Lithium cobalt oxide doped with nickel, cobalt and manganese ternary cathode material, its preparation method and application

Abstract

The present invention relates to the technical field of lithium battery materials, and specifically discloses a lithium cobaltate doped nickel cobalt manganese ternary cathode material, a preparation method thereof and an application. The preparation method comprises the following steps: mixing lithium cobaltate, nickel cobalt manganese ternary precursors with at least two different particle size distributions, lithium carbonate and a first dopant, sintering, and crushing to obtain a first-sintered product; mixing the first-sintered product with a first surface coating material, sintering, and crushing to obtain a second-sintered product; mixing the second-sintered product with a second surface coating material, sintering, and crushing to obtain the lithium cobaltate doped nickel cobalt manganese ternary cathode material. By means of the first-sintering process, the present invention uniformly dopes the lithium cobaltate material into the nickel cobalt manganese ternary cathode material, effectively protects the layered structure of the nickel cobalt manganese ternary cathode material, reduces the mixing of nickel and lithium ions, and improves the cycle stability and safety performance of the material.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery materials, and particularly relates to a lithium cobaltate-doped nickel cobalt manganese ternary cathode material, a preparation method thereof, and an application thereof. Background Art

[0002] The cathode material of a lithium ion battery is one of the key factors determining the battery performance. At present, the mainstream cathode materials for commercial applications include lithium cobaltate, lithium manganate, lithium iron phosphate, nickel cobalt manganese ternary materials, etc. Among them, lithium cobaltate has advantages such as high specific capacity, large tap density, and excellent cycling performance, and is widely used in the fields of mobile communication and portable electronic devices. However, the shortage and high price of cobalt resources limit the large-scale application of lithium cobaltate.

[0003] Nickel cobalt manganese ternary materials are considered to be the key direction for future development due to their advantages such as high energy density and low cost. However, medium and high nickel ternary cathode materials have problems such as poor cycling stability, low tap density, and poor safety performance. The main reason is that the high-valent nickel ions are unstable and prone to structural transformation, and at the same time, nickel ions react with the electrolyte to produce side reactions. Existing technologies usually adopt methods such as surface coating or doping to improve the performance of medium and high nickel ternary materials, but the effect is limited. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide a lithium cobaltate-doped nickel cobalt manganese ternary cathode material, a preparation method thereof, and an application thereof. By means of a one-burning process, the lithium cobaltate material is uniformly doped into the nickel cobalt manganese ternary cathode material, effectively protecting the layered structure of the nickel cobalt manganese ternary cathode material, reducing the mixing of nickel and lithium ions, and improving the cycling stability and safety performance of the material.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] The present invention first provides a preparation method of a lithium cobaltate-doped nickel cobalt manganese ternary cathode material, which includes the following steps:

[0007] S1. Mix lithium cobaltate, nickel cobalt manganese ternary precursors with at least two different particle size distributions, lithium carbonate, and a first dopant, sinter, and crush to obtain a first-burn product;

[0008] S2. Mix the first-burn product with a first surface coating material, sinter, and crush to obtain a second-burn product;

[0009] S3. Mix the second-burn product with a second surface coating material, sinter, and crush to obtain the lithium cobaltate-doped nickel cobalt manganese ternary cathode material.

[0010] As a further improvement of the above solution of the present invention, in step S1, the structural formula of the nickel cobalt manganese ternary precursor is Ni x Coy Mn 1-x-y (OH)2, where 0.5 ≤ x ≤ 0.9 and 0.05 ≤ y ≤ 0.3; The method for preparing the nickel-cobalt-manganese ternary precursor is as follows: Using deionized water as the solvent, nickel nitrate, cobalt nitrate, and manganese nitrate as raw materials, a metal salt solution is prepared according to the molar ratio of nickel element, cobalt element, and manganese element as x:y:1 - x - y. The metal salt solution, NaOH solution, and ammonia water are simultaneously added to a reaction kettle for co-precipitation reaction to obtain a nickel-cobalt-manganese ternary precursor with at least two different particle size distributions.

[0011] As a further improvement of the above solution of the present invention, the nickel-cobalt-manganese ternary precursor includes a nickel-cobalt-manganese ternary precursor with a particle size of D50 = 2 ± 0.2 μm and a nickel-cobalt-manganese ternary precursor with a particle size of D50 = 5 ± 0.2 μm; The mass ratio of lithium cobaltate, the nickel-cobalt-manganese ternary precursor with a particle size of D50 = 2 ± 0.2 μm, and the nickel-cobalt-manganese ternary precursor with a particle size of D50 = 5 ± 0.2 μm is (1 - 1.25):1:(3 - 8).

[0012] As a further improvement of the above solution of the present invention, in step S1, the molar ratio of lithium carbonate to the nickel-cobalt-manganese ternary precursor is 1.05:1; Based on lithium cobaltate, the first dopant includes 400 - 600 ppm of alumina, 100 - 300 ppm of zirconia, and 400 - 600 ppm of lanthanum oxide.

[0013] As a further improvement of the above solution of the present invention, in step S1, the sintering is carried out at 800 - 900 °C for 10 - 12 h in an oxygen atmosphere.

[0014] As a further improvement of the above solution of the present invention, the method for preparing lithium cobaltate is as follows: After mixing cobalt tetroxide, lithium carbonate, and a second dopant, first sinter at 700 - 750 °C for 2 - 4 h in an air atmosphere, then sinter at 1000 - 1045 °C for 8 - 10 h in an air atmosphere, and crush to obtain lithium cobaltate; Among them, based on cobalt tetroxide, the second dopant includes 100 - 300 ppm of alumina, 200 - 400 ppm of magnesia, 400 - 600 ppm of zirconia, 900 - 1200 ppm of yttrium oxide, and 400 - 600 ppm of lanthanum oxide.

[0015] As a further improvement of the above solution of the present invention, in step S2, based on the first sintered product, the first surface coating material includes 100 - 300 ppm of alumina, 200 - 400 ppm of titanium oxide, 400 - 600 ppm of zirconia, and 500 - 700 ppm of lithium niobate; The sintering is carried out at 600 - 700 °C for 6 - 10 h in an oxygen atmosphere.

[0016] As a further improvement of the above solution of the present invention, in step S3, based on the secondary sintering product, the second surface coating material contains 400-700 ppm of boric acid and 100-500 ppm of tungsten oxide; the sintering is carried out in an oxygen atmosphere at 300-400 °C for 4-8 h.

[0017] The present invention also provides a lithium cobalt oxide doped nickel cobalt manganese ternary cathode material, which is prepared by the preparation method as described above.

[0018] The present invention also provides an application of the lithium cobalt oxide doped nickel cobalt manganese ternary cathode material as described above in a lithium battery.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention first sinters lithium cobalt oxide together with nickel cobalt manganese ternary precursors having at least two different particle size distributions, so that lithium cobalt oxide is doped into the interior, surface layer and between particles of the nickel cobalt manganese ternary cathode material, completing the modification of the nickel cobalt manganese ternary material. On the one hand, small particles fill the gaps between large particles, forming a dense packing structure, improving the tap density of the material, thereby enhancing the volumetric energy density of the material. Moreover, small particles can shorten the lithium ion transmission distance, and large particles provide a stable skeleton structure, synergistically improving the rate performance and cycle stability. On the other hand, through the doping of lithium cobalt oxide, the electronic conductivity of the nickel cobalt manganese ternary cathode material can be improved, the cycle performance and rate performance of the nickel cobalt manganese ternary cathode material can be improved, and at the same time, the tap density of the nickel cobalt manganese ternary cathode material can be increased, optimizing the processing performance of the material, stabilizing the layered structure of the nickel cobalt manganese ternary cathode material, reducing the mixing of nickel and lithium ions, and reducing the volume expansion and structural stress caused by lithium ion deintercalation during charge and discharge, prolonging the cycle life. The present invention then performs double-layer coating on the nickel cobalt manganese ternary material with different particle size distributions after doping with lithium cobalt oxide, which can further improve the cycle performance and safety performance of the nickel cobalt manganese ternary cathode material. Description of the Drawings

[0021] Figure 1 It is a schematic diagram of lithium cobalt oxide doped into the nickel cobalt manganese ternary cathode material with different particle sizes in the present invention;

[0022] Figure 2 It is a SEM image of the lithium cobalt oxide doped nickel cobalt manganese ternary cathode material prepared in Example 1;

[0023] Figure 3 It is a SEM image of the lithium cobalt oxide doped nickel cobalt manganese ternary cathode material prepared in Example 2;

[0024] Figure 4 It is a SEM image of the lithium cobalt oxide doped nickel cobalt manganese ternary cathode material prepared in Example 3;

[0025] Figure 5 SEM image of the ternary cathode material obtained as a comparative example. Specific embodiments

[0026] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0028] Example 1

[0029] This example provides a lithium cobalt oxide doped nickel cobalt manganese ternary cathode material, and its preparation method includes the following steps:

[0030] S1. Prepare a medium-high nickel ternary cathode material precursor: Using deionized water as a solvent, nickel nitrate, cobalt nitrate, and manganese nitrate as raw materials, configure a metal salt solution with a concentration of 2 mol / L according to the molar ratio of nickel element, cobalt element, and manganese element of 0.6:0.2:0.2; simultaneously add the metal salt solution, NaOH solution (concentration of 32%), and ammonia water (concentration of 16%) into the reaction kettle for co-precipitation reaction to obtain a medium-high nickel ternary cathode material precursor with D50 = 2 ± 0.2 μm (denoted as small particle ternary precursor) and a medium-high nickel ternary cathode material precursor with a particle size D50 = 5 ± 0.2 μm (denoted as large particle ternary precursor);

[0031] S2. Prepare lithium cobalt oxide LiCoO2: Add cobalt tetroxide and lithium carbonate into a high-speed mixer according to a molar ratio of 1:1.06; based on cobalt tetroxide, add 200 ppm of alumina, 300 ppm of magnesia, 500 ppm of zirconia, 1000 ppm of yttrium oxide, and 500 ppm of lanthanum oxide, mix evenly, and then pre-burn in a sintering atmosphere furnace at 750 °C for 4 h in an air atmosphere, and then sinter at 1045 °C for 10 h in an air atmosphere, cool to room temperature with the furnace, crush, and screen to obtain lithium cobalt oxide with a particle size of D50 = 4 ± 0.2 μm;

[0032] S3. Add the small particle ternary precursor in step S1, the lithium cobaltate in step S2, and the large particle ternary precursor in step S1 into a high-speed mixer according to a mass ratio of 1:1:8, and then add lithium carbonate (the molar ratio of the large and small particle ternary precursors to lithium carbonate is 1:1.05); based on the lithium cobaltate, add 500 ppm of alumina, 200 ppm of zirconia, and 500 ppm of lanthanum oxide for high-speed mixing. After mixing evenly, sinter at 850 °C for 10 h in an oxygen atmosphere, crush and pass through a 325-mesh sieve to obtain a first-fired product;

[0033] S4. Perform surface coating treatment on the first-fired product obtained in step S3: Mix the first-fired product obtained in step S3 with the first surface coating material (based on the first-fired product, the first surface coating material contains 200 ppm of alumina, 300 ppm of titanium oxide, 500 ppm of zirconia, and 600 ppm of lithium niobate), then sinter at 650 °C for 8 h in an oxygen atmosphere, crush and pass through a 325-mesh sieve to obtain a second-fired product;

[0034] S5. Perform surface coating treatment on the second-fired product obtained in step S4: Mix the second-fired product obtained in step S4 with the second surface coating material (based on the second-fired product, the second surface coating material contains 500 ppm of boric acid and 300 ppm of tungsten oxide), then sinter at 320 °C for 4 h in an oxygen atmosphere, crush and pass through a 325-mesh sieve to obtain a lithium cobaltate-doped nickel cobalt manganese ternary cathode material.

[0035] Example 2

[0036] This example provides a lithium cobaltate-doped nickel cobalt manganese ternary cathode material, and its preparation method includes the following steps:

[0037] S1. Prepare a medium-high nickel ternary cathode material precursor: Using deionized water as a solvent, nickel nitrate, cobalt nitrate, and manganese nitrate as raw materials, configure a metal salt solution with a concentration of 2 mol / L according to the molar ratio of nickel element, cobalt element, and manganese element of 0.6:0.2:0.2; simultaneously add the metal salt solution, NaOH solution (concentration 32%), and ammonia water (concentration 16%) into the reaction kettle for coprecipitation reaction to obtain a medium-high nickel ternary cathode material precursor with D50 = 2 ± 0.2 μm (denoted as small particle ternary precursor) and a medium-high nickel ternary cathode material precursor with a particle size D50 = 5 ± 0.2 μm (denoted as large particle ternary precursor);

[0038] S2. Preparation of lithium cobalt oxide LiCoO₂: Cobalt tetroxide and lithium carbonate are added to a high-speed mixer at a molar ratio of 1:1.06; based on cobalt tetroxide, 150 ppm of alumina, 250 ppm of magnesia, 550 ppm of zirconia, 1050 ppm of yttria, and 550 ppm of lanthanum oxide are further added; after mixing evenly, in a sintering atmosphere furnace, pre-sintered at 700 °C for 4 h in an air atmosphere, and then sintered at 1000 °C for 12 h in an air atmosphere, cooled to room temperature with the furnace, crushed, and sieved to obtain lithium cobalt oxide with a particle size of D50 = 4 ± 0.2 μm;

[0039] S3. Add the small particle ternary precursor in step S1, the lithium cobalt oxide in step S2, and the large particle ternary precursor in step S1 to a high-speed mixer at a mass ratio of 1:1.25:4, and then add lithium carbonate (the molar ratio of the high-nickel ternary cathode material precursor in the large and small particles to lithium carbonate is 1:1.05); based on lithium cobalt oxide, 400 ppm of alumina, 100 ppm of zirconia, and 600 ppm of lanthanum oxide are further added for high-speed mixing. After mixing evenly, sinter at 800 °C for 12 h in an oxygen atmosphere, crush and screen through a 325-mesh sieve to obtain a first-fired product;

[0040] S4. Perform surface coating treatment on the first-fired product obtained in step S3: Mix the first-fired product obtained in step S3 with the first surface coating material (based on the first-fired product, the first surface coating material contains 100 ppm of alumina, 400 ppm of titanium oxide, 400 ppm of zirconia, and 700 ppm of lithium niobate), and then sinter at 700 °C for 10 h in an oxygen atmosphere, crush and screen through a 325-mesh sieve to obtain a second-fired product;

[0041] S5. Perform surface coating treatment on the second-fired product obtained in step S4: Mix the second-fired product obtained in step S4 with the second surface coating material (based on the second-fired product, the second surface coating material contains 400 ppm of boric acid and 500 ppm of tungsten oxide), and then sinter at 350 °C for 6 h in an oxygen atmosphere, crush and screen through a 325-mesh sieve to obtain a lithium cobalt oxide-doped nickel cobalt manganese ternary cathode material.

[0042] Example 3

[0043] This example presents a lithium cobalt oxide-doped nickel cobalt manganese ternary cathode material, and its preparation method includes the following steps:

[0044] S1. Preparation of medium-high nickel ternary cathode material precursor: Using deionized water as the solvent, nickel nitrate, cobalt nitrate, and manganese nitrate as raw materials, a metal salt solution with a concentration of 2 mol / L is prepared according to the molar ratio of nickel element, cobalt element, and manganese element of 0.6:0.2:0.2; the metal salt solution, NaOH solution (concentration of 32%), and ammonia water (concentration of 16%) are simultaneously added to the reaction kettle for coprecipitation reaction to obtain a medium-high nickel ternary cathode material precursor with D50 = 2 ± 0.2 μm (denoted as small particle ternary precursor) and a medium-high nickel ternary cathode material precursor with particle size D50 = 5 ± 0.2 μm (denoted as large particle ternary precursor);

[0045] S2. Preparation of lithium cobalt oxide LiCoO2: Cobalt tetroxide and lithium carbonate are added to a high-speed mixer according to a molar ratio of 1:1.06; based on cobalt tetroxide, 300 ppm of alumina, 400 ppm of magnesia, 500 ppm of zirconia, 900 ppm of yttria, and 600 ppm of lanthanum oxide are added; after mixing evenly, it is pre-sintered at 720 °C for 5 h in a sintering atmosphere furnace under an air atmosphere, and then sintered at 1045 °C for 10 h in an air atmosphere, cooled to room temperature with the furnace, crushed, and sieved to obtain lithium cobalt oxide with a particle size of D50 = 4 ± 0.2 μm;

[0046] S3. Add the small particle ternary precursor in step S1, the lithium cobalt oxide in step S2, and the large particle ternary precursor in step S1 to a high-speed mixer according to a mass ratio of 1:1:3, and then add lithium carbonate (the molar ratio of the medium-high nickel ternary cathode material precursor of large and small particles to lithium carbonate is 1:1.05); based on lithium cobalt oxide, 550 ppm of alumina, 250 ppm of zirconia, and 400 ppm of lanthanum oxide are added for high-speed mixing. After mixing evenly, it is sintered at 900 °C for 11 h in an oxygen atmosphere, crushed and sieved through a 325-mesh sieve to obtain a first-fired product;

[0047] S4. Surface coating treatment of the first-fired product obtained in step S3: Mix the first-fired product obtained in step S3 with the first surface coating material (based on the first-fired product, the first surface coating material contains 300 ppm of alumina, 400 ppm of titanium oxide, 600 ppm of zirconia, and 500 ppm of lithium niobate), and then sinter at 650 °C for 8 h in an oxygen atmosphere, crush and sieve through a 325-mesh sieve to obtain a second-fired product;

[0048] S5. Surface coating treatment of the second-fired product obtained in step S4: Mix the second-fired product obtained in step S4 with the second surface coating material (based on the second-fired product, the second surface coating material contains 700 ppm of boric acid and 200 ppm of tungsten oxide), and then sinter at 400 °C for 4 h in an oxygen atmosphere, crush and sieve through a 325-mesh sieve to obtain a lithium cobalt oxide-doped nickel cobalt manganese ternary cathode material.

[0049] Comparative Example

[0050] This comparative example presents a nickel-cobalt-manganese ternary cathode material, and its preparation method includes the following steps:

[0051] S1. Prepare a medium-high nickel ternary cathode material precursor: Using deionized water as a solvent, nickel nitrate, cobalt nitrate, and manganese nitrate as raw materials, configure a metal salt solution with a concentration of 2 mol / L according to the molar ratio of nickel element, cobalt element, and manganese element of 0.6:0.2:0.2; simultaneously add the metal salt solution, NaOH solution (concentration 32%), and ammonia water (concentration 16%) into the reaction kettle for co-precipitation reaction to obtain a medium-high nickel ternary cathode material precursor with D50 = 2 ± 0.2 μm (denoted as small particle ternary precursor) and a medium-high nickel ternary cathode material precursor with a particle size D50 = 5 ± 0.2 μm (denoted as large particle ternary precursor);

[0052] S2. Add the small particle ternary precursor in step S1 and the large particle ternary precursor in step S1 into a high-speed mixer according to a mass ratio of 1:4, then add lithium carbonate (the molar ratio of the medium-high nickel ternary cathode material precursor of large and small particles to lithium carbonate is 1:1.05), mix evenly, sinter at 800 °C for 10 h in an oxygen atmosphere, crush and pass through a 325-mesh sieve to obtain a first-fired product;

[0053] S3. Perform surface coating treatment on the first-fired product obtained in step S2: Mix the first-fired product obtained in step S2 with the first surface coating material (based on the first-fired product, the first surface coating material contains 100 ppm of alumina, 400 ppm of titanium oxide, 400 ppm of zirconium oxide, and 700 ppm of lithium niobate), sinter at 700 °C for 10 h in an oxygen atmosphere, crush and pass through a 325-mesh sieve to obtain a second-fired product;

[0054] S4. Perform surface coating treatment on the second-fired product obtained in step S3: Mix the second-fired product obtained in step S3 with the second surface coating material (based on the second-fired product, the second surface coating material contains 400 ppm of boric acid and 500 ppm of tungsten oxide), sinter at 350 °C for 6 h in an oxygen atmosphere, crush and pass through a 325-mesh sieve to obtain the ternary cathode material.

[0055] The principle of the first-firing process in step S3 of Examples 1-3 of this embodiment is as Figure 1 shown. Through the high-temperature solid-phase method, lithium cobaltate that has been sintered is doped during the ternary primary sintering process. Through processes such as sintering, crushing, and sieving, lithium cobaltate is doped into the interior of the ternary cathode material particles, the particle surface layer, and between particles, completing the modification of the ternary material, effectively protecting the layered structure of the medium-high nickel ternary cathode material, and reducing the mixing of nickel and lithium ions.

[0056] Figures 2 - 5 SEM images of the nickel-cobalt-manganese ternary cathode materials prepared in Examples 1-3 and Comparative Examples respectively. From Figures 2 - 5 the comparison, it can be seen that: in the examples of the present invention, lithium cobaltate is uniformly doped into the nickel-cobalt-manganese ternary cathode material, and the overall structure of the material is single-crystal particles, and the distribution of large and small particles conforms to the expected doping ratio distribution expectation.

[0057] Test Example 1

[0058] The particle size of the doped nickel-cobalt-manganese ternary cathode materials prepared in Examples 1-3 and Comparative Examples was measured; the nickel-cobalt-manganese ternary cathode materials prepared in Examples 1-3 and Comparative Examples were subjected to powder compaction treatment; the data in Table 1 below were obtained.

[0059] Table 1 Results of particle size measurement and powder compaction treatment

[0060]

[0061] It can be seen from the results in Table 1 that:

[0062] The D10 and D50 of the lithium cobaltate-doped nickel-cobalt-manganese ternary cathode materials prepared in Example 1, Example 2 and Example 3 are higher than those of the nickel-cobalt-manganese ternary cathode material without lithium cobaltate doping in the comparative example, and the diameter distance span is lower than that of the comparative example, while D0, D90 and D10 fluctuate within the test error range; it shows that lithium cobaltate doping is beneficial to improving the particle size distribution of the ternary cathode material and optimizing the broadening coefficient of the ternary cathode material, and Example 2 has the most obvious improvement;

[0063] The powder compaction strength of the lithium cobaltate-doped nickel-cobalt-manganese ternary cathode materials prepared in Example 1, Example 2 and Example 3 is higher than that of the nickel-cobalt-manganese ternary cathode material without lithium cobaltate doping in the comparative example, indicating that lithium cobaltate doping is beneficial to improving the compaction strength of the nickel-cobalt-manganese ternary cathode material. Example 2 has the most obvious improvement, with an increase of 0.1 g / cm 3 .

[0064] Application Example

[0065] The nickel-cobalt-manganese ternary cathode materials prepared in Examples 1-3 and Comparative Examples were respectively made into batteries, and the steps are as follows: the nickel-cobalt-manganese ternary cathode material, conductive agent SP and binder PVDF were mixed into a slurry according to a mass ratio of 90:5:5; the slurry was uniformly coated on the aluminum foil, and the electrode sheet was compacted by a rolling mill to improve the density and adhesion of the active material to obtain a positive electrode sheet; the battery core was stacked in the order of "lithium negative electrode - separator - positive electrode sheet - separator", and the tab was fixed on the current collector by ultrasonic welding; the battery core was put into an aluminum plastic film, and the side was thermally sealed to form an air bag; the electrolyte (ethylene carbonate) was injected into the glove box, and vacuum standing was ensured to be infiltrated, the battery was activated and a stable SEI film was formed, and the gas generated by formation was discharged and then completely sealed.

[0066] The electrochemical performance of each prepared battery was tested under the following conditions: 2.8V - 4.45V, normal temperature, 0.2C / 0.2C. The test results are shown in Table 2.

[0067] Table 2 Electrochemical Performance

[0068]

[0069] According to the results in Table 2, it can be seen that the initial discharge specific capacity, first efficiency, and capacity retention rate after 200 cycles of Examples 1, 2, and 3 are all higher than those of the comparative examples, and the DCR is lower than that of the comparative examples. This shows that the doping of lithium cobaltate helps to improve the electrical performance of the nickel-cobalt-manganese ternary cathode material. Among them, doping according to the ratio of Example 2 has the most obvious improvement effect. The initial discharge specific capacity of Example 2 under the test conditions of 2.8V - 4.45V, normal temperature, 0.2C / 0.2C is: 198.3 mAh / g, the first efficiency reaches 94.2%, the DCR is 16.8 mΩ, and the capacity retention rate after 200 cycles is 95.6%.

[0070] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0071] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims.

Claims

1. A preparation method of a lithium cobaltate doped with nickel cobalt manganese ternary cathode material, characterized in that, It includes the following steps: S1. Mix lithium cobaltate, nickel cobalt manganese ternary precursors with at least two different particle size distributions, lithium carbonate, and a first dopant, sinter, and crush to obtain a first-fired product; based on lithium cobaltate, the first dopant contains 400-600 ppm of aluminum oxide, 100-300 ppm of zirconium oxide, and 400-600 ppm of lanthanum oxide; S2. Mix the first-fired product with a first surface coating material, sinter, and crush to obtain a second-fired product; based on the first-fired product, the first surface coating material contains 100-300 ppm of aluminum oxide, 200-400 ppm of titanium oxide, 400-600 ppm of zirconium oxide, and 500-700 ppm of lithium niobate; S3. Mix the second-fired product with a second surface coating material, sinter, and crush to obtain a lithium cobaltate-doped nickel cobalt manganese ternary cathode material; based on the second-fired product, the second surface coating material contains 400-700 ppm of boric acid and 100-500 ppm of tungsten oxide.

2. The preparation method of the lithium cobaltate doped with nickel cobalt manganese ternary cathode material according to claim 1, wherein In step S1, the structural formula of the nickel cobalt manganese ternary precursor is Ni x Co y Mn 1-x-y (OH)2, where 0.5 ≤ x ≤ 0.9 and 0.05 ≤ y ≤ 0.3; the preparation method of the nickel cobalt manganese ternary precursor is as follows: using deionized water as a solvent, nickel nitrate, cobalt nitrate and manganese nitrate as raw materials, configuring a metal salt solution according to the molar ratio of nickel element, cobalt element and manganese element of x:y:1-x-y, and simultaneously adding the metal salt solution, NaOH solution and ammonia water into a reaction kettle for coprecipitation reaction to obtain a nickel cobalt manganese ternary precursor with at least two different particle size distributions.

3. The preparation method of the lithium cobaltate doped with nickel, cobalt and manganese ternary cathode material according to claim 1, wherein, In step S2, the nickel cobalt manganese ternary precursor includes a nickel cobalt manganese ternary precursor with a particle size of D50 = 2 ± 0.2 μm and a nickel cobalt manganese ternary precursor with a particle size of D50 = 5 ± 0.2 μm; the mass ratio of lithium cobaltate, the nickel cobalt manganese ternary precursor with a particle size of D50 = 2 ± 0.2 μm, and the nickel cobalt manganese ternary precursor with a particle size of D50 = 5 ± 0.2 μm is (1-1.25):1:(3-8).

4. The preparation method of the lithium cobalt oxide doped with nickel cobalt manganese ternary cathode material according to claim 1, wherein In step S1, the molar ratio of lithium carbonate to the nickel cobalt manganese ternary precursor is 1.05:

1.

5. The preparation method of the lithium cobaltate doped with nickel cobalt manganese ternary cathode material according to claim 1, wherein, In step S1, the sintering is carried out at 800-900 °C for 10-12 h in an oxygen atmosphere.

6. The preparation method of the lithium cobalt oxide doped with nickel cobalt manganese ternary cathode material according to claim 1, wherein The preparation method of the lithium cobaltate is: mix cobalt tetroxide, lithium carbonate, and a second dopant, first sinter at 700-750 °C for 4-6 h in an air atmosphere, then sinter at 1000-1045 °C for 10-12 h in an air atmosphere, and crush to obtain lithium cobaltate; wherein, based on cobalt tetroxide, the second dopant contains 100-300 ppm of aluminum oxide, 200-400 ppm of magnesium oxide, 400-600 ppm of zirconium oxide, 900-1200 ppm of yttrium oxide, and 400-600 ppm of lanthanum oxide.

7. The preparation method of the lithium cobaltate doped with nickel cobalt manganese ternary cathode material according to claim 1, characterized in that, In step S2, the sintering is carried out at 600-700 °C for 6-10 h in an oxygen atmosphere.

8. The preparation method of the lithium cobaltate doped with nickel cobalt manganese ternary cathode material according to claim 1, characterized in that, In step S3, the sintering is carried out at 300-400 °C for 4-8 h in an oxygen atmosphere.

9. A lithium cobalt oxide doped with nickel cobalt manganese ternary cathode material, characterized in that, It is prepared by using the preparation method described in any one of claims 1-8.

10. An application of the lithium cobaltate-doped nickel cobalt manganese ternary cathode material as described in claim 9 in a lithium battery.

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