Lithium cobalt oxide doped nickel-cobalt-manganese ternary positive electrode material and preparation method and application thereof

Abstract

The invention relates to the technical field of lithium battery materials, and particularly discloses a lithium cobalt oxide doped nickel-cobalt-manganese ternary positive electrode material and a preparation method and application thereof.The preparation method comprises the following steps that lithium cobalt oxide, a nickel-cobalt-manganese ternary precursor with at least two different particle size distributions, lithium carbonate and a first doping agent are mixed, sintered and crushed to obtain a lithium cobalt oxide doped nickel-cobalt-manganese ternary positive electrode material; a primary burning product is obtained; mixing, sintering and crushing the primary sintering product and a first surface coating material to obtain a secondary sintering product; and mixing the secondary sintering product with a second surface coating material, sintering, and crushing to obtain the lithium cobalt oxide doped nickel-cobalt-manganese ternary positive electrode material. According to the invention, the lithium cobalt oxide material is uniformly doped into the nickel-cobalt-manganese ternary positive electrode material through a one-firing process, so that the layered structure of the nickel-cobalt-manganese ternary positive electrode material is effectively protected, mixed arrangement of nickel and lithium ions is reduced, and the cycling stability and the safety performance of the material are improved.

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. Currently, the mainstream cathode materials for commercial applications include lithium cobaltate, lithium manganate, lithium iron phosphate, and nickel cobalt manganese ternary materials, etc. Among them, lithium cobaltate has advantages such as high specific capacity, large tap density, and excellent cycle 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] Due to advantages such as high energy density and low cost, nickel cobalt manganese ternary materials are considered the key development direction in the future. However, medium and high nickel ternary cathode materials have problems such as poor cycle stability, low tap density, and poor safety performance. The main reason is that high-valence nickel ions are unstable and prone to structural transformation, and at the same time, nickel ions react with the electrolyte to occur 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 effects are 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-time sintering 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 cycle stability and safety performance of the material.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions: The present invention first provides a preparation method of a lithium cobaltate-doped nickel cobalt manganese ternary cathode material, which includes the following steps: S1. Mix lithium cobaltate, a nickel cobalt manganese ternary precursor having at least two different particle size distributions, lithium carbonate, and a first doping agent, sinter, and crush to obtain a first-sintered product; S2. Mix the first-sintered product with a first surface coating material, sinter, and crush to obtain a second-sintered product; S3. Mix the second-sintered product with a second surface coating material, sinter, and crush to obtain the lithium cobaltate-doped nickel cobalt manganese ternary cathode material.

[0006] 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 Co y 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 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 as x:y:1 - x - y, adding the metal salt solution, NaOH solution, and ammonia water into a reaction kettle simultaneously, and performing a coprecipitation reaction to obtain a nickel-cobalt-manganese ternary precursor with at least two different particle size distributions.

[0007] 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 the 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).

[0008] As a further improvement of the above solution of the present invention, in step S1, the molar ratio of the lithium carbonate to the nickel-cobalt-manganese ternary precursor is 1.05:1; based on the lithium cobaltate, the first dopant includes 400 - 600 ppm of aluminum oxide, 100 - 300 ppm of zirconium oxide, and 400 - 600 ppm of lanthanum oxide.

[0009] As a further improvement of the above solution of the present invention, in step S1, the sintering is performed at 800 - 900 °C for 10 - 12 h in an oxygen atmosphere.

[0010] As a further improvement of the above solution of the present invention, the method for preparing the lithium cobaltate is as follows: mixing cobalt tetroxide, lithium carbonate, and a second dopant, first sintering at 700 - 750 °C for 2 - 4 h in an air atmosphere, then sintering at 1000 - 1045 °C for 8 - 10 h in an air atmosphere, and crushing to obtain lithium cobaltate; where, based on the cobalt tetroxide, the second dopant includes 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.

[0011] 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 aluminum oxide, 200 - 400 ppm of titanium oxide, 400 - 600 ppm of zirconium oxide, and 500 - 700 ppm of lithium niobate; the sintering is performed at 600 - 700 °C for 6 - 10 h in an oxygen atmosphere.

[0012] As a further improvement of the above solution of the present invention, in step S3, 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; the sintering is carried out in an oxygen atmosphere at 300-400 °C for 4-8 h.

[0013] The present invention also provides a lithium cobalt oxide doped nickel cobalt manganese ternary cathode material, which is prepared by the preparation method described above.

[0014] The present invention also provides an application of the lithium cobalt oxide doped nickel cobalt manganese ternary cathode material described above in a lithium battery.

[0015] Compared with the prior art, the present invention has the following beneficial effects: In the present invention, lithium cobalt oxide is first sintered 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 enhancing 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, at the same time, the tap density of the nickel cobalt manganese ternary cathode material can be increased, the processing performance of the material can be optimized, the layered structure of the nickel cobalt manganese ternary cathode material can be stabilized, the nickel lithium ion mixing can be reduced, and the volume expansion and structural stress caused by lithium ion deintercalation during charge and discharge can be reduced, prolonging the cycle life. The present invention then carries out 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 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; Figure 2 is an SEM image of the lithium cobalt oxide doped nickel cobalt manganese ternary cathode material prepared in Example 1; Figure 3 is an SEM image of the lithium cobalt oxide doped nickel cobalt manganese ternary cathode material prepared in Example 2; Figure 4 is an SEM image of the lithium cobalt oxide doped nickel cobalt manganese ternary cathode material prepared in Example 3; Figure 5 is an SEM image of the ternary cathode material prepared in the comparative example. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] 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, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0018] 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.

[0019] Example 1 This example provides a lithium cobalt oxide doped with nickel cobalt manganese ternary cathode material, and its preparation method includes the following steps: 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, a metal salt solution with a concentration of 2 mol / L is configured 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 a particle size of D50 = 5 ± 0.2 μm (denoted as large particle ternary precursor); S2. Prepare lithium cobalt oxide LiCoO 2 : 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, 200 ppm of alumina, 300 ppm of magnesia, 500 ppm of zirconia, 1000 ppm of yttrium oxide, and 500 ppm of lanthanum oxide are added and mixed evenly, and then pre-sintered in a sintering atmosphere furnace at 750 °C for 4 h in 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; 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 1:1:8, 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 lithium cobalt oxide, 500 ppm of alumina, 200 ppm of zirconia, and 500 ppm of lanthanum oxide are added for high-speed mixing. After mixing evenly, sinter at 850 °C for 10 h in an oxygen atmosphere, crush and sieve through a 325-mesh sieve to obtain a first-fired product; S4. Surface coating treatment of the product after the first firing: The product after the first firing obtained in step S3 is mixed with the first surface coating material (based on the product after the first firing, the first surface coating material contains 200 ppm of alumina, 300 ppm of titanium oxide, 500 ppm of zirconium oxide, and 600 ppm of lithium niobate), and then sintered in an oxygen atmosphere at 650 °C for 8 h. After crushing and passing through a 325-mesh sieve, a product after the second firing is obtained; S5. Surface coating treatment of the product after the second firing obtained in step S4: The product after the second firing obtained in step S4 is mixed with the second surface coating material (based on the product after the second firing, the second surface coating material contains 500 ppm of boric acid and 300 ppm of tungsten oxide), and then sintered in an oxygen atmosphere at 320 °C for 4 h. After crushing and passing through a 325-mesh sieve, a lithium cobalt oxide-doped nickel cobalt manganese ternary cathode material is obtained.

[0020] Example 2 This example provides a lithium cobalt oxide-doped nickel cobalt manganese ternary cathode material, and its preparation method includes the following steps: S1. Preparation of a medium-high nickel ternary cathode material precursor: Using deionized water as a 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 a particle size D50 = 5 ± 0.2 μm (denoted as large particle ternary precursor); S2. Preparation of lithium cobalt oxide LiCoO 2 : Cobalt tetroxide and lithium carbonate are added to a high-speed mixer in a molar ratio of 1:1.06. Based on cobalt tetroxide, 150 ppm of alumina, 250 ppm of magnesium oxide, 550 ppm of zirconium oxide, 1050 ppm of yttrium oxide, and 550 ppm of lanthanum oxide are further added. After mixing evenly, it is pre-sintered in a sintering atmosphere furnace in an air atmosphere at 700 °C for 4 h, and then sintered in an air atmosphere at 1000 °C for 12 h. It is 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; S3. Add the small particle ternary precursor in step S1, lithium cobaltate in step S2, and the large particle ternary precursor in step S1 to a high-speed mixer according to a mass ratio of 1:1.25:4, 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 cobaltate, add 400 ppm of alumina, 100 ppm of zirconia, and 600 ppm of lanthanum oxide for high-speed mixing. After mixing evenly, sinter at 800 °C for 12 h in an oxygen atmosphere, crush and pass through a 325-mesh sieve to obtain a first-fired product; 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 pass through a 325-mesh sieve to obtain a second-fired product; 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 pass through a 325-mesh sieve to obtain a lithium cobaltate-doped nickel cobalt manganese ternary cathode material.

[0021] Example 3 This example proposes a lithium cobaltate-doped nickel cobalt manganese ternary cathode material, and its preparation method includes the following steps: S1. Prepare a high-nickel ternary cathode material precursor: Use deionized water as a solvent, and use nickel nitrate, cobalt nitrate, and manganese nitrate as raw materials. Configure a metal salt solution with a concentration of 2 mol / L according to a molar ratio of nickel element, cobalt element, and manganese element of 0.6:0.2:0.2; add the metal salt solution, NaOH solution (concentration of 32%), and ammonia water (concentration of 16%) into the reaction kettle at the same time for coprecipitation reaction to obtain a high-nickel ternary cathode material precursor with D50 = 2 ± 0.2 μm (denoted as small particle ternary precursor) and a high-nickel ternary cathode material precursor with a particle size D50 = 5 ± 0.2 μm (denoted as large particle ternary precursor); S2. Prepare lithium cobaltate LiCoO 2:Add cobalt tetroxide and lithium carbonate to a high-speed mixer at a molar ratio of 1:1.06; based on cobalt tetroxide, add 300 ppm of alumina, 400 ppm of magnesia, 500 ppm of zirconia, 900 ppm of yttria, and 600 ppm of lanthanum oxide; after mixing evenly, in a sintering atmosphere furnace, pre-sinter at 720 °C for 5 h in an air atmosphere, 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 cobaltate with a particle size of D50 = 4 ± 0.2 μm; 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 to a high-speed mixer at a mass ratio of 1:1:3, and then add lithium carbonate (the molar ratio of the high-nickel ternary cathode material precursor to lithium carbonate in the large and small particles is 1:1.05); based on lithium cobaltate, add 550 ppm of alumina, 250 ppm of zirconia, and 400 ppm of lanthanum oxide for high-speed mixing. After mixing evenly, sinter at 900 °C for 11 h in an oxygen atmosphere, crush and screen through a 325-mesh sieve to obtain a first-fired product; S4. Perform a surface coating treatment on the first-fired product obtained in step S3: Mix the first-fired product obtained in step S3 with a 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. After crushing and screening through a 325-mesh sieve, a second-fired product is obtained; S5. Perform a surface coating treatment on the second-fired product obtained in step S4: Mix the second-fired product obtained in step S4 with a 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. After crushing and screening through a 325-mesh sieve, a lithium cobaltate-doped nickel cobalt manganese ternary cathode material is obtained.

[0022] Comparative Example This comparative example presents a nickel cobalt manganese ternary cathode material, and its preparation method includes the following steps: S1 Prepare a medium-high nickel ternary cathode material precursor: Use deionized water as a solvent, and use 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%) to a 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); S2. Add the small-particle ternary precursor in step S1 and the large-particle ternary precursor in step S1 to a high-speed mixer at a mass ratio of 1:4, and then add lithium carbonate (the molar ratio of the high-nickel ternary cathode material precursor to lithium carbonate in the large and small particles is 1:1.05). After mixing 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; 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), and then 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; 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), and then 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.

[0023] 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 primary ternary 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 the particles, completing the modification of the ternary material, effectively protecting the layered structure of the high-nickel ternary cathode material, and reducing the mixing of nickel and lithium ions.

[0024] Figures 2 - 5 SEM images of the nickel-cobalt-manganese ternary cathode materials prepared in Examples 1-3 and the comparative example are shown 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 composed of single-crystal particles, and the distribution of large and small particles conforms to the expected doping ratio distribution expectation.

[0025] Test Example 1 Perform particle size measurement on the nickel-cobalt-manganese ternary cathode materials prepared in Examples 1-3 and the comparative example; perform powder compaction treatment on the nickel-cobalt-manganese ternary cathode materials prepared in Examples 1-3 and the comparative example; obtain the data in Table 1 below.

[0026] Table 1 Results of particle size measurement and powder compaction treatment

[0027] It can be seen from the results in Table 1 that: The D10 and D50 of the lithium cobalt oxide-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 materials without lithium cobalt oxide doping in the comparative example, and the particle size span is lower than that of the comparative example, while D0, D90, and D10 fluctuate within the test error range; it shows that doping with lithium cobalt oxide is beneficial to improving the particle size distribution of the ternary cathode material, optimizing the broadening coefficient of the ternary cathode material, and the improvement in Example 2 is the most obvious; The powder compaction strength of the lithium cobalt oxide-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 materials without lithium cobalt oxide doping in the comparative example, indicating that doping with lithium cobalt oxide is beneficial to improving the compaction strength of the nickel cobalt manganese ternary cathode material, and the improvement in Example 2 is the most obvious, with an increase of 0.1 g / cm 3 .

[0028] Application Example The nickel cobalt manganese ternary cathode materials prepared in Example 1-3 and the comparative example were respectively made into batteries, and the steps are as follows: Mix the nickel cobalt manganese ternary cathode material, conductive agent SP, and binder PVDF in a mass ratio of 90:5:5 to make a slurry; uniformly coat the slurry on the aluminum foil, and press the electrode sheet through a roller to improve the density and adhesion of the active material to obtain a positive electrode sheet; stack the battery cells in the order of "lithium negative electrode - separator - positive electrode sheet - separator", and fix the electrode tab on the current collector by ultrasonic welding; put the battery cell into an aluminum plastic film, and form an air bag by heat sealing the side; inject electrolyte (ethylene carbonate) in a glove box, vacuum and stand still to ensure infiltration, activate the battery and form a stable SEI film, and completely seal after discharging the gas generated during formation.

[0029] Perform electrochemical performance tests on the prepared batteries, and the test conditions are: 2.8V - 4.45V, 0.2C / 0.2C at room temperature. The test results are shown in Table 2.

[0030] Table 2 Electrochemical Performance

[0031] 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 Example 1, Example 2, and Example 3 are all higher than those of the comparative example, and the DCR is lower than that of the comparative example. It shows that doping with lithium cobalt oxide helps to improve the electrical performance of the nickel cobalt manganese ternary cathode material, and the 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 at room temperature of 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%.

[0032] 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 recorded in this specification.

[0033] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof 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 shall be subject to the appended claims.

Claims

1. A method for preparing a lithium cobalt oxide doped nickel-cobalt-manganese ternary positive electrode material, characterized in that: It includes the following steps: S1. mixing lithium cobalt oxide, nickel-cobalt-manganese ternary precursors having at least two different particle size distributions, lithium carbonate and a first dopant, sintering, crushing, and obtaining a fired product; S2. The first fired product is mixed with the first surface coating material, sintered, and crushed to obtain a second fired product; S3. The second sintering product is mixed with the second surface coating material, sintered, and crushed to obtain a lithium cobalt oxide doped nickel-cobalt-manganese ternary positive electrode material.

2. The method for preparing the lithium cobalt oxide doped nickel-cobalt-manganese ternary positive electrode material according to claim 1, characterized in that: In step S1, the structural formula of the nickel-cobalt-manganese ternary precursor is Ni x Co y Mn 1-x-y (OH)2, wherein 0.5≤x≤0.9, 0.05≤y≤0.3; the preparation method of the nickel-cobalt-manganese ternary precursor is: using deionized water as a solvent, nickel nitrate, cobalt nitrate and manganese nitrate as raw materials, and configuring a metal salt solution according to the molar ratio of nickel element, cobalt element and manganese element of x:y:1-xy, adding the metal salt solution, NaOH solution and ammonia water into a reactor at the same time, and carrying out a co-precipitation reaction to obtain a nickel-cobalt-manganese ternary precursor having at least two different particle size distributions.

3. The method for preparing the lithium cobalt oxide doped nickel-cobalt-manganese ternary positive electrode material according to claim 1, characterized in that: In step S2, the nickel-cobalt-manganese ternary precursor contains a nickel-cobalt-manganese ternary precursor with a particle size of D50=2±0.2μm and a nickel-cobalt-manganese ternary precursor with a particle size of D50=5±0.2μm; the mass ratio of the lithium cobalt oxide, the nickel-cobalt-manganese ternary precursor with a particle size of D50=2±0.2μm, and the nickel-cobalt-manganese ternary precursor with a particle size of D50=5±0.2μm is (1-1.25):1:(3-8).

4. The method for preparing the lithium cobalt oxide doped nickel-cobalt-manganese ternary positive electrode material according to claim 1, characterized in that: In step S1, the molar ratio of the lithium carbonate to the nickel-cobalt-manganese ternary precursor is 1.05:1; based on lithium cobalt oxide, the first dopant includes 400-600 ppm of aluminum oxide, 100-300 ppm of zirconium oxide, and 400-600 ppm of lanthanum oxide.

5. The method for preparing the lithium cobalt oxide doped nickel-cobalt-manganese ternary positive electrode material according to claim 1, characterized in that: In step S1, the sintering is carried out at 800-900° C. for 10-12 hours in an oxygen atmosphere.

6. The method for preparing the lithium cobalt oxide doped nickel-cobalt-manganese ternary positive electrode material according to claim 1, characterized in that: The preparation method of the lithium cobalt oxide is as follows: after mixing cobalt oxide, lithium carbonate and a second dopant, first sintering at 700-750°C for 4-6 hours in an air atmosphere, then sintering at 1000-1045°C for 10-12 hours in an air atmosphere, and crushing to obtain lithium cobalt oxide; wherein, based on cobalt oxide, the second dopant contains 100-300ppm of aluminum oxide, 200-400ppm of magnesium oxide, 400-600ppm of zirconium oxide, 900-1200ppm of yttrium oxide, and 400-600ppm of lanthanum oxide.

7. The method for preparing the lithium cobalt oxide doped nickel-cobalt-manganese ternary positive electrode material according to claim 1, characterized in that: In step S2, based on the sintered product, the first surface coating material comprises 100-300 ppm aluminum oxide, 200-400 ppm titanium oxide, 400-600 ppm zirconium oxide, and 500-700 ppm lithium niobate; the sintering is carried out at 600-700° C. for 6-10 hours in an oxygen atmosphere.

8. The method for preparing the lithium cobalt oxide doped nickel-cobalt-manganese ternary positive electrode material according to claim 1, characterized in that: In step S3, based on the di-sintered product, the second surface coating material comprises 400-700 ppm of boric acid and 100-500 ppm of tungsten oxide; The sintering is carried out at 300-400° C. for 4-8 hours in an oxygen atmosphere.

9. A lithium cobalt oxide doped nickel-cobalt-manganese ternary positive electrode material, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the lithium cobalt oxide doped nickel-cobalt-manganese ternary positive electrode material as claimed in claim 9 in a lithium battery.

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