Lithium cobalt oxide positive electrode material, and preparation method and application thereof

Abstract

This invention belongs to the field of battery technology and discloses a lithium cobalt oxide cathode material, its preparation method, and its application. The general chemical formula of the lithium cobalt oxide cathode material of this invention is A((LiCo)₂)₃. 1‑ a M a O2)@N1)@N 3‑A ·B((Li 1‑b Mn x Ni y Co z Sr b R c O2)@N2)@N 3‑B Where 0.7≤A≤0.85, 0.15≤B≤0.3, A+B=1, and A is ((LiCo) 1‑a M a O2)@N1)@N 3‑A The volume percentage of B in the lithium cobalt oxide cathode material is ((Li 1‑ b Mn x Ni y Co z Sr b R c O2)@N2)@N 3‑B The volume percentage of lithium cobalt oxide cathode material. This invention provides a high-energy-density lithium cobalt oxide cathode material that simultaneously possesses high safety and stability, long cycle performance, and high storage performance, while also taking into account the good storage performance of ternary materials.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and specifically relates to a lithium cobalt oxide cathode material, its preparation method, and its application. Background Technology

[0002] Developing high-energy-density lithium cobalt oxide materials by increasing battery storage, cycling, and charging depth has long been a goal of academia and industry. High-voltage lithium cobalt oxide (LiCoO2), with its higher volumetric energy density than high-nickel 9-series ternary materials, boasts advantages such as a high discharge plateau, high compaction density, good storage performance, and long cycle life, making it a promising candidate for high-end vehicles such as commercial cars and sports cars where cost sensitivity is low. Storage capacity is a crucial indicator to consider and evaluate in both new energy electric vehicles and energy storage applications. On the one hand, good storage capacity improves the cycle life and durability of electric vehicle batteries, enhancing user comfort and experience; on the other hand, due to battery self-discharge, good storage capacity is also essential for lithium batteries in energy storage stations. However, the development of fast charging today presents certain challenges to battery storage capacity.

[0003] High voltage can damage the layered structure of LiCoO2, leading to a decline in material performance. High cost, low safety, and low storage capacity remain challenges for the commercial application of LiCoO2 batteries in electric vehicles.

[0004] Increasing the charge cutoff voltage of LiCoO2 batteries can improve the volumetric energy density, but this method suffers from structural damage to the LiCoO2 cathode, specifically, the LiCoO2 cathode is prone to lattice distortion under high voltage. In a state of high lithium depletion, LiCoO2 with a high number of lithium vacancies is thermodynamically unstable. This destructive process includes O loss and Co dissolution, leading to the degradation of Li... + Long-range diffusion pathways are blocked, and the material surface degrades (forming an electrochemically active spinel phase). Lithium-ion extraction also generates strong repulsion between O layers, increasing internal structural stress. To minimize structural instability caused by electrostatic repulsion between O layers, the CoO6 layer will slide, leading to a structural transformation from the O3 phase to the H1-3 phase. Furthermore, with increasing lithium-ion extraction, the thermal stability of LiCoO2 deteriorates, the thermal runaway initiation temperature decreases, and O2 precipitation and structural phase transitions become more severe, further worsening cycle and storage performance.

[0005] To mitigate the phase transition and thermal instability of LiCoO2 under high voltage, various modification strategies have been developed, such as conventional surface coating and doping, and newly introduced concentration gradient structures. The basic design principle of these typical strategies is based on introducing inert protective coatings to eliminate side reactions at the electrode / electrolyte interface or introducing inactive elements to modulate the local TM-O (metal-oxygen bond) environment. However, the synthesis processes for these strategies are highly complex, and the high production costs may be an insurmountable obstacle for large-scale industrial applications. Therefore, when modification strategies for single LiCoO2 cathode materials become extremely limited and complex, utilizing mature ternary cathode materials with good storage performance is more economical, offering higher cost-effectiveness and allowing each material to leverage its own advantages.

[0006] Currently, ternary lithium batteries are used in new energy electric vehicles, with advantages in high energy density and good storage performance. However, their storage performance also needs to be further developed through reasonable processes. The problem with ternary materials is that they lack the small volume advantage of high compaction density found in LiCoO2 and also have certain cycle stability issues. Electric vehicles currently have stringent requirements regarding driving range, battery lightweighting, battery cycle life, vehicle weight, and battery storage capacity, which are also key parameters for competition with other brands. At the same time, the demand for high energy density will further increase, making the marketization of high compaction density and high-voltage lithium cobalt oxide an inevitable trend. Summary of the Invention

[0007] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a lithium cobalt oxide cathode material, its preparation method, and its application, addressing the poor storage performance of existing LiCoO2 cathode materials and improving the poor cycle performance of ternary materials. The storage performance, cycle performance, and energy density of lithium-ion batteries using lithium cobalt oxide cathode materials with a cutoff voltage ≥4.5V are improved, meeting the requirements of new energy vehicles for lithium-ion battery cycle and storage performance, safety performance, and energy density. Furthermore, the addition of ternary materials in this invention can optimize performance, reducing the high cost and poor storage capacity of LiCoO2 currently due to the use of a pure cobalt system instead of incorporating ternary cathode materials.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The first aspect of the present invention provides a lithium cobalt oxide cathode material, wherein the general chemical formula of the lithium cobalt oxide cathode material is A((LiCo) 1-a M a O2)@N1)@N 3-A ·B((Li 1-b Mn x Ni y Coz Sr b R c O2)@N2)@N 3-B Where 0.7≤A≤0.85, 0.15≤B≤0.3, A+B=1, and A is ((LiCo) 1-a M a O2)@N1)@N 3-A The volume percentage of B in the lithium cobalt oxide cathode material, wherein B is ((Li 1-b Mn x Ni y Co z Sr b R c O2)@N2)@N 3-B The volume percentage of lithium cobalt oxide cathode material;

[0010] Wherein, 0.03≤a≤0.08, 0≤b≤0.005, 0.01≤c≤0.08, 0.05≤x≤0.2, 0.5≤y≤0.75, 0.1≤z≤0.25, x+y+z+c=1; preferably, 0.04≤a≤0.07, 0.0025≤b≤0.005, 0.015≤c≤0.03, 0.05≤x≤0.16, 0.5≤y≤0.64, 0.1≤z≤0.185, x+y+z+c=1; more preferably, 0.0494≤a≤0.062, b=0.0025, c=0.015, x=0.16, y=0.64, z=0.185, x+y+z+c=1;

[0011] Both M and R are used as doping elements, wherein M is selected from at least one of Al, Mn, Mg, Ni, La, Y, Sr, Mo, Sn, Ir, Ru and Zr; and R is selected from at least one of Al, Mn, Ni, Co, Mo, Ir, Ru and Zr.

[0012] The N1, N2, N 3-A and N 3-B All are used as coating agents, wherein coating agent N1 is selected from at least one of the oxides, hydroxides, fluorides, and chlorides of Ti, Li, Mn, Mg, Ni, La, Y, and Sr; coating agent N2 is selected from at least one of the oxides, hydroxides, fluorides, and chlorides of Ti, Mn, Ni, Co, Sr, Mo, Se, Ir, Ru, and Zr; coating agent N 3-A Or coating agent N 3-B It is selected from at least one of the oxides, hydroxides, fluorides, and chlorides of Al, Ti, Mn, Ni, Co, Sr, Mo, Se, Ir, Ru, and Zr.

[0013] Based on the above technical solution, this invention uses LiCoO2 and ternary material LiMnNiCoO2 as the main raw materials, and performs doping modification and coating on them respectively. Then, by adjusting the volume ratio of the two materials after graded coating, the compaction density of the lithium cobalt oxide cathode material is further increased to 4.1 g / m³. 3 and above.

[0014] In one embodiment, the (LiCo) 1-a M a O2)@N1 of D v 50 is 10μm to 14.5μm; and / or, the (LiCo) 1-a M a O2)@N1 of D n 10 represents 1μm to 5μm.

[0015] In one embodiment, the (Li) 1-b Mn x Ni y Co z Sr b R c O2)@N2 of D v 10 is 0.5μm to 1μm; and / or, the (Li) 1-b Mn x Ni y Co z Sr b R c O2)@N2 of D v 50 is 1μm to 3.5μm; and / or, the (Li) 1-b Mn x Ni y Co z Sr b R c O2)@N2 of D n 10 represents 0.5μm to 1μm.

[0016] Understandably, D v 50 indicates the particle size corresponding to a cumulative volumetric distribution percentage of 50%; D v 10 represents the particle size corresponding to a cumulative volumetric distribution percentage of 10%; D n 10 represents 1μm to 5μm, indicating that particles smaller than 1μm to 5μm account for 10% of the total number of particles; D n 10 represents 0.5μm to 1μm, indicating that particles smaller than 0.5μm to 1μm account for 10% of the total number of particles.

[0017] In one embodiment, the specific surface area of ​​the lithium cobalt oxide cathode material is 0.1 m². 2 / g~0.2m 2 / g; and / or, the compaction density of the lithium cobalt oxide cathode material is ≥4.1g / m³. 3 ; and / or, the D of the lithium cobalt oxide cathode material v 50 is 10μm to 13.5μm.

[0018] In one embodiment, the coating agent N 3-A and coating agent N 3-B The components are not entirely identical.

[0019] A second aspect of the present invention provides a method for preparing the lithium cobalt oxide cathode material described in the first aspect of the present invention, comprising the following steps:

[0020] The modified LiCoO2 primary product is obtained by mixing lithium source, cobalt source and compound containing element M and sintering in one step.

[0021] The modified LiCoO2 primary product and the coating agent N1 are mixed and sintered twice to obtain the modified LiCoO2 secondary product.

[0022] The modified LiCoO2 secondary product and the coating agent N 3-A Modified LiCoO2 was obtained by mixing and sintering three times.

[0023] The modified ternary material primary product is obtained by mixing lithium source, nickel cobalt manganese precursor with R-containing compound, or with Sr and R-containing compound and sintering in one step.

[0024] The modified ternary material primary product and the coating agent N2 are mixed and sintered twice to obtain the modified ternary material secondary product.

[0025] The modified ternary material secondary product and the coating agent N 3-B The modified ternary material was prepared by mixing and sintering three times.

[0026] The modified LiCoO2 and the modified ternary material were mixed and sintered four times to obtain the lithium cobalt oxide cathode material.

[0027] Based on the above technical solution, this invention solves the problem of uneven coating design through a three-stage sintering (pre-sintering) and four-stage sintering process. It preferentially coats particles of different sizes with their respective matching coating agents, controls the matching of particle size distribution, improves the relative mismatch between large LiCoO2 particles and small ternary materials in the distribution, better leverages their respective advantages, and solves the problem of poor storage and cycling performance of lithium cobalt oxide at high voltages of 4.5V and above. This results in a lithium cobalt oxide cathode material that simultaneously possesses high storage performance, high safety performance, long cycle performance, and high energy density.

[0028] In one embodiment, the compound containing element M is selected from at least one of oxides, hydroxides, fluorides, and chlorides of Al, Mn, Mg, Ni, La, Y, Sr, Mo, Sn, Ir, Ru, and Zr.

[0029] In one embodiment, the R-containing compound is selected from at least one of oxides, hydroxides, fluorides, and phosphides of Al, Mn, Ni, Co, Mo, Ir, Ru, and Zr.

[0030] In one embodiment, the Sr-containing compound is selected from at least one of Sr carbonates, oxides, hydroxides, fluorides, and phosphides.

[0031] In one embodiment, the compound containing element M, the compound containing element Sr, the compound containing element R, and the coating agents N1, N2, and N... 3-A N 3-B D v 50 are all ≤2μm.

[0032] In one embodiment, in the step of mixing the modified LiCoO2 primary product and the coating agent N1, the amount of coating agent N1 added is 4000ppm to 10000ppm, more preferably 4000ppm to 8000ppm, and even more preferably 4000ppm to 6000ppm.

[0033] In one embodiment, in the step of mixing the modified ternary material primary product and the coating agent N2, the amount of coating agent N2 added is 4000ppm to 10000ppm, more preferably 4000ppm to 8000ppm, and even more preferably 4000ppm to 6000ppm.

[0034] In one embodiment, coating agent N 3-A and coating agent N 3-B The total amount added by each is 2% to 2.5% of the total mass of the modified LiCoO2 secondary product and the modified ternary material secondary product, respectively.

[0035] In one embodiment, the conditions for the first sintering include: a sintering temperature of 700°C to 1250°C; and / or a sintering time of 10 hours or more.

[0036] In one embodiment, the conditions for the secondary sintering include: a sintering temperature of 450°C to 950°C; and / or a sintering time of 10 hours or more.

[0037] In one embodiment, in the steps of preparing the primary and secondary modified LiCoO2 products, the conditions for the primary sintering include: a sintering atmosphere of air or oxygen; and / or a sintering temperature of 950°C to 1250°C; and / or a sintering time of 10 hours or more; the conditions for the secondary sintering include: a sintering temperature of 500°C to 950°C; and / or a sintering time of 10 hours or more.

[0038] In one embodiment, in the steps of preparing the primary and secondary modified ternary materials, the conditions for the primary sintering include: a sintering temperature of 700℃ to 950℃; the conditions for the secondary sintering include: a sintering temperature of 450℃ to 850℃; and / or, a sintering time of 10 hours or more.

[0039] In one embodiment, the equipment used for the three-stage sintering is a rotary kiln, and the conditions for the three-stage sintering include: a sintering temperature of 100℃ to 250℃; and / or a sintering time of 0.5h to 1h; and / or a rotation speed of 10r / min to 20r / min. The three-stage sintering in this invention is also called pre-sintering. The purpose of pre-sintering is to ensure a tighter bond between the coating agent and the material, resulting in a more uniform coating than direct mixing, thereby improving the material compatibility.

[0040] In one embodiment, the conditions for the four sintering processes include: a sintering temperature of 300°C to 600°C; and / or a sintering time of 3 hours to 5 hours. This invention further improves the compactness and compatibility of the two materials through four sintering processes, resulting in a graded lithium cobalt oxide cathode material.

[0041] In one embodiment, in each step of the method for preparing the lithium cobalt oxide cathode material, the mixing speed is 10 r / min to 1500 r / min, and the mixing time is 10 min to 120 min.

[0042] In one embodiment, in each step of the method for preparing the lithium cobalt oxide cathode material, the sintering heating rate is 2.0 °C / min to 10.0 °C / min.

[0043] A third aspect of the present invention provides a positive electrode sheet, the positive electrode sheet comprising the lithium cobalt oxide positive electrode material described in the first aspect of the present invention, or comprising the lithium cobalt oxide positive electrode material prepared by the preparation method described in the second aspect of the present invention.

[0044] A fourth aspect of the present invention provides a lithium-ion battery, the lithium-ion battery comprising the positive electrode sheet described in the third aspect of the present invention.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] This invention provides a lithium cobalt oxide cathode material, in which matching coating agents are coated onto the surfaces of doped lithium cobalt oxide and doped lithium nickel cobalt manganese oxide, respectively. This allows the lithium cobalt oxide cathode material to simultaneously possess high safety and stability, long cycle life, high storage performance, and high energy density, while also maintaining the good storage performance of ternary materials. Details are as follows:

[0047] 1. A combination of large-particle lithium cobalt oxide and small-particle ternary materials is used to balance the good storage performance of ternary materials with the high density and high energy density of lithium cobalt oxide materials.

[0048] 2. To improve the uniformity of coating and prevent the coating agent from being over-concentrated on one of the materials, a pre-sintering process is adopted, which makes the coating agent and the material adhere more tightly and reliably, avoiding uneven coating or loss of some to other particles in subsequent mixing. Furthermore, the two particles have their own matching coating agents, resulting in better performance.

[0049] 3. The four-stage sintering process results in a more compact particle size distribution, promoting synergistic effects, increasing the compatibility between lithium cobalt oxide and ternary materials, and improving the surface structure of particles of different sizes. Compared with traditional coating, the special four-stage sintering process coating is more compact and better at suppressing adverse chemical reactions between the electrolyte and the surface of the cathode material, such as structural damage caused by redox reactions, and dissolution of Co elements due to structural damage and chemical reactions.

[0050] 4. For large particles, a secondary process of doping and coating is used to suppress the change of the valence state of Co in the cathode material, while suppressing the release of Co, changing the average band structure of Co, reducing the dissolution of Co, improving the channel and improving the lithium ion insertion / extraction ability, increasing the capacity, and slightly improving the rate performance and storage performance of lithium cobalt oxide cathode material.

[0051] 5. For small particles, a secondary process of doping and coating is used to stabilize the structure of the cathode material and further improve its rate performance and storage performance;

[0052] 6. In the case of two-phase composite, the small-particle ternary material of this invention has two advantages. First, the relatively large-particle ternary material can coat the surface of the lithium cobalt oxide material particles, producing a surface coating effect. The Ni and Mn elements of the ternary particles will enter the LiCoO2 surface during the four sintering processes, which can also play a role in surface doping. Second, the relatively small-particle ternary material can fill the gaps in the lithium cobalt oxide. By designing the gradation ratio, the compaction density can be further improved, thereby increasing the energy density. By controlling the D of the small particles... v 10 and D n10 ensures a relatively reasonable quantity distribution of ternary material particles with relatively large and relatively small particle sizes, so that the quantity of each type of particle is sufficient to exert their respective effects in the gradation.

[0053] 7. Since the high price of Co determines the high cost of lithium cobalt oxide, this invention uses ternary small particles instead of lithium cobalt oxide small particles, which can better reduce costs;

[0054] 8. Based on the similarity between lithium cobalt oxide and ternary material systems, a pre-sintering and four-sintering process is adopted to improve the compatibility and synergistic effect of the two materials, allowing them to leverage their respective advantages; the lithium-ion battery system of this invention is mainly improved in terms of storage and cycle life. Attached Figure Description

[0055] Figure 1 This is a SEM image of the modified LiCoO2 primary product obtained in Example 3 (Note: magnified 3000 times);

[0056] Figure 2 This is an SEM image of the modified ternary material primary product obtained in Example 3 (Note: magnified 5000 times);

[0057] Figure 3 This is a SEM image of the lithium cobalt oxide cathode material prepared in Example 3 (Note: magnified 3000 times). Detailed Implementation

[0058] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0059] Unless otherwise specified, the raw materials, reagents, and apparatus used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0060] The lithium source used below is commercially available battery-grade lithium carbonate. The large-particle-size cobalt tetroxide, large-particle-size Al-doped cobalt tetroxide (aluminum doping content 4000-10000ppm), and small-particle-size nickel-cobalt-manganese precursor and cobalt tetroxide used are all commercially available products. It should be noted that "large-particle-size" and "small-particle-size" here refer to the relative particle size of the cobalt tetroxide and nickel-cobalt-manganese precursor; there are no specific restrictions on the particle size. That is, the particle size of both large-particle-size cobalt tetroxide and large-particle-size Al-doped cobalt tetroxide is larger than that of the small-particle-size nickel-cobalt-manganese precursor, and the particle size of the small-particle-size cobalt tetroxide and the small-particle-size nickel-cobalt-manganese precursor have the same range. It is understood that the above raw materials can be screened using conventional methods such as crushing and sieving to facilitate subsequent control of the particle size of the obtained lithium cobalt oxide and lithium nickel-cobalt-manganese oxide. There are no restrictions on the particle size screening method for the above raw materials.

[0061] Example 1

[0062] A lithium cobalt oxide cathode material with the chemical formula 0.76(LiCo) 0.9662 Mg 0.0096 La 0.0023 Y 0.0012 Mo 0.0036 Sn 0.0061 Ir 0.0014 Zr 0.0096 O2)@N1)@N 3-A ·0.24((Li 0.9975 Co 0.185 Al 0.015 Sr 0.0025 Ni 0.64 Mn 0.16 O2)@N2)@N 3-B The specific preparation method includes the following steps:

[0063] S1: Lithium carbonate, large-particle cobalt tetroxide, and a compound containing element M are added to magnesium fluoride, lanthanum oxide, yttrium oxide, molybdenum dioxide, tin oxide, iridium trichloride, and zirconium oxide in a molar ratio of Li:Co:Mg:La:Y:Mo:Sn:Ir:Zr = 1:0.9662:0.0096:0.0023:0.0012:0.0036:0.0061:0.0014:0.0096. The mixture is then added to a high-speed mixer at 1200 r / min to obtain a final mixture. This mixture is then placed in a high-temperature box furnace under air atmosphere and held at 1020℃. The modified LiCoO2 primary product was obtained by sintering for 10 hours at a heating rate of 10.0℃ / min. The modified LiCoO2 primary product was then mixed with coating agent N1 (lithium fluoride, titanium dioxide, and zirconium oxide were added at 1000ppm, 2800ppm, and 800ppm, respectively) using a three-dimensional mixer at a speed of 30r / min, a ball-to-material mass ratio of 1.2:1, and a mixing time of 2 hours. The resulting mixture was then placed in a high-temperature box furnace for secondary sintering and held at 800℃ for 10 hours. After natural cooling and crushing, the mixture was pulverized and sieved to obtain modified LiCoO2 secondary product A.

[0064] S2: Lithium carbonate, small-particle-size nickel-cobalt-manganese precursor, and compounds containing Sr and R elements are added to strontium carbonate and aluminum oxide in a molar ratio of Li:Co:Ni:Mn:Al:Sr = 0.9975:0.185:0.64:0.16:0.015:0.0025 and mixed evenly. The mixture is then added to a high-speed mixer to obtain a mixture. Under an air atmosphere, the mixture is placed in a high-temperature box furnace for primary sintering at 700℃. After crushing, a modified ternary material primary product is obtained. The modified ternary material primary product is mixed with coating agent N2 (strontium carbonate and cobalt hydroxide are added at 1500ppm and 3000ppm respectively) and sintered at 650℃ for a secondary high temperature of 10h at a heating rate of 10.0℃ / min to obtain modified ternary material secondary product B.

[0065] S3: Combine the above modified LiCoO2 secondary product A with coating agent N 3-A (Titanium dioxide and aluminum hydroxide were added at 1800 ppm and 3200 ppm respectively) and mixed, then placed in a rotary kiln for three sintering stages (pre-sintering). The sintering temperature was 200℃, the rotation speed was controlled at 20 r / min, and the time was set to 0.5 h. The above modified ternary material secondary product B was then mixed with coating agent N. 3-B(Zirconium dioxide, titanium dioxide, and aluminum hydroxide were added at 1500 ppm, 900 ppm, and 1600 ppm, respectively) and mixed. The mixture was then placed in a rotary kiln for pre-sintering at 200℃, with the rotation speed controlled at 20 r / min and the time set at 0.5 h. The pre-sintered modified LiCoO2 secondary product A and the pre-sintered modified ternary material secondary product B were mixed at a volume ratio of 0.76:0.24 and placed in a ball mill mixer with a ball-to-material ratio of 0.8:1. The mixture was mixed at 10 r / min for 20 min and then sintered in a high-temperature box furnace at 600℃ for 5 h with a heating rate of 2.0℃ / min. This process was repeated four times. After sintering, the mixture was passed through a 300-mesh ultrasonic vibrating sieve to obtain the lithium cobalt oxide cathode material.

[0066] Example 2:

[0067] A lithium cobalt oxide cathode material with the chemical formula 0.76(LiCo) 0.9506 Al 0.0156 Mg 0.0096 La 0.002 3Y 0.0012 Mo 0.0036 Sn 0.0061 Ir 0.0014 Zr 0.0096 O2)@N1)@N 3-A ·0.24((Li 0.9975 Co 0.185 Al 0.015 Sr 0.0025 Ni 0.64 Mn 0.16 O2)@N2)@N 3-B The specific preparation method includes the following steps:

[0068] S1: Lithium carbonate, large-particle Al-doped cobalt tetroxide, and a compound containing element M are added to nano-sized aluminum oxide, magnesium fluoride, lanthanum oxide, yttrium oxide, molybdenum dioxide, tin oxide, iridium trichloride, and zirconium oxide in a high-speed mixer at a speed of 1200 r / min under an air atmosphere. The modified LiCoO2 primary product was obtained by sintering at 1020℃ for 10 hours in a box furnace with a heating rate of 10.0℃ / min. The modified LiCoO2 primary product was then mixed with coating agent N1 (lithium fluoride, titanium dioxide, and zirconium oxide were added at 1000ppm, 2800ppm, and 800ppm, respectively) using a three-dimensional mixer at a speed of 30r / min, a ball-to-material mass ratio of 1.2:1, and a mixing time of 2 hours. The resulting mixture was then placed in a high-temperature box furnace for secondary sintering and held at 800℃ for 10 hours. After natural cooling and crushing, the mixture was pulverized and sieved to obtain modified LiCoO2 secondary product A.

[0069] S2: Lithium carbonate, small-particle-size nickel-cobalt-manganese precursor, and compounds containing Sr and R elements are added to strontium carbonate and aluminum oxide in a molar ratio of Li:Co:Ni:Mn:Al:Sr = 0.9975:0.185:0.64:0.16:0.015:0.0025 and mixed evenly. The mixture is then added to a high-speed mixer to obtain a mixture. Under an air atmosphere, the mixture is placed in a high-temperature box furnace for primary sintering at 700℃. After crushing, a modified ternary material primary product is obtained. The modified ternary material primary product is mixed with coating agent N2 (strontium carbonate and cobalt hydroxide are added at 1500ppm and 3000ppm respectively) and sintered at 650℃ for a secondary high temperature of 10h at a heating rate of 10.0℃ / min to obtain modified ternary material secondary product B.

[0070] S3: Combine the above modified LiCoO2 secondary product A with coating agent N 3-A (Titanium dioxide and aluminum hydroxide were added at 1800 ppm and 3200 ppm respectively) and mixed, then placed in a rotary kiln for three sintering stages (pre-sintering). The sintering temperature was 200℃, the rotation speed was controlled at 20 r / min, and the time was set to 0.5 h. The above modified ternary material secondary product B was then mixed with coating agent N. 3-B(Zirconium dioxide, titanium dioxide, and aluminum hydroxide were added at 1500 ppm, 900 ppm, and 1600 ppm, respectively) and mixed. The mixture was then placed in a rotary kiln for pre-sintering at 200℃, with the rotation speed controlled at 20 r / min and the time set at 0.5 h. The pre-sintered modified LiCoO2 secondary product A and the pre-sintered modified ternary material secondary product B were mixed at a volume ratio of 0.76:0.24 and placed in a ball mill mixer with a ball-to-material ratio of 0.8:1. The mixture was mixed at 10 r / min for 20 min and then sintered in a high-temperature box furnace at 600℃ for 5 h with a heating rate of 2.0℃ / min. This process was repeated four times. After sintering, the mixture was passed through a 300-mesh ultrasonic vibrating sieve to obtain the lithium cobalt oxide cathode material.

[0071] Example 3

[0072] A lithium cobalt oxide cathode material with the chemical formula 0.76(LiCo) 0.9380 Al 0.0156 Mn 0.0044 Ni 0.0098 Mg 0.0080 La 0.0023 Y 0.0012 Mo 0.0036 Sn 0.0061 Ir 0.0014 Zr 0.0096 O2)@N1)@N 3-A ·0.24((Li 0.9975 Co 0.185 Al 0.015 Sr 0.0025 Ni 0.64 Mn 0.16 O2)@N2)@N 3-B The specific preparation method includes the following steps:

[0073] S1: Lithium carbonate, large-particle Al-doped cobalt tetroxide, and a compound containing element M are mixed in a molar ratio of Li:Co:Al:Mn:Ni:Mg:La:Y:Mo:Sn:Ir:Zr = 1:0.9380:0.0156:0.0044:0.0098:0.0080:0.0023:0.0012:0.0036:0.0061:0.0014:0.0096. Aluminum oxide, manganese dioxide, nickel oxide, magnesium fluoride, lanthanum oxide, yttrium oxide, molybdenum dioxide, tin oxide, iridium trichloride, and zirconium oxide are added to this mixture in a high-speed mixer at 1200 r / min. The resulting mixture is then subjected to air... Under a specific atmosphere, the material was placed in a high-temperature box furnace for primary sintering at 1020℃ for 10 hours, with a heating rate of 10.0℃ / min, to obtain modified LiCoO2 primary product. The modified LiCoO2 primary product was then mixed with coating agent N1 (lithium fluoride, titanium dioxide, and zirconium oxide were added at 1000ppm, 2800ppm, and 800ppm, respectively) using a three-dimensional mixer at a speed of 30r / min, a ball-to-material mass ratio of 1.2:1, and a mixing time of 2 hours to obtain a mixture. This mixture was then placed in a high-temperature box furnace for secondary sintering and held at 800℃ for 10 hours. After natural cooling and crushing, it was pulverized and sieved to obtain modified LiCoO2 secondary product A.

[0074] S2: Lithium carbonate, small-particle-size nickel-cobalt-manganese precursor, and compounds containing Sr and R elements are added to strontium carbonate and aluminum oxide in a molar ratio of Li:Co:Ni:Mn:Al:Sr = 0.9975:0.185:0.64:0.16:0.015:0.0025 and mixed evenly. The mixture is then added to a high-speed mixer to obtain a mixture. Under an air atmosphere, the mixture is placed in a high-temperature box furnace for primary sintering at 700℃. After crushing, a modified ternary material primary product is obtained. The modified ternary material primary product is mixed with coating agent N2 (strontium carbonate and cobalt hydroxide are added at 1500ppm and 3000ppm respectively) and sintered at 650℃ for a secondary high temperature of 10h at a heating rate of 10.0℃ / min to obtain modified ternary material secondary product B.

[0075] S3: Combine the above modified LiCoO2 secondary product A with coating agent N 3-A (Titanium dioxide and aluminum hydroxide were added at 1800 ppm and 3200 ppm respectively) and mixed, then placed in a rotary kiln for three sintering stages (pre-sintering). The sintering temperature was 200℃, the rotation speed was controlled at 20 r / min, and the time was set to 0.5 h. The above modified ternary material secondary product B was then mixed with coating agent N. 3-B(Zirconium dioxide, titanium dioxide, and aluminum hydroxide were added at 1500 ppm, 900 ppm, and 1600 ppm, respectively) and mixed. The mixture was then placed in a rotary kiln for pre-sintering at 200℃, with the rotation speed controlled at 20 r / min and the time set at 0.5 h. The pre-sintered modified LiCoO2 secondary product A and the pre-sintered modified ternary material secondary product B were mixed at a volume ratio of 0.76:0.24 and placed in a ball mill mixer with a ball-to-material ratio of 0.8:1. The mixture was mixed at 10 r / min for 20 min and then sintered in a high-temperature box furnace at 600℃ for 5 h with a heating rate of 2.0℃ / min. This process was repeated four times. After sintering, the mixture was passed through a 300-mesh ultrasonic vibrating sieve to obtain the lithium cobalt oxide cathode material.

[0076] Example 4

[0077] A lithium cobalt oxide cathode material with the chemical formula 0.76(LiCo) 0.9380 Al 0.0156 Mn 0.0044 Ni 0.0098 Mg 0.0080 La 0.0023 Y 0.0012 Mo 0.0036 Sn 0.0061 Ir 0.0014 Zr 0.0096 O2)@N1)@N 3-A ·0.24((Li 0.9975 Co 0.185 La 0.015 Sr 0.0025 Ni 0.64 Mn 0.16 O2)@N2)@N 3-B The specific preparation method includes the following steps:

[0078] S1: Lithium carbonate, large-particle Al-doped cobalt tetroxide, and a compound containing element M are mixed in a molar ratio of Li:Co:Al:Mn:Ni:Mg:La:Y:Mo:Sn:Ir:Zr = 1:0.9380:0.0156:0.0044:0.0098:0.0080:0.0023:0.0012:0.0036:0.0061:0.0014:0.0096. Aluminum oxide, manganese dioxide, nickel oxide, magnesium fluoride, lanthanum oxide, yttrium oxide, molybdenum dioxide, tin oxide, iridium trichloride, and zirconium oxide are added to this mixture in a high-speed mixer at 1200 r / min. The resulting mixture is then subjected to air... Under a specific atmosphere, the material was placed in a high-temperature box furnace for primary sintering at 1020℃ for 10 hours, with a heating rate of 10.0℃ / min, to obtain modified LiCoO2 primary product. The modified LiCoO2 primary product was then mixed with coating agent N1 (lithium fluoride, titanium dioxide, and zirconium oxide were added at 1000ppm, 2800ppm, and 800ppm, respectively) using a three-dimensional mixer at a speed of 30r / min, a ball-to-material mass ratio of 1.2:1, and a mixing time of 2 hours to obtain a mixture. This mixture was then placed in a high-temperature box furnace for secondary sintering and held at 800℃ for 10 hours. After natural cooling and crushing, it was pulverized and sieved to obtain modified LiCoO2 secondary product A.

[0079] S2: Lithium carbonate, small-particle-size nickel-cobalt-manganese precursor, and compounds containing Sr and R elements are added to strontium carbonate and lanthanum oxide in a molar ratio of Li:Co:Ni:Mn:Sr:La = 0.9975:0.185:0.64:0.16:0.0025:0.015 and mixed evenly. The mixture is then added to a high-speed mixer to obtain a mixture. Under an air atmosphere, the mixture is placed in a high-temperature box furnace for primary sintering at 700℃. After crushing, a modified ternary material primary product is obtained. The modified ternary material primary product is mixed with coating agent N2 (strontium carbonate and cobalt hydroxide are added at 1500ppm and 3000ppm respectively) and sintered at 650℃ for a secondary high temperature of 10h at a heating rate of 10.0℃ / min to obtain modified ternary material secondary product B.

[0080] S3: Combine the above modified LiCoO2 secondary product A with coating agent N 3-A (Titanium dioxide and aluminum hydroxide were added at 1800 ppm and 3200 ppm respectively) and mixed, then placed in a rotary kiln for three sintering stages (pre-sintering). The sintering temperature was 200℃, the rotation speed was controlled at 20 r / min, and the time was set to 0.5 h. The above modified ternary material secondary product B was then mixed with coating agent N. 3-B(Zirconium dioxide, titanium dioxide, and aluminum hydroxide were added at 1500 ppm, 900 ppm, and 1600 ppm, respectively) and mixed. The mixture was then placed in a rotary kiln for pre-sintering at 200℃, with the rotation speed controlled at 20 r / min and the time set at 0.5 h. The pre-sintered modified LiCoO2 secondary product A and the pre-sintered modified ternary material secondary product B were mixed at a volume ratio of 0.76:0.24 and placed in a ball mill mixer with a ball-to-material ratio of 0.8:1. The mixture was mixed at 10 r / min for 20 min and then sintered in a high-temperature box furnace at 600℃ for 5 h with a heating rate of 2.0℃ / min. This process was repeated four times. After sintering, the mixture was passed through a 300-mesh ultrasonic vibrating sieve to obtain the lithium cobalt oxide cathode material.

[0081] Example 5

[0082] A lithium cobalt oxide cathode material with the chemical formula 0.76(LiCo) 0.9380 Al 0.0156 Mn 0.0044 Ni 0.0098 Mg 0.0080 La 0.0023 Y 0.0012 Mo 0.0036 Sn 0.0061 Ir 0.0014 Zr 0.0096 O2)@N1)@N 3-A ·0.24((LiCo 0.185 La 0.015 Ni 0.64 Mn 0.16 O2)@N2)@N 3-B The specific preparation method includes the following steps:

[0083] S1: Lithium carbonate, large-particle Al-doped cobalt tetroxide, and a compound containing element M are mixed in a molar ratio of Li:Co:Al:Mn:Ni:Mg:La:Y:Mo:Sn:Ir:Zr = 1:0.9380:0.0156:0.0044:0.0098:0.0080:0.0023:0.0012:0.0036:0.0061:0.0014:0.0096. Aluminum oxide, manganese dioxide, nickel oxide, magnesium fluoride, lanthanum oxide, yttrium oxide, molybdenum dioxide, tin oxide, iridium trichloride, and zirconium oxide are added to this mixture in a high-speed mixer at 1200 r / min. The resulting mixture is then subjected to air... Under a specific atmosphere, the material was placed in a high-temperature box furnace for primary sintering at 1020℃ for 10 hours, with a heating rate of 10.0℃ / min, to obtain modified LiCoO2 primary product. The modified LiCoO2 primary product was then mixed with coating agent N1 (lithium fluoride, titanium dioxide, and zirconium oxide were added at 1000ppm, 2800ppm, and 800ppm, respectively) using a three-dimensional mixer at a speed of 30r / min, a ball-to-material mass ratio of 1.2:1, and a mixing time of 2 hours to obtain a mixture. This mixture was then placed in a high-temperature box furnace for secondary sintering and held at 800℃ for 10 hours. After natural cooling and crushing, it was pulverized and sieved to obtain modified LiCoO2 secondary product A.

[0084] S2: Lithium carbonate, small-particle-size nickel-cobalt-manganese precursor, and R-containing compound are added to lanthanum oxide in a molar ratio of Li:Co:Ni:Mn:La = 1:0.185:0.64:0.16:0.015 and mixed evenly. The mixture is then added to a high-speed mixer to obtain a mixture. Under air atmosphere, the material is placed in a high-temperature box furnace for primary sintering at 700℃. After crushing, a primary modified ternary material is obtained. The primary modified ternary material is mixed with coating agent N2 (lanthanum carbonate and cobalt hydroxide are added at 1500ppm and 3000ppm respectively) and sintered at 650℃ for 10h at a heating rate of 10.0℃ / min to obtain secondary modified ternary material B.

[0085] S3: Combine the above modified LiCoO2 secondary product A with coating agent N 3-A (Titanium dioxide and aluminum hydroxide were added at 1800 ppm and 3200 ppm respectively) and mixed, then placed in a rotary kiln for three sintering stages (pre-sintering). The sintering temperature was 200℃, the rotation speed was controlled at 20 r / min, and the time was set to 0.5 h. The above modified ternary material secondary product B was then mixed with coating agent N. 3-B(Zirconium dioxide, titanium dioxide, and aluminum hydroxide were added at 1500 ppm, 900 ppm, and 1600 ppm, respectively) and mixed. The mixture was then placed in a rotary kiln for pre-sintering at 200℃, with the rotation speed controlled at 20 r / min and the time set at 0.5 h. The pre-sintered modified LiCoO2 secondary product A and the pre-sintered modified ternary material secondary product B were mixed at a volume ratio of 0.76:0.24 and placed in a ball mill mixer with a ball-to-material ratio of 0.8:1. The mixture was mixed at 10 r / min for 20 min and then sintered in a high-temperature box furnace at 600℃ for 5 h with a heating rate of 2.0℃ / min. This process was repeated four times. After sintering, the mixture was passed through a 300-mesh ultrasonic vibrating sieve to obtain the lithium cobalt oxide cathode material.

[0086] Example 6

[0087] A lithium cobalt oxide cathode material with the chemical formula 0.7(LiCo) 0.9380 Al 0.0156 Mn 0.0044 Ni 0.0098 Mg 0.0080 La 0.0023 Y 0.0012 Mo 0.0036 Sn 0.0061 Ir 0.0014 Zr 0.0096 O2)@N1)@N 3-A ·0.3((Li 0.9975 Co 0.185 Al 0.015 Sr 0.0025 Ni 0.64 Mn 0.16 O2)@N2)@N 3-B The components, dosages, and process parameters applicable to each step in its preparation method are the same as in Example 3. The difference is that in S3, the volume ratio of the pre-sintered modified LiCoO2 secondary product A to the pre-sintered modified ternary material secondary product B is 0.7:0.3.

[0088] Example 7

[0089] A lithium cobalt oxide cathode material with the chemical formula 0.85(LiCo) 0.9380 Al 0.0156 Mn 0.0044 Ni 0.0098 Mg 0.0080 La 0.0023 Y 0.0012 Mo 0.0036 Sn 0.0061 Ir 0.0014 Zr 0.0096 O2)@N1)@N 3-A ·0.15((Li0.9975 Co 0.185 Al 0.015 Sr 0.0025 Ni 0.64 Mn 0.16 O2)@N2)@N 3-B The components, dosages, and process parameters applicable to each step in its preparation method are the same as in Example 3. The difference is that in S3, the volume ratio of the pre-sintered modified LiCoO2 secondary product A to the pre-sintered modified ternary material secondary product B is 0.85:0.15.

[0090] Comparative Example 1

[0091] A lithium cobalt oxide cathode material with the chemical formula 0.76(LiCo) 0.9662 Mg 0.0096 La 0.0023 Y 0.0012 Mo 0.0036 Sn 0.0061 Ir 0.0014 Zr 0.0096 O2)@N1)@N 3-A ·0.24((Li 0.9975 Co 0.985 Al 0.015 Sr 0.0025 O2)@N2)@N 3-B The components, dosages, and process parameters applicable to step S1 in the preparation method are the same as in Example 1. The difference lies in the fact that in Comparative Example 1, small-particle-size cobalt tetroxide is used instead of small-particle-size nickel-cobalt-manganese precursor in step S2. Steps S2 and S3 are as follows:

[0092] S2: Lithium carbonate, small-particle cobalt tetroxide, and compounds containing Sr and R elements are added to strontium carbonate and aluminum oxide in a molar ratio of Li:Co:Al:Sr = 0.9975:0.985:0.015:0.0025 and mixed evenly. The mixture is then added to a high-speed mixer to obtain a mixture. Under an air atmosphere, the material is placed in a high-temperature box furnace for primary sintering at 700°C. After crushing, modified LiCoO2 primary product is obtained. Modified LiCoO2 primary product is mixed with coating agent N2 (strontium carbonate and cobalt hydroxide are added at 1500 ppm and 3000 ppm respectively) and sintered at 650°C for secondary sintering for 10 h at a heating rate of 10.0°C / min to obtain modified LiCoO2 secondary product B.

[0093] S3: Combine the modified LiCoO2 secondary product A obtained in step S1 with the coating agent N. 3-A(Titanium dioxide and aluminum hydroxide were added at 1800 ppm and 3200 ppm respectively) and mixed, then placed in a rotary kiln for three sinterings (pre-sintering). The sintering temperature was 200℃, the rotation speed was controlled at 20 r / min, and the time was set to 0.5 h. The modified LiCoO2 secondary product B obtained in step S2 was mixed with coating agent N. 3-B (Zirconium dioxide, titanium dioxide, and aluminum hydroxide were added at 1500 ppm, 900 ppm, and 1600 ppm, respectively) and mixed. The mixture was then placed in a rotary kiln for pre-sintering at 200℃, with the rotation speed controlled at 20 r / min and the time set at 0.5 h. The pre-sintered modified LiCoO2 secondary product A and pre-sintered modified LiCoO2 secondary product B were mixed at a volume ratio of 0.76:0.24 and placed in a ball mill mixer with a ball-to-material ratio of 0.8:1. The mixture was mixed at 10 r / min for 20 min and then sintered in a high-temperature box furnace at 600℃ for 5 h with a heating rate of 2.0℃ / min. This process was repeated four times. After sintering, the mixture was passed through a 300-mesh ultrasonic vibrating sieve to obtain the lithium cobalt oxide cathode material.

[0094] Comparative Example 2

[0095] A lithium cobalt oxide cathode material with the chemical formula 0.76(LiCo) 0.9506 Al 0.0156 Mg 0.0096 La 0.002 3Y 0.0012 Mo 0.0036 Sn 0.0061 Ir 0.0014 Zr 0.0096 O2)@N1)@N 3-A ·0.24((Li 0.9975 Co 0.985 Al 0.015 Sr 0.0025 O2)@N2)@N 3-B The components, dosages, and process parameters applicable to step S1 in Comparative Example 2 are the same as those in Example 2. The difference lies in the fact that in Step S2 of Comparative Example 2, small-particle-size cobalt tetroxide is used instead of the small-particle-size nickel-cobalt-manganese precursor. Steps S2 and S3 are as follows:

[0096] S2: Lithium carbonate, small-particle cobalt tetroxide, and compounds containing Sr and R elements are added to strontium carbonate and aluminum oxide in a molar ratio of Li:Co:Al:Sr = 0.9975:0.985:0.015:0.0025 and mixed evenly. The mixture is then added to a high-speed mixer to obtain a mixture. Under an air atmosphere, the material is placed in a high-temperature box furnace for primary sintering at 700°C. After crushing, modified LiCoO2 primary product is obtained. Modified LiCoO2 primary product is mixed with coating agent N2 (strontium carbonate and cobalt hydroxide are added at 1500 ppm and 3000 ppm respectively) and sintered at 650°C for secondary sintering for 10 h at a heating rate of 10.0°C / min to obtain modified LiCoO2 secondary product B.

[0097] S3: Combine the modified LiCoO2 secondary product A obtained in step S1 with the coating agent N. 3-A (Titanium dioxide and aluminum hydroxide were added at 1800 ppm and 3200 ppm respectively) and mixed, then placed in a rotary kiln for three sinterings (pre-sintering). The sintering temperature was 200℃, the rotation speed was controlled at 20 r / min, and the time was set to 0.5 h. The modified LiCoO2 secondary product B obtained in step S2 was mixed with coating agent N. 3-B (Zirconium dioxide, titanium dioxide, and aluminum hydroxide were added at 1500 ppm, 900 ppm, and 1600 ppm, respectively) and mixed. The mixture was then placed in a rotary kiln for pre-sintering at 200℃, with the rotation speed controlled at 20 r / min and the time set at 0.5 h. The pre-sintered modified LiCoO2 secondary product A and pre-sintered modified LiCoO2 secondary product B were mixed at a volume ratio of 0.76:0.24 and placed in a ball mill mixer with a ball-to-material ratio of 0.8:1. The mixture was mixed at 10 r / min for 20 min and then sintered in a high-temperature box furnace at 600℃ for 5 h with a heating rate of 2.0℃ / min. This process was repeated four times. After sintering, the mixture was passed through a 300-mesh ultrasonic vibrating sieve to obtain the lithium cobalt oxide cathode material.

[0098] Comparative Example 3

[0099] A lithium cobalt oxide cathode material with the chemical formula 0.76(LiCo) 0.9380 Al 0.0156 Mn 0.0044 Ni 0.0098 Mg 0.0080 La 0.0023 Y 0.0012 Mo 0.0036 Sn 0.0061 Ir 0.0014 Zr 0.0096 O2)@N1·0.24(Li 0.9975 Co 0.185 Al 0.015 Sr0.0025 Ni 0.64 Mn 0.16 The preparation method of O2@N2 uses the same components, amounts, and process parameters as in Example 3 for steps S1 and S2. The difference is that in Comparative Example 3, no coating agent is added in step S3; the mixture is directly mixed. Step S3 is as follows:

[0100] S3: The modified LiCoO2 secondary product A obtained in step S1 and the modified ternary material secondary product B obtained in step S2 are mixed in a ball mill at a volume ratio of 0.76:0.24, with a ball-to-material ratio of 0.8:1. The mixture is mixed at a speed of 10 r / min for 20 min and then passed through a 300-mesh ultrasonic vibrating sieve. After sieving, lithium cobalt oxide cathode material is obtained.

[0101] Comparative Example 4

[0102] A lithium cobalt oxide cathode material with the chemical formula (0.76(LiCo)). 0.9380 Al 0.0156 Mn 0.0044 Ni 0.0098 Mg 0.0080 La 0.0023 Y 0.0012 Mo 0.0036 Sn 0.0061 Ir 0.0014 Zr 0.0096 O2)@N1·0.24(Li 0.9975 Co 0.185 Al 0.015 Sr 0.0025 Ni 0.64 Mn 0.16 The preparation method of O2)@N2)N3 uses the same components, amounts, and process parameters as in Example 3 for steps S1 and S2. The difference lies in that in Comparative Example 4, a coating agent is directly added for mixing and sintering in step S3. Step S3 is as follows:

[0103] S3: The modified LiCoO2 secondary product A obtained in step S1, the modified ternary material secondary product B obtained in step S2, and the coating agent N3 (titanium dioxide, aluminum hydroxide, and zirconium dioxide added at 2700 ppm, 4800 ppm, and 1500 ppm respectively) are mixed in a ball mill mixer. The volume ratio of modified LiCoO2 secondary product A to modified ternary material secondary product B is 0.76:0.24, and the ball-to-material ratio is 0.8:1. The mixture is stirred at a speed of 10 r / min for 20 min and sintered in a high-temperature box furnace at 600℃ for 5 h at a heating rate of 2.0℃ / min. After sintering, the mixture is passed through a 300-mesh ultrasonic vibrating sieve to obtain lithium cobalt oxide cathode material.

[0104] Comparative Example 5

[0105] A lithium cobalt oxide cathode material with the chemical formula 0.76(LiCo) 0.9380 Al 0.0156 Mn 0.0044 Ni 0.0098 Mg 0.0080 La 0.0023 Y 0.0012 Mo 0.0036 Sn 0.0061 Ir 0.0014 Zr 0.0096 O2)@N1)@N 3-A 0.24 (Li 0.9975 Co 0.185 Al 0.015 Sr 0.0025 Ni 0.64 Mn 0.16 The components, dosages, and process parameters applicable to steps S1 and S2 in the preparation method of O2@N2 are the same as in Example 3. The difference is that in Comparative Example 5, in S3, only the modified LiCoO2 secondary product A is coated with N. 3-A The mixture is then pre-sintered, as detailed in step S3:

[0106] S3: Combine the modified LiCoO2 secondary product A obtained in step S1 with the coating agent N. 3-A (Titanium dioxide and aluminum hydroxide were added at 1800 ppm and 3200 ppm respectively) and mixed, and then placed in a rotary kiln for three sinterings (pre-sintering). The sintering temperature was 200℃, the rotation speed was controlled at 20 r / min, and the time was set to 0.5 h. The pre-sintered modified LiCoO2 secondary product A and the modified ternary material secondary product B obtained in step S2 were mixed in a volume ratio of 0.76:0.24 and placed in a ball mill mixer with a ball-to-material ratio of 0.8:1. The mixture was mixed at a rotation speed of 10 r / min for 20 min and then sintered in a high-temperature box furnace at 600℃ for 5 h with a heating rate of 2.0℃ / min. This was a four-sintering process. After sintering, the material was passed through a 300-mesh ultrasonic vibrating sieve to obtain lithium cobalt oxide cathode material.

[0107] Comparative Example 6

[0108] A lithium cobalt oxide cathode material with the chemical formula 0.76(LiCo) 0.9380 Al 0.0156 Mn 0.0044 Ni 0.0098 Mg 0.0080 La 0.0023 Y 0.0012 Mo 0.0036 Sn 0.0061 Ir 0.0014 Zr 0.0096 O2)@N1·0.24((Li0.9975 Co 0.185 Al 0.015 Sr 0.002 5Ni 0.64 Mn 0.16 O2)@N2)@N 3-B The components, dosages, and process parameters applicable to steps S1 and S2 in the preparation method are the same as in Example 3. The difference is that in Comparative Example 6, in S3, only the modified ternary material secondary product B is coated with agent N. 3-B The mixture is then pre-sintered, as detailed in step S3:

[0109] S3: Combine the modified ternary material secondary product B obtained in step S2 with the coating agent N. 3-B (Zirconium dioxide, titanium dioxide, and aluminum hydroxide were added at 1500 ppm, 900 ppm, and 1600 ppm, respectively) and mixed. The mixture was then placed in a rotary kiln for pre-sintering at a temperature of 200℃, a rotation speed of 20 r / min, and a time of 0.5 h. The modified LiCoO2 secondary product A obtained in step S1 was mixed with the pre-sintered modified ternary material secondary product B at a volume ratio of 0.76:0.24 and placed in a ball mill mixer with a ball-to-material ratio of 0.8:1. The mixture was mixed at a speed of 10 r / min for 20 min and then sintered in a high-temperature box furnace at 600℃ for 5 h at a heating rate of 2.0℃ / min. This process was repeated four times. After sintering, the mixture was passed through a 300-mesh ultrasonic vibrating sieve to obtain the lithium cobalt oxide cathode material.

[0110] Comparative Example 7:

[0111] A lithium cobalt oxide cathode material with the chemical formula 0.76(LiCo) 0.9380 Al 0.0156 Mn 0.0044 Ni 0.0098 Mg 0.0080 La 0.0023 Y 0.0012 Mo 0.0036 Sn 0.0061 Ir 0.0014 Zr 0.0096 O2)@N1)@N 3-A ·0.24((Li 0.9975 Co 0.985 Al 0.015 Sr 0.0025 O2)@N2)@N 3-B The components, dosages, and process parameters applicable to step S1 in Comparative Example 7 are the same as those in Example 3. The difference lies in the fact that in Step S2 of Comparative Example 7, small-particle-size cobalt tetroxide is used instead of the small-particle-size nickel-cobalt-manganese precursor. Steps S2 and S3 are as follows:

[0112] S2: Lithium carbonate, small-particle cobalt tetroxide, and compounds containing Sr and R elements are added to strontium carbonate and aluminum oxide in a molar ratio of Li:Co:Al:Sr = 0.9975:0.985:0.015:0.0025 and mixed evenly. The mixture is then added to a high-speed mixer to obtain a mixture. Under an air atmosphere, the material is placed in a high-temperature box furnace for primary sintering at 700°C. After crushing, modified LiCoO2 primary product is obtained. Modified LiCoO2 primary product is mixed with coating agent N2 (strontium carbonate and cobalt hydroxide are added at 1500 ppm and 3000 ppm respectively) and sintered at 650°C for secondary sintering for 10 h at a heating rate of 10.0°C / min to obtain modified LiCoO2 secondary product B.

[0113] S3: Combine the modified LiCoO2 secondary product A obtained in step S1 with the coating agent N. 3-A (Titanium dioxide and aluminum hydroxide were added at 1800 ppm and 3200 ppm respectively) and mixed, then placed in a rotary kiln for three sinterings (pre-sintering). The sintering temperature was 200℃, the rotation speed was controlled at 20 r / min, and the time was set to 0.5 h. The modified LiCoO2 secondary product B obtained in step S2 was mixed with coating agent N. 3-B (Zirconium dioxide, titanium dioxide, and aluminum hydroxide were added at 1500 ppm, 900 ppm, and 1600 ppm, respectively) and mixed. The mixture was then placed in a rotary kiln for pre-sintering at 200℃, with the rotation speed controlled at 20 r / min and the time set at 0.5 h. The pre-sintered modified LiCoO2 secondary product A and pre-sintered modified LiCoO2 secondary product B were mixed at a volume ratio of 0.76:0.24 and placed in a ball mill mixer with a ball-to-material ratio of 0.8:1. The mixture was mixed at 10 r / min for 20 min and then sintered in a high-temperature box furnace at 600℃ for 5 h with a heating rate of 2.0℃ / min. This process was repeated four times. After sintering, the mixture was passed through a 300-mesh ultrasonic vibrating sieve to obtain the lithium cobalt oxide cathode material.

[0114] Performance testing

[0115] I. Appearance

[0116] The modified LiCoO2 primary product, the modified ternary material primary product, and the final product, lithium cobalt oxide cathode material, prepared in Example 3 were subjected to scanning electron microscopy (SEM). The SEM images are shown below. Figure 1-3 As shown; combined Figure 1-3 It can be seen that the coating process of the present invention does not have a significant impact on the particle size, and from Figure 3 It can be seen that the small ternary material particles can be adsorbed onto the surface of the large lithium cobalt oxide particles to form a surface dot coating, which can fill the gaps around the large lithium cobalt oxide particles to increase the compaction density and energy density.

[0117] II. Electrochemical Performance

[0118] 1. Prepare lithium-ion batteries using the lithium cobalt oxide cathode materials obtained in the above examples or comparative examples: Mix lithium cobalt oxide cathode material, Super P (conductive agent), and PVDF (binder) in a mass ratio of 90.5:4:4:10, add NMP (N-methylpyrrolidone) as a solvent, stir to form a slurry, coat it onto aluminum foil, and dry it at 70°C to form a cathode sheet; Mix graphite, Super P (conductive agent), PVDF binder, and dispersant PVP in a mass ratio of 96:1:2:1, add water as a solvent, stir to form a slurry, coat it onto aluminum foil, and dry it at 50°C to form a negative electrode sheet; Assemble a soft-pack battery using the cathode sheet, negative electrode, electrolyte, and separator as raw materials.

[0119] 2. Capacity test: 30 soft-pack batteries prepared above were taken as parallel samples. After formation and capacity testing, 8 better samples were selected and charged at a constant current rate of 0.2C at room temperature (25℃) to a voltage of 4.5V (V1). They were then charged further at a constant voltage of V1 until the current was below 0.05C, indicating that the battery was in a fully charged state (V1). Finally, they were discharged at a constant current rate of 0.2C to a voltage of 3.0V (V2) to obtain the discharge capacity. The results are shown in Table 1 below.

[0120] 3. Storage test: The soft-pack batteries obtained above were stored at 45℃ and 3.0~4.5V / 1.0C for 45℃ storage performance test. The higher the data, the better the storage. At the same time, the storage performance was tested at 45℃ for 60 days. The test results are shown in Table 1 below.

[0121] Table 1

[0122]

[0123]

[0124] As shown in Table 1:

[0125] 1. As can be seen from Examples 1 and 2, the Al content has a positive effect on improving cycling and storage, but it is more inclined to improve cycling. The reason for the improved cycling is that after Al replaces the Co site, it plays a role in stabilizing the structure.

[0126] 2. As can be seen from Examples 2 and 3, in Example 3, the Ni and Mn elements in the Ni and Mn doping of large lithium cobalt oxide particles improve cycling and storage performance. Typically, cobalt and oxygen have significantly overlapping band structures. Under high voltage, trivalent cobalt is easily oxidized to tetravalent cobalt, leading to cobalt dissolution and exacerbating interfacial side reactions, resulting in significant deterioration of storage. Ni and Mn elements can improve the band structure, reducing lattice oxygen evolution and improving cycling performance; Ni and Mn doping can stabilize the cobalt structure, thereby improving storage.

[0127] 3. As can be seen from Comparative Examples 1, 2, and 7, after grading large-particle LiCoO2 and small-particle ternary materials in Examples 1-7, the cycling and storage performance is significantly improved compared to the comparative examples. In the comparative examples, replacing the cobalt tetroxide precursor with small-particle LiCoO2 and grading it with large-particle LiCoO2 resulted in a certain decrease in cycling and storage performance.

[0128] 4. As can be seen from Comparative Examples 3 and 4, sintering after coating in Comparative Example 4 is beneficial for improving recycling and storage.

[0129] 5. As can be seen from Comparative Examples 4 and 6, the two processes have similar results. This is because the coating agent preferentially adheres to the small particles during the coating and mixing process. Therefore, the effect of mixing and coating large LiCoO2 particles, ternary small particles and coating agent and then sintering is similar to the effect of coating ternary small particles separately and then mixing and sintering them with large LiCoO2 particles.

[0130] 6. As can be seen from Comparative Examples 5 and 6, preferential coating of small particles is more effective than preferential coating of large particles. The reason is that when large particles are coated first and then mixed with small particles, some of the coating agent will be adsorbed onto the small particles with larger specific surface area as the mixing time increases, resulting in the depowdering of the large particles.

[0131] 7. Comparing Examples 3 and 5, it can be seen that strontium doping replaces lithium sites, reduces the degree of cation mixing, expands lithium-ion channels, and stabilizes the layered structure, resulting in a significant improvement in cycling and storage performance in Example 3.

[0132] 8. As can be seen from all the embodiments and comparative examples in the table, the present invention improves the cycle performance slightly and the storage performance significantly by superimposing a four-sintering process and a two-material mixing and gradation process, and increases the compaction density. This process method is of great significance for applications with special uses in storage.

[0133] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A lithium cobalt oxide cathode material, characterized in that, The general chemical formula of the lithium cobalt oxide cathode material is A((LiCo) 1-a M a O2)@N1)@N 3-A ·B((Li 1-b Mn x Ni y Co z Sr b R c O2)@N2)@N 3-B Where 0.7≤A≤0.85, 0.15≤B≤0.3, A+B=1, and A is ((LiCo) 1-a M a O2)@N1)@N 3-A The volume percentage of B in the lithium cobalt oxide cathode material, wherein B is ((Li 1-b Mn x Ni y Co z Sr b R c O2)@N2)@N 3-B The volume percentage of lithium cobalt oxide cathode material; Where, 0.03≤a≤0.08, 0≤b≤0.005, 0.01≤c≤0.08, 0.05≤x≤0.2, 0.5≤y≤0.75, 0.1≤z≤0.25, x+y+z+c=1; Both M and R are used as doping elements, wherein M is selected from at least one of Al, Mn, Mg, Ni, La, Y, Sr, Mo, Sn, Ir, Ru and Zr; and R is selected from at least one of Al, Mn, Ni, Co, Mo, Ir, Ru and Zr. The N1, N2, N 3-A and N 3-B All are used as coating agents, wherein coating agent N1 is selected from at least one of the oxides, hydroxides, fluorides, and chlorides of Ti, Li, Mn, Mg, Ni, La, Y, and Sr; coating agent N2 is selected from at least one of the oxides, hydroxides, fluorides, and chlorides of Ti, Mn, Ni, Co, Sr, Mo, Se, Ir, Ru, and Zr; coating agent N 3-A Or coating agent N 3-B Selected from at least one of the oxides, hydroxides, fluorides, and chlorides of Al, Ti, Mn, Ni, Co, Sr, Mo, Se, Ir, Ru, and Zr; The (LiCo) 1-a M a O2)@N1 of D v 50 is 10μm~14.5μm, the (LiCo) 1-a M a O2)@N1 of D n 10 represents 1μm to 5μm; The (Li) 1-b Mn x Ni y Co z Sr b R c O2)@N2 of D v 10 is 0.5μm~1μm, the (Li) 1-b Mn x Ni y Co z Sr b R c O2)@N2 of D v 50 is 1μm~3.5μm, the (Li) 1-b Mn x Ni y Co z Sr b R c O2)@N2 of D n 10 represents 0.5μm to 1μm.

2. The method for preparing the lithium cobalt oxide cathode material according to claim 1, characterized in that, Includes the following steps: The modified LiCoO2 primary product is obtained by mixing lithium source, cobalt source and compound containing element M and sintering in one step. The modified LiCoO2 primary product and the coating agent N1 are mixed and sintered twice to obtain the modified LiCoO2 secondary product. The modified LiCoO2 secondary product and the coating agent N 3-A Modified LiCoO2 was obtained by mixing and sintering three times. The modified ternary material primary product is obtained by mixing lithium source, nickel cobalt manganese precursor with R-containing compound, or with Sr and R-containing compound and sintering in one step. The modified ternary material primary product and the coating agent N2 are mixed and sintered twice to obtain the modified ternary material secondary product. The modified ternary material secondary product and the coating agent N 3-B The modified ternary material was prepared by mixing and sintering three times. The modified LiCoO2 and the modified ternary material were mixed and sintered four times to obtain the lithium cobalt oxide cathode material.

3. The preparation method according to claim 2, characterized in that, The conditions for the first sintering include: a sintering temperature of 700℃~1250℃; and / or a sintering time of 10 hours or more.

4. The preparation method according to claim 2, characterized in that, The conditions for the secondary sintering include: a sintering temperature of 450℃ to 950℃; and / or a sintering time of 10 hours or more.

5. The preparation method according to claim 2, characterized in that, The equipment used for the three sintering processes is a rotary kiln, and the conditions for the three sintering processes include: a sintering temperature of 100℃ to 250℃; and / or a sintering time of 0.5h to 1h; and / or a rotation speed of 10r / min to 20r / min.

6. The preparation method according to claim 2, characterized in that, The conditions for the four sintering processes include: a sintering temperature of 300℃ to 600℃; and / or a sintering time of 3h to 5h.

7. A positive electrode sheet, characterized in that, The positive electrode sheet includes the lithium cobalt oxide positive electrode material according to claim 1, or the lithium cobalt oxide positive electrode material prepared by the preparation method according to any one of claims 2 to 6.

8. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode sheet as described in claim 7.

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