Positive electrode material, preparation method thereof and lithium ion battery

Abstract

The invention relates to a positive electrode material, a preparation method thereof and a lithium ion battery, the chemical general formula of the positive electrode material is LiNiaCobMncMdO2, a is more than 0.7 and less than 0.98, b is more than 0 and less than 0.3, c is more than 0 and less than 0.3, d is more than 0 and less than or equal to 0.01, a + b + c = 1, and M is a doping element; the mass content of LiOH in the positive electrode material is alpha LH wt%, the mass content of Li2CO3 in the positive electrode material is alpha LC wt%, the molar ratio of Li to all metals Me except Li in the positive electrode material is gamma Li / Me, and the specific surface area of the positive electrode material is beta m < 2 > / g; the positive electrode material provided by the invention is less influenced by water vapor, the residual alkali content on the surface of the material is low, the surface structure stability of the positive electrode material can be improved, side reactions on the surface of the positive electrode material can be effectively reduced, and the capacity and the cycling stability of the positive electrode material are further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of cathode materials, and particularly to cathode materials, their preparation methods, and lithium-ion batteries. Background Art

[0002] Currently, there are more and more types of cathode materials for lithium-ion batteries that have been put into practical use. More representative ones include lithium cobaltate, lithium iron phosphate, lithium manganate, and ternary materials, etc. Among them, high-nickel cathode materials (Ni≥0.8) have become the focus of research and industrialization in the field of future power batteries due to their relatively high theoretical reversible capacity. However, high-nickel cathode materials have the problem of high total residual lithium content, which seriously affects the battery processing performance. Currently, for the problem that the high total residual lithium content of high-nickel materials affects the processing performance, a mature water washing process has been developed to effectively remove residual alkali, and related products have been widely used in the fields of power batteries, electric tools, etc. However, the water washing process will also bring some defects in actual use, causing irreversible chemical property changes on the surface of the cathode material particles, causing side reactions between the surface of the cathode material and the electrolyte to form a NiO-like rock salt phase, resulting in an increase in the surface resistance of the cathode material, and due to lattice mismatch, a higher interfacial lattice strain between the layered and rock salt structures, thereby reducing the electrochemical performance. These problems will become more and more obvious as the nickel content of the ternary material gradually increases. Generally speaking, the higher the nickel content, the more sensitive the cathode material is to water, and the more side reactions brought by water washing, making the water washing process no longer so applicable.

[0003] Therefore, there is an urgent need for a post-treatment method that can simultaneously remove the residual lithium compounds on the surface of the cathode material and maintain the structural stability of the cathode material. In addition, water washing to remove residual lithium makes the manufacturing process complex and increases the manufacturing cost of the material. Considering that the residual lithium compounds and the compatible coating agent can form a fast ion conductor layer and other protective layers during the second calcination stage of coating, the method of using a lithium-containing coating on the surface without water washing shows great application potential in reducing the influence of residual lithium.

[0004] However, current non-water washing research mainly focuses on post-treatment processes to specifically reduce residual lithium and stabilize the surface structure, but there is less research on controlling the source of residual lithium, and less attention is paid to the form of residual lithium formation. Currently, there are the following limitations in separately studying non-water washing post-treatment processes: 1) Low tolerance to the residual lithium content of the substrate, not suitable for processing products with too high residual lithium; 2) Most non-water washing post-treatment processes mainly use the conversion of residual lithium as the means, and have a strong dependence on the specific treatment of the amount and type of surface residual lithium morphology; 3) It is more difficult to process while converting and removing more residual lithium without destroying the surface structure.

[0005] Therefore, how to regulate residual lithium from the source and reduce the generation of residual lithium while maintaining the structural stability of the cathode material is still a problem that needs to be solved currently. Summary of the Invention

[0006] The purpose of the present application is to provide a cathode material, a preparation method thereof, and a lithium-ion battery. The cathode material is less affected by water vapor, has a low residual alkali content on the material surface, can improve the surface structure stability of the cathode material, effectively reduce the occurrence of side reactions on the cathode material surface, and thereby improve the capacity and cycle stability of the cathode material.

[0007] In the first aspect, the present application provides a cathode material, and the chemical general formula of the cathode material is LiNi a Co b Mn c M d O2, where 0.7 < a < 0.98,, 0 < b < 0.3, 0 < c < 0.3, 0 < d ≤ 0.01, a + b + c = 1, and M is a doping element;

[0008] The mass content of LiOH in the cathode material is α LH wt%, the mass content of Li2CO3 in the cathode material is α LC wt%, the molar ratio of Li to all metals Me except Li in the cathode material is γ Li / Me , the specific surface area of the cathode material is βm 2 / g; the surface structure stability coefficient of the cathode material is ε, 0.5 ≤ ε ≤ 1.5.

[0009] The present application also provides a cathode material, and the chemical general formula of the cathode material is LiNi a Co b Mn c M d O2, where 0.7 < a < 0.98, 0 < b < 0.3, 0 < c < 0.3, 0 < d ≤ 0.01, a + b + c = 1, and M is a doping element; using a potentiometric titrator and hydrochloric acid with a concentration of 0.02 mol / L to conduct an acid-base potentiometric titration test on the cathode material, a curve graph of the relationship between the differential value dE / dV obtained by differentiating the consumption volume V of hydrochloric acid with respect to the potential E and the potential E is obtained. In the curve graph of the relationship between the differential value dE / dV and the potential E, the cathode material has a first characteristic peak in the potential E range of -200 mV to -50 mV, the peak area of the first characteristic peak is A, the cathode material has a second characteristic peak between the potential E of 120 mV and 250 mV, and the peak area of the second characteristic peak is B; there is at least one characteristic peak in the potential E range of -50 mV to 120 mV, the sum of the peak areas of the at least one characteristic peak is C, and the residual alkali conversion coefficient of the cathode material is ξ, 0.2 ≤ ξ ≤ 0.35.

[0010] In some embodiments, the doping element M includes at least one of B, C, P, S, F, La, Sr, Ti, Al, Zr, Y, Ba, Mg, Nb, Mo, W, and V.

[0011] In some embodiments, the mass content of LiOH in the positive electrode material is α LH wt%, 0.1 ≤ α LH ≤ 1.0.

[0012] In some embodiments, the mass content of Li2CO3 in the positive electrode material is α LC wt%, 0.1 ≤ α LC ≤ 1.0.

[0013] In some embodiments, the molar ratio of Li to all metals Me other than Li in the positive electrode material is γ Li / Me , 0.95 < γ Li / Me < 1.05.

[0014] In some embodiments, the specific surface area of the positive electrode material is β m 2 / g, 0.2 < β < 1.5.

[0015] In some embodiments, the peak area of the first characteristic peak is A, 2000 ≤ A ≤ 200000.

[0016] In some embodiments, the peak area of the second characteristic peak is B, 2000 ≤ B ≤ 200000.

[0017] In some embodiments, the sum of the peak areas of the at least one characteristic peak is C, 2000 ≤ C ≤ 200000.

[0018] Second, the present application provides a method for preparing a positive electrode material, including the following steps:

[0019] Performing a primary sintering treatment on a mixture containing a nickel-cobalt-manganese-based precursor, a lithium source, and a dopant containing a metal element in an oxygen-containing atmosphere to obtain a matrix material; the temperature of the primary sintering treatment is 200°C to 900°C, and the pressure during the primary sintering treatment increases in a gradient manner, and the pressure range is 3 Pa to 13 Pa;

[0020] Performing a secondary sintering treatment on the matrix material and a coating agent to obtain a positive electrode material.

[0021] In some embodiments, the chemical formula of the nickel-cobalt-manganese-based precursor is Ni a Co b Mn c (OH)2, where 0.7 < a < 0.98, 0 < b < 0.3, 0 < c < 0.3, and a + b + c = 1.

[0022] In some embodiments, the mass content of metal elements in the nickel-cobalt-manganese-based precursor is 60.5 wt% to 63.5 wt%.

[0023] In some embodiments, the mass ratio of the nickel-cobalt-manganese-based precursor, the lithium source, and the metal element-containing dopant is 1:(1.0 - 1.05):(0 - 0.01).

[0024] In some embodiments, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate, and lithium acetate.

[0025] In some embodiments, the metal element-containing dopant includes at least one of Nb2O5, Nb2O3, MoO3, WO2, V2O5, V2O3, Sr(OH)2, SrO, TiO2, Al2O3, Al(OH)3, ZrO2, Zr(OH)4, Y2O3, BaO, MgO, and Mg(OH)2.

[0026] In some embodiments, the mixing conditions for obtaining the mixture are: dry mixing at 10°C to 50°C for 0.3 h to 2 h.

[0027] In some embodiments, the mass content of oxygen in the oxygen-containing atmosphere is ≥95%.

[0028] In some embodiments, the primary sintering treatment includes a first stage, a second stage, and a third stage.

[0029] In some embodiments, the first stage includes: heating the mixture from 200°C to 550°C within 2 h to 5 h, controlling the pressure P1 to be 7 Pa to 11 Pa, wherein the inlet amount of the oxygen-containing atmosphere is controlled to be 10 m 3 / h to 30 m 3 / h, and controlling the exhaust gas volume of the reaction system to be 10% to 30%.

[0030] In some embodiments, the second stage includes: heating the mixture from 550°C to 700°C within 2 h to 5 h, controlling the pressure P2 to be 8 Pa to 12 Pa, wherein the inlet amount of the oxygen-containing atmosphere is controlled to be 20 m 3 / h to 30 m 3 / h, and controlling the exhaust gas volume of the reaction system to be 10% to 20%.

[0031] In some embodiments, the third stage includes: sintering the mixture at 700°C to 900°C for 5 h to 10 h, controlling the pressure P3 to be 9 Pa to 13 Pa, wherein the inlet amount of the oxygen-containing atmosphere is controlled to be 20 m 3 / h to 30 m 3 / h.

[0032] In some embodiments, the average particle size D of the matrix material 50 is 9 μm to 12 μm.

[0033] In some embodiments, the coating agent includes at least one of La(NO3)3·6H2O, NH4F, NH4HF, (NH4)3PO4, (NH4)2HPO4, (NH4)2MoO4, (NH4)2SO4, NH4HSO4, (NH4)6W7O 24 ·6H2O, (NH4)3PW 12 O 40 ·3H2O, Zr(SO4)2·4H2O, H 28 N6O 41 W 12 , WO3, Al2O3, Al(OH)3.

[0034] In some embodiments, the mass ratio of the matrix material to the coating agent is 1:(0.001 - 0.05).

[0035] In some embodiments, the secondary sintering treatment is carried out in an oxygen-containing atmosphere.

[0036] In some embodiments, the secondary sintering treatment is carried out in an oxygen-containing atmosphere, and the mass content of oxygen in the oxygen-containing atmosphere is ≥95%.

[0037] In some embodiments, the temperature of the secondary sintering treatment is 200°C to 700°C.

[0038] In some embodiments, the time of the secondary sintering treatment is 10 h to 20 h.

[0039] In some embodiments, before the secondary sintering treatment of the matrix material and the coating agent, the preparation method further includes: dissolving the coating agent in water to form a coating solution; and performing a coating treatment on the coating solution and the matrix material by an atomization method. In some embodiments, the pressure of the atomization is 0 Mpa to 0.05 Mpa.

[0040] In some embodiments, the coating treatment is carried out under a stirring state, and the stirring frequency is controlled to be 20 Hz to 50 Hz.

[0041] In some embodiments, the temperature of the coating treatment is 150°C to 250°C.

[0042] In some embodiments, the time of the coating treatment is 3 h to 8 h.

[0043] Thirdly, the present application provides a lithium-ion battery, which includes the positive electrode material described in the first aspect or the positive electrode material prepared by the preparation method described in the second aspect.

[0044] Compared with the prior art, the technical solution of the present application has at least the following beneficial effects:

[0045] For the positive electrode material provided by the present application, the mass content of LiOH in the positive electrode material is α LH wt%, the mass content of Li2CO3 in the positive electrode material is α LC wt%, the molar ratio of Li to all metals Me other than Li in the positive electrode material is γ Li / Me , the specific surface area of the positive electrode material is β m 2 / g; the surface structure stability coefficient of the positive electrode material is ε, 0.5 ≤ ε ≤ 1.5. The surface structure stability coefficient ε of the positive electrode material can reflect the degree to which the positive electrode material is affected by water vapor. In the present application, the surface structure stability coefficient ε of the positive electrode material is within the above range, the degree to which the positive electrode material is affected by water vapor is small, the side reaction between the positive electrode material and water vapor can be reduced, and thus the residual alkali content on the surface of the positive electrode material can be reduced, the surface structure stability of the positive electrode material can be improved, and the occurrence of side reactions on the surface of the positive electrode material can be effectively reduced, and the capacity and cycle stability of the positive electrode material can be improved.

[0046] For the positive electrode material provided by the present application, the residual alkali conversion coefficient of the positive electrode material is ξ, 0.2 ≤ ξ ≤ 0.35. Among them, the A value can reflect the mass content of LiOH in the positive electrode material, the B value can reflect the mass content of Li2CO3 in the positive electrode material, and the C value can reflect the conversion degree of LiOH and Li2CO3 in the positive electrode material. In the present application, the residual alkali conversion coefficient ξ of the positive electrode material is within the above range, and part of the residual alkali can be converted to form lithium composite metal oxide attached to the surface of the positive electrode material, reducing the residual alkali content on the surface of the positive electrode material, improving the surface structure stability of the positive electrode material, and further reducing the occurrence of side reactions on the surface of the positive electrode material, and improving the capacity and cycle performance of the positive electrode material.

[0047] The method for preparing the cathode material provided by this application first performs a primary sintering treatment on a mixture containing a nickel-cobalt-manganese-based precursor, a lithium salt, and a dopant containing a metal element in an oxygen-containing atmosphere to obtain a matrix material. By controlling the temperature and pressure during the primary sintering process and simultaneously controlling the pressure of the sintering system to increase in a gradient manner during the heating process of the primary sintering, water vapor can be discharged as much as possible in the low-temperature stage of the sintering process. Furthermore, the side reaction between unreacted lithium and water vapor during the primary sintering process can be reduced, and the residual alkali content on the surface of the matrix material can be decreased. At the same time, during the primary sintering process, the metal element in the dopant can increase the thermal diffusion rate of lithium ions, accelerate the crystallization rate of lithium ions inside the matrix material, optimize the lattice structure of the cathode material, and improve the structural stability of the cathode material. In addition, the metal element in the dopant can form a Li-M-O structure on the surface of the matrix material during the primary sintering process, which can reduce the corrosion of the surface structure of the material by water vapor, thereby strengthening the surface structure of the cathode material. Secondly, by performing a secondary sintering treatment on the matrix material and the coating agent, during the secondary sintering treatment, the coating agent can form a coating layer on the surface of the cathode material, reducing the side reaction between the cathode material and the electrolyte and further improving the surface structure stability of the cathode material. At the same time, the residual lithium on the surface of the matrix material can react with the coating agent to form a lithium composite metal oxide, which adheres to the surface of the matrix material to form a coating layer, improving the surface structure stability of the cathode material. By preparing the cathode material through the above preparation method, the influence of water vapor on the cathode material can be effectively reduced, the residual alkali content on the surface of the cathode material can be decreased, thereby improving the surface structure stability of the cathode material, reducing the occurrence of side reactions on the surface of the cathode material, and enabling the cathode material to have better capacity and cycle stability. Description of the Drawings

[0048] The present invention will be further described below with reference to the drawings and embodiments.

[0049] Figure 1 It is a test curve graph of E-dE / dV of the cathode material provided by this application;

[0050] Figure 2 It is a relationship graph between the surface structure stability coefficient ε and the capacity of the cathode material provided by this application;

[0051] Figure 3 It is a relationship graph between the surface structure stability coefficient ε and the room temperature cycle of the cathode material provided by this application;

[0052] Figure 4 It is a relationship graph between the surface structure stability coefficient ε and the high temperature cycle of the cathode material provided by this application;

[0053] Figure 5 It is a relationship graph between the residual alkali conversion coefficient ξ and the capacity of the cathode material provided by this application;

[0054] Figure 6 The relationship diagram between the residual alkali conversion coefficient ξ of the cathode material provided by this application and room temperature cycling;

[0055] Figure 7 The relationship diagram between the residual alkali conversion coefficient ξ of the cathode material provided by this application and high temperature cycling. Specific embodiments

[0056] For a better understanding of the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0057] It should be clear that the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0058] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "the" and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0059] It should be understood that the term " / and" used herein is only a description of the associated relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0060] In a first aspect, this application provides a cathode material, and the chemical general formula of the cathode material is LiNi a Co b Mn c M d O2, where 0.7 < a < 0.98, 0 < b < 0.3, 0 < c < 0.3, 0 < d ≤ 0.01, a + b + c = 1, and M is a doping element;

[0061] The mass content of LiOH in the cathode material is α LH wt%, the mass content of Li2CO3 in the cathode material is α LC wt%, the molar ratio of Li to all metals Me other than Li in the cathode material is γ Li / Me , the specific surface area of the cathode material is βm 2 / g; the surface structure stability coefficient of the cathode material is ε, 0.5 ≤ ε ≤ 1.5.

[0062] The positive electrode material provided by this application has a mass content of LiOH in the positive electrode material of α LH wt%, and the mass content of Li2CO3 in the positive electrode material is α LC wt%. The molar ratio of Li to all metals Me other than Li in the positive electrode material is γ Li / Me , and the specific surface area of the positive electrode material is β m 2 / g; the surface structure stability coefficient of the positive electrode material is ε, 0.5 ≤ ε ≤ 1.5. The surface structure stability coefficient ε of the positive electrode material can reflect the degree to which the positive electrode material is affected by water vapor. In this application, since the surface structure stability coefficient ε of the positive electrode material is within the above range, the degree to which the positive electrode material is affected by water vapor is small, which can reduce the side reaction between the positive electrode material and water vapor, and further reduce the residual alkali content on the surface of the positive electrode material, improve the surface structure stability of the positive electrode material, and thus effectively reduce the occurrence of side reactions on the surface of the positive electrode material and improve the capacity and cycle stability of the positive electrode material.

[0063] In this application, LiNi a Co b Mn c M d O2, where 0.7 < a < 0.98, 0 < b < 0.3, 0 < c < 0.3, 0 < d ≤ 0.01, a + b + c = 1. The specific value of a can be 0.71, 0.75, 0.78, 0.8, 0.83, 0.86, 0.89, 0.9, 0.91, 0.95 or 0.97, etc. The value of b can be 0.001, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25 or 0.29, etc. The value of c can be 0.001, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25 or 0.29, etc. The value of d can be 0.001, 0.002, 0.005, 0.006, 0.008 or 0.01, etc. Of course, it can also be other values within the above range, which are not limited here.

[0064] In this application, the surface structure stability coefficient ε of the positive electrode material can specifically be 0.5, 0.55, 0.6, 0.65, 0.7, 0.8, 0.9, 0.97, 1.0, 1.15, 1.2, 1.3, 1.4 or 1.5, which is not limited here. It can be understood that the surface structure stability coefficient ε of the positive electrode material can reflect the degree to which the positive electrode material is affected by water vapor. If ε is too large, it means that the degree to which the positive electrode material is affected by water vapor is large, which will cause the surface structure of the positive electrode material to be corroded and damaged by water vapor, and the capacity and cycle performance of the positive electrode material will decline. Once water vapor affects the positive electrode material, the lattice lithium on the surface of the positive electrode material will be corroded by water vapor to form residual alkali again, resulting in α LH +α LCIncrease; at the same time, part of the lithium will be carried away by water vapor, resulting in an abnormal decrease in γLi / Me in the cathode material, then (α LH +α LC ) / γ Li / Me as a whole becomes higher, which in turn leads to an increase in the value of the surface structure stability coefficient ε of the cathode material.

[0065] In some embodiments, the mass content of LiOH in the cathode material is α LH wt%, 0.1 ≤ α LH ≤ 1.0. Specifically, it can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95 or 1.0, etc. Of course, it can also be other values within the above range, which are not limited here.

[0066] In some embodiments, the mass content of Li2CO3 in the cathode material is α LC wt%, 0.1 ≤ α LC ≤ 1.0. Specifically, it can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95 or 1.0, etc. Of course, it can also be other values within the above range, which are not limited here.

[0067] It can be understood that the residual alkali in the cathode material mainly exists in the forms of LiOH and Li2CO3. When the mass contents of LiOH and Li2CO3 in the cathode material of the present application are within the above ranges, the surface of the cathode material can maintain a low residual alkali content, and the cathode material is not likely to have side reactions with water vapor, that is, the influence degree of water vapor on the cathode material is small, and the surface structure of the cathode material is not easily corroded and damaged by water vapor. Furthermore, it can enable the cathode material to maintain good surface structure stability and improve the capacity and cycle performance of the cathode material.

[0068] In some embodiments, the molar ratio of Li to all metals Me other than Li in the cathode material is γ Li / Me , 0.95 < γ Li / Me < 1.05. Specifically, it can be 0.951, 0.96, 0.965, 0.97, 0.98, 0.99, 1.0, 1.01, 1.02, 1.03 or 1.04, etc. Of course, it can also be other values within the above range, which are not limited here. It can be understood that once the water vapor affects the cathode material, the lithium ions in the cathode material are likely to have side reactions with water vapor, resulting in an increase in the residual alkali content on the surface of the cathode material and a decrease in the surface structure stability of the cathode material. At the same time, the lithium ions that can be embedded and removed in the cathode material decrease, resulting in a decrease in the capacity and cycle performance of the cathode material. In the present application, the molar ratio of Li to all metals Me other than Li in the cathode material is controlled to be γLi / Me Within the above range, it is beneficial to improve the surface structure stability of the positive electrode material, and it can also ensure that there are sufficient lithium ions in the positive electrode material, realizing the stable insertion and extraction of lithium ions during the cycling process of the positive electrode material, and ensuring the normal performance of lithium ion capacity and cycling performance.

[0069] In some embodiments, the specific surface area of the positive electrode material is β m 2 / g, 0.2 < β < 1.5. Specifically, it can be 0.21, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 1.0, 1.1, 1.2, 1.35 or 1.48, etc. Of course, it can also be other values within the above range, which are not limited herein. It can be understood that in this application, controlling the specific surface area of the positive electrode material within the above range is beneficial to improving the surface structure stability of the negative electrode material and is beneficial to improving the capacity and cycling performance of the positive electrode material.

[0070] This application also provides a positive electrode material, and the chemical general formula of the positive electrode material is LiNi a Co b Mn c M d O2, where 0.7 < a < 0.98, 0 < b < 0.3, 0 < c < 0.3, 0 < d ≤ 0.01, a + b + c = 1, and M is a doping element;

[0071] Using a potentiometric titrator and hydrochloric acid with a concentration of 0.02 mol / L to conduct an acid-base potentiometric titration test on the positive electrode material, a curve graph of the relationship between the differential value dE / dV obtained by differentiating the consumption volume V of hydrochloric acid with respect to the potential E and the potential E is obtained. As Figure 1 shown, in the curve graph of the relationship between the differential value dE / dV and the potential E, the positive electrode material has a first characteristic peak in the potential range of E = -200 mV to -50 mV, and the peak area of the first characteristic peak is A. The positive electrode material has a second characteristic peak between E = 120 mV and 250 mV, and the peak area of the second characteristic peak is B; there is at least one characteristic peak in the potential range of E = -50 mV to 120 mV, and the sum of the peak areas of the at least one characteristic peak is C. The residual base conversion coefficient of the positive electrode material is ξ, 0.2 ≤ ξ ≤ 0.35.

[0072] For the positive electrode material provided by this application, the residual base conversion coefficient of the positive electrode material is ξ, 0.2 ≤ ξ ≤ 0.35, where the value of A can reflect the mass content of LiOH in the cathode material, the value of B can reflect the mass content of Li₂CO₃ in the cathode material, and the value of C can reflect the conversion degree of LiOH and Li₂CO₃ in the cathode material. In the present application, the residual alkali conversion coefficient ξ of the cathode material is within the above range, and part of the residual alkali can be converted to form lithium composite metal oxide attached to the surface of the cathode material, reducing the content of residual alkali on the surface of the cathode material, improving the surface structure stability of the cathode material, and further reducing the occurrence of side reactions on the surface of the cathode material, improving the capacity and cycle performance of the cathode material.

[0073] In the present application, the value of ξ can specifically be 0.2, 0.22, 0.25, 0.26, 0.2 / 7, 0.28, 0.3, 0.31, 0.32, 0.33, 0.34, or 0.35, etc., which is not limited herein.

[0074] In some embodiments, the doping element M includes at least one of B, P, S, F, La, Sr, Ti, Al, Zr, Y, Ba, Mg, Nb, Mo, W, and V.

[0075] In some embodiments, the peak area of the first characteristic peak is A, 2000 ≤ A ≤ 200000, and specifically can be 2000, 5000, 10000, 30000, 50000, 80000, 100000, 120000, 150000, 180000, or 200000, etc. Of course, it can also be other values within the above range, which is not limited herein.

[0076] In some embodiments, the peak area of the second characteristic peak is B, 2000 ≤ B ≤ 200000, and specifically can be 2000, 5000, 10000, 30000, 50000, 80000, 100000, 120000, 150000, 180000, or 200000, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0077] In some embodiments, the sum of the peak areas of at least one characteristic peak is C, 2000 ≤ C ≤ 200000, and specifically can be 2000, 5000, 10000, 30000, 50000, 80000, 100000, 120000, 150000, 180000, or 200000, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0078] In a second aspect, the present application provides a method for preparing a cathode material, including the following steps:

[0079] Step S10: Subject a mixture containing a nickel-cobalt-manganese-based precursor, a lithium source, and a dopant containing a metal element to a first sintering treatment in an oxygen-containing atmosphere to obtain a matrix material. The temperature of the first sintering treatment is 200°C to 900°C, and the pressure during the first sintering treatment increases in a gradient manner, with the pressure range being 3 Pa to 13 Pa.

[0080] Step S20: Subject the matrix material and a coating agent to a second sintering treatment to obtain a cathode material.

[0081] The method for preparing a cathode material provided by this application first subjects a mixture containing a nickel-cobalt-manganese-based precursor, a lithium salt, and a dopant containing a metal element to a first sintering treatment in an oxygen-containing atmosphere to obtain a matrix material. By controlling the temperature and pressure during the first sintering process and simultaneously controlling the pressure of the sintering system to increase in a gradient manner during the heating-up process of the first sintering, water vapor can be discharged as much as possible in the low-temperature stage of the sintering process, thereby reducing the side reaction between unreacted lithium and water vapor during the first sintering process and reducing the residual alkali content on the surface of the matrix material. At the same time, during the first sintering process, the metal element in the dopant can increase the thermal diffusion rate of lithium ions, accelerate the crystallization rate of lithium ions inside the matrix material, optimize the lattice structure of the cathode material, and improve the structural stability of the cathode material. In addition, the metal element in the dopant can form a Li-M-O structure on the surface of the matrix material during the first sintering process, which can reduce the corrosion of the material surface structure by water vapor, thereby strengthening the surface structure of the cathode material. Secondly, by subjecting the matrix material and a coating agent to a second sintering treatment, during the second sintering treatment, the coating agent can form a coating layer on the surface of the cathode material, reducing the side reaction between the cathode material and the electrolyte and further improving the surface structural stability of the cathode material. At the same time, the residual lithium on the surface of the matrix material can react with the coating agent to form a lithium composite metal oxide, which adheres to the surface of the matrix material to form a coating layer, improving the surface structural stability of the cathode material. By preparing the cathode material through the above preparation method, the influence of water vapor on the cathode material can be effectively reduced, the residual alkali content on the surface of the cathode material can be reduced, thereby improving the surface structural stability of the cathode material, reducing the occurrence of side reactions on the surface of the cathode material, and enabling the cathode material to have better capacity and cycle stability.

[0082] The following specifically introduces the preparation method of this application in combination with examples:

[0083] Before step S10, the method further includes:

[0084] Prepare a nickel-cobalt-manganese-based precursor by the co-precipitation method, and mix a metal salt solution, a complexing agent, and a pH regulator to obtain a nickel-cobalt-manganese-based precursor.

[0085] In some embodiments, the mass ratio of the metal salt solution, the complexing agent, and the pH regulator is (2 - 5):(2 - 5):(1 - 4). Specifically, it can be 2:2:1, 2:3:2, 2:4:3, 3:2:1, 4:4:4, 5:3:3, or 5:5:4, etc. Of course, it can also be other values within the above range, which is not limited herein.

[0086] In some embodiments, the metal salt solution includes nickel ions, cobalt ions, and manganese ions.

[0087] In some embodiments, the concentration of nickel ions in the metal salt solution is a' mol / L, where 0.7 < a' < 0.98. Specifically, it can be 0.71, 0.75, 0.78, 0.8, 0.83, 0.86, 0.89, 0.9, 0.91, 0.95, or 0.97, etc. Of course, it can also be other values within the above range, which is not limited herein.

[0088] In some embodiments, the concentration of cobalt ions in the metal salt solution is b' mol / L, where 0 < b' < 0.3. Specifically, it can be 0.001, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, or 0.29, etc. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0089] In some embodiments, the concentration of manganese ions in the metal salt solution is c' mol / L, where 0 < c' < 0.3. Specifically, it can be 0.001, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, or 0.29, etc. Of course, it can also be other values within the above range, which is not limited herein.

[0090] In some embodiments, the concentration of the pH regulator is 1 mol / L to 6 mol / L. Specifically, it can be 1 mol / L, 1.5 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, or 6 mol / L, etc. Of course, it can also be other values within the above range, which is not limited herein.

[0091] In some embodiments, the concentration of the complexing agent is 2 mol / L to 10 mol / L. Specifically, it can be 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, or 10 mol / L, etc. Of course, it can also be other values within the above range, which is not limited herein.

[0092] In some embodiments, the complexing agent includes ammonia water.

[0093] In some embodiments, the pH regulator includes at least one of sodium hydroxide and potassium hydroxide.

[0094] In some embodiments, the temperature of the mixing treatment is 45°C to 85°C, specifically it can be 45°C, 50°C, 60°C, 65°C, 70°C, 75°C, 80°C or 85°C, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0095] In some embodiments, the time of the mixing treatment is 5h to 20h, specifically it can be 5h, 8h, 10h, 12h, 15h, 16h, 18h or 20h, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0096] In some embodiments, the mixing treatment is carried out under a stirring state, and the stirring rate is controlled to be 150r / min to 850r / min, specifically it can be 150r / min, 200r / min, 300r / min, 400r / min, 500r / min, 600r / min, 750r / min or 850r / min, etc. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0097] In some embodiments, the metal composite hydroxide precursor prepared by the mixing treatment is a slurry-like suspension, and the metal composite hydroxide precursor is obtained through solid-liquid separation, washing and drying.

[0098] In some embodiments, the method of solid-liquid separation includes any one of centrifugation and filtration. The purpose of solid-liquid separation is to separate the metal composite hydroxide from the solvent.

[0099] In some embodiments, washing is carried out with deionized water multiple times to remove impurities.

[0100] In some embodiments, the drying temperature is 100°C to 130°C. The drying temperature can specifically be 100°C, 110°C, 120°C and 130°C, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0101] In some embodiments, the drying time is 12h to 24h. The drying time can specifically be 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h and 24h, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0102] Step S10, subject a mixture containing a nickel-cobalt-manganese-based precursor, a lithium source and a dopant containing a metal element to a primary sintering treatment in an oxygen-containing atmosphere to obtain a matrix material; the temperature of the primary sintering treatment is 200°C to 900°C, and the pressure during the primary sintering treatment shows a gradient upward state, and the pressure range is 3Pa to 13Pa.

[0103] In some embodiments, the chemical formula of the nickel-cobalt-manganese-based precursor is Ni a Co b Mn c (OH)2, where 0.7 < a < 0.98, 0 < b < 0.3, 0 < c < 0.3, and a + b + c = 1. The specific value of a can be 0.71, 0.75, 0.78, 0.8, 0.83, 0.86, 0.89, 0.9, 0.91, 0.95, 0.97, etc.; the value of b can be 0.001, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.29, etc.; the value of c can be 0.001, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.29, etc. It is not limited herein.

[0104] In some embodiments, the mass content of metal elements in the nickel-cobalt-manganese-based precursor is 60.5 wt% to 63.5 wt%, specifically it can be 60.5 wt%, 60.8 wt%, 61 wt%, 61.3 wt%, 61.5 wt%, 62 wt%, 62.1 wt%, 60.5 wt%, 62.8 wt%, 63 wt%, 63.5 wt%, etc., but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0105] In some embodiments, the mass ratio of the nickel-cobalt-manganese-based precursor, the lithium source, and the dopant containing metal elements is 1:(1.0 - 1.05):(0 - 0.01), specifically it can be 1:1.0:0, 1:1.01:0.001, 1:1.02:0.003, 1:1.03:0.005, 1:1.01:0.007, 1:1.05:0.009, 1:1.05:0.01, etc. Of course, it can also be other values within the above range, which is not limited herein.

[0106] In some embodiments, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate, and lithium acetate.

[0107] In some embodiments, the dopant containing metal elements includes at least one of Nb2O5, Nb2O3, MoO3, WO2, V2O5, V2O3, Sr(OH)2, SrO, TiO2, Al2O3, Al(OH)3, ZrO2, Zr(OH)4, Y2O3, BaO, MgO, and Mg(OH)2. Preferably, the dopant is Al(OH)3, Sr(OH)2, or TiO2.

[0108] In some embodiments, the mixing conditions for obtaining the mixture are as follows: dry mixing is carried out at 10°C to 50°C for 0.3 h to 2 h. The temperature of dry mixing can specifically be 10°C, 20°C, 30°C, 40°C, 50°C, etc., and of course, other values within the above range are also possible. The time of dry mixing can specifically be 0.3 h, 0.5 h, 0.8 h, 1 h, 1.5 h, 2 h, etc., and of course, other values within the above range are also possible.

[0109] In some embodiments, the mass content of oxygen in the oxygen-containing atmosphere ≥ 95%, specifically it can be 95%, 95.5%, 96%, 97%, 97.5%, 98% or 99%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0110] It should be noted that since most of the water vapor in the primary sintering process comes from the combined water and structural water formed by the dehydration of the nickel-cobalt-manganese-based precursor and the lithium source, it is necessary to study the weight loss curve of the mixture containing the nickel-cobalt-manganese-based precursor, lithium salt and metal element dopant to determine the temperature at which water vapor is generated. The inventor found through research that the mixture has an obvious weight loss at 250°C to 300°C, and a relatively slow weight loss at 300°C to 550°C. These water vapor losses are all due to the dehydration of the structural water of LiOH and the precursor. And at 550°C to 700°C, the structural water is slowly and completely removed. When the primary sintering temperature reaches 700°C, all the structural water is completely removed. Therefore, in order to prevent water vapor from entering the high-temperature zone and reacting with the material, it is necessary to exhaust as much water vapor as possible before 700°C. Most of the primary sintering kilns on the market also have exhaust ducts in the front heating zone, but there are no exhaust ducts in the high-temperature zone or the insulation zone. However, even so, some water vapor will still enter the high-temperature zone or the insulation zone during the actual production process. Therefore, it is necessary to set an additional obstacle to the diffusion of water vapor. Therefore, the inventor designed a gradient furnace pressure of 200°C to 900°C. By controlling the temperature of the primary sintering process to be 200°C to 900°C, and by making the pressure during the primary sintering process rise in a gradient state, it is possible to effectively prevent the diffusion of water vapor into the high-temperature sintering zone and reduce the influence of water vapor on the cathode material. In addition, because once water vapor enters the high-temperature zone (there is no corresponding exhaust duct in the high-temperature zone), it is very difficult for the water vapor to escape in the high-temperature zone, and the damage to the material will be greater. Therefore, 700°C is the red line for the diffusion of water vapor. To ensure that water vapor does not enter the high-temperature zone, the present application can reduce the diffusion of high-temperature water vapor and reduce the damage of water vapor to the material by controlling the furnace pressure during the primary sintering process to rise in a gradient state.

[0111] In some embodiments, the primary sintering process includes a first stage, a second stage and a third stage.

[0112] In some embodiments, the first stage includes: heating the mixture from 200 °C to 550 °C within 2 h to 5 h, controlling the pressure P1 to be 7 Pa to 11 Pa, wherein the input amount of the oxygen-containing atmosphere is controlled to be 10 m 3 / h to 30 m 3 / h, and controlling the exhaust gas volume of the reaction system to be 10% to 30%. It can be understood that by controlling the input amount of the oxygen-containing atmosphere and the exhaust gas volume of the reaction system, the pressure in the first stage of the sintering treatment can be controlled within the above range.

[0113] Optionally, the heating time in the first stage can be 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h or 5 h, etc., which is not limited herein.

[0114] Optionally, the pressure P1 in the first stage can specifically be 7 Pa, 7.5 Pa, 8 Pa, 8.5 Pa, 9 Pa, 10 Pa, 10.5 Pa or 11 Pa, etc., which is not limited herein.

[0115] Optionally, the input amount of the oxygen-containing atmosphere in the first stage can specifically be 10 m 3 / h, 12 m 3 / h, 15 m 3 / h, 18 m 3 / h, 20 m 3 / h, 25 m 3 / h, 28 m 3 / h or 30 m 3 / h, etc., which is not limited herein; the exhaust gas volume of the reaction system can specifically be 10%, 12%, 15%, 18%, 20%, 25% or 30%, etc., which is not limited herein. Specifically, the input amount of the oxygen-containing atmosphere and the exhaust gas volume of the reaction system are adjusted according to the required pressure during sintering, which is not specifically limited herein.

[0116] In some embodiments, the second stage includes: heating the mixture from 550 °C to 700 °C within 2 h to 5 h, controlling the pressure P2 to be 8 Pa to 12 Pa, wherein the input amount of the oxygen-containing atmosphere is controlled to be 20 m 3 / h to 30 m 3 / h, and controlling the exhaust gas volume of the reaction system to be 10% to 20%.

[0117] Optionally, the heating time in the second stage can be 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h or 5 h, etc., which is not limited herein.

[0118] Optionally, the pressure P2 in the second stage can specifically be 8 Pa, 8.5 Pa, 9 Pa, 10 Pa, 10.5 Pa, 11 Pa, 11.5 Pa or 12 Pa, etc., which is not limited herein.

[0119] Optionally, the input amount of the oxygen-containing atmosphere in the first stage may specifically be 20 m 3 / h, 22 m 3 / h, 25 m 3 / h, 26 m 3 / h, 27 m 3 / h, 28 m 3 / h, 29 m 3 / h or 30 m 3 / h, etc., which are not limited herein; the exhaust gas volume of the reaction system may specifically be 10%, 12%, 15%, 16%, 18%, 19% or 20%, etc., which are not limited herein. Specifically, the input amount of the oxygen-containing atmosphere and the exhaust gas volume of the reaction system are adjusted according to the pressure required during sintering, which is not specifically limited herein.

[0120] In some embodiments, the third stage includes: sintering the mixture at 700 °C to 900 °C for 5 h to 10 h, controlling the pressure P3 to be 9 Pa to 13 Pa, wherein the input amount of the oxygen-containing atmosphere is controlled to be 20 m 3 / h to 30 m 3 / h. It can be understood that the third stage is a high-temperature sintering treatment stage, and the pressure during sintering treatment is also higher. By controlling the input amount of the oxygen-containing atmosphere, the pressure in the third stage can be controlled within the above range.

[0121] The sintering temperature in the third stage may specifically be 700 °C, 720 °C, 750 °C, 800 °C, 830 °C, 850 °C or 900 °C, etc. Of course, it may also be other values within the above range, which are not limited herein.

[0122] The sintering time in the third stage may specifically be 5 h, 5.5 h, 6 h, 7 h, 8 h, 9 h or 10 h, etc. Of course, it may also be other values within the above range, which are not limited herein.

[0123] Optionally, the pressure P3 in the third stage may be 9 Pa, 9.5 Pa, 10 Pa, 11 Pa, 12 Pa, 12.5 Pa or 13 Pa, etc., which are not limited herein.

[0124] Optionally, the input amount of the oxygen-containing atmosphere may be 20 m 3 / h, 21 m 3 / h, 23 m 3 / h, 25 m 3 / h, 26 m 3 / h, 27 m 3 / h, 28 m 3 / h or 30 m 3 / h, etc. The input amount of the oxygen-containing atmosphere is adjusted according to the pressure required during sintering, which is not limited herein.

[0125] In some embodiments, it further includes shaping and screening the sintered product, and the shaping includes at least one of crushing, mixing, ball milling or air crushing.

[0126] In some embodiments, ultrasonic vibration sieving is used for screening. The frequency of the ultrasonic vibration sieve used is 10 KHz to 50 KHz, and specifically it can be 10 KHz, 15 KHz, 20 KHz, 30 KHz, 40 KHz, 45 KHz or 50 KHz, etc., which is not limited herein. It can be understood that screening the sintered product with an ultrasonic vibration sieve can ensure uniform dispersion of the matrix material particles, reduce the agglomeration of the matrix material particles, and improve the coating uniformity of the matrix material and the coating material.

[0127] In some embodiments, the average particle size D of the matrix material 50 is 9 μm to 12 μm, and specifically it can be 9 μm, 9.2 μm, 9.5 μm, 10 μm, 11 μm, 11.5 μm, 11.8 μm or 12 μm, etc. Of course, it can also be other values within the above range, which is not limited herein.

[0128] In some embodiments, the specific surface area of the matrix material is 0.2 m 2 / g to 0.8 m 2 / g, and specifically it can be 0.2 m 2 / g, 0.3 m 2 / g, 0.4 m 2 / g, 0.5 m 2 / g, 0.6 m 2 / g, 0.7 m 2 / g or 0.8 m 2 / g, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0129] Step S20: Perform secondary sintering treatment on the matrix material and the coating agent to obtain the cathode material.

[0130] Before step S20, it further includes: dissolving the coating agent in water to form a coating solution; and performing coating treatment on the matrix material with the coating solution by an atomization method.

[0131] It can be understood that performing coating treatment on the matrix material and the coating agent by an atomization method can improve the coating uniformity of the coating layer on the matrix material, which is beneficial to improving the electrochemical performance of the cathode material.

[0132] In some embodiments, the atomization pressure is 0 Mpa to 0.05 Mpa, specifically it can be 0 Mpa, 0.01 Mpa, 0.015 Mpa, 0.2 Mpa, 0.3 Mpa, 0.4 Mpa, 0.045 Mpa or 0.05 Mpa, etc. Of course, it can also be other values within the above range, which are not limited herein. It can be understood that the atomized coating solution can form a sheet-like water jet under the action of this pressure, and can maintain the tangential direction with the stirred matrix material and penetrate the stirred matrix material, so as to ensure that the matrix material can uniformly and accurately contact and react with the coating agent.

[0133] In some embodiments, the coating treatment is carried out under a stirring state, and the stirring frequency is controlled to be 20 Hz to 50 Hz. Specifically, it can be 20 Hz, 25 Hz, 30 Hz, 35 Hz, 40 Hz, 45 Hz or 50 Hz, etc., but it is not limited to the listed values. Other unlisted values within this value range are equally applicable.

[0134] In some embodiments, the temperature of the coating treatment is 150 °C to 250 °C. Specifically, it can be 150 °C, 180 °C, 200 °C, 220 °C, 230 °C or 250 °C, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0135] In some embodiments, the time of the coating treatment is 3 h to 8 h. Specifically, it can be 3 h, 4 h, 5 h, 6 h, 7 h, 7.5 h or 8 h, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0136] By controlling the stirring rate and temperature in the coating treatment process within the above range in this application, the reaction activity between the coating agent and the matrix material can be improved, and the coating uniformity of the coating agent on the matrix material can be improved.

[0137] In some embodiments, the coating agent includes at least one of La(NO3)3·6H2O, NH4F, NH4HF, (NH4)3PO4, (NH4)2HPO4, (NH4)2MoO4, (NH4)2SO4, NH4HSO4, (NH4)6W7O 24 ·6H2O, (NH4)3PW 12 O40·3H2O, Zr(SO4)2·4H2O, H 28 N6O 41 W 12 、WO3, Al2O3 and Al(OH)3.

[0138] In some embodiments, the mass ratio of the matrix material to the coating agent is 1:(0.001 - 0.05), specifically it can be 1:0.001, 1:0.005, 1:0.01, 1:0.015, 1:0.02, 1:0.03, 1:0.04 or 1:0.05, etc. Of course, it can also be other values within the above range, which are not limited herein. Preferably, the mass ratio of the matrix material to the coating agent is 1:(0.01 - 0.04).

[0139] In some embodiments, the secondary sintering treatment is carried out in an oxygen-containing atmosphere, and the mass content of oxygen in the oxygen-containing atmosphere ≥ 95%, specifically it can be 95%, 95.5%, 96%, 96.5%, 97%, 98% or 99%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0140] In some embodiments, the temperature of the secondary sintering treatment is 200°C - 700°C, specifically it can be 200°C, 300°C, 300°C, 400°C, 450°C, 500°C, 600°C, 650°C or 700°C, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0141] In some embodiments, the time of the secondary sintering treatment is 10h - 20h, specifically it can be 10h, 11h, 12h, 15h, 16h, 18h or 20h, etc. Of course, it can also be other values within the above range, which are not limited herein.

[0142] It can be understood that through the secondary sintering treatment, the coating layer can be more tightly coated on the surface of the matrix material, further improving the structural stability of the positive electrode material and being beneficial to improving the cycle performance of the positive electrode material.

[0143] In a third aspect, the present application provides a lithium-ion battery, including a positive electrode plate, a negative electrode plate, an electrolyte, and a separator located between the positive electrode plate and the negative electrode plate. The positive electrode plate includes a current collector and a positive electrode active material layer coated on the current collector. The current collector can be aluminum foil or nickel foil. The positive electrode active material layer includes the positive electrode material described in the first aspect or the positive electrode material prepared by the preparation method of the positive electrode material described in the second aspect, a conductive agent, and a binder; the negative electrode plate includes a negative electrode active material layer and a negative electrode current collector, and the negative electrode current collector can be copper foil or nickel foil.

[0144] In some embodiments, the conductive agent is one of conductive carbon black, Ketjen black, graphite, and acetylene black.

[0145] In some embodiments, the binder is one of sodium carboxymethyl cellulose, cyclodextrin, and polyvinylidene fluoride.

[0146] In some embodiments, the solvent in the positive electrode active material layer is selected from one of deionized water, N-methylpyrrolidone, and N,N-dimethylformamide.

[0147] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the scope of protection of the present invention.

[0148] Example 1

[0149] (1) Weigh nickel sulfate, cobalt sulfate, and manganese sulfate according to n Ni :n Co :n Mn =0.9:0.06:0.04, dissolve them with deionized water to obtain 100 mL of a metal salt solution. In this metal salt solution, the molar concentration of nickel ions is 0.9 mol / L, the molar concentration of cobalt ions is 0.06 mol / L, and the molar concentration of manganese ions is 0.04 mol / L; after adding a 4 mol / L NaOH solution and a 6 mol / L NH3·H2O to the above metal salt solution, place it at 65 °C and stir for 15 h, control the stirring rate at 450 r / min, perform solid-liquid separation to obtain the nickel-cobalt-manganese-based precursor Ni 0.9 Co 0.06 Mn 0.04 (OH)2.

[0150] (2) Dry-mix the nickel-cobalt-manganese-based precursor Ni 0.9 Co 0.06 Mn 0.04 (OH)2, LiOH, Ba(OH)2, and ZrO2 at 40 °C for 1 h to obtain a mixture, where n (Ni+Co+Al) :n Li =1:1.03, n (Ni+Co+Al) :n (Ba) =1:0.003, n (Ni+Co+Al) :n (Zr) =1:0.002.

[0151] (3) Place the above mixture in an oxygen atmosphere with an oxygen concentration of 95% for a first sintering treatment. The first treatment is divided into a first stage, a second stage, and a third stage. The pressure during the sintering treatment increases in a gradient manner. The specific parameters are as follows: First stage: Heat the above mixture from 200 °C to 550 °C within 4 h, control the pressure P1 at 9 Pa, where control the inlet volume of the oxygen-containing atmosphere at 20 m 3 / h, and control the exhaust volume of the reaction system at 20%; Second stage: Heat the above mixture from 550 °C to 700 °C within 5 h, control the pressure P2 at 10 Pa, where control the inlet volume of the oxygen-containing atmosphere at 25 m3 / h, control the exhaust gas volume of the reaction system to be 20%; the third stage includes: heating the mixture to 750 °C and sintering for 10 h, controlling the pressure P3 to be 11 Pa, wherein, control the input volume of the oxygen-containing atmosphere to be 20 m 3 / h. After the sintered product is crushed and screened, the matrix material is obtained.

[0152] (4) Based on the mass of the matrix material being 100%, dissolve 6500 ppm of tungsten oxide (WO3) in deionized water to obtain a coating solution; add the above matrix material into a stirrable and heatable reaction kettle, set the temperature of the reaction kettle to 200 °C, control the stirring frequency to be 40 Hz, atomize and spray the coating solution into the reaction kettle, the atomization pressure is 0.01 Mpa. After all the coating solution is sprayed into the reaction kettle, continue stirring for 5 h to obtain a coated product.

[0153] (5) Sinter the above coated product at 500 °C for 20 h in an oxygen atmosphere with an oxygen concentration of 95%, cool, crush and screen to obtain the positive electrode material.

[0154] The chemical formula of the positive electrode material prepared in this example is LiNi 0.9 Co 0.06 Mn 0.04 Ba 0.003 Zr 0.002 W 0.002 O2.

[0155] Example 2

[0156] The difference from Example 1 is that in step (2), the dopant is Al(OH)3, n (Ni+Co+Al) : n (Al) = 1:0.001, and other conditions are exactly the same as those in Example 1.

[0157] The chemical formula of the positive electrode material prepared in this example is LiNi 0.9 Co 0.06 Mn 0.04 Al 0.001 W 0.002 O2.

[0158] Example 3

[0159] The difference from Example 1 is that in step (2), the dopant is Sr(OH)2, n (Ni+Co+Al) : n (Sr) = 1:0.01, and other conditions are exactly the same as those in Example 1.

[0160] The chemical formula of the positive electrode material prepared in this example is LiNi 0.9 Co 0.06 Mn 0.04 Sr 0.01W 0.002 O2。

[0161] Example 4

[0162] The difference from Example 1 is that no dopant is added in step (2), and other conditions are exactly the same as those in Example 1.

[0163] The chemical formula of the cathode material prepared in this example is LiNi 0.9 Co 0.06 Mn 0.04 W 0.002 O2。

[0164] Example 5

[0165] The difference from Example 1 is that in step (2), n (Ni+Co+Al) : n Li = 1:1.01, and other conditions are exactly the same as those in Example 1.

[0166] The chemical formula of the cathode material prepared in this example is LiNi 0.9 Co 0.06 Mn 0.04 Ba 0.003 Zr 0.002 W 0.002 O2。

[0167] Example 6

[0168] The difference from Example 1 is that in step (2), n (Ni+Co+Al) : n Li = 1:1.05, and other conditions are exactly the same as those in Example 1.

[0169] The chemical formula of the cathode material prepared in this example is LiNi 0.9 Co 0.06 Mn 0.04 Ba 0.003 Zr 0.002 W 0.002 O2。

[0170] Example 7

[0171] The difference from Example 1 is that in step (2), n (Ni+Co+Al) : n Li = 1:1, and other conditions are exactly the same as those in Example 1.

[0172] The cathode material prepared in this example includes a matrix material and a coating layer located on at least part of the surface of the matrix material. The chemical formula of the matrix material is LiNi 0.9 Co 0.06 Mn 0.04 Ba 0.003 Zr0.002 O2, with the coating element being W, and based on the mass of the cathode material being 100%, the mass content of the coating layer is 0.5%.

[0173] Example 8

[0174] The difference from Example 1 is that

[0175] (2) The nickel-cobalt-manganese-based precursor Ni 0.9 Co 0.06 Mn 0.04 (OH)2 and LiOH are dry-mixed at 40°C for 1 h to obtain a mixture, where n (Ni+Co+Al) : n Li = 1:1.03.

[0176] (3) The above mixture is heated to 750°C in an oxygen atmosphere with an oxygen concentration of 95% and sintered for 20 h, controlling the pressure during the sintering process to be 8 Pa to 12 Pa, with the pressure rising in a gradient state. After crushing and screening, the matrix material is obtained.

[0177] Other conditions are exactly the same as those in Example 1.

[0178] The chemical formula of the cathode material prepared in this example is LiNi 0.9 Co 0.06 Mn 0.04 Ba 0.003 Zr 0.002 W 0.002 O2.

[0179] Example 9

[0180] The difference from Example 1 is that

[0181] (2) The nickel-cobalt-manganese-based precursor Ni 0.9 Co 0.06 Mn 0.04 (OH)2, LiOH, Ba(OH)2 and ZrO2 are dry-mixed at 40°C for 1 h to obtain a mixture, where n (Ni+Co+Al) : n Li = 1:1.03, n (Ni+Co+Al) : n (Ba) = 1:0.0005, n (Ni+Co+Al) : n (Zr) = 1:0.0005.

[0182] (3) Place the above mixture in an oxygen atmosphere with an oxygen concentration of 95% for a primary sintering treatment. The primary treatment is divided into a first stage, a second stage, and a third stage. The pressure during the sintering treatment increases in a gradient manner. The specific parameters are as follows: First stage: Heat the above mixture from 200 °C to 550 °C within 4 h, control the pressure P1 to be 7 Pa, where the inlet volume of the oxygen-containing atmosphere is controlled to be 10 m 3 / h, and control the exhaust volume of the reaction system to be 15%; Second stage: Heat the above mixture from 550 °C to 700 °C within 5 h, control the pressure P2 to be 9 Pa, where the inlet volume of the oxygen-containing atmosphere is controlled to be 20 m 3 / h, and control the exhaust volume of the reaction system to be 20%; The third stage includes: Heat the mixture to 750 °C and sinter for 10 h, control the pressure P3 to be 13 Pa, where the inlet volume of the oxygen-containing atmosphere is controlled to be 25 m 3 / h. After the sintered product is crushed and screened, a matrix material is obtained.

[0183] Other conditions are exactly the same as those in Example 1.

[0184] The chemical formula of the positive electrode material prepared in this example is LiNi 0.9 Co 0.06 Mn 0.04 Ba 0.00053 Zr 0.0005 W 0.002 O2.

[0185] Example 10

[0186] The difference from Example 1 is that

[0187] (3) Place the above mixture in an oxygen atmosphere with an oxygen concentration of 95% for a primary sintering treatment. The primary treatment is divided into a first stage, a second stage, and a third stage. The pressure during the sintering treatment increases in a gradient manner. The specific parameters are as follows: First stage: Heat the above mixture from 200 °C to 550 °C within 4 h, control the pressure P1 to be 9 Pa, where the inlet volume of the oxygen-containing atmosphere is controlled to be 20 m 3 / h, and control the exhaust volume of the reaction system to be 20%; Second stage: Heat the above mixture from 550 °C to 700 °C within 5 h, control the pressure P2 to be 8 Pa, where the inlet volume of the oxygen-containing atmosphere is controlled to be 12 m 3 / h, and control the exhaust volume of the reaction system to be 15%; The third stage includes: Heat the mixture to 750 °C and sinter for 10 h, control the pressure P3 to be 12 Pa, where the inlet volume of the oxygen-containing atmosphere is controlled to be 22 m 3 / h. After the sintered product is crushed and screened, a matrix material is obtained.

[0188] Other conditions are exactly the same as those in Example 1.

[0189] The chemical formula of the cathode material prepared in this example is LiNi 0.9 Co 0.06 Mn 0.04 Ba 0.003 Zr 0.002 W 0.002 O2.

[0190] Example 11

[0191] The difference from Example 1 is that in step (2), n (Ni+Co+Al) : n Li = 1:1.07, and other conditions are exactly the same as those in Example 1.

[0192] The chemical formula of the cathode material prepared in this example is LiNi 0.9 Co 0.06 Mn 0.04 Ba 0.003 Zr 0.002 W 0.002 O2.

[0193] Comparative Example 1

[0194] The difference from Example 1 is that

[0195] (2) The nickel-cobalt-manganese-based precursor Ni 0.9 Co 0.06 Mn 0.04 (OH)2 and LiOH are dry-mixed at 40 °C for 1 h to obtain a mixture, where n (Ni+C o+Al): n Li = 1:1.03.

[0196] (3) The above mixture is placed in an oxygen atmosphere with an oxygen concentration of 95% for a first sintering treatment. The first treatment is divided into a first stage, a second stage, and a third stage. The pressure during the sintering treatment increases in a gradient manner. The specific parameters are as follows: First stage: The above mixture is heated from 200 °C to 550 °C within 4 h, and the pressure P1 is controlled to be 11.5 Pa, where the inlet volume of the oxygen-containing atmosphere is controlled to be 25 m 3 / h, and the exhaust volume of the reaction system is controlled to be 20%; Second stage: The above mixture is heated from 550 °C to 700 °C within 5 h, and the pressure P2 is controlled to be 10.5 Pa, where the inlet volume of the oxygen-containing atmosphere is controlled to be 22 m 3 / h, and the exhaust volume of the reaction system is controlled to be 20%; The third stage includes: heating the mixture to 750 °C and sintering for 10 h, controlling the pressure P3 to be 9.5 Pa, where the inlet volume of the oxygen-containing atmosphere is controlled to be 18 m 3 / h. After the sintered product is crushed and screened, a matrix material is obtained.

[0197] Other conditions are exactly the same as those in Example 1.

[0198] The chemical formula of the positive electrode material obtained in this comparative example is LiNi 0.9 Co 0.06 Mn 0.04 W 0.002 O2.

[0199] Comparative Example 2

[0200] The difference from Example 1 is that

[0201] (3) The above mixture was heated to 750 °C in an oxygen atmosphere with an oxygen concentration of 95% and sintered for 20 h, and the pressure during the sintering process was controlled to be constant at 10 Pa. After crushing and screening, a matrix material was obtained.

[0202] Other conditions are exactly the same as those in Example 1.

[0203] The chemical formula of the positive electrode material obtained in this example is LiNi 0.9 Co 0.06 Mn 0.04 Ba 0.003 Zr 0.002 W 0.002 O2.

[0204] Testing method

[0205] (1) Testing method for the residual alkali content of the positive electrode material:

[0206] Take 5 g of the positive electrode material and disperse it in 100 ml of deionized water, and dissolve the residual carbonate and hydroxide by magnetic stirring. After suction filtration, a filtrate is obtained, and hydrochloric acid solution is added to an automatic potentiometric titrator, and titration is carried out in an equivalent point dropwise manner. The contents of carbonate and hydroxide in the positive electrode material are calculated based on the situation of the inflection point and the consumption degree of the hydrochloric acid solution.

[0207] (2) Testing method for the element content in the positive electrode material:

[0208] The temperature of the inductively coupled plasma torch can reach 6000 - 8000 K. When the sample is introduced into the nebulizer by the sampler and carried into the torch by the argon carrier gas, the components in the sample are atomized, ionized, and excited, and emit energy in the form of light. When the atoms of different elements return to the ground state after excitation or ionization, they emit characteristic spectra of different wavelengths. Therefore, qualitative analysis can be carried out according to the wavelength of the characteristic light; when the contents of elements are different, the intensities of the emitted characteristic light are also different, and based on this, quantitative analysis can be carried out to obtain the contents of the corresponding elements.

[0209] (3) Testing method for the specific surface area of the positive electrode material:

[0210] The specific surface area of the positive electrode material was measured by the method of adsorbing gas. Specifically, Micromeritics TristarⅡ was used to conduct N2 adsorption tests and calculate the adsorption amount values at different equilibrium pressures, obtaining the isothermal adsorption curve and then calculating the specific surface area of the positive electrode material.

[0211] (4) Electrochemical performance test:

[0212] Take 0.8 g of the positive electrode material, 0.1 g of conductive carbon black, and 0.1 g of polyvinylidene fluoride and put them into a ball milling tank. Add 15 mL of N-methylpyrrolidone and ball mill to form a uniform slurry. Then, coat it evenly on the aluminum foil and vacuum dry it at 110 °C for 12 h to obtain the positive electrode sheet. Cut the dried sheet into circular pieces with a diameter of 15 mm. Assemble and seal it in a glove box according to the order of positive electrode case, electrode sheet, electrolyte (EC / DMC / EMC volume ratio 1:1:1, LiPF6 concentration is 1 mol / L), separator (Celgard PP / PE / PP three-layer composite membrane), lithium sheet, electrolyte, nickel foam, and negative electrode case to obtain a button cell, and let it stand for 24 h. Then, put the obtained cell into a constant temperature oven for testing.

[0213] Use the LAND battery test system to conduct discharge capacity (0.1C / 0.5C / 1C) and first-cycle charge-discharge efficiency performance tests at 25 °C and 3.0 V - 4.3 V. The reference capacity is set to 200 mA / g, and 1C corresponds to a current density of 200 mA / g.

[0214] The above test results are shown in Table 1 and Table 2.

[0215] Table 1 Performance test results of the positive electrode materials in the examples and comparative examples

[0216]

[0217] Table 2 Electrochemical performance test results of the positive electrode materials prepared in the examples and comparative examples

[0218]

[0219]

[0220] According to the test results in Table 1 and Table 2, it can be seen that in this application, by controlling the surface structure stability coefficient ε between 0.5 and 1.5 and the residual alkali conversion coefficient ξ of the positive electrode material between 0.15 and 0.4, the influence degree of water vapor on the positive electrode material can be reduced, the side reaction between the positive electrode material and water vapor can be reduced, the surface structure stability of the positive electrode material can be improved, and then the occurrence of side reactions on the surface of the positive electrode material can be effectively reduced, and the capacity and cycle stability of the positive electrode material can be improved.

[0221] According to the test results of Examples 1 to 11, it can be seen that in this application, by controlling the temperature and pressure during the primary sintering process, and simultaneously controlling the pressure of the sintering system to increase in a gradient manner during the heating process of the primary sintering, it is possible to discharge water vapor as much as possible in the low-temperature stage of the sintering process. Furthermore, it can reduce the side reaction between unreacted lithium and water vapor during the primary sintering process, reduce the residual alkali content on the surface of the matrix material, and thus improve the surface structure stability of the cathode material, as well as the capacity and cycling performance of the cathode material.

[0222] Figure 2 This is a graph showing the relationship between the surface structure stability coefficient ε and the capacity of the cathode material provided by this application, as Figure 2 shown, the capacity of the cathode material shows a downward trend as the surface structure stability coefficient ε increases.

[0223] Figure 3 This is a graph showing the relationship between the surface structure stability coefficient ε and the room temperature cycling of the cathode material provided by this application; Figure 4 This is a graph showing the relationship between the surface structure stability coefficient ε and the high temperature cycling of the cathode material provided by this application; as Figure 3 and Figure 4 shown, the cycling capacity retention rate of the cathode material shows a downward trend as the surface structure stability coefficient ε increases.

[0224] Figure 5 This is a graph showing the relationship between the residual alkali conversion coefficient ξ and the capacity of the cathode material provided by the embodiment of this application; as Figure 5 shown, the capacity of the cathode material shows an upward trend as the residual alkali conversion coefficient ξ increases.

[0225] Figure 6 This is a graph showing the relationship between the residual alkali conversion coefficient ξ and the room temperature cycling of the cathode material provided by the embodiment of this application; Figure 7 This is a graph showing the relationship between the residual alkali conversion coefficient ξ and the high temperature cycling of the cathode material provided by the embodiment of this application; as Figure 6 and Figure 7 shown, the cycling capacity retention rate of the cathode material shows an upward trend as the residual alkali conversion coefficient ξ increases.

[0226] Comparing the test data of Example 1, Example 5, Example 6, and Example 7, it can be seen that during the primary sintering process, as the lithium source addition amount decreases, the residual alkali content (α LH +α LC ) on the surface of the cathode material also decreases accordingly. Furthermore, it can reduce the value of the surface structure stability coefficient ε of the cathode material and improve the cycling performance of the cathode material. However, as the lithium source addition amount decreases, γ in the cathode material Li / MeIt will decrease. The amount of lithium ions that can be embedded and de-embedded in the cathode material decreases, which in turn leads to a decrease in the capacity of the cathode material. This shows that appropriately controlling the lithium ratio during the first firing is beneficial to improving the surface structure stability of the cathode material, and can also ensure that there are sufficient lithium ions in the cathode material to achieve the stable embedding and de-embedding of lithium ions during the cycling process of the cathode material, and ensure the normal performance of the lithium ion capacity and cycling performance.

[0227] According to the test data of Example 1 and Comparative Example 1, it can be seen that in Comparative Example 1, no dopant was added during the first sintering, and the crystallization rate of lithium ions inside the matrix material was slow, resulting in an increase in the amount of unreacted lithium during the sintering process. At the same time, during the heating process of the first sintering, the pressure of the sintering system showed a gradient decrease. Therefore, it was difficult to discharge water vapor in the low-temperature section of the sintering process, resulting in a large amount of water vapor entering the high-temperature section of the sintering process. These water vapors underwent side reactions with the unreacted lithium during the sintering process in the high-temperature section, resulting in an increase in the residual alkali content (α LH +α LC ) on the material surface, an increase in the value of the surface structure stability coefficient ε of the cathode material. At the same time, it was difficult to convert the excessive residual alkali on the material surface, and the value of the residual alkali conversion coefficient ξ of the material decreased, the surface structure stability of the cathode material decreased, and the side reactions on the material surface increased, which in turn led to a decrease in the capacity and cycling performance of the material.

[0228] According to the test data of Example 1 and Comparative Example 1, it can be seen that in Comparative Example 2, the pressure of the sintering system showed a constant pressure state during the heating process of the first sintering. Therefore, it was difficult to discharge water vapor in the low-temperature section of the sintering process, resulting in a large amount of water vapor entering the high-temperature section of the sintering process. These water vapors underwent side reactions with the unreacted lithium during the sintering process in the high-temperature section, resulting in an increase in the residual alkali content (α LH +α LC ) on the material surface, an increase in the value of the surface structure stability coefficient ε of the cathode material. At the same time, it was difficult to convert the excessive residual alkali on the material surface, and the value of the residual alkali conversion coefficient ξ of the material decreased, the surface structure stability of the cathode material decreased, and the side reactions on the material surface increased, which in turn led to a decrease in the capacity and cycling performance of the material.

Claims

1. A cathode material, characterized in that, The chemical general formula of the positive electrode material is LiNi a Co b Mn c M d O2, where 0.7 < a < 0.98, 0 < b < 0.3, 0 < c < 0.3, 0 < d ≤ 0.01, a + b + c = 1, and M is a doping element; The mass content of LiOH in the positive electrode material is α LH wt%, the mass content of Li2CO3 in the positive electrode material is α LC wt%, the molar ratio of Li to all metals Me other than Li in the positive electrode material is γ Li / Me , the specific surface area of the positive electrode material is β m 2 / g; the surface structure stability coefficient of the positive electrode material is ε, 0.5 ≤ ε ≤ 1.

5.

2. A cathode material, characterized in that, The chemical general formula of the positive electrode material is LiNi a Co b Mn c M d O2, where 0.7 < a < 0.98, 0 < b < 0.3, 0 < c < 0.3, 0 < d ≤ 0.01, a + b + c = 1, and M is a doping element; The acid-base potentiometric titration test is carried out on the positive electrode material by using a potentiometric titrator and hydrochloric acid with a concentration of 0.02 mol / L, and a curve graph of the relationship between the differential value dE / dV obtained by differentiating the potential E with respect to the consumed volume V of hydrochloric acid and the potential E is obtained. In the curve graph of the relationship between the differential value dE / dV and the potential E, the positive electrode material has a first characteristic peak in the potential E range of -200 mV to -50 mV, the peak area of the first characteristic peak is A, the positive electrode material has a second characteristic peak between the potential E of 120 mV and 250 mV, and the peak area of the second characteristic peak is B; there is at least one characteristic peak in the potential E range of -50 mV to 120 mV, and the sum of the peak areas of the at least one characteristic peak is C, and the residual alkali conversion coefficient of the positive electrode material is ξ. 0.2 ≤ ξ ≤ 0.

35.

3. The cathode material according to any one of claims 1 or 2, characterized in that, The positive electrode material includes at least one of the following characteristics: (1) The doping element M includes at least one of B, P, S, F, La, Sr, Ti, Al, Zr, Y, Ba, Mg, Nb, Mo, W, and V; (2) The mass content of LiOH in the positive electrode material is α LH wt%, 0.1 ≤ α LH ≤ 1.0; (3) The mass content of Li2CO3 in the positive electrode material is α LC wt%, 0.1 ≤ α LC ≤ 1.0; (4) The molar ratio of Li to all metals Me other than Li in the positive electrode material is γ Li / Me , 0.95 < γ Li / Me < 1.05; (5) The specific surface area of the positive electrode material is β m 2 / g, where 0.2 < β < 1.5; (6) The peak area of the first characteristic peak is A, where 2000 ≤ A ≤ 200000; (7) The peak area of the second characteristic peak is B, where 2000 ≤ B ≤ 200000; (8) The sum of the peak areas of the at least one characteristic peak is C, where 2000 ≤ C ≤ 200000.

4. A method for preparing a cathode material, characterized in that, It includes the following steps: Performing a primary sintering treatment on a mixture containing a nickel-cobalt-manganese-based precursor, a lithium source, and a dopant containing a metal element in an oxygen-containing atmosphere to obtain a matrix material; the temperature of the primary sintering treatment is 200°C to 900°C, and the pressure during the primary sintering treatment increases in a gradient manner, with the pressure range being 3 Pa to 13 Pa; Performing a secondary sintering treatment on the matrix material and a coating agent to obtain a positive electrode material.

5. The preparation method according to claim 4, characterized in that, The chemical formula of the nickel-cobalt-manganese-based precursor is Ni a Co b Mn c (OH)2, where 0.7 < a < 0.98, 0 < b < 0.3, 0 < c < 0.3, and a + b + c = 1.

6. The preparation method according to claim 4, wherein, The preparation method includes at least one of the following characteristics: (1) The mass content of the metal element in the nickel-cobalt-manganese-based precursor is 60.5 wt% to 63.5 wt%; (2) The mass ratio of the nickel-cobalt-manganese-based precursor, the lithium source, and the dopant containing a metal element is 1:(1.0 to 1.05):(0 to 0.01); (3) The lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate, and lithium acetate; (4) The dopant containing a metal element includes at least one of Nb2O5, Nb2O3, MoO3, WO2, V2O5, V2O3, Sr(OH)2, SrO, TiO2, Al2O3, Al(OH)3, ZrO2, Zr(OH)4, Y2O3, BaO, MgO, and Mg(OH)2; (5) The mixing conditions for obtaining the mixture are: dry mixing at 10°C to 50°C for 0.3 h to 2 h; (6) The mass content of oxygen in the oxygen-containing atmosphere is ≥ 95%.

7. The preparation method according to claim 4, characterized in that, The primary sintering treatment includes a first stage, a second stage, and a third stage. The preparation method includes at least one of the following characteristics: (1) The first stage includes: heating the mixture from 200 °C to 550 °C within 2 h to 5 h, controlling the pressure P1 to be 7 Pa to 11 Pa, wherein the input amount of the oxygen-containing atmosphere is controlled to be 10 m 3 / h to 30 m 3 / h, and controlling the exhaust gas volume of the reaction system to be 10% to 30%; (2) The second stage includes: heating the mixture from 550 °C to 700 °C within 2 h to 5 h, controlling the pressure P2 to be 8 Pa to 12 Pa, wherein the input amount of the oxygen-containing atmosphere is controlled to be 20 m 3 / h to 30 m 3 / h, and controlling the exhaust gas volume of the reaction system to be 10% to 20%; (3) The third stage includes: sintering the mixture at 700°C to 900°C for 5 h to 10 h, controlling the pressure P3 to be 9 Pa to 13 Pa, wherein the input amount of the oxygen-containing atmosphere is controlled to be 20 m 3 / h to 30 m 3 / h.

8. The preparation method according to claim 4, characterized in that, The preparation method includes at least one of the following characteristics: (1) The average particle size D of the matrix material 50 is 9 μm to 12 μm; (2) The coating agent includes at least one of La(NO3)3·6H2O, NH4F, NH4HF2, (NH4)3PO4, (NH4)2HPO4, (NH4)2MoO4, (NH4)2SO4, NH4HSO4, (NH4)6W7O 24 ·6H2O, (NH4)3PW 12 O 40 ·3H2O, Zr(SO4)2·4H2O, H 28 N6O 41 W 12 , WO3, Al2O3 and Al(OH)3; (3) The mass ratio of the matrix material to the coating agent is 1:(0.001 to 0.05); (4) The secondary sintering treatment is carried out in an oxygen-containing atmosphere; (5) The secondary sintering treatment is carried out in an oxygen-containing atmosphere, and the mass content of oxygen in the oxygen-containing atmosphere is ≥ 95%; (6) The temperature of the secondary sintering treatment is 200°C to 700°C; (7) The time of the secondary sintering treatment is 10 h to 20 h.

9. The preparation method according to claim 4, characterized in that, Before performing the secondary sintering treatment on the matrix material and the coating agent, the preparation method further includes: dissolving the coating agent in water to form a coating solution; performing a coating treatment on the matrix material with the coating solution by an atomization method; it satisfies at least one of the following characteristics: (1) The pressure of the atomization is 0 Mpa to 0.05 Mpa; (2) The coating treatment is carried out under a stirring state, and the stirring frequency is controlled at 20 Hz to 50 Hz; (3) The temperature of the coating treatment is 150°C to 250°C; (4) The time of the coating treatment is 3 h to 8 h.

10. A lithium-ion battery, characterized in that, The lithium ion battery includes the positive electrode material described in any one of claims 1 to 3 or the positive electrode material prepared by the preparation method described in any one of claims 4 to 9.

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