratio of the total number of moles of Ni, M, M', M" elements to the number of moles of Li element is 0.984.

[0130] Comparative Example 3

[0131] In this example, a cathode material was prepared by the same method as in Comparative Example 1, except that in step (1), the lithium hydroxide monohydrate and the precursor were mixed in a molar ratio of 1.4. The XRD diffraction pattern of the obtained cathode material obtained under CuKa radiation shows that there are multiple diffraction peaks at 20°-35°, and the value of A / B is 0.012. Similarly, there are no obvious holes on the surface of the cathode material particles. The molar ratio of Ni element to Li element is 0.693, and the ratio of the total number of moles of Ni, M, M', M" elements to the number of moles of Li element is 0.717.

[0132] Performance Test

[0133] ​The positive electrode material prepared in the above examples and comparative examples was mixed with conductive agent carbon black and binder polyvinylidene fluoride at a mass ratio of 90:5:5, added into a solvent N-methyl-2-pyrrolidone (NMP) to prepare a slurry (the mass ratio of the solvent was 16wt%±1%), uniformly coated on a carbon-coated aluminum foil current collector to obtain a positive electrode film, a metal lithium sheet was used as a negative electrode, a polypropylene microporous membrane (Celgard 2400) was used as a separator, 1 mol / L LiPF6 (the solvent was a mixed solution of ethylene carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) at a volume ratio of 1:1:1) was used as an electrolyte, and a 2430 button cell was assembled in an argon glove box.

[0134] The assembled battery was subjected to constant current charge and discharge test on a blue charge and discharge tester, the test temperature was 25°C, and the charge and discharge was carried out at 0.1C (equivalent to 20mAg -1 ) rate. Among them, the charge and discharge curves of the 2430 button cell assembled by the high-nickel layered positive electrode material prepared in Example 1 in different rates and different voltage ranges are shown in Figure 11 、 Figure 12 、 Figure 13 ,the cycle curves of the button cell assembled by the materials of Example 1 and Comparative Example 1 are shown in Figure 14 . The high-nickel layered positive electrode material prepared in other examples and comparative examples of the application was assembled into a lithium battery according to the above method, and its electrochemical performance was tested, and the results are shown in Table 1.

[0135] Table 1

[0136]

[0137]

[0138] From the data in Table 1, it can be seen that the lithium-rich high-nickel porous positive electrode material prepared according to the example scheme of the application has higher discharge specific capacity, rate performance and cycle stability, and has obvious advantages compared with the comparative example. It is thus shown that the present scheme has significant progress. Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 The morphology characteristics of the application are verified, Figure 8 Figure 7 the local area magnification characteristics, and the characteristic peaks verify the structural characteristics of the lithium-rich high-nickel porous positive electrode material in the application. Figure 15 It is an optical photograph of the positive electrode material produced in Example 3 in an industrial kiln, which shows that the present scheme is suitable for large-scale production of high-nickel layered positive electrode materials and has high commercial value.

[0139] In the present application, the first step of heat treatment (S1) forms a primary sintered sample by introducing an oxygen-containing atmosphere into the mixture of the precursor (containing Ni elements and M elements) and the lithium source. This process helps to preliminarily form the desired crystal structure and promotes the chemical reaction between lithium elements and elements in the precursor, laying a good foundation for subsequent steps. In the second step (S2) and the third step (S3), M' precursor material and M" precursor material are introduced respectively and mixed with the sintered sample of the previous step for secondary heat treatment. This step-by-step addition of different element precursors can achieve fine control of the element distribution in the positive electrode material, optimize the distribution of lithium, transition metals (such as Ni, M, M', M") and other elements in the material, and thus improve the electrochemical performance and structural stability of the material. Through multiple heat treatments, the chemical reaction and crystal structure inside the material can be further promoted, and the crystallinity and density of the material can be improved. This helps to improve the ion and electron conduction performance of the material, thereby improving the charge and discharge rate and energy density of the battery. Multiple heat treatments can also reduce defects and stress inside the material to some extent, enhancing the structural stability of the material. This is of great significance to prolong the cycle life of the battery and improve the safety performance. The preparation process is carried out in multiple steps, and each step can be independently optimized and controlled. This helps to achieve precise control and optimization of the performance of the positive electrode material, improving the quality and consistency of the product.

[0140] The chemical formula of the positive electrode material is Li 1+x (Ni a M b M' c M" d ) 1-x O 2+α ; in the formula, 0 < x < 0.17; 0.9 ≤ a ≤ 1; 0 ≤ b ≤ 0.02; 0 ≤ c ≤ 0.02; 0 ≤ d ≤ 0.01; a + b + c + d = 1; -0.05 ≤ α ≤ 0.05, in which α is used to balance the valence. The valence of oxygen is -2, the valence of Li is +1, and the valence of the remaining transition metal is +N (specifically depending on the actual transition metal), and Ni ions exist in +2 and +3 valence (assuming the content of +3 valence Ni is y). The valence balance relationship is as follows: 1 + x + (a × (2 × (1 - y) + 3 × y) + M × b + c × M' + d × M") × (1 - X) = 2 × (2 + α). The value of α is non-zero and does not significantly change the overall effect.

[0141] The above has made a detailed description of the embodiments of the present application, but the present application is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the purpose of the present application.

Claims

1. A positive electrode material, characterized in that: The positive electrode material is composed of Li, Ni, M, M', M' and O elements; wherein the molar ratio of Ni element to Li element is above 0.64; the ratio of the total molar number of Ni, M, M', M' elements to the molar number of Li element is n, 0.7 <n<1; M is selected from at least one metal element in periods 3 to 6; M' is selected from at least one metal element in periods 2 to 5; M' is selected from at least one metal or non-metal element in periods 2 to 6 and is different from both M and M'; In the X-ray diffraction pattern of the positive electrode material obtained under CuKa radiation, at least one characteristic peak appears at 2θ between 20° and 35°; the positive electrode material has a superlattice structure; The positive electrode material has a pore structure, and the pore structure includes closed pores and open pores; The chemical formula of the positive electrode material is Li 1+x (Ni a M b M' c M” d ) 1-x O 2+α Where, 0 <x≤0.17;0.9≤a≤1;0≤b≤0.02;0≤c≤0.02;0≤d≤0.01;a+b+c+d=1;-0.05≤α≤0.05; The preparation method of the positive electrode material comprises the following steps: S1. subjecting a mixture I containing a precursor and a lithium source to a primary heat treatment in an oxygen-containing atmosphere to form a primary sintered sample; wherein the precursor includes a Ni precursor material and an M element precursor material; S2, mixing the primary sintered sample with an M' element precursor material to obtain a mixture II, and performing a secondary heat treatment on the mixture II in an oxygen-containing atmosphere to form a secondary sintered sample; S3, mixing the secondary sintered sample with an M" element precursor material to obtain a mixture III, and subjecting the mixture III to three heat treatments in an oxygen-containing atmosphere to obtain a positive electrode material; The Ni precursor material has a filamentous whisker morphology and a BET of 10 m 2 / g or more; the oxygen intake in step S1 and step S2 independently satisfies the following relationship: 100≤(C / D)*T≤800; where C is the oxygen ventilation volume, m 3 / h; D is the weight of the heat treatment object, kg; T is the heat treatment temperature in the highest temperature section, °C; the volume concentration of oxygen in the oxygen-containing atmosphere in steps S1, S2 and S3 is independently selected from 98% to 100%.

2. A positive electrode material according to claim 1, characterized in that: In the XRD spectrum of the positive electrode material, the peak intensity with the strongest signal among the characteristic peaks in the 20°~35° region is recorded as A, and the peak intensity representing the (003) crystal plane is recorded as B. The ratio of A to B satisfies: 0 The ratio of A to B satisfies: 0.0001≤A / B≤0.

05.

3. A positive electrode material according to claim 2, characterized in that: The ratio of A to B satisfies: 0.0001≤A / B≤0.

02.

4. A positive electrode material according to claim 2, characterized in that: The ratio of A to B satisfies: 0.0001≤A / B≤0.

01.

5. The positive electrode material according to claim 2, characterized in that: The ratio of A to B satisfies: 0.004≤A / B≤0.

01.

6. A positive electrode material according to claim 2, characterized in that: The positive electrode material comprises a plurality of secondary particles composed of primary particles, and the maximum cross-sectional porosity of the secondary particles is 1% to 15%.

7. The positive electrode material according to claim 1, characterized in that: The maximum cross-sectional porosity of the secondary particles is 5% to 10%.

8. The positive electrode material according to claim 7, characterized in that: M is selected from at least one of Co, Mn, Al, Zr, W, Nb, Sn, Sb, Ta, Sr, Y, Ti, La, Mo or Mg; and / or, M' is selected from at least one of Al, Nb, Co, Mg, Li, Sn, Zr or Ti; and / or, the M" is selected from at least one of Ti, Nb, P, Co, B, W, Li or Al.

9. The positive electrode material according to claim 1, characterized in that: The steps include:

10. A method for preparing a positive electrode material according to any one of claims 1 to 9, characterized in that: S1. subjecting a mixture I containing a precursor and a lithium source to a primary heat treatment in an oxygen-containing atmosphere to form a primary sintered sample; wherein the precursor includes a Ni precursor material and an M element precursor material; S2, mixing the primary sintered sample with an M' element precursor material to obtain a mixture II, and performing a secondary heat treatment on the mixture II in an oxygen-containing atmosphere to form a secondary sintered sample; ​ S3, mixing the secondary sintered sample with an M" element precursor material to obtain a mixture III, and subjecting the mixture III to three heat treatments in an oxygen-containing atmosphere to obtain a positive electrode material; The Ni precursor material has a filamentous whisker morphology and a BET of 10 m 2 / g or more; the oxygen intake in step S1 and step S2 independently satisfies the following relationship: 100≤(C / D)*T≤800; where C is the oxygen ventilation volume, m 3 / h; D is the weight of the heat treatment object, kg; T is the heat treatment temperature in the highest temperature section, °C; the volume concentration of oxygen in the oxygen-containing atmosphere in steps S1, S2 and S3 is independently selected from 98% to 100%.

11. The preparation method according to claim 10, characterized in that: The Ni precursor material has at least one of the following characteristics: 1) a BET range of 15-50 m 2 / g; 2) the diameter of the whiskers is in the range of 5-50nm; 3) the particle size Dv50 of the Ni precursor material is in the range of 2-5µm; 4) the Ni precursor material is selected from Ni(OH)2, Ni 0.97 Co 0.03 (OH)2 or Ni 0.98 Mn 0.01 Co 0.01 At least one of (OH)2.

12. The preparation method according to claim 10, characterized in that: The lithium source has at least one of the following characteristics: 1) a component is selected from at least one of LiOH and LiOH·H2O; 2) a particle size Dv50 ranges from 3 to 15 μm.

13. The preparation method according to claim 10, characterized in that: At least one of the M element precursor material, the M' element precursor material, and the M" element precursor material contains an anionic group; the anionic group is selected from: 2- OH - WO4 2- 、AlO2 - 、ZrO3 2- 、Ti5O 12 4- PO4 3- 、C6H5O7 3- 、CH3COO - 、HC2O4 - At least one of .

14. The preparation method according to any one of claims 10 to 13, characterized in that: The preparation method satisfies at least one of the following conditions: 1) The temperature of the highest temperature section of the primary heat treatment is 300-500°C; and / or the treatment time of the highest temperature section is 5-15 hours; 2) The secondary heat treatment has a maximum temperature of 500-720°C; and / or a maximum temperature treatment time of 10-25 hours; 3) The temperature of the highest temperature section of the three heat treatments is 280-600° C.; and / or the treatment time of the highest temperature section is 5-20 hours.

15. A lithium-ion battery, characterized in that: The positive electrode material comprises the positive electrode material according to any one of claims 1 to 9 or the positive electrode material prepared by the preparation method according to any one of claims 10 to 13.

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