Cobalt-aluminum-titanium co-coated positive electrode material, and preparation method therefor and use thereof

Abstract

A cobalt-aluminum-titanium co-coated positive electrode material, and a preparation method therefor and a use thereof. The cobalt-aluminum-titanium co-coated positive electrode material comprises a high-nickel nickel-cobalt-aluminum-based ternary positive electrode material; a coating layer is provided on the surface of the high-nickel nickel-cobalt-aluminum-based ternary positive electrode material; the coating layer contains Co, Al, and Ti; and on the basis of the total mass of the high-nickel nickel-cobalt-aluminum-based ternary positive electrode material, the contents of Co, Al, and Ti in the coating layer satisfy: the content ω1 of Co ranges from 500 ppm to 8000 ppm; the content ω2 of Al ranges from 500 ppm to 6000 ppm; the content ω3 of Ti is greater than 0 ppm and not greater than 1500 ppm, wherein ω1+ω2 ranges from 1500 ppm to 12000 ppm, and ω1≥ω2. According to the positive electrode material, the charge transfer impedance of a positive electrode can be effectively reduced while the surface of the positive electrode material is strengthened and gas production is reduced.

Description

A cobalt-aluminum-titanium co-coated cathode material, its preparation method and application Technical Field

[0001] This invention relates to the field of battery technology, and specifically to a cobalt-aluminum-titanium co-coated cathode material, its preparation method, and its application. Background Technology

[0002] Today, lithium-ion batteries are widely used in various industries as an environmentally friendly green energy source. High-rate electronic tools place increasingly stringent requirements on the electrical abuse and safety characteristics of lithium-ion batteries under high-temperature conditions. Considering the practical application scenarios of high-rate cylindrical cells, it is required that the cells, during high-temperature (e.g., 45℃ or 60℃) charge-discharge cycles, will not fail due to gas generation triggering the current interrupt device (CID) within a specified number of cycles; furthermore, it is required that the cells do not catch fire or explode during the process of constant current charging from open-circuit voltage to cutoff voltage (exceeding the normal application upper limit voltage, such as 5V).

[0003] To meet customer requirements, the cathode material, a crucial component of the battery cell, must prevent the high-valence Ni from reacting with the electrolyte and prevent interlayer separation within the primary grains under conditions of high delithiation and high temperature. It must also prevent separation between primary grains and more severe structural collapse under conditions of drastic changes in structural volume.

[0004] Currently, to meet the above requirements, cathode materials undergo surface treatment, including optimization using coating elements (such as Al, Co, B, etc.) to enhance adhesion between surface grain boundaries or stabilize oxygen atoms in the lattice. This also includes adding a water washing step to reduce residual alkali on the material surface and to form a passivation layer. However, these measures significantly worsen the surface charge transfer impedance, increasing the lithium-ion insertion / extraction barrier and consequently deteriorating the cell's direct current internal resistance (DCR), affecting its cycle life and high-rate discharge performance. Furthermore, these measures are insufficiently effective in reducing gas generation under high-temperature and highly decoupled conditions.

[0005] Therefore, how to enhance the surface of the cathode material and reduce gas production while effectively reducing the charge transfer impedance of the cathode is a technical problem that needs to be solved. Summary of the Invention

[0006] In view of the above-mentioned technical problems existing in the prior art, the purpose of this invention is to provide a cobalt-aluminum-titanium co-coated cathode material, its preparation method and application.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a cobalt-aluminum-titanium co-coated cathode material, wherein the cobalt-aluminum-titanium co-coated cathode material comprises a high-nickel nickel-cobalt-aluminum-based ternary cathode material, and the chemical composition of the high-nickel nickel-cobalt-aluminum-based ternary cathode material is Li. α Ni x Co y Al z A m O2, 1≤α≤1.05, 0.80≤x≤0.95, 0.04≤y≤0.15, 0.005≤z≤0.06, 0≤m≤0.02, x+y+z+m=1, where A includes one or more of Zr, Mg, Sr, Y, La, Nb, Ba and Ti;

[0009] The surface of the high-nickel nickel-cobalt-aluminum based ternary cathode material is coated with a layer containing Co, Al, and Ti elements. Based on the total mass of the high-nickel nickel-cobalt-aluminum based ternary cathode material, the content of Co, Al, and Ti elements in the coating layer satisfies the following:

[0010] The content of Co element ω1 is 500ppm~8000ppm;

[0011] The content of Al element ω2 is 500ppm~6000ppm;

[0012] The content of Ti element ω3 is 0ppm~1500ppm and does not contain 0ppm;

[0013] ω1+ω2 is 1500ppm~12000ppm;

[0014] Where ω1+ω2≥ω3.

[0015] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0016] Preferably, (ω1+ω2) / ω3≥2, more preferably (ω1+ω2) / ω3≥3, and even more preferably 4≤(ω1+ω2) / ω3≤20.

[0017] Preferably, ω1 is 1000ppm~8000ppm.

[0018] Preferably, ω2 is 1000ppm~4000ppm.

[0019] Preferably, ω3 is 1000ppm~1500ppm.

[0020] Preferably, the content of Co element in the coating layer is greater than the content of Al element in the coating layer, or,

[0021] The ratio of the Al content in the coating layer to the Co content in the coating layer is 1 to 1.2.

[0022] Preferably, in the coating layer, Co, Al, and Ti elements exist in the form of one or more compounds, and the total mass of the compounds accounts for more than 80%, preferably more than 90%, of the total mass of the coating layer.

[0023] In a second aspect, the present invention provides a method for preparing a cobalt-aluminum-titanium co-coated cathode material as described in the first aspect, the preparation method comprising the following steps:

[0024] (1) Nickel-cobalt hydroxide, dopant source and lithium source are mixed and sintered to obtain high-nickel nickel-cobalt-aluminum based ternary cathode material;

[0025] The doping elements in the doping source include Al and A elements, wherein A includes one or more of Zr, Mg, Sr, Y, La, Nb, Ba and Ti;

[0026] (2) The high-nickel nickel-cobalt-aluminum-based ternary cathode material is mixed with the coating material and sintered to obtain the cobalt-aluminum-titanium co-coated cathode material;

[0027] The coating material includes Co source, Al source and Ti source.

[0028] Preferably, in step (1), the molar ratio of each element satisfies that Li / (Ni+Co+Al+A) is 1~1.05.

[0029] Preferably, in step (1), the sintering temperature is 400℃~1000℃.

[0030] Preferably, in step (1), the sintering time is 6h to 20h.

[0031] Preferably, in step (2), the Co source includes at least one of cobalt oxide, cobalt hydroxide, and cobalt hydroxyoxide.

[0032] Preferably, in step (2), the Al source includes at least one of aluminum oxide, aluminum hydroxide, and aluminum hydroxyoxide.

[0033] Preferably, in step (2), the Ti source is titanium oxide.

[0034] Preferably, the titanium oxide includes at least one of titanium dioxide, titanium monoxide, titanium trioxide, and titanium tetroxide.

[0035] Preferably, in step (2), the sintering temperature is 350℃~800℃.

[0036] Preferably, in step (2), the sintering time is 8h~24h.

[0037] Preferably, in step (2), after the sintering is completed, the temperature is reduced at a rate of 0.01℃ / min to 3℃ / min.

[0038] As a preferred technical solution of the preparation method of the present invention, the method further includes: washing the high-nickel nickel-cobalt-aluminum based ternary cathode material prepared in step (1) with water, and then mixing it with Co source, Al source and Ti source and sintering it to prepare a cobalt-aluminum-titanium co-coated cathode material.

[0039] As another preferred technical solution of the preparation method described in this invention, step (2) includes: mixing a high-nickel nickel-cobalt-aluminum-based ternary cathode material with a portion of the coating material and performing a first sintering, washing the product of the first sintering with water, and then mixing it with another portion of the coating material and performing a second sintering to obtain the cobalt-aluminum-titanium co-coated cathode material.

[0040] Preferably, the temperatures of the primary sintering and the secondary sintering are independently between 350°C and 800°C. Here, "independently" means that the temperatures of the primary and secondary sintering can be the same or different, and they are independent of each other.

[0041] Preferably, the total time for the first sintering and the second sintering is 8h to 24h.

[0042] Thirdly, the present invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode and a separator, wherein the positive electrode comprises the cobalt-aluminum-titanium co-coated positive electrode material described in the first aspect.

[0043] Compared with existing technologies, the present invention has the following beneficial effects:

[0044] The cathode material of this invention uses a high-nickel nickel-cobalt-aluminum ternary cathode material as its core, which has good rate performance under high voltage. Furthermore, on the basis of Al and / or Co element coating, Ti element co-coating is added, and the content and content relationship of Co, Al and Ti elements are strictly controlled to obtain a cathode material with low impedance and stable surface structure, thereby reducing battery gas generation at high temperature.

[0045] Compared with cathode materials coated with Al and / or Co elements, the cathode material of the present invention reduces the charge transfer impedance per unit area by 15% to 30% when used in 18650 cylindrical cells, reduces the DCR by 0.5mΩ to 1mΩ, reduces gas production by 10% to 30% after 400 cycles at 45°C, and reduces gas production by 30% to 50% when fully charged and stored at 70°C. Attached Figure Description

[0046] Figure 1 is a scan of the cobalt-aluminum-titanium co-coated cathode material of Example 1.

[0047] Figure 2 is an XRD comparison diagram of the cobalt-aluminum-titanium co-coated cathode material of Example 1 and the cobalt-aluminum co-coated cathode material of Comparative Example 1. Detailed Implementation

[0048] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0049] The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0050] In one embodiment, this invention provides a cobalt-aluminum-titanium co-coated cathode material, wherein the cobalt-aluminum-titanium co-coated cathode material comprises a high-nickel nickel-cobalt-aluminum-based ternary cathode material, and the chemical composition of the high-nickel nickel-cobalt-aluminum-based ternary cathode material is Li. α Ni x Co y Al z A m O2, 1≤α≤1.05, 0.80≤x≤0.95, 0.04≤y≤0.15, 0.005≤z≤0.06, 0≤m≤0.02, x+y+z+m=1, where A includes one or more of Zr, Mg, Sr, Y, La, Nb, Ba and Ti;

[0051] The surface of the high-nickel nickel-cobalt-aluminum based ternary cathode material is coated with a layer containing Co, Al, and Ti elements. Based on the total mass of the high-nickel nickel-cobalt-aluminum based ternary cathode material, the content of Co, Al, and Ti elements in the coating layer satisfies the following:

[0052] The content of Co element ω1 is 500ppm~8000ppm;

[0053] The content of Al element ω2 is 500ppm~6000ppm;

[0054] The content of Ti element ω3 is 0ppm~1500ppm and does not contain 0ppm;

[0055] ω1+ω2 is 1500ppm~12000ppm;

[0056] Where ω1+ω2≥ω3.

[0057] In one embodiment of the present invention, the cobalt-aluminum-titanium co-coated cathode material has a chemical composition of Li. α Ni x Co y Al z A m O2, 1≤α≤1.05, 0.80≤x≤0.95, 0.04≤y≤0.15, 0.005≤z≤0.06, 0≤m≤0.02, x+y+z+m=1, where A includes one or more of Zr, Mg, Sr, Y, La, Nb, Ba, and Ti. For example, 1≤α≤1.05 can be 1, 1.01, 1.02, 1.03, 1.04, or 1.05; 0.80≤x≤0.95 can be 0.80, 0.82, 0.83, 0.85, 0.88, 0.89, 0.90, 0.92, 0.93, 0.94, or 0.95; 0.04≤y≤0.15 can be 0.04, 0.06, or 0.08. The values ​​can be 0.10, 0.12, 0.13, 0.14, or 0.15, etc.; 0.005≤z≤0.06, for example, 0.01, 0.02, 0.03, 0.04, 0.05, or 0.06, etc.; 0≤m≤0.02, for example, 0, 0.001, 0.003, 0.005, 0.007, 0.008, 0.01, 0.012, 0.015, 0.017, or 0.02, etc. When m is 0, it indicates that the chemical composition does not contain element A.

[0058] In one embodiment of the present invention, the cobalt-aluminum-titanium co-coated cathode material has a Co content ω1 in the coating layer of 500ppm to 8000ppm, for example, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1200ppm, 1300ppm, 1400ppm, 1500ppm, 1700ppm, 1800ppm, 2000ppm, 2200ppm, 2400ppm, 2500ppm, 2650ppm, 2800ppm, 3000ppm, 3200ppm, 3300ppm, or 3500ppm. The concentrations are typically 3700ppm, 3800ppm, 4000ppm, 4200ppm, 4400ppm, 4500ppm, 4700ppm, 4800ppm, 5000ppm, 5200ppm, 5500ppm, 5600ppm, 5800ppm, 6000ppm, 6200ppm, 6300ppm, 6400ppm, 6500ppm, 6700ppm, 6800ppm, 7000ppm, 7200ppm, 7400ppm, 7600ppm, 7800ppm, or 8000ppm, with a further preferred concentration of 1000ppm to 8000ppm. If the Co content is too low, the total Co and Al content will decrease, resulting in insufficient coating and inadequate interfacial protection, and the impedance will not be improved; that is, both impedance and interfacial improvement will deteriorate. If the Co content is too high, exceeding 8000 ppm, most of the Co will eventually be converted into LiCoO2, leading to a significant increase in LiCoO2. This substance is unstable under high temperature and high voltage and is prone to explosion. Therefore, the product design of this invention needs to strictly control the Co content, which must not exceed 8000 ppm.

[0059] In one embodiment of the present invention, the cobalt-aluminum-titanium co-coated cathode material has an Al content (ω2) of 500 ppm to 6000 ppm, for example, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, 1700 ppm, 1800 ppm, 2000 ppm, 2200 ppm, 2400 ppm, 2500 ppm. ppm, 2650ppm, 2800ppm, 3000ppm, 3200ppm, 3300ppm, 3500ppm, 3700ppm, 3800ppm, 4000ppm, 4200ppm, 4400ppm, 4500ppm, 4700ppm, 4800ppm, 5000ppm, 5200ppm, 5500ppm, 5600ppm, 5800ppm or 6000ppm, etc., preferably 1000ppm~4000ppm.

[0060] In one embodiment of the present invention, the cobalt-aluminum-titanium co-coated cathode material has a Ti element content ω3 in the coating layer ranging from 0 ppm to 1500 ppm and excluding 0 ppm. For example, it can be 0.01 ppm, 0.05 ppm, 0.1 ppm, 0.5 ppm, 1 ppm, 3 ppm, 5 ppm, 10 ppm, 15 ppm, 20 ppm, 25 ppm, 30 ppm, 35 ppm, 40 ppm, 45 ppm, 50 ppm, 60 ppm, 70 ppm, 8 ppm, etc. The concentrations of Ti (ω3) are 0 ppm, 100 ppm, 120 ppm, 150 ppm, 170 ppm, 185 ppm, 200 ppm, 230 ppm, 260 ppm, 280 ppm, 300 ppm, 350 ppm, 400 ppm, 450 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1300 ppm, 1400 ppm, or 1500 ppm, etc. If the Ti content ω3 exceeds 1500 ppm, it will significantly affect the discharge capacity of the cathode material; if Ti is not added, it cannot work synergistically with Co and Al to reduce impedance. When the coating amount is less than 50 ppm and greater than 0 ppm, the impedance reduction effect is slightly weaker, but the technical effect of this invention can still be achieved. Therefore, the preferred Ti content ω3 is: ω3 ≥ 50 ppm.

[0061] In one implementation, ω3 is 1000ppm to 1500ppm.

[0062] In one embodiment of the present invention, by limiting the content of cobalt to 1000ppm~8000ppm and the content of Ti to 1000ppm~1500ppm, it is more conducive to the formation of fast ion conductors during the sintering process (especially at higher sintering temperatures), thereby improving the performance of the cathode material.

[0063] In one embodiment of the present invention, the cobalt-aluminum-titanium co-coated cathode material has ω1+ω2 of 1500ppm~12000ppm, for example, it can be 1500ppm, 1700ppm, 1800ppm, 2000ppm, 2200ppm, 2400ppm, 2500ppm, 2650ppm, 2800ppm, 3000ppm, 3200ppm, 3300ppm, 3500ppm, 3700ppm, 3800ppm, 4000ppm, 4200ppm, etc. ppm、4400ppm、4500ppm、4700ppm、4800ppm、5000ppm、5200ppm、5500ppm、5600ppm、5800ppm、6000ppm、6500ppm、7 000ppm, 7500ppm, 8000ppm, 8500ppm, 9000ppm, 9500ppm, 10000ppm, 10500ppm, 11000ppm, 11500ppm or 12000ppm, etc.

[0064] In one embodiment of the present invention, since (ω1+ω2) / ω3≥1, the contents of Co and Al are within a specific range. The introduction of Ti can significantly reduce cell impedance and gas generation during high-temperature storage and cycling. However, if the Ti content is too high, it will significantly deteriorate the specific capacity of the cathode material. Therefore, the Ti coating content must be limited. The present invention controls the Ti content to be less than or equal to the sum of the contents of Co and Al, and controls the Ti element content to prevent deterioration of the specific capacity of the cathode material, while ensuring the effectiveness of Co and Al coating, and simultaneously achieving the technical effects of ensuring complete interface coating and reducing high-temperature gas generation.

[0065] In the cathode material of the present invention, the content of Al and Co in the coating layer is not required to be greater than that of Al. If there are only two coating elements, Co and Al, the presence of Al will significantly reduce the impedance of the cell. In this case, in order to balance the overall impedance of the cell and the overcharge gas generation performance, the content of Al must, in principle, be less than that of Co.

[0066] However, in this invention, because Ti is introduced into the coating layer, it can significantly reduce the cell impedance. Therefore, the introduction of Ti can increase the tolerance to Al, and the introduction of Ti can offset the increase in impedance caused by the increase in Al, so that the maximum Al content can slightly exceed that of Co. For example, in one embodiment, the ratio of the Al content to the Co content in the coating layer is 1 to 1.2, such as 1, 1.05, 1.1, 1.15, or 1.2; in another embodiment, the Co content in the coating layer is greater than the Al content in the coating layer; in yet another embodiment, the Al content in the coating layer is 300 ppm to 600 ppm more than the Co content in the coating layer, such as 300 ppm, 350 ppm, 400 ppm, 450 ppm, 500 ppm, 550 ppm, or 600 ppm.

[0067] As a preferred embodiment, the content of Co element in the coating layer is greater than the content of Al element in the coating layer, that is, ω1 > ω2.

[0068] One embodiment of the present invention uses a high-nickel nickel-cobalt-aluminum ternary cathode material as the core, which has good rate performance under high voltage. Furthermore, on the basis of Al and / or Co element coating, Ti element co-coating is added, and the content and content relationship of Co, Al and Ti elements are strictly controlled to obtain a cathode material with low impedance and stable surface structure.

[0069] The cathode material of one embodiment of the present invention, compared with cathode materials coated with Al and / or Co elements, reduces the charge transfer impedance per unit area of ​​the prepared cathode sheet by 15% to 30%, reduces the DCR by 0.5mΩ to 1mΩ when applied to 18650 cylindrical cells, reduces gas production by 10% to 30% after 400 cycles at 45°C, and reduces gas production by 30% to 50% when fully charged and stored at 70°C.

[0070] In one embodiment of the present invention, the cobalt-aluminum-titanium co-coated cathode material has (ω1+ω2) / ω3≥2. Exemplarily, (ω1+ω2) / ω3 can be, for example, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, 20.5, 21, 21.5, 22, 22.5, 23, 23.5, 24, 24.5, or 25. In one embodiment, (ω1+ω2) / ω3≥3.

[0071] In one implementation, 4≤(ω1+ω2) / ω3≤20.

[0072] In one implementation, ω1 is 1000ppm to 8000ppm.

[0073] In one embodiment, ω2 is 1000ppm to 4000ppm.

[0074] In one embodiment, the Co, Al, and Ti elements are present in the coating layer in the form of one or more compounds, and the total mass of the compounds accounts for more than 80% of the total mass of the coating layer, for example, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%, preferably more than 90%, and more preferably more than 95%.

[0075] In another embodiment of the present invention, a method for preparing the cobalt-aluminum-titanium co-coated cathode material as described above is provided, the method comprising the following steps:

[0076] (1) Nickel-cobalt hydroxide, dopant source and lithium source are mixed and sintered to obtain high-nickel nickel-cobalt-aluminum based ternary cathode material;

[0077] The doping elements in the doping source include Al and A elements, wherein A includes one or more of Zr, Mg, Sr, Y, La, Nb, Ba and Ti;

[0078] (2) The high-nickel nickel-cobalt-aluminum-based ternary cathode material is mixed with the coating material and sintered to obtain the cobalt-aluminum-titanium co-coated cathode material;

[0079] The coating material includes Co source, Al source and Ti source.

[0080] This scheme is a preferred secondary dry sintering preparation method of the present invention. The secondary dry sintering preparation method can enhance the surface of the cathode material, reduce gas generation, and effectively reduce the charge transfer impedance of the cathode.

[0081] In one embodiment of the present invention, the method for preparing a cobalt-aluminum-titanium co-coated cathode material involves the reaction of the Co and Ti sources in the coating material with residual lithium on the surface of the high-nickel nickel-cobalt-aluminum ternary cathode material, which partially generates a fast-ion conductor. In particular, the introduction of the Ti source can significantly reduce the surface impedance of the material without significantly affecting the cycle performance. At the same time, the Al source in the coating material forms an inert layer, which, although it increases the impedance to a certain extent, can significantly improve the cycle performance and suppress gas generation.

[0082] In one embodiment, in step (1), the molar ratio of each element satisfies that Li / (Ni+Co+Al+A) is 1~1.05, for example, it can be 1, 1.01, 1.02, 1.03, 1.04 or 1.05, etc.

[0083] In one embodiment, in step (1), the sintering temperature is 400℃~1000℃, for example, it can be 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃ or 1000℃, etc.

[0084] In one embodiment, in step (1), the sintering time is 6h to 20h, for example, it can be 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h or 20h.

[0085] In one embodiment, in step (2), the Co source includes at least one of cobalt oxide, cobalt hydroxide, and cobalt hydroxyoxide.

[0086] In one embodiment, in step (2), the Al source includes at least one of aluminum oxide, aluminum hydroxide, and aluminum hydroxyoxide.

[0087] In one embodiment, in step (2), the Ti source is titanium oxide.

[0088] In one embodiment, the titanium oxide includes at least one selected from titanium dioxide, titanium monoxide, titanium dioxide, and titanium tetroxide. However, it is not limited to the types listed above, and other titanium oxides commonly used in the art are also applicable to this invention.

[0089] In one embodiment, in step (2), the sintering temperature is 350℃~800℃, for example, it can be 350℃, 370℃, 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃ or 800℃, etc.

[0090] In one embodiment, in step (2), the sintering time is 8h to 24h, for example, it can be 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 22h or 24h.

[0091] In one embodiment, in step (2), after sintering is completed, the temperature is lowered at a rate of 0.01℃ / min to 3℃ / min. For example, the cooling rate can be 0.01℃ / min, 0.05℃ / min, 0.1℃ / min, 0.2℃ / min, 0.5℃ / min, 0.7℃ / min, 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min, or 3℃ / min, etc.

[0092] In one embodiment, the method further includes: washing the high-nickel nickel-cobalt-aluminum-based ternary cathode material prepared in step (1) with water, and then mixing it with a Co source, an Al source, and a Ti source before sintering to prepare a cobalt-aluminum-titanium co-coated cathode material. By adding the water washing step, the residual alkali on the surface of the high-nickel nickel-cobalt-aluminum-based ternary cathode material obtained in one sintering step can be reduced.

[0093] In one embodiment, step (2) includes: mixing a high-nickel nickel-cobalt-aluminum-based ternary cathode material with a portion of the coating material and sintering it once; washing the product of the first sintering with water; then mixing it with another portion of the coating material and sintering it a second time to obtain the cobalt-aluminum-titanium co-coated cathode material.

[0094] Washing with water can reduce residual alkali on the surface and reduce gas generation during circulation and high-temperature storage.

[0095] In one embodiment, the temperatures of the primary sintering and the secondary sintering are independently between 350°C and 800°C, for example, they can be 350°C, 370°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, or 800°C. Here, "independently" means that the temperatures of the primary and secondary sintering can be the same or different, and they are independent of each other.

[0096] In one embodiment, the total time for the first sintering and the second sintering is 8h to 24h, for example, it can be 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 22h or 24h.

[0097] In another embodiment of the present invention, a lithium-ion battery is provided, comprising a positive electrode, a negative electrode and a separator, wherein the positive electrode comprises the cobalt-aluminum-titanium co-coated positive electrode material described in the first aspect.

[0098] The following are typical but non-limiting embodiments:

[0099] Example 1

[0100] This embodiment provides a cobalt-aluminum-titanium co-coated cathode material, which includes a high-nickel nickel-cobalt-aluminum based ternary cathode material (chemical formula see Table 1). The surface of the high-nickel nickel-cobalt-aluminum based ternary cathode material is provided with a coating layer, which contains Co, Al and Ti elements. Based on the total mass of the high-nickel nickel-cobalt-aluminum based ternary cathode material, the contents of Co ω1, Al ω2, Ti ω3, the sum of Co and Al contents ω1+ω2, and the ratio of the sum of Co and Al contents to the Ti content (ω1+ω2) / ω3 in the coating layer are shown in Table 1.

[0101] This embodiment also provides a method for preparing the above-mentioned cobalt-aluminum-titanium co-coated cathode material, including the following steps:

[0102] Step 1: Preparation of high-nickel nickel-cobalt-aluminum based ternary cathode material:

[0103] Nickel-cobalt hydroxide, a dopant source, and a lithium source are mixed and ground, and then sintered once to obtain a high-nickel nickel-cobalt-aluminum-based ternary cathode material. The dopant source is aluminum hydroxide, the lithium source is LiOH, the Li / (Ni+Co+Al) molar ratio is 1.03, the sintering temperature is 710℃, and the sintering time is 18h.

[0104] Step 2, Coating process:

[0105] After the high-nickel nickel-cobalt-aluminum-based ternary cathode material and the coating material are mixed and ground evenly, a second sintering is carried out in an air atmosphere, and the material is cooled to room temperature at a cooling rate of 1℃ / min to obtain the cobalt-aluminum-titanium co-coated cathode material; wherein the coating material is cobalt hydroxide, aluminum hydroxide and titanium dioxide, the sintering temperature is 500℃ and the sintering time is 10h.

[0106] Figure 1 is a scanned image of the cobalt-aluminum-titanium co-coated cathode material of this embodiment. As can be seen from the figure, the material coating is uniform, with no coating residue or fine powder.

[0107] Example 2

[0108] This embodiment provides a cobalt-aluminum-titanium co-coated cathode material, which includes a high-nickel nickel-cobalt-aluminum based ternary cathode material (chemical formula see Table 1). The surface of the high-nickel nickel-cobalt-aluminum based ternary cathode material is provided with a coating layer, which contains Co, Al and Ti elements. Based on the total mass of the high-nickel nickel-cobalt-aluminum based ternary cathode material, the contents of Co ω1, Al ω2, Ti ω3, the sum of Co and Al contents ω1+ω2, and the ratio of the sum of Co and Al contents to the Ti content (ω1+ω2) / ω3 in the coating layer are shown in Table 1.

[0109] This embodiment also provides a method for preparing the above-mentioned cobalt-aluminum-titanium co-coated cathode material, including the following steps:

[0110] Step 1: Preparation of high-nickel nickel-cobalt-aluminum based ternary cathode material:

[0111] Nickel-cobalt hydroxide, a dopant source, and a lithium source are mixed and ground, and then sintered once to obtain a high-nickel nickel-cobalt-aluminum-based ternary cathode material. The dopant source is aluminum hydroxide, the lithium source is Li2CO3, the Li / (Ni+Co+Al) molar ratio is 1.02, the sintering temperature is 720℃, and the sintering time is 19h.

[0112] Step 2, Coating process:

[0113] After the high-nickel nickel-cobalt-aluminum-based ternary cathode material and the coating material are mixed and ground evenly, a second sintering is carried out in an oxygen atmosphere, and the temperature is cooled to room temperature at a cooling rate of 0.5℃ / min to obtain the cobalt-aluminum-titanium co-coated cathode material; wherein the coating material is cobalt hydroxide, aluminum hydroxide and titanium monoxide, the sintering temperature is 600℃ and the sintering time is 13h.

[0114] Example 3

[0115] This embodiment provides a cobalt-aluminum-titanium co-coated cathode material, which includes a high-nickel nickel-cobalt-aluminum based ternary cathode material (chemical formula see Table 1). The surface of the high-nickel nickel-cobalt-aluminum based ternary cathode material is provided with a coating layer, which contains Co, Al and Ti elements. Based on the total mass of the high-nickel nickel-cobalt-aluminum based ternary cathode material, the contents of Co ω1, Al ω2, Ti ω3, the sum of Co and Al contents ω1+ω2, and the ratio of the sum of Co and Al contents to the Ti content (ω1+ω2) / ω3 in the coating layer are shown in Table 1.

[0116] This embodiment also provides a method for preparing the above-mentioned cobalt-aluminum-titanium co-coated cathode material, including the following steps:

[0117] Step 1: Preparation of high-nickel nickel-cobalt-aluminum based ternary cathode material:

[0118] Nickel-cobalt hydroxide, a dopant source, and a lithium source are mixed and ground, and then sintered once to obtain a high-nickel nickel-cobalt-aluminum-based ternary cathode material. The dopant source is aluminum hydroxide, the lithium source is LiOH, the Li / (Ni+Co+Al) molar ratio is 1.05, the sintering temperature is 695℃, and the sintering time is 14h.

[0119] Step 2, Coating process:

[0120] After the high-nickel nickel-cobalt-aluminum-based ternary cathode material and the coating material are mixed and ground evenly, a second sintering is carried out in an air atmosphere, and the temperature is cooled to room temperature at a cooling rate of 0.8℃ / min to obtain the cobalt-aluminum-titanium co-coated cathode material; wherein the coating material is cobalt hydroxide, aluminum hydroxide and titanium trioxide, the sintering temperature is 650℃ and the sintering time is 9h.

[0121] Example 4

[0122] This embodiment provides a cobalt-aluminum-titanium co-coated cathode material, which includes a high-nickel nickel-cobalt-aluminum based ternary cathode material (chemical formula see Table 1). The surface of the high-nickel nickel-cobalt-aluminum based ternary cathode material is provided with a coating layer, which contains Co, Al and Ti elements. Based on the total mass of the high-nickel nickel-cobalt-aluminum based ternary cathode material, the contents of Co ω1, Al ω2, Ti ω3, the sum of Co and Al contents ω1+ω2, and the ratio of the sum of Co and Al contents to the Ti content (ω1+ω2) / ω3 in the coating layer are shown in Table 1.

[0123] This embodiment also provides a method for preparing the above-mentioned cobalt-aluminum-titanium co-coated cathode material, including the following steps:

[0124] Step 1: Preparation of high-nickel nickel-cobalt-aluminum based ternary cathode material:

[0125] Nickel-cobalt hydroxide, a dopant source, and a lithium source are mixed and ground, and then sintered once to obtain a high-nickel nickel-cobalt-aluminum-based ternary cathode material. The dopant source is aluminum hydroxide, the lithium source is LiOH, the Li / (Ni+Co+Al) molar ratio is 1.01, the sintering temperature is 690℃, and the sintering time is 15h.

[0126] Step 2, Coating process:

[0127] After the high-nickel nickel-cobalt-aluminum-based ternary cathode material and the coating material are mixed and ground evenly, a second sintering is carried out in an air atmosphere, and the temperature is cooled to room temperature at a cooling rate of 1.5℃ / min to obtain the cobalt-aluminum-titanium co-coated cathode material; wherein, the coating material is cobalt hydroxide, aluminum hydroxide and titanium dioxide, the sintering temperature is 680℃ and the sintering time is 12h.

[0128] Example 5

[0129] This embodiment provides a cobalt-aluminum-titanium co-coated cathode material, which includes a high-nickel nickel-cobalt-aluminum based ternary cathode material (chemical formula see Table 1). The surface of the high-nickel nickel-cobalt-aluminum based ternary cathode material is provided with a coating layer, which contains Co, Al and Ti elements. Based on the total mass of the high-nickel nickel-cobalt-aluminum based ternary cathode material, the contents of Co ω1, Al ω2, Ti ω3, the sum of Co and Al contents ω1+ω2, and the ratio of the sum of Co and Al contents to the Ti content (ω1+ω2) / ω3 in the coating layer are shown in Table 1.

[0130] This embodiment also provides a method for preparing the above-mentioned cobalt-aluminum-titanium co-coated cathode material, including the following steps:

[0131] Step 1: Preparation of high-nickel nickel-cobalt-aluminum based ternary cathode material:

[0132] Nickel-cobalt hydroxide, a dopant source, and a lithium source are mixed and ground, and then sintered once to obtain a high-nickel nickel-cobalt-aluminum-based ternary cathode material. The dopant source is aluminum hydroxide, the lithium source is LiOH, the Li / (Ni+Co+Al) molar ratio is 1.04, the sintering temperature is 650℃, and the sintering time is 12h.

[0133] Step 2, Coating process:

[0134] After the high-nickel nickel-cobalt-aluminum-based ternary cathode material and the coating material are mixed and ground evenly, a second sintering is carried out in an air atmosphere, and the material is cooled to room temperature at a cooling rate of 1℃ / min to obtain the cobalt-aluminum-titanium co-coated cathode material; wherein the coating material is cobalt hydroxide, aluminum hydroxide and titanium dioxide, the sintering temperature is 580℃ and the sintering time is 10h.

[0135] Example 6

[0136] This embodiment provides a cobalt-aluminum-titanium co-coated cathode material, which includes a high-nickel nickel-cobalt-aluminum based ternary cathode material (chemical formula see Table 1). The surface of the high-nickel nickel-cobalt-aluminum based ternary cathode material is provided with a coating layer, which contains Co, Al and Ti elements. Based on the total mass of the high-nickel nickel-cobalt-aluminum based ternary cathode material, the contents of Co ω1, Al ω2, Ti ω3, the sum of Co and Al contents ω1+ω2, and the ratio of the sum of Co and Al contents to the Ti content (ω1+ω2) / ω3 in the coating layer are shown in Table 1.

[0137] This embodiment also provides a method for preparing the above-mentioned cobalt-aluminum-titanium co-coated cathode material, including the following steps:

[0138] Step 1: Preparation of high-nickel nickel-cobalt-aluminum based ternary cathode material:

[0139] Nickel-cobalt hydroxide, a dopant source, and a lithium source are mixed and ground, and then sintered once to obtain a high-nickel nickel-cobalt-aluminum-based ternary cathode material. The dopant source is aluminum hydroxide, the lithium source is LiOH, the Li / (Ni+Co+Al) molar ratio is 1.02, the sintering temperature is 670℃, and the sintering time is 14h.

[0140] Step 2, Coating process:

[0141] After the high-nickel nickel-cobalt-aluminum-based ternary cathode material and the coating material are mixed and ground evenly, a second sintering is carried out in an oxygen atmosphere, and the material is cooled to room temperature at a cooling rate of 1℃ / min to obtain the cobalt-aluminum-titanium co-coated cathode material; wherein the coating material is cobalt hydroxide, aluminum hydroxide and titanium dioxide, the sintering temperature is 560℃ and the sintering time is 10h.

[0142] Example 7

[0143] This embodiment provides a cobalt-aluminum-titanium co-coated cathode material, which includes a high-nickel nickel-cobalt-aluminum based ternary cathode material (chemical formula see Table 1). The surface of the high-nickel nickel-cobalt-aluminum based ternary cathode material is provided with a coating layer, which contains Co, Al and Ti elements. Based on the total mass of the high-nickel nickel-cobalt-aluminum based ternary cathode material, the contents of Co ω1, Al ω2, Ti ω3, the sum of Co and Al contents ω1+ω2, and the ratio of the sum of Co and Al contents to the Ti content (ω1+ω2) / ω3 in the coating layer are shown in Table 1.

[0144] This embodiment also provides a method for preparing the above-mentioned cobalt-aluminum-titanium co-coated cathode material, including the following steps:

[0145] Step 1: Preparation of high-nickel nickel-cobalt-aluminum based ternary cathode material:

[0146] Nickel-cobalt hydroxide, a dopant source, and a lithium source are mixed and ground, and then sintered once to obtain a high-nickel nickel-cobalt-aluminum-based ternary cathode material. The dopant source is aluminum hydroxide, the lithium source is LiOH, the Li / (Ni+Co+Al) molar ratio is 1.02, the sintering temperature is 720℃, and the sintering time is 14h.

[0147] Step 2, Coating process:

[0148] After the high-nickel nickel-cobalt-aluminum-based ternary cathode material and the coating material are mixed and ground evenly, a second sintering is carried out in an air atmosphere, and the material is cooled to room temperature at a cooling rate of 1℃ / min to obtain the cobalt-aluminum-titanium co-coated cathode material; wherein the coating material is cobalt hydroxide, aluminum hydroxide and titanium dioxide, the sintering temperature is 700℃ and the sintering time is 10h.

[0149] Example 8

[0150] This embodiment provides a cobalt-aluminum-titanium co-coated cathode material, which includes a high-nickel nickel-cobalt-aluminum based ternary cathode material (chemical formula see Table 1). The surface of the high-nickel nickel-cobalt-aluminum based ternary cathode material is provided with a coating layer, which contains Co, Al and Ti elements. Based on the total mass of the high-nickel nickel-cobalt-aluminum based ternary cathode material, the contents of Co ω1, Al ω2, Ti ω3, the sum of Co and Al contents ω1+ω2, and the ratio of the sum of Co and Al contents to the Ti content (ω1+ω2) / ω3 in the coating layer are shown in Table 1.

[0151] This embodiment also provides a method for preparing the above-mentioned cobalt-aluminum-titanium co-coated cathode material, including the following steps:

[0152] Step 1: Preparation of high-nickel nickel-cobalt-aluminum based ternary cathode material:

[0153] Nickel-cobalt hydroxide, a dopant source, and a lithium source are mixed and ground, and then sintered once to obtain a high-nickel nickel-cobalt-aluminum-based ternary cathode material. The dopant source is aluminum oxide, the lithium source is LiOH, the Li / (Ni+Co+Al) molar ratio is 1.02, the sintering temperature is 720℃, and the sintering time is 14h.

[0154] Step 2, Coating process:

[0155] After the high-nickel nickel-cobalt-aluminum-based ternary cathode material and the coating material are mixed and ground evenly, a second sintering is carried out in an air atmosphere, and the material is cooled to room temperature at a cooling rate of 1℃ / min to obtain the cobalt-aluminum-titanium co-coated cathode material; wherein the coating material is cobalt hydroxide, aluminum hydroxide and titanium dioxide, the sintering temperature is 700℃ and the sintering time is 10h.

[0156] Example 9

[0157] This embodiment provides a cobalt-aluminum-titanium co-coated cathode material, which includes a high-nickel nickel-cobalt-aluminum based ternary cathode material (chemical formula see Table 1). The surface of the high-nickel nickel-cobalt-aluminum based ternary cathode material is provided with a coating layer, which contains Co, Al and Ti elements. Based on the total mass of the high-nickel nickel-cobalt-aluminum based ternary cathode material, the contents of Co ω1, Al ω2, Ti ω3, the sum of Co and Al contents ω1+ω2, and the ratio of the sum of Co and Al contents to the Ti content (ω1+ω2) / ω3 in the coating layer are shown in Table 1.

[0158] This embodiment also provides a method for preparing the above-mentioned cobalt-aluminum-titanium co-coated cathode material, including the following steps:

[0159] Step 1: Preparation of high-nickel nickel-cobalt-aluminum based ternary cathode material:

[0160] Nickel-cobalt hydroxide, a dopant source, and a lithium source are mixed and ground, and then sintered once to obtain a high-nickel nickel-cobalt-aluminum-based ternary cathode material. The dopant source is aluminum hydroxide, the lithium source is LiOH, the Li / (Ni+Co+Al) molar ratio is 1.02, the sintering temperature is 720℃, and the sintering time is 14h.

[0161] Step 2, Coating process:

[0162] After the high-nickel nickel-cobalt-aluminum-based ternary cathode material and the coating material are mixed and ground evenly, a second sintering is carried out in an air atmosphere, and the material is cooled to room temperature at a cooling rate of 1℃ / min to obtain the cobalt-aluminum-titanium co-coated cathode material; wherein the coating material is cobalt hydroxide, aluminum hydroxide and titanium dioxide, the sintering temperature is 700℃ and the sintering time is 10h.

[0163] Example 10

[0164] The difference between this embodiment and Embodiment 1 is that the high-nickel nickel-cobalt-aluminum based ternary cathode material obtained in step 1 is washed with water and then used in step 2 for the coating process.

[0165] Example 11

[0166] The difference between this embodiment and embodiment 1 is that step (2) includes:

[0167] A high-nickel nickel-cobalt-aluminum-based ternary cathode material was mixed with 50 wt% of coating material and sintered once. The product from the first sintering was washed with water and then mixed with the remaining coating material and sintered a second time to obtain the cobalt-aluminum-titanium co-coated cathode material. The atmosphere for both the first and second sintering was air, the temperature was 500℃, the sintering time was 5 h, and the cooling rate after sintering was 1℃ / min.

[0168] Comparative Example 1

[0169] The difference from Example 1 is that titanium dioxide is removed from the coating material in step 2, resulting in a cobalt-aluminum co-coated cathode material, referred to simply as Li. 1.03 (Ni 0.88 Co 0.10 Al 0.02 )O2@(CoAl), the elemental coating amounts in the coating layer are shown in Table 1.

[0170] Figure 2 shows a comparison of the XRD patterns of the cobalt-aluminum-titanium co-coated cathode material of Example 1 and the cobalt-aluminum co-coated cathode material of Comparative Example 1. As can be seen from the figure, the Ti coating does not affect the crystal structure of the material.

[0171] Comparative Example 2

[0172] The difference from Example 1 is that aluminum hydroxide is removed from the coating material in step 2, resulting in a cobalt-titanium co-coated cathode material, referred to simply as Li. 1.03 (Ni 0.88 Co 0.10 Al 0.02 )O2@(CoTi), the elemental coating amounts in the coating layer are shown in Table 1.

[0173] Comparative Example 3

[0174] The difference from Example 1 is that cobalt hydroxide is removed from the coating material in step 2, resulting in an aluminum-titanium co-coated cathode material, referred to simply as Li. 1.03 (Ni 0.88 Co 0.10 Al 0.02 The elemental coating amounts in the coating layer are shown in Table 1.

[0175] Comparative Example 4

[0176] The difference from Example 1 is that cobalt hydroxide and aluminum hydroxide are removed from the coating material in step 2, resulting in a titanium-coated cathode material, referred to simply as Li. 1.03 (Ni 0.88 Co 0.10 Al0.02 For the elemental coatings in the O2@(Ti) coating layer, please refer to Table 1.

[0177] Comparative Example 5

[0178] The difference from Example 1 is that the content of Co and Al elements in the coating layer is 500 ppm, and the content of Ti element is 1500 ppm.

[0179] Table 1

[0180]

[0181] Positive electrodes were prepared and batteries were assembled using the positive electrode materials of Examples 1-9 and Comparative Examples 1-5, specifically:

[0182] Battery fabrication:

[0183] (1) Preparation of positive electrode:

[0184] Using the positive electrode materials of Examples 1-9 and Comparative Examples 1-5 as active materials, the active materials were mixed with the conductive agent Super P and the binder PVDF in NMP at a mass ratio of 95:2:3 to obtain a positive electrode slurry. The positive electrode slurry was coated on the surface of aluminum foil and dried to obtain a positive electrode sheet.

[0185] (2) Preparation of negative electrode:

[0186] Artificial graphite anode material is mixed with conductive agent Super P, binder CMC and thickener SBR in water at a mass ratio of 96:0.5:1.5:2 to obtain anode slurry. The anode slurry is coated on the surface of copper foil and dried to obtain anode sheet.

[0187] (3) Provide a diaphragm and an electrolyte, wherein the diaphragm is a multilayer composite diaphragm, the substrate material is a polyolefin polymer, and the composite material is a high heat-resistant inorganic ceramic; the electrolyte is obtained by dissolving LiPF6 in a mixed solvent of EC, DMC and FEC, wherein EC:DMC:FEC:LiPF6 (mass ratio) = 20:60:5:15.

[0188] (4) After the above positive electrode, negative electrode and separator are wound, a cylindrical cell is obtained. The cylindrical cell is installed in the battery case and injected with electrolyte to obtain an 18650 battery.

[0189] Performance testing:

[0190] (1) Charge transfer impedance per unit area R of a 50% SOC positive electrode ctTest: A cylindrical cell with 50% SOC was disassembled to obtain the positive electrode sheet. Several positive electrode sheets were then cut, and a symmetrical battery was assembled from one positive electrode sheet, one separator layer, and one positive electrode sheet layer. An AC impedance test was then performed using a Blue Electric testing system, and the R value in the final AC impedance test data was obtained. ct data.

[0191] (2) DC internal resistance (DCR) test of 50% SOC 18650 battery: 18650 cylindrical cells with 50% SOC were used without disassembly and DC impedance was directly tested in the Blue Electric test system to obtain the DC internal resistance.

[0192] (3) Under the conditions of 70℃ and 100% SOC, test the impedance before storage and the impedance after 30 days of storage, and calculate the gas production and impedance growth rate after 30 days of storage.

[0193] (4) Charge and discharge the 18650 battery under the following conditions: 45℃, 2C charging, 3C discharging, 400 cycles, record the amount of gas produced and calculate the capacity retention rate after 400 cycles.

[0194] The test results are shown in Table 2.

[0195] Table 2

[0196]

[0197] As shown in Table 2, compared with the cobalt-aluminum co-coated cathode material (Comparative Example 1), the cathode material of the present invention has a lower charge transfer impedance R per unit area for the cathode sheet prepared using the cathode material. ct The DCR is reduced by 15.0~33.5% when applied to 18650 cylindrical cells; the gas production is reduced by 0.5 mΩ~1.0 mΩ when stored at 100% SOC and 70℃ for 30 days, and the impedance growth rate is reduced by 11.0%~18.5%; after 400 cycles at 45℃, the gas production is reduced by 22.0%~28.0%, and the capacity retention is improved by 4.0%~6.0%.

[0198] In particular, it is necessary to explain the value of "50% SOC DC internal resistance". Since the positive electrode is only one component in the entire cylindrical cell, if this data shows an increase of 0.5 mΩ, it indicates that it is a very large increase in impedance, which will have a significant impact on the entire cell.

[0199] In Examples 6 and 7, the content of Co and Ti elements is relatively high, and the secondary sintering temperature is relatively high, so it is more likely to form a fast ion conductor with low impedance. However, the content of Al element in the coating layer of Example 7 is higher, so the group with the best impedance performance is Example 6, while the group with the best gas production performance is Example 7.

[0200] The coating layer of Comparative Example 1 lacks Ti, and the coating layer of Comparative Example 3 lacks Co. In addition, the coating amount of Al in Comparative Example 3 is the largest, and its impedance performance is the worst. The coating layers of Comparative Example 2 and Comparative Example 4 both lack Al, and their cycle performance deteriorates. Moreover, the coating layer of Comparative Example 4 has a larger Ti coating amount, and its gas production is improved to a certain extent compared with Comparative Example 2, but both are far higher than those of the examples.

[0201] Although the coating layer of Comparative Example 5 contains Co, Al, and Ti elements, the total coating amount of Co and Al is relatively small, and the sum of the contents of Co and Al is less than the contents of Ti. Although the charge transfer impedance per unit area of ​​its positive electrode did not deteriorate significantly, the DCR of its 18650 cell was 21.5mΩ, which was slightly increased. At 70℃, the gas production at full charge was 15.73ml, and the impedance growth rate was 51.2%, indicating significant degradation. After 400 cycles at 45℃, the gas production was 32.7ml, and the cycle retention rate after 400 cycles was only 77.20%.

[0202] Meanwhile, we can see that although the content of Co+Al≥Ti is a basic requirement, as can be seen from Examples 1-9, when actually designing the coating scheme, the content of Ti will be adjusted at any time with the change of Co+Al. Overall, the content of Ti and the content of Co+Al are positively correlated.

[0203] A further preferred option is (ω1+ω2) / ω3≥2, more preferably (ω1+ω2) / ω3≥3, and even more preferably 4≤(ω1+ω2) / ω3≤20. Ti coating is a subordinate secondary coating element to Co and Al, which is a supplement to the main coating elements Co and Al. At the same time, it enhances the performance and plays a role in further strengthening the Co+Al coating system.

[0204] When (ω1+ω2) / ω3≥2, the increase in Co improves the specific capacity of the material, and coating does improve specific capacity. However, Ti and Al do not provide capacity improvement. In fact, Ti is essentially a modifier for the co-coating of Co and Al, which can alleviate the impedance deterioration caused by Al, and further reduce gas generation during high-temperature storage and high-temperature cycling. If chosen, when (ω1+ω2) / ω3≥2, the capacity loss is smaller compared to (ω1+ω2) / ω3≥1.

[0205] When (ω1+ω2) / ω3≥3, similarly, this composition can better balance the material's specific capacity, material impedance, and high-temperature storage and high-temperature gas generation performance. Similarly, we prefer 4≤(ω1+ω2) / ω3≤20.

[0206] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0207] The applicant declares that the detailed method of the present invention is illustrated by the above embodiments, but the present invention is not limited to the above detailed method, that is, it does not mean that the present invention must rely on the above detailed method to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A cobalt-aluminum-titanium co-coated cathode material, wherein, The cobalt-aluminum-titanium co-coated cathode material includes a high-nickel nickel-cobalt-aluminum based ternary cathode material, the chemical composition of which is Li. α Ni x Co y Al z A m O2, 1≤α≤1.05, 0.80≤x≤0.95, 0.04≤y≤0.15, 0.005≤z≤0.06, 0≤m≤0.02, x+y+z+m=1, where A includes one or more of Zr, Mg, Sr, Y, La, Nb, Ba and Ti; The surface of the high-nickel nickel-cobalt-aluminum based ternary cathode material is coated with a layer containing Co, Al, and Ti elements. Based on the total mass of the high-nickel nickel-cobalt-aluminum based ternary cathode material, the content of Co, Al, and Ti elements in the coating layer satisfies the following: The content of Co element ω1 is 500ppm~8000ppm; The content of Al element ω2 is 500ppm~6000ppm; The content of Ti element ω3 is 0ppm~1500ppm and does not contain 0ppm; Where ω1+ω2≥ω3.

2. The cobalt-aluminum-titanium co-coated cathode material according to claim 1, wherein, ω1+ω2 is 1500ppm~12000ppm.

3. The cobalt-aluminum-titanium co-coated cathode material according to claim 1, wherein, (ω1+ω2) / ω3≥2.

4. The cobalt-aluminum-titanium co-coated cathode material according to claim 1, wherein, (ω1+ω2) / ω3≥3.

5. The cobalt-aluminum-titanium co-coated cathode material according to claim 1, wherein, 4≤(ω1+ω2) / ω3≤20.

6. The cobalt-aluminum-titanium co-coated cathode material according to claim 1, wherein, ω1 is 1000ppm~8000ppm.

7. The cobalt-aluminum-titanium co-coated cathode material according to claim 1, wherein, ω2 is 1000ppm~4000ppm.

8. The cobalt-aluminum-titanium co-coated cathode material according to claim 1, wherein, ω3 is 1000ppm~1500ppm.

9. The cobalt-aluminum-titanium co-coated cathode material according to claim 1 or 2, wherein, The content of Co in the coating layer is greater than the content of Al in the coating layer.

10. The cobalt-aluminum-titanium co-coated cathode material according to any one of claims 1-9, wherein, In the coating layer, Co, Al, and Ti elements exist in the form of one or more compounds, and the total mass of the compounds accounts for more than 80% of the total mass of the coating layer.

11. The cobalt-aluminum-titanium co-coated cathode material according to claim 1, wherein, In the coating layer, Co, Al, and Ti elements exist in the form of one or more compounds, and the total mass of the compounds accounts for more than 90% of the total mass of the coating layer.

12. A method for preparing a cobalt-aluminum-titanium co-coated cathode material as described in any one of claims 1-11, wherein, The preparation method includes the following steps: (1) Nickel-cobalt hydroxide, dopant source and lithium source are mixed and sintered to obtain high-nickel nickel-cobalt-aluminum based ternary cathode material; The doping elements in the doping source include Al and A elements, wherein A includes one or more of Zr, Mg, Sr, Y, La, Nb, Ba and Ti; (2) The high-nickel nickel-cobalt-aluminum-based ternary cathode material is mixed with the coating material and sintered to obtain the cobalt-aluminum-titanium co-coated cathode material; The coating material includes Co source, Al source and Ti source.

13. The preparation method according to claim 12, wherein, In step (1), the molar ratio of each element satisfies that Li / (Ni+Co+Al+A) is 1~1.

05.

14. The preparation method according to claim 12, wherein, In step (1), the sintering temperature is 400℃~1000℃.

15. The preparation method according to claim 12, wherein, In step (1), the sintering time is 6h~20h.

16. The preparation method according to claim 12 or 13, wherein, In step (2), the Co source includes at least one of cobalt oxide, cobalt hydroxide and cobalt hydroxyoxide.

17. The preparation method according to claim 12, wherein, In step (2), the Al source includes at least one of aluminum oxide, aluminum hydroxide and aluminum hydroxyoxide.

18. The preparation method according to claim 12, wherein, In step (2), the Ti source is titanium oxide.

19. The preparation method according to claim 12, wherein, The titanium oxide includes at least one of titanium dioxide, titanium monoxide, titanium trioxide, and titanium tetroxide.

20. The preparation method according to claim 12, wherein, In step (2), the sintering temperature is 350℃~800℃.

21. The preparation method according to claim 12, wherein, In step (2), the sintering time is 8h~24h.

22. The preparation method according to claim 12, wherein, In step (2), after sintering is completed, the temperature is reduced at a rate of 0.01℃ / min to 3℃ / min.

23. The preparation method according to any one of claims 12-22, wherein, The method further includes: washing the high-nickel nickel-cobalt-aluminum-based ternary cathode material prepared in step (1) with water, and then mixing it with Co source, Al source and Ti source and sintering it to prepare a cobalt-aluminum-titanium co-coated cathode material.

24. The preparation method according to any one of claims 12-22, wherein, Step (2) includes: mixing a high-nickel nickel-cobalt-aluminum-based ternary cathode material with a portion of the coating material and sintering it once; washing the product from the first sintering with water; then mixing it with another portion of the coating material and sintering it a second time to obtain the cobalt-aluminum-titanium co-coated cathode material.

25. The preparation method according to claim 24, wherein, The temperatures for the first sintering and the second sintering are independently 350℃~800℃.

26. The preparation method according to claim 24, wherein, The total time for the first sintering and the second sintering is 8h to 24h.

27. A lithium-ion battery, comprising a positive electrode, a negative electrode, and a separator, wherein, The cathode includes the cobalt-aluminum-titanium co-coated cathode material as described in any one of claims 1-11.

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