Composite lithium cobalt oxide positive electrode material and preparation method therefor, positive electrode sheet, and lithium ion battery

Abstract

Embodiments of the present application provide a composite lithium cobalt oxide positive electrode material and a preparation method therefor, a positive electrode sheet, and a lithium ion battery. The composite lithium cobalt oxide positive electrode material comprises first lithium cobalt oxide having a D50 of 13 μm to 16 μm, second lithium cobalt oxide having a D50 of 5.5 μm to 6.5 μm, first lithium aluminum titanium phosphate having a D50 of 300 nm to 500 nm, and second lithium aluminum titanium phosphate having a D50 of 100 nm to 280 nm; the weight ratio of the first lithium cobalt oxide to the first lithium aluminum titanium phosphate is (100-300):1; the weight ratio of the second lithium cobalt oxide to the second lithium aluminum titanium 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. In the present application, by controlling the mixing ratios and mixing orders of lithium cobalt oxide and lithium aluminum titanium phosphate of different particle sizes, the obtained composite lithium cobalt oxide positive electrode material can have both high compaction density and high rate capability.

Description

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

[0001] This application claims priority to Chinese Patent Application No. 202411944656.9, filed on December 26, 2024, entitled "Composite Lithium Cobalt Oxide Cathode Material, Preparation Method Thereof, Cathode Sheet and Lithium-ion Battery", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of lithium-ion batteries, and more specifically, to a composite lithium cobalt oxide cathode material, its preparation method, cathode sheet, and lithium-ion battery. Background Technology

[0003] High energy density (ED) is the research focus for most rechargeable batteries, while high rate capability is also a performance requirement that consumer batteries must consider. For cathode materials, high ED often corresponds to high voltage, high tap density (PD), and high tap density (TD), while high rate capability corresponds to high specific surface area (BET), low tap density, and low tap density.

[0004] In other words, from the perspective of the materials themselves, it is difficult to improve energy density and rate performance simultaneously. Compared to other cathode materials, lithium cobalt oxide has higher tap density, higher voltage, and better rate performance. In the production of lithium cobalt oxide, the particle size can generally be controlled by adjusting the process. Larger particle size capacity-type lithium cobalt oxide tends to have higher tap density and compacted density, lower BET, and poorer rate performance; smaller particle size rate-type lithium cobalt oxide tends to have lower tap density and compacted density, higher BET, and better rate performance.

[0005] To further improve the energy density of lithium cobalt oxide cathode materials, their compaction density needs to be increased. The common method to increase the compaction density of cathode materials is to increase the particle size, which inevitably reduces the specific surface area of ​​the material. Combined with the hindered lithium-ion migration under high compaction conditions, this makes it difficult for the battery to meet the 5C discharge requirement. For example, current high-capacity lithium cobalt oxide materials can achieve a compaction density of 4.2 g / cm³. 3 This technology can deliver high energy density, but its rate performance is limited to below 3C. For example, CN116768282B provides a high-rate lithium cobalt oxide, and the full cell prepared using this lithium cobalt oxide has a discharge capacity of over 95% of the 0.2C capacity at 4.45V and 20C, but its compaction density is only 3.7~3.9 g / cm³. 3 CN114220645A provides a lithium cobalt oxide with a bimodal particle size distribution and a compaction density of up to 4.1 g / cm³. 3However, this material is only suitable for a voltage of 4.45V, and the large particle size distribution will lead to a loss of rate performance. Technical issues

[0006] Therefore, how to balance the density and specific surface area of ​​lithium cobalt oxide so that it can achieve both high energy density and excellent rate performance when used as a cathode material is one of the important technical problems that need to be solved in this field. Technical solutions

[0007] The main objective of this application is to provide a composite lithium cobalt oxide cathode material, its preparation method, cathode sheet, and lithium-ion battery, so as to solve the problem that existing lithium cobalt oxide cathode materials are difficult to achieve both high energy density and excellent rate performance.

[0008] To achieve the above objectives, the first aspect of this application provides a composite lithium cobalt oxide cathode material, comprising: a first lithium cobalt oxide with a D50 of 13 μm to 16 μm, a second lithium cobalt oxide with a D50 of 5.5 μm to 6.5 μm, a first lithium titanium aluminum phosphate with a D50 of 300 nm to 500 nm, and a second lithium titanium aluminum phosphate with a D50 of 100 nm to 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.

[0009] The second aspect of this application provides a method for preparing the above-mentioned composite lithium cobalt oxide cathode material, comprising: step S1, mixing a first lithium cobalt oxide with a first lithium titanium aluminum phosphate to obtain a first composite lithium cobalt oxide; step S2, mixing a second lithium cobalt oxide with a second lithium titanium aluminum phosphate to obtain a second composite lithium cobalt oxide; and step S3, mixing the first composite lithium cobalt oxide with the second composite lithium cobalt oxide to obtain a composite lithium cobalt oxide cathode material.

[0010] A third aspect of this application provides a positive electrode sheet comprising the aforementioned composite lithium cobalt oxide positive electrode material.

[0011] A fourth aspect of this application provides a lithium-ion battery comprising the aforementioned positive electrode. Beneficial effects

[0012] By applying the technical solution of this application and precisely controlling the mixing ratio and mixing order of lithium cobalt oxide and lithium titanium aluminum phosphate with different particle sizes, the resulting composite lithium cobalt oxide cathode material can achieve both high density and high specific surface area, ultimately improving its electrochemical performance, including increased specific capacity, cycle stability, and rate performance. The prepared composite lithium cobalt oxide cathode material has optimized particle size distribution and physical properties, which can significantly improve the energy density of lithium-ion batteries and extend their cycle life at high rates. Embodiments of the present invention

[0013] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.

[0014] As described in the background section, existing lithium cobalt oxide cathode materials suffer from the problem of simultaneously achieving high energy density and excellent rate performance. To address this technical problem, the first aspect of this application provides a composite lithium cobalt oxide cathode material, comprising: a first lithium cobalt oxide with a D50 of 13 μm to 16 μm, a second lithium cobalt oxide with a D50 of 5.5 μm to 6.5 μm, a first lithium titanium aluminum phosphate with a D50 of 300 nm to 500 nm, and a second lithium titanium aluminum phosphate with a D50 of 100 nm to 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.

[0015] By meticulously designing and strictly defining the particle size distribution of the components in the composite lithium cobalt oxide material, the particle size distribution and physicochemical properties were optimized. In particular, the resulting composite lithium cobalt oxide cathode material was able to achieve both high density and high specific surface area, thereby exhibiting excellent electrochemical performance.

[0016] Crucially, the aforementioned material composition formulation strictly limits the particle size ranges of the two types of lithium cobalt oxide and the two types of lithium titanium aluminum phosphate, allowing for more effective doping and resulting in composite lithium cobalt oxide with significantly improved rate performance. Furthermore, the particle size matching of the aforementioned lithium cobalt oxide and lithium titanium aluminum phosphate optimizes the rate performance of the resulting composite lithium cobalt oxide while further enhancing its structural stability. Moreover, by strictly controlling the weight ratio of the first lithium cobalt oxide to the second lithium cobalt oxide at (1.5~4.0):1, a balance can be achieved in the particle size, density, and specific surface area of ​​the resulting composite lithium cobalt oxide cathode material, thus achieving both high density and specific surface area, and consequently, high energy density and rate performance when used as a cathode material. Simultaneously, this weight relationship also balances the electrochemical and processing properties of the resulting cathode material, ensuring its uniformity and stability in subsequent applications, thereby improving the consistency and safety of the battery in which it is used.

[0017] To more significantly enhance the rate performance of the resulting composite lithium cobalt oxide material by utilizing the combined lithium titanium aluminum phosphate (LFP) and lithium titanium aluminum phosphate (LAP), the weight ratio of LFP to LFP is limited to (100~300):1; the weight ratio of LFP to LAP is also limited to (100~300):1. These ratios not only effectively improve the cycle performance and high-rate discharge capability of lithium cobalt oxide but also protect its intrinsic particle size distribution characteristics, resulting in a composite lithium cobalt oxide cathode material with excellent overall performance.

[0018] In other words, the composite lithium cobalt oxide cathode material provided in this application has optimized particle size distribution and physical properties, which can significantly improve the energy density of the lithium-ion battery in which it is located, and at the same time improve its cycle life at high rates.

[0019] Furthermore, based on the rate performance improvement provided by lithium titanium aluminum phosphate to lithium cobalt oxide, the molecular formulas of the first and second lithium titanium aluminum phosphates are independently Li... 1+x A1 x Ti 2-x (PO4)3, where 0.01 ≤ x < 1, is used to better match the molecular structures of the first and second lithium cobalt oxide materials, optimize the ion transport path, and improve the rate performance of the resulting composite lithium cobalt oxide material. Furthermore, through extensive experiments, the inventors further determined that x in the molecular formula to be 0.2–0.4, thereby obtaining an even higher lithium-ion diffusion rate and resulting in superior electrochemical performance of the composite lithium cobalt oxide material.

[0020] To more effectively coordinate the physicochemical properties of the two lithium cobalt oxide materials and obtain a composite lithium cobalt oxide material with a more suitable particle size, thereby enabling the resulting composite lithium cobalt oxide cathode material to exhibit higher energy density, the D10 of the first lithium cobalt oxide is further set to 4.8 μm to 6.5 μm, and the D10 of the second lithium cobalt oxide is set to 3.0 μm to 4.0 μm; and / or, the D90 of the first lithium cobalt oxide is set to 25.0 μm to 28.0 μm, and the D90 of the second lithium cobalt oxide is set to 10.0 μm to 12.0 μm. Furthermore, regarding the aforementioned particle size range, in some embodiments, the specific particle size distribution value (D90 - D10) / D50 of the first lithium cobalt oxide is 1.25 to 1.55, and the specific particle size distribution value (D90 - D10) / D50 of the second lithium cobalt oxide is 1.00 to 1.20, so as to achieve a comprehensive improvement in the cathode material density and specific surface area by optimizing the particle size distribution of the two lithium cobalt oxides. This also more effectively avoids agglomeration, thereby more effectively improving the high energy density of the obtained composite lithium cobalt oxide cathode material in subsequent applications, as well as its long cycle life at high rates.

[0021] Furthermore, in order to more effectively balance the density and specific surface area of ​​the resulting composite lithium cobalt oxide cathode material, thereby effectively improving its energy density and performance under high-rate conditions as a lithium-ion battery cathode material, the inventors conducted numerous experiments to achieve a tap density of 2.7 g / cm³ for the first lithium cobalt oxide. 3 ~3.0g / cm 3 The tap density of the second lithium cobalt oxide is 2.0 g / cm³. 3 ~2.6g / cm 3 ; and / or, the specific surface area of ​​the first lithium cobalt oxide is 0.15 m². 2 / g~0.25m 2 / g, the specific surface area of ​​lithium cobalt oxide II is 0.35m². 2 / g~0.50m 2 / g.

[0022] In several embodiments, the specific surface area of ​​the composite lithium cobalt oxide cathode material is 0.25 m². 2 / g~0.35m 2 / g, tap density is 2.5g / cm³ 3 ~2.8g / cm 3 Furthermore, the composite lithium cobalt oxide cathode material has a D10 of 3.8 μm to 5.0 μm, a D50 of 11.4 μm to 12.9 μm, and a D90 of 24.8 μm to 27.7 μm, with a specific particle size distribution value (D90 - D10) / D50 of 1.6 to 2.1. In other words, the composite lithium cobalt oxide cathode material provided in this application possesses excellent physicochemical properties and particle size distribution, enabling it to achieve efficient energy storage and release in batteries while maintaining good cycle stability and safety.

[0023] The second aspect of this application provides a method for preparing the above-mentioned composite lithium cobalt oxide cathode material, comprising: step S1, mixing a first lithium cobalt oxide with a first lithium titanium aluminum phosphate to obtain a first composite lithium cobalt oxide; step S2, mixing a second lithium cobalt oxide with a second lithium titanium aluminum phosphate to obtain a second composite lithium cobalt oxide; and step S3, mixing the first composite lithium cobalt oxide with the second composite lithium cobalt oxide to obtain a composite lithium cobalt oxide cathode material.

[0024] Compared to the method of mixing two types of lithium titanium aluminum phosphate together into the lithium cobalt oxide material system, the mixing sequence based on particle size matching provided in this application can ensure the uniform dispersion of lithium titanium aluminum phosphate throughout the entire preparation process of the composite lithium cobalt oxide material, thereby enabling the obtained cathode material to exhibit better electrochemical performance, including high energy density, rate performance and cycle stability.

[0025] In several typical implementations, in order to improve the intrinsic rate performance of the first and second composite lithium cobalt oxides and to obtain a composite lithium cobalt oxide cathode material with better overall performance at higher efficiency when they are mixed, the first mixing, the second mixing and the third mixing are all carried out by batch mixers, and the spindle frequency of the batch mixers used for the first mixing, the second mixing and the third mixing are each independently 20Hz~60Hz, and the mixing time is each independently 1h~5h.

[0026] In several more typical embodiments, the inventors, through extensive experiments, screened the corresponding condition parameters for the three mixing processes and obtained the following: the spindle frequency of the batch mixer used for the first mixing is 50Hz~60Hz, and the mixing time is 4h~5h; and / or, the spindle frequency of the batch mixer used for the second mixing is 20Hz~30Hz, and the mixing time is 1h~2h; and / or, the spindle frequency of the batch mixer used for the third mixing is 35Hz~45Hz, and the mixing time is 2.5h~3.5h. Through these more precise mixing parameter settings, the particle size of the material in each mixing process can be further and separately adapted, thereby making the mixing of the first lithium titanium aluminum phosphate with the first lithium cobalt oxide, the second lithium titanium aluminum phosphate with the second lithium cobalt oxide, and the first composite lithium cobalt oxide with the second composite lithium cobalt oxide more efficient, and improving the uniformity of the mixed material. This more effectively optimizes the microstructure, particle size and distribution, and density of the obtained material, improving its overall electrochemical performance and resulting in a composite lithium cobalt oxide cathode material with higher energy density and better rate performance.

[0027] A third aspect of this application provides a positive electrode sheet comprising the aforementioned composite lithium cobalt oxide positive electrode material. This positive electrode material possesses both high density and high specific surface area, thereby enabling the positive electrode sheet in which it is located to exhibit superior overall performance.

[0028] A fourth aspect of this application provides a lithium-ion battery comprising the aforementioned positive electrode sheet. Because the positive electrode material in the positive electrode sheet obtained in this application has superior performance, the lithium-ion battery in which it is located exhibits higher energy density and higher rate performance, while also possessing excellent cycle stability.

[0029] In several preferred embodiments, under conditions of 25°C and 4.5V, charging at 1C, discharging at 5C, and cycling for 800 cycles, the resulting lithium-ion battery retains a capacity of 77.5%~84.5%, and at this time, the compaction density of the composite lithium cobalt oxide cathode material in the positive electrode sheet of the lithium-ion battery is 4.0 g / cm³. 3 In other words, when the composite lithium cobalt oxide cathode material obtained in this invention is used to prepare cathode sheets with high compaction density, the lithium-ion battery containing the cathode sheets can still maintain high cycle stability.

[0030] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0031] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of this application.

[0032] Example 1

[0033] A method for preparing a composite lithium cobalt oxide cathode material:

[0034] Material specifications: The D10, D50, D90, specific particle size distribution (D90-D10) / D50, tap density, and specific surface area parameters of the first lithium cobalt oxide used are shown in Table 1-1. The D10, D50, D90, specific particle size distribution (D90-D10) / D50, tap density, and specific surface area parameters of the second lithium cobalt oxide used are also shown in Table 1-1.

[0035] Using the molecular formula Li 1+x A1 x Ti 2-x (PO4)3 (where x is 0.3) titanium aluminum lithium phosphate materials are used as the first titanium aluminum lithium phosphate and the second titanium aluminum lithium phosphate, respectively, and the D50 of the first titanium aluminum lithium phosphate and the second titanium aluminum lithium phosphate are shown in Table 1-1.

[0036] Table 1-1

[0037] D10D50D90(D90-D10) / D50 Tap Density Specific Surface Area First Lithium Cobalt Oxide 6.44μm 15.14μm 27.96μm 1.42 2.83g / cm³ 3 0.22m 2 / g First, lithium titanium aluminum phosphate\500nm\\\\ Second, lithium cobalt oxide 3.76μm 6.49μm 10.99μm 1.11 2.38g / cm 3 0.38m 2 / g lithium titanium aluminum phosphate\100nm\\\\

[0038] Method and steps:

[0039] (1) The first lithium cobalt oxide and the first lithium titanium aluminum phosphate are mixed in a weight ratio of 100:1 using a batch mixer. The spindle frequency of the batch mixer is 60Hz and the mixing time is 5h to obtain the first composite lithium cobalt oxide.

[0040] (2) The second lithium cobalt oxide and the second lithium titanium aluminum phosphate are mixed in a weight ratio of 100:1 using a batch mixer. The spindle frequency of the batch mixer is 20Hz and the mixing time is 1h to obtain the second composite lithium cobalt oxide.

[0041] (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 for the third time by a batch mixer. The spindle frequency of the batch mixer during mixing is 40Hz and the mixing time is 3h, thus obtaining the composite lithium cobalt oxide cathode material.

[0042] Example 2

[0043] A method for preparing a composite lithium cobalt oxide cathode material:

[0044] The difference between this embodiment and Embodiment 1 lies only in the method steps, specifically:

[0045] (1) The first lithium cobalt oxide and the first lithium titanium aluminum phosphate are mixed in a weight ratio of 300:1 using a batch mixer. The spindle frequency of the batch mixer is 50Hz and the mixing time is 4h to obtain the first composite lithium cobalt oxide.

[0046] (2) The second lithium cobalt oxide and the second lithium titanium aluminum phosphate are mixed in a weight ratio of 300:1 using a batch mixer. The spindle frequency of the batch mixer is 20Hz and the mixing time is 1h to obtain the second composite lithium cobalt oxide.

[0047] (3) Under the condition that the weight ratio of the first lithium cobalt oxide to the second lithium cobalt oxide is 4:1, the first composite lithium cobalt oxide and the second composite lithium cobalt oxide are mixed for the third time by a batch mixer. The spindle frequency of the batch mixer during mixing is 35Hz and the mixing time is 3.5h, thus obtaining the composite lithium cobalt oxide cathode material.

[0048] Example 3

[0049] A method for preparing a composite lithium cobalt oxide cathode material:

[0050] The difference between this embodiment and Embodiment 1 lies only in the method steps, specifically:

[0051] (1) The first lithium cobalt oxide and the first lithium titanium aluminum phosphate are mixed in a weight ratio of 100:1 using a batch mixer. The spindle frequency of the batch mixer is 60Hz and the mixing time is 5h to obtain the first composite lithium cobalt oxide.

[0052] (2) The second lithium cobalt oxide and the second lithium titanium aluminum phosphate are mixed in a weight ratio of 100:1 using a batch mixer. The spindle frequency of the batch mixer is 20Hz and the mixing time is 2h to obtain the second composite lithium cobalt oxide.

[0053] (3) Under the condition that the weight ratio of the first lithium cobalt oxide to the second lithium cobalt oxide is 1.5:1, the first composite lithium cobalt oxide and the second composite lithium cobalt oxide are mixed for the third time by a batch mixer. The spindle frequency of the batch mixer during mixing is 45Hz and the mixing time is 2.5h, thus obtaining the composite lithium cobalt oxide cathode material.

[0054] Example 4

[0055] A method for preparing a composite lithium cobalt oxide cathode material:

[0056] The only difference between this embodiment and Embodiment 1 is the type of raw materials, as detailed in Tables 1-2.

[0057] Table 1-2

[0058] D10D50D90(D90-D10) / D50 Tap Density Specific Surface Area First Lithium Cobalt Oxide 6.44μm 15.14μm 27.96μm 1.42 2.83g / cm³ 3 0.22m 2 / g First, lithium titanium aluminum phosphate 500nm Second, lithium cobalt oxide 3.36μm 5.96μm 10.04μm 1.12 2.04g / cm 3 0.47m 2 / g lithium titanium aluminum phosphate\250nm\\\\

[0059] Example 5

[0060] A method for preparing a composite lithium cobalt oxide cathode material:

[0061] The only difference between this embodiment and Embodiment 1 is the type of raw materials, as detailed in Tables 1-3.

[0062] Table 1-3

[0063] D10D50D90(D90-D10) / D50 Tap Density Specific Surface Area First Lithium Cobalt Oxide 5.03μm 15.92μm 25.04μm 1.25 2.87g / cm³ 3 0.24m 2 / g First, lithium titanium aluminum phosphate 300nm Second, lithium cobalt oxide 3.76μm 6.49μm 10.99μm 1.11 2.38g / cm 3 0.38m 2 / g lithium titanium aluminum phosphate\100nm\\\\

[0064] Example 6

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

[0066] The only difference between this embodiment and Example 1 is that in the preparation step, 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 Example 1. The spindle frequency of the batch mixer during mixing is 40 Hz, and the mixing time is 3 hours, thus obtaining the composite lithium cobalt oxide cathode material.

[0067] Example 7

[0068] A method for preparing a composite lithium cobalt oxide cathode material:

[0069] The only difference between this embodiment and Embodiment 1 is that the molecular formulas of the first and second lithium titanium aluminum phosphates are changed, so that Li 1+x A1 x Ti 2-x In (PO4)3, the value of x is 0.8.

[0070] Example 8

[0071] A method for preparing a composite lithium cobalt oxide cathode material:

[0072] The only difference between this embodiment and Embodiment 1 is that the molecular formulas of the first and second lithium titanium aluminum phosphates are changed, so that Li 1+x A1 x Ti 2-x In (PO4)3, the value of x is 0.01.

[0073] Example 9

[0074] A method for preparing a composite lithium cobalt oxide cathode material:

[0075] The only difference between this embodiment and Embodiment 1 is the type of raw materials, as detailed in Tables 1-4.

[0076] Table 1-4

[0077] D10D50D90(D90-D10) / D50 Tap Density Specific Surface Area First Lithium Cobalt Oxide 4.52μm 13.09μm 30.45μm 1.98 2.65g / cm³ 3 0.39m 2 / g First, lithium titanium aluminum phosphate 300nm Second, lithium cobalt oxide 3.76μm 6.49μm 10.99μm 1.11 2.38g / cm 3 0.38m 2 / g lithium titanium aluminum phosphate\100nm\\\\

[0078] Example 10

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

[0080] The only difference between this embodiment and Embodiment 1 is the type of raw materials, as detailed in Tables 1-5.

[0081] Table 1-5

[0082] D10D50D90(D90-D10) / D50 Tap Density Specific Surface Area First Lithium Cobalt Oxide 6.44μm 15.14μm 27.96μm 1.42 2.83g / cm³ 3 0.22m 2 / g First, lithium titanium aluminum phosphate 500nm Second, lithium cobalt oxide 2.37μm 5.53μm 13.76μm 1.28 1.97g / cm 3 0.52m 2 / g lithium titanium aluminum phosphate\100nm\\\\

[0083] Example 11

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

[0085] The difference between this embodiment and Embodiment 1 lies only in the method steps, specifically:

[0086] (1) The first lithium cobalt oxide and the first lithium titanium aluminum phosphate are mixed in a weight ratio of 100:1 using a batch mixer. The spindle frequency of the batch mixer is 70Hz and the mixing time is 3h to obtain the first composite lithium cobalt oxide.

[0087] (2) The second lithium cobalt oxide and the second lithium titanium aluminum phosphate are mixed in a weight ratio of 100:1 using a batch mixer. The spindle frequency of the batch mixer is 40Hz and the mixing time is 0.5h to obtain the second composite lithium cobalt oxide.

[0088] (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 for the third time by a batch mixer. The spindle frequency of the batch mixer during mixing is 50Hz and the mixing time is 2h, thus obtaining the composite lithium cobalt oxide cathode material.

[0089] In this embodiment, the stirring frequency is relatively high, which may cause the lithium cobalt oxide particles and lithium titanium aluminum phosphate particles to break during the mixing process, thereby leading to a decrease in performance.

[0090] Example 12

[0091] A method for preparing a composite lithium cobalt oxide cathode material:

[0092] The difference between this embodiment and Embodiment 1 lies only in the method steps, specifically:

[0093] (1) The first lithium cobalt oxide and the first lithium titanium aluminum phosphate are mixed in a weight ratio of 100:1 using a batch mixer. The spindle frequency of the batch mixer is 50Hz and the mixing time is 6h to obtain the first composite lithium cobalt oxide.

[0094] (2) The second lithium cobalt oxide and the second lithium titanium aluminum phosphate are mixed in a weight ratio of 100:1 using a batch mixer. The spindle frequency of the batch mixer is 10Hz and the mixing time is 3h to obtain the second composite lithium cobalt oxide.

[0095] (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 for the third time by a batch mixer. The spindle frequency of the batch mixer during mixing is 30Hz and the mixing time is 4h, thus obtaining the composite lithium cobalt oxide cathode material.

[0096] In this embodiment, the stirring frequency is low and the mixing time is long, which may cause micro-agglomeration of lithium titanium aluminum phosphate particles during the mixing process, resulting in a decrease in rate performance.

[0097] Comparative Example 1

[0098] A method for preparing a composite lithium cobalt oxide cathode material:

[0099] The only difference between this comparative example and Example 1 is the type of raw materials, as detailed in Tables 1-6.

[0100] Table 1-6

[0101] D10D50D90(D90-D10) / D50 Tap Density Specific Surface Area First Lithium Cobalt Oxide 7.21μm 17.15μm 29.64μm 1.31 2.93g / cm³ 3 0.18m 2 / g Lithium aluminum titanium phosphate 600nm \\ Lithium cobalt oxide 3.76μm 6.49μm 10.99μm 1.11 2.38g / cm 3 0.38m 2 / g lithium titanium aluminum phosphate\100nm\\\\

[0102] Comparative Example 2

[0103] A method for preparing a composite lithium cobalt oxide cathode material:

[0104] The only difference between this comparative example and Example 1 is the type of raw materials, as detailed in Tables 1-7.

[0105] Table 1-7

[0106] D10D50D90(D90-D10) / D50 Tap Density Specific Surface Area First Lithium Cobalt Oxide 6.44μm 15.14μm 27.96μm 1.42 2.83g / cm³ 3 0.22m 2 / g First, lithium titanium aluminum phosphate 500nm Second, lithium cobalt oxide 4.65μm 8.05μm 12.46μm 0.97 2.58g / cm 3 0.33m 2 / g lithium titanium aluminum phosphate\50nm\\\\

[0107] Comparative Example 3

[0108] A method for preparing a composite lithium cobalt oxide cathode material:

[0109] The only difference between this comparative example and Example 1 is that in step (3), the first composite lithium cobalt oxide and the second composite lithium cobalt oxide are mixed in a weight ratio of 1:1.

[0110] Comparative Example 4

[0111] A method for preparing a composite lithium cobalt oxide cathode material:

[0112] The only difference between this comparative example and Example 1 is that in step (3), the first composite lithium cobalt oxide and the second composite lithium cobalt oxide are mixed in a weight ratio of 5:1.

[0113] Comparative Example 5

[0114] A method for preparing a composite lithium cobalt oxide cathode material:

[0115] The only difference between this comparative example and Example 1 is that steps (1) and (2) were not performed in the preparation process. Instead, the first lithium cobalt oxide and the second lithium cobalt oxide were directly mixed in a weight ratio of 7:3 using a batch mixer. The spindle frequency of the batch mixer was 40 Hz and the mixing time was 3 h, thus obtaining the composite lithium cobalt oxide cathode material.

[0116] That is, lithium titanium aluminum phosphate material was not introduced in this comparative example.

[0117] Comparative Example 6

[0118] A method for preparing a composite lithium cobalt oxide cathode material:

[0119] The difference between this comparative example and Example 1 lies only in the method steps, specifically:

[0120] (1) The first lithium cobalt oxide and the first lithium titanium aluminum phosphate are mixed in a weight ratio of 50:1 using a batch mixer. The spindle frequency of the batch mixer during mixing is 60Hz and the mixing time is 5h to obtain the first composite lithium cobalt oxide.

[0121] (2) The second lithium cobalt oxide and the second lithium titanium aluminum phosphate are mixed in a weight ratio of 400:1 using a batch mixer. The spindle frequency of the batch mixer is 20Hz and the mixing time is 1h to obtain the second composite lithium cobalt oxide.

[0122] (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 for the third time by a batch mixer. The spindle frequency of the batch mixer during mixing is 40Hz and the mixing time is 3h, thus obtaining the composite lithium cobalt oxide cathode material.

[0123] Test methods

[0124] D10, D50, D90, and the specific particle size distribution value SPAN ((D90-D10) / D50): were all obtained through testing according to GB19077.

[0125] Tap density: obtained by testing according to GB / T 5162-2021.

[0126] Specific surface area: obtained by testing according to GB / T 19587.

[0127] Battery sample preparation and performance testing:

[0128] (1) Preparation of positive electrode sheet: The composite lithium cobalt oxide positive electrode materials obtained in each example and comparative example were formulated into positive electrode slurry, and aluminum foil was used as the current collector. The compaction density of each sample was controlled to be 4.0 g / cm³. 3(2) Assembly of battery samples: Copper foil was used as the negative electrode, a PP membrane with a thickness of 12 μm was used as the battery separator, and an electrolyte system of 15% LiPF6+FEC+HTCN+EC / PC / DEC / EP / PP was used as the battery electrolyte. A soft-pack battery sample with a capacity of 2100mAh was assembled. (3) Performance test: Under the conditions of 25℃ and 4.5V, 1C charging and 5C discharging were performed for 800 cycles to test the capacity retention rate of each battery sample. The larger the value, the better the cycle stability of the battery sample under high rate conditions, that is, it has higher rate performance. The results of the above tests are shown in Table 2.

[0129] Table 2

[0130]

[0131] As can be seen from the above description, the embodiments of this application have achieved the preparation of composite lithium cobalt oxide materials that balance high density and high specific surface area. When used as a cathode material in lithium-ion batteries, the resulting lithium-ion battery samples exhibit good rate performance and demonstrate excellent long-term cycle stability after 800 cycles under 1C charging and 5C discharging conditions.

[0132] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A composite lithium cobalt oxide cathode material, characterized in that, include: Lithium cobalt oxide with a D50 of 13μm~16μm, lithium cobalt oxide with a D50 of 5.5μm~6.5μm, lithium titanium aluminum phosphate with a D50 of 300nm~500nm, and 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 cobalt oxide is (1.5~4.0):

1.

2. The composite lithium cobalt oxide cathode material according to claim 1, characterized in that, The first lithium titanium aluminum phosphate and the second lithium titanium aluminum phosphate each have the independent molecular formula Li. 1+x A1 x Ti 2-x (PO4)3, where 0.01 ≤ x < 1.

3. The composite lithium cobalt oxide cathode material according to claim 1 or 2, characterized in that, The first lithium cobalt oxide has a D10 of 4.8 μm to 6.5 μm, and the second lithium cobalt oxide has a D10 of 3.0 μm to 4.0 μm; and / or, the first lithium cobalt oxide has a D90 of 25.0 μm to 28.0 μm, and the second lithium cobalt oxide has a D90 of 10.0 μm to 12.0 μm.

4. The composite lithium cobalt oxide cathode 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 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.

5. The composite lithium cobalt oxide cathode material according to any one of claims 1 to 4, characterized in that, The tap density of the first lithium cobalt oxide is 2.7 g / cm³. 3 ~3.0g / cm 3 The tap density of the second lithium cobalt oxide is 2.0 g / cm³. 3 ~2.6g / cm 3 ; and / or, The specific surface area of ​​the first lithium cobalt oxide is 0.15 m². 2 / g~0.25m 2 / g, the specific surface area of ​​the second lithium cobalt oxide is 0.35m². 2 / g~0.50m 2 / g.

6. The composite lithium cobalt oxide cathode material according to any one of claims 1 to 5, characterized in that, The specific surface area of ​​the composite lithium cobalt oxide cathode material is 0.25 m². 2 / g~0.35m 2 / g, tap density is 2.5g / cm³ 3 ~2.8g / cm 3 ; Preferably, the composite lithium cobalt oxide cathode material has a D10 of 3.8 μm to 5.0 μm, a D50 of 11.4 μm to 12.9 μm, a D90 of 24.8 μm to 27.7 μm, and a specific particle size distribution value (D90-D10) / D50 of 1.6 to 2.

1.

7. A method for preparing a composite lithium cobalt oxide cathode material according to any one of claims 1 to 6, characterized in that, include: Step S1: Mix the first lithium cobalt oxide with the first lithium titanium aluminum phosphate to obtain the first composite lithium cobalt oxide; Step S2: The second lithium cobalt oxide and the second lithium titanium aluminum phosphate are mixed for the second time to obtain the second composite lithium cobalt oxide; Step S3: The first composite lithium cobalt oxide and the second composite lithium cobalt oxide are mixed for a third time to obtain the composite lithium cobalt oxide cathode material.

8. The preparation method according to claim 7, characterized in that, The first mixing, the second mixing, and the third mixing are all achieved by batch mixers, and the spindle frequency of each batch mixer used for the first mixing, the second mixing, and the third mixing is independently 20Hz~60Hz, and the mixing time is independently 1h~5h.

9. A positive electrode sheet, characterized in that, The positive electrode sheet comprises the composite lithium cobalt oxide positive electrode material according to any one of claims 1 to 6.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode sheet as described in claim 9.

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