A ternary positive electrode active material, a preparation method and application thereof

Abstract

The application belongs to the technical field of lithium batteries, and particularly relates to a ternary positive electrode active material and a preparation method and application thereof. 1.05 Ni a Co b Mn c M (1‑a‑b‑c) O2, wherein 0.4 < a < 0.8, 0 < b < 0.3, 0 < c < 0.5, a + b + c < 1, and M is a doping element selected from one or more of Zr, Sr, Y and Al. The lithium ions in the ternary positive electrode active material are more uniformly distributed, the capacity is higher, and the rate performance and cycle stability are more excellent.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to a ternary cathode active material, its preparation method, and its application. Background Technology

[0002] Lithium nickel manganese cobalt oxide (NCM) ternary cathode materials possess advantages such as structural stability, high capacity, and good cycle performance, making them one of the fastest-growing cathode materials for lithium-ion batteries in recent years, and they are widely used in the field of new energy vehicles. The comprehensive performance requirements for NCM ternary cathode materials are also increasing, therefore, the modification of ternary cathode materials has become a current research hotspot. In existing technologies, modification through internal doping and surface coating of ternary materials easily leads to uneven coating and doping, which not only fails to effectively improve the performance of NCM ternary cathode materials but also results in high costs and low efficiency.

[0003] Currently, solid-state coating of oxides is commonly used as a stabilizing coating layer, such as the solid-state coating of sodium silicate material used in patent CN201910301581.5. The coating layer formed by the oxide solid-state method has an island-like structure and is uneven, which cannot effectively suppress the electrode / electrolyte interface reaction. Furthermore, in the existing technology for preparing lithium nickel cobalt manganese oxide, the precursor is usually mixed with lithium carbonate and then directly sintered at a high temperature of around 940℃. The product is then crushed by an air jet mill and coated again to obtain a single-crystal cathode material. Using this method, lithium ions tend to be unevenly distributed within the precursor, leading to a decrease in product capacity and rate performance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a ternary cathode active material, its preparation method, and its application. The cathode active material possesses higher capacity and superior rate performance.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a ternary cathode active material, the cathode active material comprising a matrix and a coating layer covering the surface of the matrix; the coating layer is a metal oxide.

[0007] In the above-mentioned ternary cathode active material, as a preferred embodiment, the metal oxide is at least one selected from titanium oxide, aluminum oxide, tungsten oxide, magnesium oxide, and cobalt oxide; preferably, the metal element in the coating layer accounts for 0.07% to 0.2% of the mass of the ternary cathode active material (e.g., 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%).

[0008] In the above-mentioned ternary cathode active material, as a preferred embodiment, the matrix is ​​Li. 1.05 Ni a Co b Mn c M (1-a-b-c) O2, where 0.4 < a < 0.8, 0 < b < 0.3, 0 < c < 0.5, a + b + c < 1, and M is a dopant element selected from one or more of Zr, Sr, Y, and Al.

[0009] The matrix of the ternary cathode active material of the present invention is lithium nickel cobalt manganese oxide doped with metal elements. The doped metal elements are at least one of zirconium, strontium, yttrium and aluminum. After doping, the particle size of the primary particles of the material becomes smaller (the doping element replaces part of the nickel cobalt manganese metal element position). After the particle size is reduced, the lithium ion insertion and extraction path becomes shorter during charging and discharging, making it easier to insert and extract. Therefore, the discharge specific capacity of the material increases after doping.

[0010] Secondly, the present invention provides a method for preparing a ternary cathode active material, the method comprising the following steps in sequence:

[0011] S1. Mix nickel cobalt manganese hydroxide (precursor), lithium hydroxide and additives and pre-calcine to obtain pre-calcine material;

[0012] S2. Mix the pre-calcined material obtained in step S1 with lithium carbonate and sinter once to obtain a first-calcined material.

[0013] S3. The sintered material (i.e., the matrix) obtained in step S2 is mixed with the coating agent and subjected to secondary sintering to obtain the ternary positive electrode active material.

[0014] In this invention, the pre-sintering treatment allows the additives to be fully mixed and uniformly distributed with the precursor (i.e., nickel-cobalt-manganese hydroxide). During the first sintering stage, the metal elements are uniformly doped into the lithium nickel-cobalt-manganese oxide material, replacing some of the nickel-cobalt-manganese metal element positions. The particle size of the primary particles in the doped material becomes smaller, thus shortening the lithium-ion insertion / extraction path during charging and discharging, making it easier to insert and extract, thereby increasing the discharge specific capacity of the doped material.

[0015] In the above preparation method, as a preferred embodiment, the chemical formula of the nickel-cobalt-manganese hydroxide is Ni x Co y Mn z (OH)2, where 0.6≤x<1, 0<y≤0.2, 0<z≤0.3, x+y+z=1.

[0016] In the above preparation method, as a preferred embodiment, the average particle size D of the nickel-cobalt-manganese hydroxide is... 50It is 3-4 μm.

[0017] In the above preparation method, as a preferred embodiment, in step S1, the molar ratio of lithium in the lithium hydroxide to the total amount of nickel, cobalt and manganese in the nickel-cobalt-manganese hydroxide is 0.2 to 0.5:1 (e.g., 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1).

[0018] In the above preparation method, as a preferred embodiment, the temperature of the pre-firing treatment in step S1 is 450-550℃ (e.g., 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃); preferably, the holding time of the pre-firing treatment is 4-6 hours (e.g., 4.5h, 5h, 5.5h); preferably, the pre-firing treatment is carried out in an air atmosphere; preferably, the pre-firing treatment is heated to 450-550℃ (e.g., 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃) at a heating rate of 2-4℃ / min (e.g., 2.5℃ / min, 3℃ / min, 3.5℃ / min) and held for 4-6 hours (e.g., 4.5h, 5h, 5.5h).

[0019] In this invention, nickel cobalt manganese hydroxide, lithium hydroxide, and additives are first mixed and pre-calcined. This process ensures more uniform mixing of the raw materials, facilitating better dispersion of the additives within the lithium cobalt manganese hydroxide during the first calcination step. Furthermore, pre-calcination increases the loose packing density and the amount of material packed in the first calcination. In a preferred embodiment, the pre-calcination temperature is close to the melting point of lithium hydroxide. If the pre-calcination temperature is too low, the lithium hydroxide will not melt; if the temperature is too high, the nickel cobalt manganese hydroxide will begin to dehydrate before the lithium penetrates into it, potentially causing micropores within the hydroxide, forming a salt-rock phase, and resulting in deteriorated electrical properties.

[0020] In the above preparation method, as a preferred embodiment, in step S1, the average particle size of the lithium hydroxide is 300-500 μm; preferably, the additive is at least one of zirconium oxide, strontium oxide, yttrium oxide, and aluminum oxide; preferably, in the ternary cathode active material, the mass content of the metal elements (zirconium, strontium, yttrium, and aluminum) introduced by the additive is 0.18-0.22% (e.g., 0.19%, 0.20%, and 0.21%).

[0021] In the above preparation method, as a preferred embodiment, in step S2, the molar ratio of lithium to the total amount of nickel, cobalt and manganese in the calcined material is (1.03 to 1.06):1 (e.g., 1.04:1, 1.05:1).

[0022] In the above preparation method, as a preferred embodiment, in step S2, the temperature of the first sintering is 930-960℃ (e.g., 935℃, 940℃, 945℃, 950℃, 955℃); preferably, the holding time of the first sintering is 10-14h (e.g., 11h, 12h, 13h); preferably, the first sintering is carried out in an air atmosphere; preferably, the first sintering is heated to 930-960℃ (e.g., 935℃, 940℃, 945℃, 950℃, 955℃) at a heating rate of 2-4℃ / min (e.g., 2.5℃ / min, 3℃ / min, 3.5℃ / min) and held for 10-14 hours (e.g., 11h, 12h, 13h).

[0023] In the above preparation method, as a preferred embodiment, in step S3, the sintered material is pulverized and sieved, then mixed with the coating agent for secondary sintering; preferably, the pulverization method is air jet milling; preferably, the temperature of the secondary sintering is 430-470℃ (e.g., 440℃, 450℃, 460℃); preferably, the holding time of the secondary sintering is 8-12h (e.g., 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h); preferably, the secondary sintering is carried out in an air atmosphere. The secondary sintering is carried out in a manner that, preferably, involves heating the temperature to 430–470°C (e.g., 440°C, 450°C, 460°C) at a heating rate of 2–4°C / min (e.g., 2.5°C / min, 3°C / min, 3.5°C / min) and holding the temperature for 8–12 hours (e.g., 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h); preferably, the coating agent is a metal oxide; preferably, the metal oxide is at least one of titanium oxide, aluminum oxide, tungsten oxide, magnesium oxide, and cobalt oxide.

[0024] In the above preparation method, as a preferred embodiment, in step S3, the coating agent is titanium oxide and aluminum oxide, the mass content of titanium in the ternary positive electrode active material is 0.07-0.09%, and the mass content of aluminum in the ternary positive electrode active material is 0.09-0.11%.

[0025] Alternatively, the coating agent is tungsten oxide, and the tungsten content in the ternary cathode active material is 0.08–0.2% by mass; or, the coating agent is magnesium oxide, and the magnesium content in the ternary cathode active material is 0.08–0.2% by mass; or, the coating agent is cobalt oxide, and the cobalt content in the ternary cathode active material is 0.08–0.2% by mass.

[0026] Within the secondary sintering temperature range of the present invention, the coating agent can be better and more uniformly and tightly bonded to the substrate surface, while preventing the coating agent from entering the interior of the substrate.

[0027] Thirdly, the present invention provides the application of the ternary cathode active material described in the first aspect or the ternary cathode active material prepared by the preparation method described in the second aspect in lithium battery cathode materials.

[0028] Fourthly, a positive electrode material, the positive electrode material comprising the ternary positive electrode active material described in the first aspect or the ternary positive electrode active material prepared by the preparation method described in the second aspect, as well as a conductive agent and a binder.

[0029] Fifthly, a lithium-ion battery, the lithium-ion battery comprising the positive electrode material described in the third aspect above, the battery further comprising a battery casing and a positive electrode, a separator and a negative electrode located within the battery casing, the positive electrode comprising a positive electrode current collector and a positive electrode material located on the positive electrode current collector.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects:

[0031] 1. The ternary cathode active material prepared by this invention exhibits superior electrical performance. In a preferred embodiment of this invention, two lithium salts are used: coarse-particle lithium hydroxide and lithium carbonate. Lithium hydroxide has a low melting point of 471°C, while lithium carbonate has a high melting point of 723°C. This invention first mixes coarse-particle lithium hydroxide with a precursor (nickel-cobalt-manganese hydroxide) and pre-calcines it, which pre-lithiates the precursor, allowing lithium ions to diffuse into the central region of the precursor and reducing the formation of micropores and rock salt phases during the preparation process. This results in a more uniform lithium ion distribution in the final cathode active material, leading to higher capacity, better rate performance, and improved cycle stability.

[0032] 2. The preparation method of the present invention can also reduce production costs. After pre-calcination at 500°C, the loose density of the pre-calcined material is higher than that of the mixture of precursor and lithium carbonate. The increased loose density during the first sintering increases the amount of material that can be packed in one sintering. The pre-calcination process is shorter and at a lower temperature. Overall, the preparation method of the present invention can reduce costs by about 30%. Attached Figure Description

[0033] Figure 1 The image shows the SEM image of the ternary cathode active material prepared in Example 1. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0035] The embodiments of the present invention are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and processes are given. However, the protection scope of the present invention is not limited to the following embodiments. The process parameters in the following embodiments that do not specify specific conditions are generally in accordance with conventional conditions.

[0036] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0037] In this invention, unless otherwise specified and / or stated, all values ​​relating to component amounts are in parts by weight throughout. Process parameters in the following examples that do not specify particular conditions are generally performed under conventional conditions.

[0038] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0039] Example 1

[0040] (1) Use commercially available nickel-cobalt-manganese hydroxide Ni 0.6 Co 0.1 Mn 0.3 (OH)₂ and coarse-particle lithium hydroxide, nickel-cobalt-manganese hydroxide D 50 The average particle size of lithium hydroxide is 300-500 μm, with a particle size of 3.4-4.0 μm. The nickel, cobalt, and manganese atoms are mixed evenly with the lithium atoms in a ratio of 1:0.4. Zirconia is added as an additive (the mass content of zirconium in the finished ternary cathode active material obtained in this example is 0.2%). The material is heated to 500°C at 3°C / min under air conditions, calcined at 500°C for 5 hours, and then cooled to room temperature to obtain the pre-calcined material.

[0041] (2) The pre-calcined material obtained in step (1) is mixed with lithium carbonate powder and sintered once to obtain a first-calcined material. The ratio of the total number of nickel, cobalt and manganese atoms to the number of lithium atoms in the first-calcined material is 1:1.05. The first-calcined material has a loading of 5.0 kg (of which 3.968 kg is pre-calcined material and 3.935 kg is corresponding nickel-cobalt-manganese hydroxide). The parameters for the first sintering are: heating to 945℃ at 3℃ / min under air conditions, calcining at 945℃ for 12 hours, then cooling to room temperature and crushing by air jet milling to control the particle size D of the first-calcined material. 50 =3.0~3.5μm.

[0042] (3) The calcined material Li obtained in step (2) 1.05 Ni 0.6 Co 0.1 Mn 0.3 Zr 0.002 O2 (matrix) and coating agents titanium oxide and aluminum oxide are mixed for 15 min, wherein the amount of titanium added is 0.08% (the mass content of titanium in the finished ternary positive electrode active material obtained in this embodiment) and the amount of aluminum added is 0.1% (the mass content of aluminum in the finished ternary positive electrode active material obtained in this embodiment). Under air conditions, the temperature is increased to 450°C at 3°C / min, and heat-treated at 450°C for 10 hours. Then, it is cooled to room temperature and sieved through a 350-mesh sieve to obtain the ternary positive electrode active material.

[0043] The lithium tricarboxylate cathode active material prepared in this embodiment was analyzed by SEM, and the results are shown below. Figure 1 As shown.

[0044] Battery preparation: 90wt% of the ternary positive electrode active material, 5wt% of PVDF, and 5wt% of SuperP obtained in Example 1 were uniformly mixed, then slurry-treated, coated on aluminum foil, dried, and rolled to obtain the positive electrode sheet. The positive electrode sheet was assembled into a CR2032 coin cell. The negative electrode was a lithium sheet, the separator was a 16μm thick ceramic membrane, and the electrolyte was 1.0mol / L LiPF6 (solvents were EC, DMC, and EMC in a volume ratio of 1:1:1). The coin cell's performance at room temperature under conditions of 3.0–4.4V was tested.

[0045] Example 2

[0046] (1) Use commercially available nickel-cobalt-manganese hydroxide Ni 0.6 Co 0.1 Mn 0.3 (OH)₂ and coarse-particle lithium hydroxide, nickel-cobalt-manganese hydroxide D 50The average particle size of lithium hydroxide is 300-500 μm, with a particle size of 3.4-4.0 μm. The nickel, cobalt, and manganese atoms are mixed evenly with a ratio of 1:0.3 to the number of lithium atoms. Zirconia (the mass content of zirconium in the finished ternary cathode active material obtained in this example is 0.2%) is added. The material is heated to 500°C at 3°C / min under air conditions, calcined at 500°C for 5 hours, and then cooled to room temperature to obtain the pre-calcined material.

[0047] (2) The pre-calcined material obtained in step (1) of this embodiment is mixed with lithium carbonate powder and sintered once to obtain a first-calcined material. The ratio of the total number of nickel, cobalt and manganese atoms to the number of lithium atoms in the first-calcined material is 1:1.05; the first-calcined material has a loading of 5.0 kg; the parameters for the first sintering are: under air conditions, the temperature is increased to 945℃ at 3℃ / min, calcined at 945℃ for 12 hours, and then cooled to room temperature and crushed by air jet milling to control the particle size D of the first-calcined material. 50 =3.0~3.5μm.

[0048] (3) The Li obtained in step (2) of this embodiment is calcined into a single material. 1.05 Ni 0.6 Co 0.1 Mn 0.3 Zr 0.002 O2 (matrix) and coating agents titanium oxide and aluminum oxide are mixed for 15 min, wherein the amount of titanium added is 0.08% (the mass content of titanium in the finished ternary positive electrode active material obtained in this embodiment) and the amount of aluminum added is 0.1% (the mass content of aluminum in the finished ternary positive electrode active material obtained in this embodiment). Under air conditions, the temperature is increased to 450°C at 3°C / min, and heat-treated at 450°C for 10 hours. Then, it is cooled to room temperature and sieved through a 350-mesh sieve to obtain the ternary positive electrode active material.

[0049] Example 3

[0050] (1) Use commercially available nickel-cobalt-manganese hydroxide Ni 0.6 Co 0.1 Mn 0.3 (OH)₂ and coarse-particle lithium hydroxide, nickel-cobalt-manganese hydroxide D 50 The average particle size of lithium hydroxide is 300-500 μm, with a particle size of 3.4-4.0 μm. The nickel, cobalt, and manganese atoms are mixed evenly at a ratio of 1:0.5 to the number of lithium atoms. Zirconia (the mass content of zirconium in the finished ternary cathode active material obtained in this example is 0.2%) is added as an additive. The material is heated to 500°C at 3°C / min under air conditions, calcined at 500°C for 5 hours, and then cooled to room temperature to obtain the pre-calcined material.

[0051] (2) The pre-calcined material obtained in step (1) of this embodiment is mixed with lithium carbonate powder and sintered once. A first-calcined material is obtained, in which the ratio of the total number of nickel, cobalt and manganese atoms to the number of lithium atoms is 1:1.05; the first-calcined material has a pot weight of 5.0 kg; the parameters for the first sintering are: under air conditions, the temperature is increased to 945℃ at 3℃ / min, calcined at 945℃ for 12 hours, and then cooled to room temperature and crushed by air jet milling to control the particle size D of the first-calcined material. 50 =3.0~3.5μm.

[0052] (3) The Li obtained in step (2) of this embodiment is calcined into a single material. 1.05 Ni 0.6 Co 0.1 Mn 0.3 Zr 0.002 O2 (matrix) and coating agents titanium oxide and aluminum oxide are mixed for 15 min, wherein the amount of titanium added is 0.08% (the mass content of titanium in the finished ternary positive electrode active material obtained in this embodiment) and the amount of aluminum added is 0.1% (the mass content of aluminum in the finished ternary positive electrode active material obtained in this embodiment). Under air conditions, the temperature is increased to 450°C at 3°C / min, and heat-treated at 450°C for 10 hours. Then, it is cooled to room temperature and sieved through a 350-mesh sieve to obtain the ternary positive electrode active material.

[0053] Comparative Example 1

[0054] (1) Use commercially available nickel-cobalt-manganese hydroxide Ni 0.6 Co 0.1 Mn 0.3 (OH)₂ and lithium carbonate, nickel cobalt manganese hydroxide D 50 The particle size was 3.4–4.0 μm. Nickel, cobalt, and manganese atoms were mixed uniformly at a ratio of 1:1.05 to lithium atoms. Zirconia (the zirconium content in the finished ternary cathode active material prepared in this comparative example was 0.2%) was added. The initial sintering load was 4.0 kg (including 2.810 kg of nickel-cobalt-manganese hydroxide). The parameters for the initial sintering were: heating to 945 °C at a rate of 3 °C / min under oxygen-air conditions, calcining at 945 °C for 12 hours, then cooling to room temperature and crushing by air jet milling to control the particle size D of the initial sintered material. 50 =3.0~3.5μm.

[0055] (2) The calcined material (matrix) obtained in step (1) of this comparative example is mixed with the coating agents titanium oxide and aluminum oxide for 15 min, wherein the amount of titanium added is 0.08% (the mass content of titanium in the finished ternary positive electrode active material obtained in this example) and the amount of aluminum added is 0.1% (the mass content of aluminum in the finished ternary positive electrode active material obtained in this example). Under air conditions, the temperature is raised to 450°C at 3°C / min, and heat-treated at 450°C for 10 hours. Then, it is cooled to room temperature and sieved through a 350-mesh sieve to obtain the ternary positive electrode active material.

[0056] Comparative Example 2

[0057] This comparative example is basically the same as Example 1, except that zirconium oxide is not added in this comparative example.

[0058] Comparative Example 3

[0059] This comparative example is basically the same as Example 1, except that the heat preservation temperature of the pre-firing treatment in this comparative example is 700°C.

[0060] The pre-calcination temperature used in this comparative example was too high. Before lithium could penetrate into the nickel-cobalt-manganese hydroxide, the nickel-cobalt-manganese hydroxide began to dehydrate, resulting in micropores inside the nickel-cobalt-manganese hydroxide, forming a salt rock phase, and deteriorating its electrical properties.

[0061] Test case

[0062] Following the battery preparation method described in Example 1, tungsten cathode active materials prepared in Examples 1-3 and Comparative Examples 1-3 were used to prepare coin cells, and their electrical performance was tested. The test results are shown in Tables 1 and 2 below.

[0063] The method for testing the electrical performance of button cells at different rates is as follows: the cells are charged and discharged at different rates under the conditions of 25℃ and voltage range of 2.8~4.4V. The results are shown in Table 1 below.

[0064] The test method for the capacity retention rate of button cell batteries during room temperature cycle discharge is as follows: the battery is charged and discharged at 1.0C under the conditions of voltage range: 2.8~4.4V and 25℃. The results are shown in Table 2 below.

[0065] Table 1. Electrical performance of button cells at different rate

[0066]

[0067] Table 2. Capacity Retention Rate of Button Cells During Room Temperature Cyclic Discharge

[0068] 10 Cyc (%) 30 Cyc (%) 50 Cyc (%) 70 Cyc (%) 100 Cyc (%) Example 1 99.5 98.6 98.1 97.3 96.8 Example 2 99.4 98.2 97.6 96.3 95.8 Example 3 99.4 98.6 97.9 97.3 96.9 Comparative Example 1 99.1 97.9 96.4 95.8 94.9 Comparative Example 2 99.1 97.8 96.1 95.3 94.2 Comparative Example 3 99.3 98.0 97.2 96.0 94.8

[0069] Comparing the pre-calcination temperature of 500℃ in Example 1 with that of 700℃ in Comparative Example 3, increasing the pre-calcination temperature resulted in a decrease in cycle performance. The electrical performance of the pre-calcined lithium ratio of 0.4 in Example 1 and 0.5 in Example 3 was similar. The electrical performance of the pre-calcined lithium ratio of 0.3 in Example 2 was better than that of Comparative Example 1, which used a process entirely with lithium carbonate, but worse than that of Examples 1 and 3. This indicates that when coarse-particle lithium hydroxide is used for pre-calcination with a lithium ratio of 0.4, the material performance is significantly improved. Further increasing the proportion of lithium hydroxide does not significantly improve the performance. This invention uses an appropriate lithium ratio (the molar ratio of lithium element in lithium hydroxide to the total amount of nickel, cobalt, and manganese elements in nickel-cobalt-manganese hydroxide is 0.2-0.5:1) to mix the precursor, coarse-particle lithium hydroxide, and additives for pre-calcination. This not only ensures that lithium ions are evenly distributed in the precursor, but also that the metal elements introduced by the additives are evenly distributed in the precursor. This improves the electrochemical performance of the ternary cathode active material and reduces production costs, which is conducive to large-scale promotion and application.

[0070] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A ternary cathode active material, characterized in that, The positive electrode active material includes a matrix and a coating layer covering the surface of the matrix; the coating layer is a metal oxide. The metal oxide is at least one of titanium oxide, aluminum oxide, tungsten oxide, magnesium oxide, and cobalt oxide; The matrix is ​​Li 1.05 Ni a Co b Mn c M (1-a-b-c) O2, where 0.4 < a < 0.8, 0 < b < 0.3, 0 < c < 0.5, a + b + c < 1, and M is a dopant element selected from one or more of Zr, Sr, Y, and Al; The preparation method of the ternary cathode active material includes the following steps: S1. Mix nickel cobalt manganese hydroxide, lithium hydroxide and additives and pre-calcine to obtain pre-calcine material; The pre-firing temperature is 450~550℃; S2. Mix the pre-calcined material obtained in step S1 with lithium carbonate and sinter once to obtain a first-calcined material. S3. Mix the sintered material obtained in step S2 with the coating agent and perform secondary sintering to obtain the ternary positive electrode active material. In step S1, the average particle size of the lithium hydroxide is 300~500μm.

2. The ternary cathode active material as described in claim 1, characterized in that, The metal elements in the coating layer account for 0.07% to 0.2% of the mass of the ternary cathode active material.

3. The ternary cathode active material as described in claim 1, characterized in that, In step S1, the chemical formula of the nickel-cobalt-manganese hydroxide is Ni x Co y Mn z (OH)2, where 0.6≤x<1, 0<y≤0.2, 0<z≤0.3, x+y+z=1; And / or, in step S1, the average particle size D of the nickel-cobalt-manganese hydroxide 50 It is 3~4μm; And / or, in step S1, the molar ratio of lithium in the lithium hydroxide to the total amount of nickel, cobalt and manganese in the nickel-cobalt-manganese hydroxide is 0.2~0.5:1; And / or, in step S1, the heat preservation time for pre-firing treatment is 4 to 6 hours; And / or, in step S1, the pre-firing process is carried out in an air atmosphere; And / or, in step S1, the pre-firing treatment involves heating the temperature to 450-550°C at a heating rate of 2-4°C / min and holding it at that temperature for 4-6 hours; And / or, in step S1, the additive is at least one of zirconium oxide, strontium oxide, yttrium oxide, and aluminum oxide; And / or, in the ternary cathode active material, the mass content of the metal element introduced by the additive is 0.18~0.22%.

4. The ternary cathode active material as described in claim 1, characterized in that, In step S2, the molar ratio of lithium to the total amount of nickel, cobalt and manganese in the calcined material is (1.03~1.06):1; And / or, in step S2, the temperature of the first sintering is 930~960℃; And / or, in step S2, the holding time for the first sintering is 10~14h; And / or, in step S2, the first sintering is carried out in an air atmosphere; And / or, in step S2, the first sintering is performed by heating to 930-960°C at a heating rate of 2-4°C / min and holding at that temperature for 10-14 hours.

5. The ternary cathode active material as described in claim 1, characterized in that, In step S3, the sintered material is pulverized and sieved, and then mixed with the coating agent for secondary sintering; the pulverization method is air jet milling. And / or, in step S3, the temperature of the secondary sintering is 430~470℃; And / or, in step S3, the holding time for the secondary sintering is 8~12h; And / or, in step S3, the secondary sintering is carried out in an air atmosphere; And / or, in step S3, the secondary sintering is performed by heating to 430-470°C at a heating rate of 2-4°C / min and holding at that temperature for 8-12 hours; And / or, in step S3, the coating agent is a metal oxide, and the metal oxide is at least one of titanium oxide, aluminum oxide, tungsten oxide, magnesium oxide, and cobalt oxide.

6. The ternary cathode active material as described in claim 1, characterized in that, The coating agent is titanium oxide and aluminum oxide, and the mass content of titanium in the ternary cathode active material is 0.07~0.09%, and the mass content of aluminum in the ternary cathode active material is 0.09~0.11%. Alternatively, the coating agent is tungsten oxide, and the tungsten content in the ternary cathode active material is 0.08~0.2% by mass. Alternatively, the coating agent is magnesium oxide, and the mass content of magnesium in the ternary cathode active material is 0.08~0.2%; Alternatively, the coating agent is cobalt oxide, and the mass content of cobalt in the ternary cathode active material is 0.08~0.2%.

7. The application of a ternary cathode active material as described in any one of claims 1-6 in lithium battery cathode materials.

8. A positive electrode material, characterized in that, The positive electrode material includes the ternary positive electrode active material as described in any one of claims 1-6, as well as a conductive agent and a binder.

9. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode material as described in claim 8, and the battery further includes a battery casing and a positive electrode, a separator and a negative electrode located within the battery casing. The positive electrode includes a positive electrode current collector and a positive electrode material located on the positive electrode current collector.

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