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

Abstract

The present invention belongs to the technical field of batteries, and relates to a cobalt-aluminum-titanium co-coated cathode material, a preparation method thereof, and an application. The cobalt-aluminum-titanium co-coated cathode material includes a high-nickel nickel-cobalt-aluminum-based ternary cathode material, and a coating layer is provided on the surface thereof. The coating layer contains Co element, Al element and Ti element. Based on the total mass of the high-nickel nickel-cobalt-aluminum-based ternary cathode material, the contents of Co element, Al element and Ti element in the coating layer satisfy: the content ω1 of Co element is 500 ppm to 8000 ppm; the content ω2 of Al element is 500 ppm to 6000 ppm; the content ω3 of Ti element is 0 ppm to 1500 ppm and does not contain 0 ppm; ω1 + ω2 is 1500 ppm to 12000 ppm; wherein, ω1 ≥ ω2. The present invention can effectively reduce the charge transfer impedance of the cathode while enhancing the surface of the cathode material and reducing gas generation.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and relates to a cathode material co-coated with cobalt, aluminum and titanium, a preparation method and an application thereof. Background Art

[0002] At present, lithium-ion batteries are widely used in various industries as environment-friendly green energy. High-rate tool-like electronic products have higher and higher requirements for the electrical abuse and safety characteristics of lithium-ion batteries under high-temperature conditions. Considering the actual application scenarios of high-rate cylindrical battery cells, it is required that during charge and discharge cycles at high temperatures (such as 45 °C or 60 °C), the battery cells will not fail due to gas generation triggering the Current Interrupt Device (CID) within the specified number of cycles; and it is also required that the battery cells do not catch fire or explode during the process of constant-current charging from the open-circuit voltage to the cut-off voltage (exceeding the upper limit voltage of normal application, such as 5V).

[0003] In order to meet the needs of customers, it is required that the cathode material, which is an important component of the battery cell, under the conditions of high-degree de-lithiation and accompanied by high temperature, the high-valence Ni does not react with the electrolyte and there is no interlayer separation inside the primary grains; and it is required that when the structure volume changes violently, the primary grains do not separate and there is no more serious structural collapse.

[0004] At present, in order to meet the above requirements, the surface treatment of the cathode material is carried out, including optimization by relying on coating elements (such as Al, Co, B, etc.) to enhance the adhesion between the surface grain boundaries or stabilize the oxygen atoms in the crystal lattice. It also includes increasing the water washing step to reduce the residual alkali on the material surface and form a passivation layer. However, these above measures will significantly deteriorate the surface charge transfer impedance, increase the lithium-ion de-insertion energy barrier, and further deteriorate the direct current internal resistance (DCR) of the battery cell, affecting its performance such as battery cell cycling and high-rate discharge; moreover, the above measures are insufficient for reducing gas generation under high temperature and high-degree de-lithiated states.

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

[0006] Aiming at the above technical problems existing in the prior art, the purpose of the present invention is to provide a cathode material co-coated with cobalt, aluminum and titanium, a preparation method and an application thereof.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a cobalt-aluminum-titanium co-coated cathode material, and the cobalt-aluminum-titanium co-coated cathode material includes 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, where 1≤α≤1.05, 0.80≤x≤0.95, 0.04≤y≤0.15, 0.005≤z≤0.06, 0≤m≤0.02, and x + y + z + m = 1. Here, A includes one or more of Zr, Mg, Sr, Y, La, Nb, Ba, and Ti.

[0009] A coating layer is provided on the surface of the high-nickel nickel-cobalt-aluminum-based ternary cathode material, and the coating layer contains Co element, Al element, and Ti element. Based on the total mass of the high-nickel nickel-cobalt-aluminum-based ternary cathode material, the contents of Co element, Al element, and Ti element in the coating layer satisfy:

[0010] The content ω1 of Co element is 500 ppm to 8000 ppm; the content ω2 of Al element is 500 ppm to 6000 ppm; the content ω3 of Ti element is 0 ppm to 1500 ppm and does not contain 0 ppm; ω1 + ω2 is 1500 ppm to 12000 ppm; where ω1 + ω2 ≥ ω3.

[0011] The following are preferred technical solutions of the present invention, but do not limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved.

[0012] Preferably, (ω1 + ω2) / ω3 ≥ 2, preferably (ω1 + ω2) / ω3 ≥ 3, and more preferably 4 ≤ (ω1 + ω2) / ω3 ≤ 20.

[0013] Preferably, ω1 is 1000 ppm to 8000 ppm.

[0014] Preferably, ω2 is 1000 ppm to 4000 ppm.

[0015] Preferably, ω3 is 1000 ppm to 1500 ppm.

[0016] Preferably, the content of Co element in the coating layer is greater than the content of Al element in the coating layer, or the ratio of the content of Al element to the content of Co element in the coating layer is 1-1.2, or the content of Al element in the coating layer is 300 ppm - 600 ppm more than the content of Co element in the coating layer. Preferably, in the coating layer, Co element, Al element and Ti element 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.

[0017] 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, and the preparation method includes the following steps:

[0018] (1) Mix nickel cobalt hydroxide, doping source and lithium source and sinter them to obtain a high-nickel-type nickel cobalt aluminum-based ternary cathode material;

[0019] Among them, the doping elements in the doping source include Al element and A element, where A includes one or more of Zr, Mg, Sr, Y, La, Nb, Ba and Ti;

[0020] (2) Mix the high-nickel-type nickel cobalt aluminum-based ternary cathode material with the coating material and sinter them to obtain the cobalt-aluminum-titanium co-coated cathode material;

[0021] Among them, the coating material includes Co source, Al source and Ti source.

[0022] Preferably, in step (1), the molar ratio of each element satisfies that Li / (Ni + Co + Al + A) is 1-1.05.

[0023] Preferably, in step (1), the sintering temperature is 400 °C - 1000 °C.

[0024] Preferably, in step (1), the sintering time is 6 h - 20 h.

[0025] Preferably, in step (2), the Co source includes at least one of cobalt oxide, cobalt hydroxide and cobalt oxyhydroxide.

[0026] Preferably, in step (2), the Al source includes at least one of aluminum oxide, aluminum hydroxide and aluminum oxyhydroxide.

[0027] Preferably, in step (2), the Ti source is titanium oxide.

[0028] Preferably, the titanium oxide includes at least one of titanium dioxide, titanium monoxide, titanium sesquioxide and titanium tetroxide.

[0029] Preferably, in step (2), the sintering temperature is 350°C to 800°C.

[0030] Preferably, in step (2), the sintering time is 8 h to 24 h.

[0031] Preferably, in step (2), after the sintering is completed, the temperature is decreased at a rate of 0.01°C / min to 3°C / min.

[0032] As a preferred technical solution of the preparation method of the present invention, the method further includes: washing the high-nickel-type nickel cobalt aluminum-based ternary cathode material prepared in step (1), and then mixing it with a Co source, an Al source, and a Ti source and sintering to prepare a cathode material co-coated with cobalt, aluminum, and titanium.

[0033] As another preferred technical solution of the preparation method of the present invention, step (2) includes: mixing the high-nickel-type nickel cobalt aluminum-based ternary cathode material with a part of the coating material and performing a first sintering, washing the product of the first sintering, and then mixing it with another part of the coating material and performing a second sintering to obtain the cathode material co-coated with cobalt, aluminum, and titanium.

[0034] Preferably, the temperatures of the first sintering and the second sintering are independently 350°C to 800°C. Herein, "independently" means that the temperatures of the first sintering and the second sintering can be the same or different, and they are independent of each other.

[0035] Preferably, the total time of the first sintering and the second sintering is 8 h to 24 h.

[0036] In a third aspect, the present invention provides a lithium-ion battery, including a positive electrode, a negative electrode, and a separator, wherein the positive electrode includes the cathode material co-coated with cobalt, aluminum, and titanium described in the first aspect.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The cathode material of the present invention uses a high-nickel-type nickel cobalt aluminum-based ternary cathode material as the core, which has good rate performance at high voltages; further, on the basis of coating with Al element and / or Co element, adding Ti element for co-coating, and strictly controlling the contents and content relationships of Co element, Al element, and Ti element, a cathode material with low impedance and stable surface structure can be obtained, reducing gas generation of the battery at high temperatures.

[0039] The positive electrode material of the present invention, compared with the positive electrode material coated with Al element and / or Co element, the charge transfer impedance per unit area of the prepared positive electrode sheet is reduced by 15% - 30%, the DCR is reduced by 0.5 mΩ - 1 mΩ when applied to 18650 cylindrical battery cells, the gas generation amount is reduced by 10% - 30% after 400 cycles at 45°C, and the gas generation amount during full charge storage at 70°C is reduced by 30 - 50%. Description of the Drawings

[0040] Figure 1 It is a scanning electron microscope image of the cobalt-aluminum-titanium co-coated positive electrode material of Example 1.

[0041] Figure 2 It is an XRD comparison chart of the cobalt-aluminum-titanium co-coated positive electrode material of Example 1 and the cobalt-aluminum co-coated positive electrode material of Comparative Example 1. Detailed Embodiments

[0042] The technical solution of the present invention will be further described below in conjunction with the drawings and through specific embodiments.

[0043] The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0044] In one embodiment of the present invention, a cobalt-aluminum-titanium co-coated positive electrode material is provided. The cobalt-aluminum-titanium co-coated positive electrode material includes a high-nickel-type nickel-cobalt-aluminum-based ternary positive electrode material. The chemical composition of the high-nickel-type nickel-cobalt-aluminum-based ternary positive electrode 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.

[0045] A coating layer is provided on the surface of the high-nickel-type nickel-cobalt-aluminum-based ternary positive electrode material. The coating layer contains Co element, Al element, and Ti element. Based on the total mass of the high-nickel-type nickel-cobalt-aluminum-based ternary positive electrode material, the contents of Co element, Al element, and Ti element in the coating layer satisfy:[[]]

[0046] The content ω1 of Co element is 500 ppm - 8000 ppm; the content ω2 of Al element is 500 ppm - 6000 ppm; the content ω3 of Ti element is 0 ppm - 1500 ppm and does not contain 0 ppm; ω1 + ω2 is 1500 ppm - 12000 ppm; where ω1 + ω2 ≥ ω3.

[0047] In a cobalt-aluminum-titanium co-coated cathode material provided by an embodiment of the present invention, 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, where 1 ≤ α ≤ 1.05, 0.80 ≤ x ≤ 0.95, 0.04 ≤ y ≤ 0.15, 0.005 ≤ z ≤ 0.06, 0 ≤ m ≤ 0.02, and x + y + z + m = 1. Here, A includes one or more of Zr, Mg, Sr, Y, La, Nb, Ba, and Ti.

[0048] Exemplarily, 1 ≤ α ≤ 1.05, for example, it can be 1, 1.01, 1.02, 1.03, 1.04, or 1.05, etc.; 0.80 ≤ x ≤ 0.95, for example, it 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, etc.; 0.04 ≤ y ≤ 0.15, for example, it can be 0.04, 0.06, 0.08, 0.10, 0.12, 0.13, 0.14, or 0.15, etc.; 0.005 ≤ z ≤ 0.06, for example, it can be 0.01, 0.02, 0.03, 0.04, 0.05, or 0.06, etc.; 0 ≤ m ≤ 0.02, for example, it can be 0, 0.001, 0.003, 0.005, 0.007, 0.008, 0.01, 0.012, 0.015, 0.017, or 0.02, etc. Here, when m is 0, it means that the chemical composition does not contain element A.

[0049] In a cobalt-aluminum-titanium co-coated cathode material provided by an embodiment of the present invention, the content ω1 of Co element in the coating layer is 500 ppm to 8000 ppm. For example, it can be 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, 2650 ppm, 2800 ppm, 3000 ppm, 3200 ppm, 3300 ppm, 3500 ppm, 3700 ppm, 3800 ppm, 4000 ppm, 4200 ppm, 4400 ppm, 4500 ppm, 4700 ppm, 4800 ppm, 5000 ppm, 5200 ppm, 5500 ppm, 5600 ppm, 5800 ppm, 6000 ppm, 6200 ppm, 6300 ppm, 6400 ppm, 6500 ppm, 6700 ppm, 6800 ppm, 7000 ppm, 7200 ppm, 7400 ppm, 7600 ppm, 7800 ppm or 8000 ppm, etc., and is further preferably 1000 ppm to 8000 ppm. If the content of Co is too low, the total content of Co and Al will decrease, and the insufficient coating amount results in insufficient interface protection and impedance improvement not achieved. That is, both impedance and interface improvement deteriorate. If the content of Co is too high, when the Co content is greater than 8000 ppm, most of the final compounds of Co are converted into LiCoO2, which leads to a significant increase in LiCoO2. This substance is unstable at high temperatures and high voltages and is prone to explosion. Therefore, the product design of the present invention needs to strictly restrict the content of Co and must not exceed 8000 ppm strictly.

[0050] In a cathode material co-coated with cobalt, aluminum, and titanium provided by an embodiment of the present invention, the content ω2 of Al element in the coating layer is 500 ppm to 6000 ppm. For example, it can be 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, 2650 ppm, 2800 ppm, 3000 ppm, 3200 ppm, 3300 ppm, 3500 ppm, 3700 ppm, 3800 ppm, 4000 ppm, 4200 ppm, 4400 ppm, 4500 ppm, 4700 ppm, 4800 ppm, 5000 ppm, 5200 ppm, 5500 ppm, 5600 ppm, 5800 ppm, or 6000 ppm, etc. Preferably, it is 1000 ppm to 4000 ppm.

[0051] In a cathode material co-coated with cobalt, aluminum, and titanium provided by an embodiment of the present invention, the content ω3 of Ti element in the coating layer is 0 ppm to 1500 ppm and does not contain 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, 80 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 content ω3 of Ti element exceeds 1500 ppm, it will significantly affect the discharge capacity of the cathode material; if Ti element is not added, the synergistic effect with Co element and Al element cannot be achieved to reduce the impedance. When the coating amount is less than 50 ppm and greater than 0 ppm, the effect of reducing impedance will be a little worse, but the technical effect of the present invention can still be achieved. Therefore, the content ω3 of Ti element is preferably: ω3 ≥ 50 ppm.

[0052] In one embodiment, ω3 is 1000 ppm to 1500 ppm.

[0053] In an embodiment of the present invention, by limiting the content of cobalt element to 1000 ppm to 8000 ppm and the content of Ti element to 1000 ppm to 1500 ppm, it is more conducive to forming a fast ion conductor during the sintering process (especially at a relatively high sintering temperature), thereby improving the performance of the cathode material.

[0054] In the cobalt-aluminum-titanium co-coated cathode material provided by an embodiment of the present invention, ω1 + ω2 is 1500 ppm to 12000 ppm, and for example, it can be 1500 ppm, 1700 ppm, 1800 ppm, 2000 ppm, 2200 ppm, 2400 ppm, 2500 ppm, 2650 ppm, 2800 ppm, 3000 ppm, 3200 ppm, 3300 ppm, 3500 ppm, 3700 ppm, 3800 ppm, 4000 ppm, 4200 ppm, 4400 ppm, 4500 ppm, 4700 ppm, 4800 ppm, 5000 ppm, 5200 ppm, 5500 ppm, 5600 ppm, 5800 ppm, 6000 ppm, 6500 ppm, 7000 ppm, 7500 ppm, 8000 ppm, 8500 ppm, 9000 ppm, 9500 ppm, 10000 ppm, 10500 ppm, 11000 ppm, 11500 ppm or 12000 ppm, etc.

[0055] In an embodiment of the present invention, since (ω1 + ω2) / ω3 ≥ 1 and the contents of Co element and Al element are within specific ranges respectively, the introduction of Ti can significantly reduce the impedance of the battery cell and significantly reduce the gas generation during high-temperature storage and high-temperature cycling. However, if the content of Ti is too high, it will significantly deteriorate the specific capacity of the cathode material. Therefore, the coating content of Ti must be limited. The present invention controls the content of Ti to be less than or equal to the sum of the contents of Co and Al, and controls the content of Ti element, so that the specific capacity of the cathode material will not deteriorate, and at the same time, the coating effects of Co and Al can be ensured, and the technical effects of ensuring the integrity of the interface coating and reducing the gas generation at high temperature can be achieved.

[0056] In the cathode material of the present invention, it is not mandatory that the content of Co in the coating layer is greater than the content of Al in the coating layer. If there are only two coating elements, Co and Al, in the coating layer, the presence of Al will significantly reduce the impedance of the battery cell. In this case, in order to balance the overall impedance and overcharge gas generation performance of the battery cell, the content of Al must be less than the content of Co in principle.

[0057] However, in the present invention, since Ti is introduced into the coating layer, it can significantly reduce the impedance of the battery cell. Therefore, the introduction of Ti can increase the tolerance to Al element, and the introduction of Ti can offset the increase in impedance caused by the increase of Al element, so that the highest content of Al can also slightly exceed Co. For example, in one embodiment, the ratio of the content of Al element in the coating layer to the content of Co element in the coating layer is 1 to 1.2, such as 1, 1.05, 1.1, 1.15 or 1.2, etc.; in another embodiment, the content of Co element in the coating layer is greater than the content of Al element in the coating layer; in yet another embodiment, the content of Al element in the coating layer is 300 ppm to 600 ppm more than the content of Co element in the coating layer, such as 300 ppm, 350 ppm, 400 ppm, 450 ppm, 500 ppm, 550 ppm or 600 ppm, etc.

[0058] As a preferred solution, 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.

[0059] The positive electrode material of one embodiment of the present invention uses a high-nickel nickel-cobalt-aluminum-based ternary positive electrode material as the core, which has good rate performance at high voltage; further, on the basis of coating with Al element and / or Co element, Ti element is co-coated, and the contents and content relationships of Co element, Al element, and Ti element are strictly controlled, so as to obtain a positive electrode material with low impedance and stable surface structure.

[0060] The positive electrode material of one embodiment of the present invention, compared with the positive electrode material coated with Al element and / or Co element, the charge transfer impedance per unit area of the prepared positive electrode sheet is reduced by 15% to 30%, the DCR is reduced by 0.5 mΩ to 1 mΩ when applied to 18650 cylindrical battery cells, the gas generation amount is reduced by 10% to 30% after 400 cycles at 45 °C, and the gas generation amount during full charge storage at 70 °C is reduced by 30 to 50%.

[0061] In the cobalt-aluminum-titanium co-coated positive electrode material provided by one embodiment of the present invention, (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, etc. In one embodiment, (ω1 + ω2) / ω3 ≥ 3.

[0062] In one embodiment, 4 ≤ (ω1 + ω2) / ω3 ≤ 20.

[0063] In one embodiment, ω1 is from 1000 ppm to 8000 ppm.

[0064] In one embodiment, ω2 is from 1000 ppm to 4000 ppm.

[0065] In one embodiment, in the coating layer, Co element, Al element and Ti element 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, such as 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100%, etc., preferably more than 90%, more preferably more than 95%.

[0066] In another embodiment of the present invention, a method for preparing the cobalt-aluminum-titanium co-coated cathode material as described above is provided, and the preparation method includes the following steps:

[0067] (1) Mix nickel cobalt hydroxide, doping source and lithium source and then sinter to obtain a high-nickel type nickel cobalt aluminum-based ternary cathode material;

[0068] Among them, the doping elements in the doping source include Al element and A element, where A includes one or more of Zr, Mg, Sr, Y, La, Nb, Ba and Ti;

[0069] (2) Mix the high-nickel type nickel cobalt aluminum-based ternary cathode material with the coating material and sinter to obtain the cobalt-aluminum-titanium co-coated cathode material;

[0070] Among them, the coating material includes Co source, Al source and Ti source.

[0071] This solution is a relatively preferred secondary dry sintering preparation method of the present invention. Through the secondary dry sintering preparation method, the surface of the cathode material can be enhanced, gas generation can be reduced, and the charge transfer impedance of the cathode can be effectively reduced at the same time.

[0072] In the method for preparing the cobalt-aluminum-titanium co-coated cathode material provided by one embodiment of the present invention, the Co source and Ti source in the coating material react with the residual lithium on the surface of the high-nickel type nickel cobalt aluminum-based ternary cathode material, and part of them generate fast ion conductors. In particular, the introduction of the Ti source can significantly reduce the surface impedance of the material and has no significant impact on the cycle performance; at the same time, the Al source in the coating material will form an inert layer, although it has a certain increase in impedance, but it can significantly improve the cycle performance and curb gas generation.

[0073] In one embodiment, in step (1), the molar ratio of each element satisfies that Li / (Ni + Co + Al + A) is 1 to 1.05, and for example, it can be 1, 1.01, 1.02, 1.03, 1.04, or 1.05, etc.

[0074] In one embodiment, in step (1), the sintering temperature is 400°C to 1000°C, and for example, it can be 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, or 1000°C, etc.

[0075] In one embodiment, in step (1), the sintering time is 6 h to 20 h, and for example, it can be 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, or 20 h, etc.

[0076] In one embodiment, in step (2), the Co source includes at least one of cobalt oxide, cobalt hydroxide, and cobalt oxyhydroxide.

[0077] In one embodiment, in step (2), the Al source includes at least one of aluminum oxide, aluminum hydroxide, and aluminum oxyhydroxide.

[0078] In one embodiment, in step (2), the Ti source is a titanium oxide.

[0079] In one embodiment, the titanium oxide includes at least one of titanium dioxide, titanium monoxide, titanium sesquioxide, and titanium tetroxide. However, it is not limited to the above-listed types, and other commonly used titanium oxides in the art are also applicable to the present invention.

[0080] In one embodiment, in step (2), the sintering temperature is 350°C to 800°C, and for example, it 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, etc.

[0081] In one embodiment, in step (2), the sintering time is 8 h to 24 h, and for example, it can be 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 22 h, or 24 h, etc.

[0082] In one embodiment, in step (2), after sintering is completed, the temperature is decreased at a rate of 0.01 °C / min to 3 °C / min. Exemplarily, the cooling rate can be 0.01 °C / min, 0.05 °C / min, 0.1 °C / min, 0.2 °C / min, 0.5 °C / min, 0.7 °C / min, 1 °C / min, 1.5 °C / min, 2 °C / min, 2.5 °C / min, or 3 °C / min, etc.

[0083] In one embodiment, the method further includes: washing the high-nickel type nickel cobalt aluminum-based ternary cathode material prepared in step (1), and then mixing it with a Co source, an Al source, and a Ti source and sintering to prepare a cathode material with cobalt-aluminum-titanium co-coating. By adding the washing step, the residual alkali on the surface of the high-nickel type nickel cobalt aluminum-based ternary cathode material obtained by the first sintering can be reduced.

[0084] In one embodiment, step (2) includes: mixing the high-nickel type nickel cobalt aluminum-based ternary cathode material with a part of the coating material and performing a first sintering, washing the product of the first sintering, and then mixing it with another part of the coating material and performing a second sintering to obtain the cobalt-aluminum-titanium co-coated cathode material.

[0085] Washing can reduce the surface residual alkali and reduce the gas generation during cycling and high-temperature storage.

[0086] In one embodiment, the temperatures of the first sintering and the second sintering are independently 350 °C to 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, etc. Herein, "independently" means that the temperatures of the first sintering and the second sintering can be the same or different, and the two are independent of each other.

[0087] In one embodiment, the total time of the first sintering and the second sintering is 8 h to 24 h, for example, it can be 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 22 h, or 24 h, etc.

[0088] In another embodiment of the present invention, a lithium-ion battery is provided, including a positive electrode, a negative electrode, and a separator, and the positive electrode includes the cobalt-aluminum-titanium co-coated cathode material described in the first aspect.

[0089] The following are typical but non-limiting examples:

[0090] Example 1

[0091] This embodiment provides a cathode material co-coated with cobalt, aluminum, and titanium. The cathode material co-coated with cobalt, aluminum, and titanium includes a high-nickel-type nickel cobalt aluminum-based ternary cathode material (the chemical formula is shown in Table 1). A coating layer is provided on the surface of the high-nickel-type nickel cobalt aluminum-based ternary cathode material. The coating layer contains Co element, Al element, and Ti element. Based on the total mass of the high-nickel-type nickel cobalt aluminum-based ternary cathode material, the content ω1 of Co element, the content ω2 of Al element, the content ω3 of Ti element, the sum ω1+ω2 of the contents of Co element and Al element, and the ratio (ω1+ω2) / ω3 of the sum of the contents of Co element and Al element to the content of Ti element are shown in Table 2.

[0092] This embodiment also provides a preparation method of the above cathode material co-coated with cobalt, aluminum, and titanium, including the following steps:

[0093] Step 1: Prepare a high-nickel-type nickel cobalt aluminum-based ternary cathode material:

[0094] After mixing and grinding nickel cobalt hydroxide, a doping source, and a lithium source, perform a first sintering to obtain a high-nickel-type nickel cobalt aluminum-based ternary cathode material. Among them, the doping source is aluminum hydroxide, the lithium source is LiOH, the molar ratio of Li / (Ni+Co+Al) is 1.03, the sintering temperature is 710 °C, and the sintering time is 18 h.

[0095] Step 2: Coating process:

[0096] After mixing and grinding the high-nickel-type nickel cobalt aluminum-based ternary cathode material and the coating material evenly, perform a second sintering in an air atmosphere, and cool down to room temperature at a cooling rate of 1 °C / min to obtain the cathode material co-coated with cobalt, aluminum, and titanium. Among them, the coating material is cobalt hydroxide, hydroxyaluminum oxide, and titanium dioxide, the sintering temperature is 500 °C, and the sintering time is 10 h.

[0097] Figure 1 It is a scanning electron microscope image of the cathode material co-coated with cobalt, aluminum, and titanium in this embodiment. It can be seen from the figure that the material is evenly coated, without residue of the coating and fine powder.

[0098] Example 2

[0099] This embodiment provides a cobalt-aluminum-titanium co-coated cathode material. The cobalt-aluminum-titanium co-coated cathode material includes a high-nickel-type nickel-cobalt-aluminum-based ternary cathode material (the chemical formula is shown in Table 1). A coating layer is provided on the surface of the high-nickel-type nickel-cobalt-aluminum-based ternary cathode material. The coating layer contains Co element, Al element and Ti element. Based on the total mass of the high-nickel-type nickel-cobalt-aluminum-based ternary cathode material, the content ω1 of Co element, the content ω2 of Al element, the content ω3 of Ti element, the sum ω1 + ω2 of the contents of Co element and Al element, and the ratio (ω1 + ω2) / ω3 of the sum of the contents of Co element and Al element to the content of Ti element are shown in Table 2.

[0100] This embodiment also provides a preparation method of the above cobalt-aluminum-titanium co-coated cathode material, including the following steps:

[0101] Step 1, prepare a high-nickel-type nickel-cobalt-aluminum-based ternary cathode material:

[0102] After mixing and grinding nickel-cobalt hydroxide, a doping source and a lithium source, perform a first sintering to obtain a high-nickel-type nickel-cobalt-aluminum-based ternary cathode material. Among them, the doping source is aluminum hydroxide, the lithium source is Li2CO3, the molar ratio of Li / (Ni + Co + Al) is 1.02, the sintering temperature is 720 °C, and the sintering time is 19 h.

[0103] Step 2, coating process:

[0104] After mixing and grinding the high-nickel-type nickel-cobalt-aluminum-based ternary cathode material and the coating material evenly, perform a second sintering in an oxygen atmosphere, and cool down to room temperature at a cooling rate of 0.5 °C / min to obtain the cobalt-aluminum-titanium co-coated cathode material. Among them, the coating material is cobalt hydroxide, hydroxyaluminum oxide and titanium monoxide, the sintering temperature is 600 °C, and the sintering time is 13 h.

[0105] Example 3

[0106] This embodiment provides a cobalt-aluminum-titanium co-coated cathode material. The cobalt-aluminum-titanium co-coated cathode material includes a high-nickel-type nickel-cobalt-aluminum-based ternary cathode material (the chemical formula is shown in Table 1). A coating layer is provided on the surface of the high-nickel-type nickel-cobalt-aluminum-based ternary cathode material. The coating layer contains Co element, Al element and Ti element. Based on the total mass of the high-nickel-type nickel-cobalt-aluminum-based ternary cathode material, the content ω1 of Co element, the content ω2 of Al element, the content ω3 of Ti element, the sum ω1 + ω2 of the contents of Co element and Al element, and the ratio (ω1 + ω2) / ω3 of the sum of the contents of Co element and Al element to the content of Ti element are shown in Table 2.

[0107] This embodiment also provides a preparation method of the above cobalt-aluminum-titanium co-coated cathode material, including the following steps:

[0108] Step 1. Preparation of high-nickel nickel cobalt aluminum-based ternary cathode material:

[0109] After mixing and grinding nickel cobalt hydroxide, doping source and lithium source, perform a primary sintering to obtain a high-nickel nickel cobalt aluminum-based ternary cathode material; wherein, the doping source is aluminum hydroxide, the lithium source is LiOH, the molar ratio of Li / (Ni + Co + Al) is 1.05, the sintering temperature is 695 °C, and the sintering time is 14 h.

[0110] Step 2. Coating process:

[0111] After mixing and grinding the high-nickel nickel cobalt aluminum-based ternary cathode material and the coating material evenly, perform a secondary sintering in an air atmosphere, and cool down to room temperature at a cooling rate of 0.8 °C / 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 650 °C, and the sintering time is 9 h.

[0112] Example 4

[0113] This example provides a cobalt aluminum titanium co-coated cathode material, and the cobalt aluminum titanium co-coated cathode material includes a high-nickel nickel cobalt aluminum-based ternary cathode material (the chemical formula is shown in Table 1); a coating layer is provided on the surface of the high-nickel nickel cobalt aluminum-based ternary cathode material, and the coating layer contains Co element, Al element and Ti element. Based on the total mass of the high-nickel nickel cobalt aluminum-based ternary cathode material, the content ω1 of Co element, the content ω2 of Al element, the content ω3 of Ti element, the sum ω1 + ω2 of the contents of Co element and Al element, and the ratio (ω1 + ω2) / ω3 of the sum of the contents of Co element and Al element to the content of Ti element are shown in Table 2.

[0114] This example also provides a preparation method of the above cobalt aluminum titanium co-coated cathode material, including the following steps:

[0115] Step 1. Preparation of high-nickel nickel cobalt aluminum-based ternary cathode material:

[0116] After mixing and grinding nickel cobalt hydroxide, doping source and lithium source, perform a primary sintering to obtain a high-nickel nickel cobalt aluminum-based ternary cathode material; wherein, the doping source is aluminum hydroxide, the lithium source is LiOH, the molar ratio of Li / (Ni + Co + Al) is 1.01, the sintering temperature is 690 °C, and the sintering time is 15 h.

[0117] Step 2. Coating process:

[0118] After mixing and grinding the high-nickel nickel-cobalt-aluminum-based ternary cathode material and the coating material evenly, secondary sintering is carried out in an air atmosphere, and the temperature is lowered to room temperature at a cooling rate of 1.5 °C / min to obtain the cobalt-aluminum-titanium co-coated cathode material; wherein, the coating material is cobalt hydroxide, hydroxyaluminum oxide and titanium dioxide, the sintering temperature is 680 °C, and the sintering time is 12 h.

[0119] Example 5

[0120] This example provides a cobalt-aluminum-titanium co-coated cathode material, and the cobalt-aluminum-titanium co-coated cathode material includes a high-nickel nickel-cobalt-aluminum-based ternary cathode material (the chemical formula is shown in Table 1); a coating layer is provided on the surface of the high-nickel nickel-cobalt-aluminum-based ternary cathode material, and the coating layer contains Co element, Al element and Ti element. Based on the total mass of the high-nickel nickel-cobalt-aluminum-based ternary cathode material, the content ω1 of Co element, the content ω2 of Al element, the content ω3 of Ti element, the sum ω1+ω2 of the contents of Co element and Al element, and the ratio (ω1+ω2) / ω3 of the sum of the contents of Co element and Al element to the content of Ti element are shown in Table 2.

[0121] This example also provides a preparation method of the above cobalt-aluminum-titanium co-coated cathode material, including the following steps:

[0122] Step 1, prepare a high-nickel nickel-cobalt-aluminum-based ternary cathode material:

[0123] After mixing and grinding nickel-cobalt hydroxide, a doping source and a lithium source, primary sintering is carried out to obtain a high-nickel nickel-cobalt-aluminum-based ternary cathode material; wherein, the doping source is aluminum hydroxide, the lithium source is LiOH, the molar ratio of Li / (Ni+Co+Al) is 1.04, the sintering temperature is 650 °C, and the sintering time is 12 h.

[0124] Step 2, coating process:

[0125] After mixing and grinding the high-nickel nickel-cobalt-aluminum-based ternary cathode material and the coating material evenly, secondary sintering is carried out in an air atmosphere, and the temperature is lowered to room temperature at a cooling rate of 1 °C / min to obtain the cobalt-aluminum-titanium co-coated cathode material; wherein, the coating material is cobalt hydroxide, hydroxyaluminum oxide and titanium dioxide, the sintering temperature is 580 °C, and the sintering time is 10 h.

[0126] Example 6

[0127] This embodiment provides a cathode material co-coated with cobalt, aluminum, and titanium. The cathode material co-coated with cobalt, aluminum, and titanium includes a high-nickel nickel-cobalt-aluminum-based ternary cathode material (the chemical formula is shown in Table 1). A coating layer is provided on the surface of the high-nickel nickel-cobalt-aluminum-based ternary cathode material. The coating layer contains Co element, Al element, and Ti element. Based on the total mass of the high-nickel nickel-cobalt-aluminum-based ternary cathode material, the content ω1 of Co element, the content ω2 of Al element, the content ω3 of Ti element, the sum ω1+ω2 of the contents of Co element and Al element, and the ratio (ω1+ω2) / ω3 of the sum of the contents of Co element and Al element to the content of Ti element are shown in Table 2.

[0128] This embodiment also provides a preparation method of the above-mentioned cathode material co-coated with cobalt, aluminum, and titanium, including the following steps:

[0129] Step 1: Prepare a high-nickel nickel-cobalt-aluminum-based ternary cathode material:

[0130] After mixing and grinding nickel-cobalt hydroxide, a doping source, and a lithium source, perform a first sintering to obtain a high-nickel nickel-cobalt-aluminum-based ternary cathode material. Among them, the doping source is aluminum hydroxide, the lithium source is LiOH, the molar ratio of Li / (Ni+Co+Al) is 1.02, the sintering temperature is 670 °C, and the sintering time is 14 h.

[0131] Step 2: Coating process:

[0132] After mixing and grinding the high-nickel nickel-cobalt-aluminum-based ternary cathode material and the coating material evenly, perform a second sintering in an oxygen atmosphere, and cool down to room temperature at a cooling rate of 1 °C / min to obtain the cathode material co-coated with cobalt, aluminum, and titanium. Among them, the coating material is cobalt hydroxide, hydroxyaluminum oxide, and titanium dioxide, the sintering temperature is 560 °C, and the sintering time is 10 h.

[0133] Example 7

[0134] This embodiment provides a cathode material co-coated with cobalt, aluminum, and titanium. The cathode material co-coated with cobalt, aluminum, and titanium includes a high-nickel nickel-cobalt-aluminum-based ternary cathode material (the chemical formula is shown in Table 1). A coating layer is provided on the surface of the high-nickel nickel-cobalt-aluminum-based ternary cathode material. The coating layer contains Co element, Al element, and Ti element. Based on the total mass of the high-nickel nickel-cobalt-aluminum-based ternary cathode material, the content ω1 of Co element, the content ω2 of Al element, the content ω3 of Ti element, the sum ω1+ω2 of the contents of Co element and Al element, and the ratio (ω1+ω2) / ω3 of the sum of the contents of Co element and Al element to the content of Ti element are shown in Table 2.

[0135] This embodiment also provides a preparation method of the above-mentioned cathode material co-coated with cobalt, aluminum, and titanium, including the following steps:

[0136] Step 1: Prepare a high-nickel nickel-cobalt-aluminum-based ternary cathode material:

[0137] After mixing and grinding nickel-cobalt hydroxide, a doping source, and a lithium source, perform a first sintering to obtain a high-nickel nickel-cobalt-aluminum-based ternary cathode material; wherein, the doping source is aluminum hydroxide, the lithium source is LiOH, the molar ratio of Li / (Ni + Co + Al) is 1.02, the sintering temperature is 720 °C, and the sintering time is 14 h.

[0138] Step 2: Coating process:

[0139] After mixing and grinding the high-nickel nickel-cobalt-aluminum-based ternary cathode material and a coating material evenly, perform a second sintering in an air atmosphere, and cool down to room temperature at a cooling rate of 1 °C / min to obtain the cobalt-aluminum-titanium co-coated cathode material; wherein, the coating material is cobalt hydroxide, hydroxyaluminum oxide, and titanium dioxide, the sintering temperature is 700 °C, and the sintering time is 10 h.

[0140] Example 8

[0141] This example provides a cobalt-aluminum-titanium co-coated cathode material, and the cobalt-aluminum-titanium co-coated cathode material includes a high-nickel nickel-cobalt-aluminum-based ternary cathode material (the chemical formula is shown in Table 1); a coating layer is provided on the surface of the high-nickel nickel-cobalt-aluminum-based ternary cathode material, and the coating layer contains Co element, Al element, and Ti element. Based on the total mass of the high-nickel nickel-cobalt-aluminum-based ternary cathode material, the content ω1 of Co element, the content ω2 of Al element, the content ω3 of Ti element, the sum ω1 + ω2 of the contents of Co element and Al element, and the ratio (ω1 + ω2) / ω3 of the sum of the contents of Co element and Al element to the content of Ti element are shown in Table 2.

[0142] This example also provides a preparation method of the above cobalt-aluminum-titanium co-coated cathode material, including the following steps:

[0143] Step 1: Prepare a high-nickel nickel-cobalt-aluminum-based ternary cathode material:

[0144] After mixing and grinding nickel-cobalt hydroxide, a doping source, and a lithium source, perform a first sintering to obtain a high-nickel nickel-cobalt-aluminum-based ternary cathode material; wherein, the doping source is aluminum oxide, the lithium source is LiOH, the molar ratio of Li / (Ni + Co + Al) is 1.02, the sintering temperature is 720 °C, and the sintering time is 14 h.

[0145] Step 2: Coating process:

[0146] After uniformly mixing and grinding the high-nickel nickel-cobalt-aluminum-based ternary cathode material with the coating material, secondary sintering is carried out in an air atmosphere, and the temperature is lowered to room temperature at a cooling rate of 1 °C / 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 °C, and the sintering time is 10 h.

[0147] Example 9

[0148] This example provides a cobalt-aluminum-titanium co-coated cathode material, and the cobalt-aluminum-titanium co-coated cathode material includes a high-nickel nickel-cobalt-aluminum-based ternary cathode material (the chemical formula is shown in Table 1); a coating layer is provided on the surface of the high-nickel nickel-cobalt-aluminum-based ternary cathode material, and the coating layer contains Co element, Al element and Ti element. Based on the total mass of the high-nickel nickel-cobalt-aluminum-based ternary cathode material, the content ω1 of Co element, the content ω2 of Al element, the content ω3 of Ti element, the sum ω1 + ω2 of the contents of Co element and Al element, and the ratio (ω1 + ω2) / ω3 of the sum of the contents of Co element and Al element to the content of Ti element are shown in Table 2.

[0149] This example also provides a preparation method of the above cobalt-aluminum-titanium co-coated cathode material, including the following steps:

[0150] Step 1, prepare a high-nickel nickel-cobalt-aluminum-based ternary cathode material:

[0151] After mixing and grinding nickel-cobalt hydroxide, doping source and lithium source, primary sintering is carried out to obtain a high-nickel nickel-cobalt-aluminum-based ternary cathode material; wherein, the doping source is aluminum hydroxide, the lithium source is LiOH, the molar ratio of Li / (Ni + Co + Al) is 1.02, the sintering temperature is 720 °C, and the sintering time is 14 h.

[0152] Step 2, coating process:

[0153] After uniformly mixing and grinding the high-nickel nickel-cobalt-aluminum-based ternary cathode material with the coating material, secondary sintering is carried out in an air atmosphere, and the temperature is lowered to room temperature at a cooling rate of 1 °C / 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 °C, and the sintering time is 10 h.

[0154] Example 10

[0155] The difference between this example and Example 1 is that the high-nickel nickel-cobalt-aluminum-based ternary cathode material obtained in Step 1 is washed with water and then used for the coating process in Step 2.

[0156] Example 11

[0157] The difference between this embodiment and Embodiment 1 is that step (2) includes:

[0158] Mix the high-nickel nickel-cobalt-aluminum-based ternary cathode material with 50 wt% of the coating material and conduct a first sintering. Wash the product of the first sintering, then mix it with the remaining coating material and conduct a second sintering to obtain the cobalt-aluminum-titanium co-coated cathode material. The atmospheres for both the first sintering and the second sintering are air atmospheres, the temperature is 500 °C for both, the sintering time is 5 h for both, and the cooling rate after sintering is 1 °C / min.

[0159] Comparative Example 1

[0160] The difference from Embodiment 1 is that titanium dioxide is removed from the coating material in step 2 to obtain a cobalt-aluminum co-coated cathode material, abbreviated 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 2.

[0161] Figure 2 It is an XRD comparison chart of the cobalt-aluminum-titanium co-coated cathode material of Embodiment 1 and the cobalt-aluminum co-coated cathode material of Comparative Example 1. It can be seen from the figure that Ti coating does not affect the crystal structure of the material.

[0162] Comparative Example 2

[0163] The difference from Embodiment 1 is that boehmite is removed from the coating material in step 2 to obtain a cobalt-titanium co-coated cathode material, abbreviated 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 2.

[0164] Comparative Example 3

[0165] The difference from Embodiment 1 is that cobalt hydroxide is removed from the coating material in step 2 to obtain an aluminum-titanium co-coated cathode material, abbreviated as Li 1.03 (Ni 0.88 Co 0.10 Al 0.02 )O2@(AlTi). The elemental coating amounts in the coating layer are shown in Table 2.

[0166] Comparative Example 4

[0167] The difference from Embodiment 1 is that cobalt hydroxide and boehmite are removed from the coating material in step 2 to obtain a titanium-coated cathode material, abbreviated as Li 1.03 (Ni 0.88 Co0.10 Al 0.02 )O2@(Ti), and the element coating amounts in the coating layer are shown in Table 2.

[0168] Comparative Example 5

[0169] The difference from Example 1 is that the contents of Co element and Al element in the coating layer are both 500 ppm, and the content of Ti element is 1500 ppm.

[0170] Table 1

[0171]

[0172] Table 2

[0173]

[0174] The positive electrode materials of Examples 1-9 and Comparative Examples 1-5 were used to prepare the positive electrode and assemble the battery. Specifically:

[0175] Prepare the battery:

[0176] (1) Prepare the positive electrode sheet:

[0177] The positive electrode materials of Examples 1-9 and Comparative Examples 1-5 were used as the active substances. The active substances, conductive agent Super P, and binder PVDF were mixed in a mass ratio of 95:2:3 in NMP to obtain a positive electrode slurry. The positive electrode slurry was coated on the surface of the aluminum foil and dried to obtain the positive electrode sheet.

[0178] (2) Prepare the negative electrode sheet:

[0179] The artificial graphite negative electrode, conductive agent Super P, binder CMC, and thickener SBR were mixed in a mass ratio of 96:0.5:1.5:2 in water to obtain a negative electrode slurry. The negative electrode slurry was coated on the surface of the copper foil and dried to obtain the negative electrode sheet.

[0180] (3) Provide a separator and an electrolyte. Among them, the separator is a multi-layer composite separator, the base 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, where EC:DMC:FEC:LiPF6 (mass ratio) = 20:60:5:15.

[0181] (4) After winding the above positive electrode sheet, negative electrode sheet, and separator, a cylindrical battery cell was obtained. The cylindrical battery cell was placed in a battery case and the electrolyte was injected to obtain a 18650 battery.

[0182] Performance test:

[0183] (1)Charge transfer impedance R per unit area of the positive electrode sheet at 50% SOC ct Test: Disassemble the cylindrical battery cell at 50% SOC to obtain the positive electrode sheet, then cut several pieces of the positive electrode sheet. Then, a symmetrical battery is composed of one layer of positive electrode sheet, one layer of separator, and one layer of positive electrode sheet. Then, an AC impedance test is carried out using a Blue Energy test system, and finally, the R in the AC impedance test data is obtained. ct Data.

[0184] (2)DC internal resistance DCR test of 18650 battery at 50% SOC: Use the 18650 cylindrical battery cell at 50% SOC without disassembling, and directly carry out a DC impedance test on the Blue Energy test system to obtain the DC internal resistance.

[0185] (3)Under the conditions of 70 °C and 100% SOC, test the impedance before storage and the impedance after 30 days of storage, and calculate the gas generation amount and impedance growth rate during 30 days of storage.

[0186] (4)Charge and discharge the 18650 battery under the conditions of: 45 °C, 2C charging, 3C discharging, and cycling 400 times. Record the gas generation amount and calculate the capacity retention rate when cycling to 400 times.

[0187] The test results are shown in Table 3.

[0188] Table 3

[0189]

[0190] As can be seen from Table 3, for the positive electrode material of the present invention, compared with the positive electrode material with cobalt-aluminum co-coating (Comparative Example 1), the charge transfer impedance R per unit area of the positive electrode sheet prepared by using the positive electrode material ct is reduced by 15.0 - 33.5%; when applied to the 18650 cylindrical battery cell, the DCR is reduced by 0.5 mΩ - 1.0 mΩ; the gas generation amount during 30 days of storage at 70 °C and 100% SOC is reduced by 13.5 - 23.5%, and the impedance growth rate is reduced by 11.0% - 18.5%; the gas generation amount is reduced by 22.0% - 28.0% after cycling 400 times at 45 °C, and the capacity retention rate is increased by 4.0% - 6.0%.

[0191] In particular, regarding the value of "DC internal resistance at 50% SOC", it should be explained that since the positive electrode sheet is only one component in the entire cylindrical battery cell, if there is a 0.5 mΩ increase in this data, it indicates that it already belongs to a very large impedance increase, which will have a greater impact on the entire battery cell.

[0192] In Examples 6 and 7, the contents of Co element and Ti element are relatively high, and the temperature of secondary sintering is relatively high, so it is more inclined to form a fast ion conductor with low impedance. However, the content of Al element in the coating layer of Example 7 is more, so the optimal group for impedance performance is Example 6, while for the gas generation performance, the optimal group is Example 7.

[0193] In the coating layer of Comparative Example 1, Ti element is missing. In the coating layer of Comparative Example 3, Co element is missing, and the coating amount of Al element in Comparative Example 3 is the largest, and its impedance performance is the worst. In the coating layers of Comparative Example 2 and Comparative Example 4, Al element is missing, and their cycling performance deteriorates. Moreover, the coating amount of Ti element in the coating layer of Comparative Example 4 is larger, and its gas generation amount is improved to a certain extent compared with Comparative Example 2, but they are all much higher than those of the examples.

[0194] Although the coating layer of Comparative Example 5 contains Co element, Al element and Ti element at the same time, the total coating amount of Co element and Al element is relatively small, and the sum of the contents of Co element and Al element is less than the content of Ti element. Although the charge transfer impedance per unit area of its positive electrode sheet does not deteriorate significantly, its DCR after being made into 18650 battery cells is 21.5 mΩ, which also increases slightly. The gas generation amount during full charge storage at 70 °C is 15.73 mL, and the impedance growth rate is 51.2%, and the deterioration is obvious. The gas generation amount after 400 cycles at 45 °C is 32.7 mL, and the final cycle retention rate after 400 cycles is only 77.20%.

[0195] At the same time, we can see that although the content of Co + Al ≥ Ti is the basic requirement, however, 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. Generally, the content of Ti and the content of Co + Al are positively correlated.

[0196] A further preferred scheme is that (ω1 + ω2) / ω3 ≥ 2, more preferably (ω1 + ω2) / ω3 ≥ 3, and further preferably 4 ≤ (ω1 + ω2) / ω3 ≤ 20. Ti coating belongs to a subordinate secondary coating element of Co and Al, and is a supplement to the main coating elements Co and Al, and at the same time a supplement to the performance, which plays a role in further strengthening the Co + Al coating system.

[0197] When (ω1 + ω2) / ω3 ≥ 2, the improvement of Co is beneficial to the specific capacity of the material. The coating can improve the specific capacity, but Ti and Al do not provide capacity improvement. Essentially, Ti is a modification component for the co - coating of Co and Al. It can alleviate the impedance deterioration brought by Al, and at the same time further reduce the gas generation during high - temperature storage and high - temperature cycling. If selected, when (ω1 + ω2) / ω3 ≥ 2, compared with (ω1 + ω2) / ω3 ≥ 1, the capacity loss is smaller.

[0198] When (ω1 + ω2) / ω3 ≥ 3, similarly, this component can better balance the specific capacity, impedance, high-temperature storage performance, and high-temperature gas generation performance of the material. Similarly, we more preferably select 4 ≤ (ω1 + ω2) / ω3 ≤ 20.

[0199] The numerical ranges described in the present invention not only include the point values listed above, but also any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0200] The present invention illustrates the detailed method of the present invention through 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 improvement to the present invention, the equivalent substitution of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A cobalt-aluminum-titanium co-coated cathode material, characterized in that, The cobalt-aluminum-titanium co-coated cathode material includes 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, where 1 ≤ α ≤ 1.05, 0.80 ≤ x ≤ 0.95, 0.04 ≤ y ≤ 0.15, 0.005 ≤ z ≤ 0.06, 0 ≤ m ≤ 0.02, and x + y + z + m = 1. Here, A includes one or more of Zr, Mg, Sr, Y, La, Nb, Ba, and Ti; A coating layer is provided on the surface of the high-nickel nickel-cobalt-aluminum-based ternary cathode material. The coating layer contains Co element, Al element and Ti element. Based on the total mass of the high-nickel nickel-cobalt-aluminum-based ternary cathode material, the contents of Co element, Al element and Ti element in the coating layer satisfy: The content ω1 of Co element is 500 ppm to 8000 ppm; The content ω2 of Al element is 500 ppm to 6000 ppm; The content ω3 of Ti element is 0 ppm to 1500 ppm and does not contain 0 ppm; ω1 + ω2 is 1500 ppm to 12000 ppm; wherein, ω1 + ω2 ≥ ω3.

2. The cobalt-aluminum-titanium co-coated cathode material according to claim 1, wherein (ω1 + ω2) / ω3 ≥ 2; and / or, ω1 is 1000 ppm to 8000 ppm; and / or, ω2 is 1000 ppm to 4000 ppm; and / or, ω3 is 1000 ppm to 1500 ppm.

3. The cobalt-aluminum-titanium co-coated cathode material according to claim 2, characterized in that, 4 ≤ (ω1 + ω2) / ω3 ≤ 20.

4. The cobalt-aluminum-titanium co-coated cathode material according to claim 1, characterized in that, The content of Co element in the coating layer is greater than the content of Al element in the coating layer, or, the ratio of the content of Al element in the coating layer to the content of Co element in the coating layer is 1 to 1.2, or, the content of Al element in the coating layer is 300 ppm to 600 ppm more than the content of Co element in the coating layer.

5. The cobalt-aluminum-titanium co-coated cathode material according to any one of claims 1-4, characterized in that, In the coating layer, Co element, Al element and Ti element 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.

6. A method for preparing a cobalt-aluminum-titanium co-coated cathode material according to any one of claims 1-5, characterized in that, The preparation method includes the following steps: (1) Mix nickel-cobalt hydroxide, doping source and lithium source and sinter them to obtain a high-nickel nickel-cobalt-aluminum-based ternary cathode material; wherein, the doping elements in the doping source include Al element and A element, and A includes one or more of Zr, Mg, Sr, Y, La, Nb, Ba and Ti; (2) Mix the high-nickel nickel-cobalt-aluminum-based ternary cathode material with a coating material and sinter them to obtain the cobalt-aluminum-titanium co-coated cathode material; wherein, the coating material includes Co source, Al source and Ti source; In step (1), the molar ratio of each element satisfies that Li / (Ni + Co + Al + A) is 1 to 1.05; In step (1), the sintering temperature is 400 °C to 1000 °C.

7. The preparation method according to claim 6, characterized in that, In step (2), the Co source includes at least one of cobalt oxide, cobalt hydroxide and cobalt oxyhydroxide; and / or, In step (2), the Al source includes at least one of aluminum oxide, aluminum hydroxide and aluminum oxyhydroxide; and / or, In step (2), the Ti source is titanium oxide; and / or, the titanium oxide includes at least one of titanium dioxide, titanium monoxide, titanium sesquioxide and titanium tetroxide; and / or, In step (2), the sintering temperature is 350 °C to 800 °C; and / or, In step (2), the sintering time is 8 h to 24 h; and / or, In step (2), after the sintering is completed, the temperature is decreased at a rate of 0.01 °C / min to 3 °C / min.

8. The preparation method according to claim 6, characterized in that, The method further includes: washing the high-nickel nickel cobalt aluminum-based ternary cathode material prepared in step (1), and then mixing it with Co source, Al source and Ti source and sintering to prepare a cathode material co-coated with cobalt, aluminum and titanium.

9. The preparation method according to claim 6, characterized in that, Step (2) includes: mixing the high-nickel nickel cobalt aluminum-based ternary cathode material with a part of the coating material and performing a first sintering, washing the product of the first sintering, and then mixing it with another part of the coating material and performing a second sintering to obtain the cathode material co-coated with cobalt, aluminum and titanium; and / or, The temperature of the first sintering and the second sintering is independently 350°C to 800°C; and / or, The total time of the first sintering and the second sintering is 8h to 24h.

10. A lithium-ion battery, comprising a positive electrode, a negative electrode and a separator, characterized in that, The cathode includes the cathode material co-coated with cobalt, aluminum and titanium according to any one of claims 1-5.

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