Composite lithium cobalt oxide cathode material, preparation method thereof, cathode sheet and lithium ion battery

Abstract

The application provides a composite lithium cobalt oxide positive electrode material, a preparation method thereof, a positive electrode sheet and a lithium ion battery. The composite lithium cobalt oxide positive electrode material comprises first lithium cobalt oxide with a D50 of 13-16 microns, second lithium cobalt oxide with a D50 of 5.5-6.5 microns, first lithium titanium aluminum phosphate with a D50 of 300-500 nm and second lithium titanium aluminum phosphate with a D50 of 100-280 nm; the weight ratio of the first lithium cobalt oxide to the first lithium titanium aluminum phosphate is (100-300):1; the weight ratio of the second lithium cobalt oxide to the second lithium titanium aluminum phosphate is (100-300):1; and the weight ratio of the first lithium cobalt oxide to the second lithium cobalt oxide is (1.5-4.0):1. By controlling the mixing ratio and mixing sequence of the lithium cobalt oxide and the lithium titanium aluminum phosphate with different particle sizes, the composite lithium cobalt oxide positive electrode material obtained has high compaction density and rate performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion batteries, in particular, relates to a composite lithium cobalt oxide cathode material, a preparation method thereof, a cathode sheet and a lithium ion battery. BACKGROUND

[0002] High energy density (ED) is the research direction of most secondary batteries, and high rate is also a performance that must be considered for consumer batteries. For cathode materials, high ED often corresponds to high voltage, high pressure density (PD) and high tap density (TD), and high rate corresponds to high specific surface (BET), low pressure density and low tap density.

[0003] That is to say, from the material end itself, the energy density and rate performance are difficult to improve at the same time. Compared with other cathode materials, lithium cobalt oxide has higher pressure density, higher voltage and better rate performance. In the production of lithium cobalt oxide, the particle size of lithium cobalt oxide can be controlled by adjusting the process. The capacity type lithium cobalt oxide with larger particle size often has larger tap density and pressure density, smaller BET and poorer rate performance; the rate type lithium cobalt oxide with smaller particle size often has smaller tap density and pressure density, larger BET and better rate performance.

[0004] In order to further improve the energy density of lithium cobalt oxide cathode material, it is necessary to improve its pressure density, and the general means to improve the pressure density of the cathode material is to increase the particle size of the particles, which inevitably reduces the specific surface area of the material, and the lithium ion migration is blocked under high pressure state, which makes it difficult for the battery to meet the demand of 5C discharge. For example, the current capacity type lithium cobalt oxide material has a pressure of 4.2g / cm 3 , which can bring higher energy density, but at the same time its rate performance is only below 3C. For example, CN116768282B provides a high rate type lithium cobalt oxide, and the full battery prepared by using the lithium cobalt oxide has a discharge capacity of more than 95% of 0.2C at 4.45V and 20C, but its pressure density is only 3.7~3.9g / cm 3 .

[0005] Therefore, how to balance the density and specific surface area of lithium cobalt oxide so that it can have high energy density and excellent rate performance as a cathode material is one of the important technical problems to be solved in the field. SUMMARY

[0006] The main purpose of the present application is to provide a composite lithium cobalt oxide cathode material, a preparation method thereof, a cathode sheet and a lithium ion battery, so as to solve the problem that the lithium cobalt oxide cathode material in the prior art cannot have high energy density and excellent rate performance.

[0007] In order to achieve the above-mentioned objectives, the first aspect of the present application provides a composite lithium cobalt oxide positive electrode material, including: a first lithium cobalt oxide with a D50 of 13μm~16μm, a second lithium cobalt oxide with a D50 of 5.5μm~6.5μm, a first lithium titanium aluminum phosphate with a D50 of 300nm~500nm, and a second lithium titanium aluminum phosphate with a D50 of 100nm~280nm; the weight ratio of the first lithium cobalt oxide to the first lithium titanium aluminum phosphate is (100~300):1; the weight ratio of the second lithium cobalt oxide to the second lithium titanium aluminum phosphate is (100~300):1; the weight ratio of the first lithium cobalt oxide to the second lithium titanium aluminum phosphate is (100~300):1; and the weight ratio of the first lithium cobalt oxide to the second lithium cobalt oxide is (1.5~4.0):1.

[0008] Furthermore, the molecular formulas of the first lithium aluminum titanium phosphate and the second lithium aluminum titanium phosphate are independently Li 1+ x A1 x Ti 2-x (PO4)3, where 0.01≤x<1.

[0009] Furthermore, D10 of the first lithium cobaltate is 4.8 μm-6.5 μm, and D10 of the second lithium cobaltate is 3.0 μm-4.0 μm; and / or D90 of the first lithium cobaltate is 25.0 μm-28.0 μm, and D90 of the second lithium cobaltate is 10.0 μm-12.0 μm.

[0010] Furthermore, the specific particle size distribution value (D90-D10) / D50 of the first lithium cobaltate is 1.25-1.55, and the specific particle size distribution value (D90-D10) / D50 of the second lithium cobaltate is 1.00-1.20.

[0011] Furthermore, the tap density of the first lithium cobalt oxide is 2.7 g / cm 3 ~3.0g / cm 3 The tap density of the second lithium cobalt oxide is 2.0g / cm 3 ~2.6g / cm 3 ; and / or, the specific surface area of ​​the first lithium cobaltate is 0.15m 2 / g~0.25m 2 / g, the specific surface area of ​​the second lithium cobaltate is 0.35m 2 / g~0.50m 2 / g.

[0012] Furthermore, the specific surface area of ​​the composite lithium cobalt oxide positive electrode material is 0.25m 2 / g~0.35m 2 / g, tap density is 2.5g / cm 3 ~2.8g / cm 3Further, the D10 of the composite lithium cobalt oxide positive electrode material is 3.8 μm to 5.0 μm, the D50 is 11.4 μm to 12.9 μm, the D90 is 24.8 μm to 27.7 μm, and the specific particle size distribution value (D90-D10) / D50 is 1.6 to 2.1.

[0013] The second aspect of the present application provides a preparation method of the composite lithium cobalt oxide positive electrode material, comprising: step S1, first mixing a first lithium cobalt oxide and a first lithium titanium aluminum phosphate to obtain a first composite lithium cobalt oxide; step S2, second mixing a second lithium cobalt oxide and a second lithium titanium aluminum phosphate to obtain a second composite lithium cobalt oxide; and step S3, third mixing the first composite lithium cobalt oxide and the second composite lithium cobalt oxide to obtain the composite lithium cobalt oxide positive electrode material.

[0014] Further, the first mixing, the second mixing and the third mixing are all realized by using a batch mixer, and the spindle frequency of the batch mixer used for the first mixing, the second mixing and the third mixing is independently 20 Hz to 60 Hz, and the mixing time is independently 1 h to 5 h.

[0015] The third aspect of the present application provides a positive electrode sheet, which comprises the composite lithium cobalt oxide positive electrode material.

[0016] The fourth aspect of the present application provides a lithium ion battery, which comprises the positive electrode sheet.

[0017] By using the technical solution of the present application, the mixing ratio and the mixing order of the lithium cobalt oxide and the lithium titanium aluminum phosphate with different particle sizes are finely controlled, so that the composite lithium cobalt oxide positive electrode material obtained has high density and high specific surface area, and finally the electrochemical performance is improved, including the specific capacity, the cycle stability and the rate performance. The composite lithium cobalt oxide positive electrode material prepared has an optimized particle size distribution and physical properties, can significantly improve the energy density of the lithium ion battery, and prolong the cycle life under high rate. DETAILED DESCRIPTION

[0018] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments.

[0019] As described in the background, the existing lithium cobaltate positive electrode material has the problem of being difficult to balance high energy density and excellent rate performance. In order to solve the above technical problems, the first aspect of the present application provides a composite lithium cobaltate positive electrode material, comprising: a first lithium cobaltate with a D50 of 13-16 μm, a second lithium cobaltate with a D50 of 5.5-6.5 μm, a first lithium titanium aluminum phosphate with a D50 of 300-500 nm, and a second lithium titanium aluminum phosphate with a D50 of 100-280 nm; the weight ratio of the first lithium cobaltate to the first lithium titanium aluminum phosphate is (100-300):1; the weight ratio of the second lithium cobaltate to the second lithium titanium aluminum phosphate is (100-300):1; the weight ratio of the first lithium cobaltate to the second lithium cobaltate is (1.5-4.0):1.

[0020] By fine design and strict limitation of the particle size matching relationship of each component of the composite lithium cobaltate material, the optimization of the particle size distribution and the improvement of the physical and chemical properties are realized, especially the obtained composite lithium cobaltate positive electrode material can balance high density and high specific surface area, and thus exhibits excellent electrochemical performance.

[0021] And indispensably, the above material component formula strictly limits the particle size range of the two kinds of lithium cobaltate and the two kinds of lithium titanium aluminum phosphate, so that the doping is more effective, and the composite lithium cobaltate with significantly improved rate performance is obtained. And the particle size matching of the above lithium cobaltate and lithium titanium aluminum phosphate can further enhance the structural stability while optimizing the rate performance of the obtained composite lithium cobaltate. And by strictly controlling the weight ratio of the first lithium cobaltate to the second lithium cobaltate to be (1.5-4.0):1, the balance of the particle size, density and specific surface area of the obtained composite lithium cobaltate positive electrode material can be realized, so that it can balance high density and specific surface area, and thus has high energy density and rate performance as a positive electrode material. At the same time, this weight relationship can also balance the electrochemical performance and processing performance of the obtained positive electrode material, ensuring its uniformity and stability in subsequent application process, thereby improving the consistency and safety of the battery it is in.

[0022] And in order to more significantly exert the gain effect of the first lithium titanium aluminum phosphate and the second lithium titanium aluminum phosphate on the rate performance of the obtained composite lithium cobaltate material, the weight ratio of the first lithium cobaltate to the first lithium titanium aluminum phosphate is limited to (100-300):1; the weight ratio of the second lithium cobaltate to the second lithium titanium aluminum phosphate is (100-300):1. These two proportional relationships can not only effectively improve the cycle performance and high-rate discharge capacity of lithium cobaltate, but also protect its intrinsic particle size distribution characteristics, thereby obtaining a composite lithium cobaltate positive electrode material with excellent comprehensive performance.

[0023] That is to say, the composite lithium cobalt oxide cathode material provided by the present application has an optimized particle size distribution and physical properties, which can significantly improve the energy density of the lithium ion battery in which it is used, and at the same time, improve the cycle life under high rate.

[0024] Further, based on the improvement of the rate performance of lithium cobalt oxide provided by lithium titanium aluminum phosphate, the molecular formula of the first lithium titanium aluminum phosphate and the second lithium titanium aluminum phosphate is independently Li 1+x A1 x Ti 2-x (PO4)3, wherein 0.01≤x<1, so as to better match the molecular structure of the first lithium cobalt oxide and the second lithium cobalt oxide material, optimize the ion transmission path, and improve the rate performance of the mixed lithium cobalt oxide material. On this basis, the inventors further make x in the molecular formula 0.2~0.4 through a large number of experiments, so as to obtain a higher lithium ion diffusion rate and make the electrochemical performance of the obtained composite lithium cobalt oxide material more superior.

[0025] In order to more effectively coordinate the physicochemical properties of the two lithium cobalt oxide materials, obtain a composite lithium cobalt oxide material with more suitable particle size, and further make the obtained composite lithium cobalt oxide cathode material exhibit higher energy density, further, the D10 of the first lithium cobalt oxide is 4.8μm~6.5μm, and the D10 of the second lithium cobalt oxide is 3.0μm~4.0μm; and / or, the D90 of the first lithium cobalt oxide is 25.0μm~28.0μm, and the D90 of the second lithium cobalt oxide is 10.0μm~12.0μm. And on the basis of the cooperation of the above particle size range, in some embodiments, the specific particle size distribution value (D90-D10) / D50 of the first lithium cobalt oxide is 1.25~1.55, and the specific particle size distribution value (D90-D10) / D50 of the second lithium cobalt oxide is 1.00~1.20, so as to realize the comprehensive improvement of the density and specific surface area of the cathode material by optimizing the particle size distribution of the two lithium cobalt oxides. At the same time, it is also more effective to avoid the agglomeration phenomenon, and further more effectively improve the high energy density and long cycle life under high rate of the obtained composite lithium cobalt oxide cathode material in subsequent application.

[0026] Further, in order to more effectively balance the density and specific surface area of the obtained composite lithium cobalt oxide cathode material, and thus effectively improve the energy density and performance under high rate as a lithium ion battery cathode material, the inventors make the tap density of the first lithium cobalt oxide 2.7g / cm 3 ~3.0g / cm 3 , and the tap density of the second lithium cobalt oxide 2.0g / cm 3 ~2.6g / cm 3 ; and / or, the specific surface area of the first lithium cobalt oxide is 0.15m 2 / g~0.25m2 / g, the specific surface area of the second lithium cobalt oxide is 0.35 m 2 / g~0.50 m 2 / g.

[0027] In several embodiments, the specific surface area of the composite lithium cobalt oxide positive electrode material is 0.25 m 2 / g~0.35 m 2 / g, the tap density is 2.5 g / cm 3 ~2.8 g / cm 3 Further, the D10 of the composite lithium cobalt oxide positive electrode material is 3.8 μm~5.0 μm, the D50 is 11.4 μm~12.9 μm, and the D90 is 24.8 μm~27.7 μm, and the specific particle size distribution value (D90-D10) / D50 is 1.6~2.1. That is to say, the composite lithium cobalt oxide positive electrode material provided in the present application has excellent physicochemical properties and particle size distribution, and can realize efficient energy storage and release in the battery while maintaining good cycle stability and safety as a positive electrode material.

[0028] The second aspect of the present application provides a preparation method of the above-mentioned composite lithium cobalt oxide positive electrode material, comprising: step S1, first mixing the first lithium cobalt oxide and the first lithium aluminum titanium phosphate to obtain a first composite lithium cobalt oxide; step S2, second mixing the second lithium cobalt oxide and the second lithium aluminum titanium phosphate to obtain a second composite lithium cobalt oxide; and step S3, third mixing the first composite lithium cobalt oxide and the second composite lithium cobalt oxide to obtain the composite lithium cobalt oxide positive electrode material.

[0029] Compared with the way of mixing two kinds of lithium aluminum titanium phosphate into the lithium cobalt oxide material system, the above-mentioned mixing order based on the particle size matching relationship provided in the present application can ensure the uniformity of the dispersion of the lithium aluminum titanium phosphate in the whole preparation process of the composite lithium cobalt oxide material, and thus the obtained positive electrode material exhibits more excellent electrochemical performance, including high energy density, rate performance and cycle stability.

[0030] In several typical embodiments, in order to realize the intrinsic rate performance improvement of the first composite lithium cobalt oxide and the second composite lithium cobalt oxide, and to obtain a composite lithium cobalt oxide positive electrode material with better comprehensive performance at a higher efficiency when mixed, the first mixing, the second mixing and the third mixing are all realized by a batch mixer, and the spindle frequency of the batch mixer used in the first mixing, the second mixing and the third mixing is independently 20 Hz~60 Hz, and the mixing time is independently 1 h~5 h.

[0031] In several more typical embodiments, the inventors, through a large number of experiments, screened the corresponding condition parameters in the three mixing processes and obtained: the main shaft frequency of the batch mixer used in the first mixing is 50-60 Hz, and the mixing time is 4-5 h; and / or, the main shaft frequency of the batch mixer used in the second mixing is 20-30 Hz, and the mixing time is 1-2 h; and / or, the main shaft frequency of the batch mixer used in the third mixing is 35-45 Hz, and the mixing time is 2.5-3.5 h. Via the above more accurate mixing parameter settings, the material particle size in each mixing process can be further and respectively adapted, so that the mixing of the first lithium aluminum titanium phosphate and the first lithium cobalt oxide, the second lithium aluminum titanium phosphate and the second lithium cobalt oxide, and the first and second composite lithium cobalt oxide is more efficient, and the uniform consistency after mixing is also improved. Thus, the micro-morphology, particle size and distribution, and density and other physical properties of the obtained material are more effectively optimized, the comprehensive electrochemical performance is improved, and the composite lithium cobalt oxide positive electrode material with greater energy density and better rate performance is obtained.

[0032] The third aspect of the present application provides a positive electrode sheet, which comprises the composite lithium cobalt oxide positive electrode material described above. The positive electrode material described above has high density and high specific surface area, so that the positive electrode sheet in which it is located has more excellent comprehensive performance.

[0033] The fourth aspect of the present application provides a lithium ion battery, which comprises the positive electrode sheet described above. Since the positive electrode material in the positive electrode sheet obtained by the present application has excellent performance, the lithium ion battery in which it is located thus exhibits higher energy density and higher rate performance, and also has excellent cycle stability.

[0034] In several preferred embodiments, under the condition of 25℃ and 4.5V, the capacity retention rate of the obtained lithium ion battery is 77.5%-84.5% when charged at 1C and discharged at 5C and cycled for 800 cycles, and at this time the compaction density of the composite lithium cobalt oxide positive electrode material in the positive electrode sheet of the lithium ion battery is 4.0 g / cm 3 . That is to say, when the composite lithium cobalt oxide positive electrode material obtained by the present application is used to prepare a positive electrode sheet at a high compaction density, the lithium ion battery in which the positive electrode sheet is located can still maintain high cycle stability.

[0035] The present application will be further described in detail below in combination with specific embodiments, which cannot be understood as limiting the scope of the present application.

[0036] Unless otherwise defined, all the professional terms used below have the same meaning as generally understood by those skilled in the art. The professional terms used in the present application are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present application.

[0037] Example 1

[0038] A preparation method of a composite lithium cobalt oxide cathode material

[0039] Material description: the D10, D50, D90, specific particle size distribution value (D90-D10) / D50, tap density and specific surface area parameters of the first lithium cobalt oxide used are shown in Table 1. The D10, D50, D90, specific particle size distribution value (D90-D10) / D50, tap density and specific surface area parameters of the second lithium cobalt oxide used are shown in Table 1.

[0040] The molecular formula of the lithium cobalt oxide used is Li 1+x A1 x Ti 2-x The lithium titanium aluminum phosphate material with the formula (PO4)3 (wherein x is 0.3) is used as the first lithium titanium aluminum phosphate and the second lithium titanium aluminum phosphate, and the D50 of the first lithium titanium aluminum phosphate and the second lithium titanium aluminum phosphate is shown in Table 1-1.

[0041] Table 1-1

[0042]

[0043] Method steps:

[0044] (1) The first lithium cobalt oxide and the first lithium titanium aluminum phosphate are mixed in a weight ratio of 100:1 by a batch mixer for the first mixing, the main shaft frequency of the batch mixer during mixing is 60 Hz, and the mixing time is 5 h, to obtain the first composite lithium cobalt oxide;

[0045] (2) The second lithium cobalt oxide and the second lithium titanium aluminum phosphate are mixed in a weight ratio of 100:1 by a batch mixer for the second mixing, the main shaft frequency of the batch mixer during mixing is 20 Hz, and the mixing time is 1 h, to obtain the second composite lithium cobalt oxide;

[0046] (3) Under the condition that the weight ratio of the first lithium cobalt oxide to the second lithium cobalt oxide is 7:3, the first composite lithium cobalt oxide and the second composite lithium cobalt oxide are mixed by a batch mixer for the third mixing, the main shaft frequency of the batch mixer during mixing is 40 Hz, and the mixing time is 3 h, to obtain the composite lithium cobalt oxide cathode material.

[0047] Example 2

[0048] A preparation method of a composite lithium cobalt oxide cathode material

[0049] The difference between this embodiment and Example 1 is only in the method steps, specifically:

[0050] (1) First mixing of the first lithium cobalt oxide and the first lithium aluminum titanium phosphate with a weight ratio of 300:1 is performed by a batch mixer, the spindle frequency of the batch mixer during mixing is 50 Hz, and the mixing time is 4 h, to obtain the first composite lithium cobalt oxide;

[0051] (2) Second mixing of the second lithium cobalt oxide and the second lithium aluminum titanium phosphate with a weight ratio of 300:1 is performed by a batch mixer, the spindle frequency of the batch mixer during mixing is 20 Hz, and the mixing time is 1 h, to obtain the second composite lithium cobalt oxide;

[0052] (3) Third mixing of the first composite lithium cobalt oxide and the second composite lithium cobalt oxide is performed by a batch mixer under the condition that the weight ratio of the first lithium cobalt oxide to the second lithium cobalt oxide is 4:1, the spindle frequency of the batch mixer during mixing is 35 Hz, and the mixing time is 3.5 h, to obtain the composite lithium cobalt oxide positive electrode material.

[0053] Example 3

[0054] A preparation method of a composite lithium cobalt oxide positive electrode material:

[0055] The difference between this example and Example 1 is only in the method steps, specifically:

[0056] (1) First mixing of the first lithium cobalt oxide and the first lithium aluminum titanium phosphate with a weight ratio of 100:1 is performed by a batch mixer, the spindle frequency of the batch mixer during mixing is 60 Hz, and the mixing time is 5 h, to obtain the first composite lithium cobalt oxide;

[0057] (2) Second mixing of the second lithium cobalt oxide and the second lithium aluminum titanium phosphate with a weight ratio of 100:1 is performed by a batch mixer, the spindle frequency of the batch mixer during mixing is 20 Hz, and the mixing time is 2 h, to obtain the second composite lithium cobalt oxide;

[0058] (3) Third mixing of the first composite lithium cobalt oxide and the second composite lithium cobalt oxide is performed by a batch mixer under the condition that the weight ratio of the first lithium cobalt oxide to the second lithium cobalt oxide is 1.5:1, the spindle frequency of the batch mixer during mixing is 45 Hz, and the mixing time is 2.5 h, to obtain the composite lithium cobalt oxide positive electrode material.

[0059] Example 4

[0060] A preparation method of a composite lithium cobalt oxide positive electrode material:

[0061] The difference between this example and Example 1 is only in the type of raw material, and the specific contents are shown in Tables 1-2.

[0062] Table 1-2

[0063]

[0064] Example 5

[0065] A method for preparing a composite lithium cobalt oxide cathode material:

[0066] The difference between this embodiment and embodiment 1 is only in the kind of raw materials, and the details are shown in Tables 1-3.

[0067] Table 1-3

[0068]

[0069] Embodiment 6

[0070] A method for preparing a composite lithium cobalt oxide cathode material:

[0071] The difference between this embodiment and embodiment 1 is only in the preparation step, in which the first lithium cobalt oxide, the second lithium cobalt oxide, the first lithium titanium aluminum phosphate and the second lithium titanium aluminum phosphate are mixed in the same weight ratio as in embodiment 1, the main shaft frequency of the batch mixer during mixing is 40 Hz, and the mixing time is 3 h, thereby obtaining the composite lithium cobalt oxide cathode material.

[0072] Embodiment 7

[0073] A method for preparing a composite lithium cobalt oxide cathode material:

[0074] The difference between this embodiment and embodiment 1 is only in the molecular formula of the first lithium titanium aluminum phosphate and the second lithium titanium aluminum phosphate, i.e., Li 1+x A1 x Ti 2-x x in (PO4)3 is 0.8.

[0075] Embodiment 8

[0076] A method for preparing a composite lithium cobalt oxide cathode material:

[0077] The difference between this embodiment and embodiment 1 is only in the molecular formula of the first lithium titanium aluminum phosphate and the second lithium titanium aluminum phosphate, i.e., Li 1+x A1 x Ti 2-x x in (PO4)3 is 0.01.

[0078] Embodiment 9

[0079] A method for preparing a composite lithium cobalt oxide cathode material:

[0080] The difference between this embodiment and embodiment 1 is only in the kind of raw materials, and the details are shown in Table 1-4.

[0081] Table 1-4

[0082]

[0083] Embodiment 10

[0084] A method for preparing a composite lithium cobalt oxide cathode material:

[0085] The difference between this embodiment and embodiment 1 is only the kind of raw materials, see tables 1-5 for details.

[0086] Tables 1-5

[0087]

[0088] Embodiment 11

[0089] A method for preparing a composite lithium cobalt oxide cathode material:

[0090] The difference between this embodiment and embodiment 1 is only the method steps, specifically:

[0091] (1) First mix the first lithium cobalt oxide and the first lithium titanium aluminum phosphate with a weight ratio of 100:1 by a batch mixer, the main shaft frequency of the batch mixer is 70Hz, and the mixing time is 3h, to obtain the first composite lithium cobalt oxide;

[0092] (2) Second mix the second lithium cobalt oxide and the second lithium titanium aluminum phosphate with a weight ratio of 100:1 by a batch mixer, the main shaft frequency of the batch mixer is 40Hz, and the mixing time is 0.5h, to obtain the second composite lithium cobalt oxide;

[0093] (3) Third mix the first composite lithium cobalt oxide and the second composite lithium cobalt oxide by a batch mixer with a weight ratio of 7:3, the main shaft frequency of the batch mixer is 50Hz, and the mixing time is 2h, to obtain the composite lithium cobalt oxide cathode material.

[0094] In this embodiment, the stirring frequency is relatively high, which may cause the lithium cobalt oxide particles and the lithium titanium aluminum phosphate particles to be broken during the mixing process, thereby causing the performance to decrease.

[0095] Embodiment 12

[0096] A method for preparing a composite lithium cobalt oxide cathode material:

[0097] The difference between this embodiment and embodiment 1 is only the method steps, specifically:

[0098] (1) First mix the first lithium cobalt oxide and the first lithium titanium aluminum phosphate with a weight ratio of 100:1 by a batch mixer, the main shaft frequency of the batch mixer is 50Hz, and the mixing time is 6h, to obtain the first composite lithium cobalt oxide;

[0099] (2) The second lithium cobalt oxide and the second lithium titanium aluminum phosphate are mixed by a batch mixer at a weight ratio of 100:1, the spindle frequency of the batch mixer is 10 Hz, and the mixing time is 3 h, to obtain the second composite lithium cobalt oxide;

[0100] (3) The first composite lithium cobalt oxide and the second composite lithium cobalt oxide are mixed by a batch mixer at a weight ratio of 7:3, the spindle frequency of the batch mixer is 30 Hz, and the mixing time is 4 h, to obtain the composite lithium cobalt oxide positive electrode material.

[0101] In this embodiment, the stirring frequency is small and the mixing time is long, which may cause the lithium titanium aluminum phosphate particles to be micro-agglomerated during the mixing process, resulting in a decrease in the rate performance.

[0102] Comparative Example 1

[0103] A preparation method of a composite lithium cobalt oxide positive electrode material comprises the following steps:

[0104] The difference between this comparative example and Example 1 is only the type of raw materials, and specific contents are shown in Tables 1-6.

[0105] Tables 1-6

[0106]

[0107] Comparative Example 2

[0108] A preparation method of a composite lithium cobalt oxide positive electrode material comprises the following steps:

[0109] The difference between this comparative example and Example 1 is only the type of raw materials, and specific contents are shown in Table 1-7.

[0110] Table 1-7

[0111]

[0112] Comparative Example 3

[0113] A preparation method of a composite lithium cobalt oxide positive electrode material comprises the following steps:

[0114] The difference between this comparative example and Example 1 is only that, in step (3), the first composite lithium cobalt oxide and the second composite lithium cobalt oxide are mixed at a weight ratio of 1:1.

[0115] Comparative Example 4

[0116] A preparation method of a composite lithium cobalt oxide positive electrode material comprises the following steps:

[0117] The difference between this comparative example and Example 1 is only that, in step (3), the third mixing of the first composite lithium cobalt oxide and the second composite lithium cobalt oxide is performed at a weight ratio of the first lithium cobalt oxide to the second lithium cobalt oxide of 5:1.

[0118] Comparative Example 5

[0119] A method for preparing a composite lithium cobalt oxide cathode material:

[0120] The difference between this comparative example and Example 1 is only that, in the preparation step, steps (1) and (2) are not performed, but the first lithium cobalt oxide and the second lithium cobalt oxide are directly mixed by a batch mixer at a weight ratio of 7:3, the spindle frequency of the batch mixer during mixing is 40 Hz, and the mixing time is 3 h, thereby obtaining the composite lithium cobalt oxide cathode material.

[0121] That is, the lithium titanium aluminum phosphate material is not introduced in this comparative example.

[0122] Comparative Example 6

[0123] A method for preparing a composite lithium cobalt oxide cathode material:

[0124] The difference between this comparative example and Example 1 is only the method steps, specifically:

[0125] (1) The first mixing of the first lithium cobalt oxide and the first lithium titanium aluminum phosphate is performed by a batch mixer at a weight ratio of 50:1, the spindle frequency of the batch mixer during mixing is 60 Hz, and the mixing time is 5 h, thereby obtaining the first composite lithium cobalt oxide;

[0126] (2) The second mixing of the second lithium cobalt oxide and the second lithium titanium aluminum phosphate is performed by a batch mixer at a weight ratio of 400:1, the spindle frequency of the batch mixer during mixing is 20 Hz, and the mixing time is 1 h, thereby obtaining the second composite lithium cobalt oxide;

[0127] (3) The third mixing of the first composite lithium cobalt oxide and the second composite lithium cobalt oxide is performed by a batch mixer at a weight ratio of the first lithium cobalt oxide to the second lithium cobalt oxide of 7:3, the spindle frequency of the batch mixer during mixing is 40 Hz, and the mixing time is 3 h, thereby obtaining the composite lithium cobalt oxide cathode material.

[0128] Test method

[0129] D10, D50, D90, and specific particle size distribution value SPAN ((D90-D10) / D50): all obtained by GB 19077 test.

[0130] Tap density: obtained by GB / T 5162-2021 test.

[0131] Specific surface area: obtained by GB / T 19587 test.

[0132] Battery sample preparation and performance test:

[0133] (1) Preparation of positive electrode sheet: The composite lithium cobalt oxide positive electrode material obtained in each example and comparative example was prepared into a positive electrode slurry, and an aluminum foil was used as a current collector, and the compaction density of each sample was controlled to be 4.0 g / cm 3 (2) Assembly of battery sample: A copper foil was used as a negative electrode sheet, a PP separator with a thickness of 12 μm was used as a battery separator, and an electrolyte system of 15% LiPF6+FEC+HTCN+EC / PC / DEC / EP / PP was used as a battery electrolyte, to assemble a soft package battery sample with a capacity of 2100 mAh.

[0134] The results obtained by the above test are shown in Table 2.

[0135] Table 2

[0136]

[0137] From the above description, it can be seen that the above-mentioned embodiments of the present application realize the preparation of composite lithium cobalt oxide materials with high density and high specific surface area. When used as a positive electrode material in a lithium ion battery, the obtained lithium ion battery sample has good rate performance, and under the condition of 1C charging and 5C discharging, it still shows excellent long cycle stability after 800 cycles.

[0138] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application are used to distinguish similar objects, and do not necessarily have to describe a specific order or chronological sequence. It should be understood that the terms thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that described herein.

[0139] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A composite lithium cobalt oxide positive electrode material, characterized in that: include: A first lithium cobalt oxide having a D50 of 13 μm to 16 μm, a second lithium cobalt oxide having a D50 of 5.5 μm to 6.5 μm, a first lithium aluminum titanium phosphate having a D50 of 300 nm to 500 nm, and a second lithium aluminum titanium phosphate having a D50 of 100 nm to 280 nm; The weight ratio of the first lithium cobaltate to the first lithium aluminum titanium phosphate is (100-300):1; The weight ratio of the second lithium cobaltate to the second lithium aluminum titanium phosphate is (100-300):1; The weight ratio of the first lithium cobalt oxide to the second lithium cobalt oxide is (1.5-4.0):

1.

2. The composite lithium cobalt oxide positive electrode material according to claim 1, characterized in that The molecular formulas of the first lithium aluminum titanium phosphate and the second lithium aluminum titanium phosphate are each independently Li 1+x A1 x Ti 2-x (PO4)3, where 0.01≤x<1.

3. The composite lithium cobalt oxide positive electrode material according to claim 1, characterized in that The D10 of the first lithium cobaltate is 4.8 μm to 6.5 μm, and the D10 of the second lithium cobaltate is 3.0 μm to 4.0 μm; and / or the D90 of the first lithium cobaltate is 25.0 μm to 28.0 μm, and the D90 of the second lithium cobaltate is 10.0 μm to 12.0 μm.

4. The composite lithium cobalt oxide positive electrode material according to any one of claims 1 to 3, characterized in that The specific particle size distribution value (D90-D10) / D50 of the first lithium cobaltate is 1.25-1.55, and the specific particle size distribution value (D90-D10) / D50 of the second lithium cobaltate is 1.00-1.

20.

5. The composite lithium cobalt oxide positive electrode material according to any one of claims 1 to 3, characterized in that The tap density of the first lithium cobalt oxide is 2.7 g / cm 3 ~3.0g / cm 3 The tap density of the second lithium cobalt oxide is 2.0 g / cm 3 ~2.6g / cm 3 and / or, The specific surface area of ​​the first lithium cobaltate is 0.15m 2 / g~0.25m 2 / g, the specific surface area of ​​the second lithium cobaltate is 0.35m 2 / g~0.50m 2 / g.

6. The composite lithium cobalt oxide positive electrode material according to any one of claims 1 to 3, characterized in that The specific surface area of ​​the composite lithium cobalt oxide positive electrode material is 0.25m 2 / g~0.35m 2 / g, tap density is 2.5g / cm 3 ~2.8g / cm 3 .

7. The composite lithium cobalt oxide positive electrode material according to any one of claims 1 to 3, characterized in that The D10 of the composite lithium cobalt oxide positive electrode material is 3.8 μm to 5.0 μm, the D50 is 11.4 μm to 12.9 μm, the D90 is 24.8 μm to 27.7 μm, and the specific particle size distribution value (D90-D10) / D50 is 1.6-2.

1.

8. A method for preparing the composite lithium cobalt oxide positive electrode material according to any one of claims 1 to 7, characterized in that: include: Step S1, performing a first mixing of the first lithium cobalt oxide and the first lithium aluminum titanium phosphate to obtain a first composite lithium cobalt oxide; Step S2, performing a second mixing of the second lithium cobalt oxide and the second lithium aluminum titanium phosphate to obtain a second composite lithium cobalt oxide; Step S3: performing a third mixing of the first composite lithium cobalt oxide and the second composite lithium cobalt oxide to obtain the composite lithium cobalt oxide positive electrode material.

9. The preparation method according to claim 8, characterized in that The first mixing, the second mixing and the third mixing are all achieved by a batch mixer, and the main shaft frequency of the batch mixer used for the first mixing, the second mixing and the third mixing is independently 20 Hz to 60 Hz, and the mixing time is independently 1 hour to 5 hours.

10. A positive electrode plate, characterized in that: The positive electrode plate comprises the composite lithium cobalt oxide positive electrode material according to any one of claims 1 to 7.

11. A lithium-ion battery, characterized in that: The lithium-ion battery comprises the positive electrode sheet according to claim 10.

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