A composite-coated modified nickel-cobalt-manganese ternary cathode material, its preparation method and application

Abstract

This invention discloses a composite-coated modified nickel-cobalt-manganese ternary cathode material, its preparation method, and its application, belonging to the field of battery material technology. The preparation of this composite-coated modified nickel-cobalt-manganese ternary cathode material includes: firstly coating a nickel-cobalt-manganese cathode material to be coated with a primary coating source to obtain a cathode material to be coated a second time; secondly coating the cathode material to be coated a second time with a secondary coating source; the primary coating source is a bimetallic acid salt compound containing at least cobalt; the secondary coating source includes nano-sized alumina and boric acid powder. The method of first coating with a bimetallic acid salt compound, followed by a second coating with alumina and boric acid, can improve problems such as low structural stability, high residual lithium, low capacity after coating, and poor rate and cycle performance.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and more specifically, to a composite-coated modified nickel-cobalt-manganese ternary cathode material, its preparation method, and its application. Background Technology

[0002] Nickel-rich ternary cathodes in liquid lithium-ion batteries (LIBs) are derived from typical layered lithium nickel oxide (LiNiO2), which has a layered crystal structure similar to lithium cobalt oxide (LCO). Doped with other transition metal elements (such as Co, Mn, and Al), they offer higher weight (approximately 350 Wh / kg) and volumetric energy density (approximately 750 Wh / L) while also offering advantages in cost and safety, making them a popular choice for cathode materials in power lithium batteries. However, due to the presence of Ni as an active chemical in nickel-rich cathodes... 4+ The high content of lithium makes it more likely to interact with organic electrolytes at the cathode-electrolyte interface (CEI), leading to more severe parasitic side reactions and a decrease in the capacity of active lithium. At the same time, the instability of the surface structure during charge-discharge cycles will further reduce its cycle stability.

[0003] Related research indicates that with increasing nickel content, ultra-high nickel ternary cathode materials exhibit significantly deteriorating cycle stability and safety compared to high-nickel systems. Production processes require more stringent requirements, necessitating enhanced equipment sealing, temperature and humidity control, and CO2 protection levels. At the material level, higher Li... + / Ni 2+ Mixing tendency, increased lattice distortion, enhanced microcrack propagation and lattice oxygen release, more severe surface side reactions, and accumulated surface residual lithium problems all contribute to the degradation of the safety performance and cycle life of ultra-high nickel ternary materials.

[0004] To address the aforementioned issues, it is of great importance to develop a modified nickel-cobalt-manganese ternary cathode material that can overcome the performance defects of existing nickel-cobalt-manganese ternary cathode materials, such as poor cycle stability and reduced capacity after coating.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a composite-coated modified nickel-cobalt-manganese ternary cathode material, its preparation method and application, so as to solve or improve the above-mentioned technical problems.

[0007] This invention can be implemented as follows: In a first aspect, the present invention provides a method for preparing a composite-coated modified nickel-cobalt-manganese ternary cathode material, comprising the following steps: coating a primary coating source onto a nickel-cobalt-manganese cathode material to be coated a first time to obtain a cathode material to be coated a second time; and coating a secondary coating source onto the cathode material to be coated a second time. The primary coating source is a bimetallic acid salt compound containing at least cobalt; the secondary coating source includes nano-sized alumina and boric acid micro powder.

[0008] In an optional embodiment, the preparation of the nickel-cobalt-manganese cathode material to be coated in one step includes: mixing the precursor, lithium source and M source nanoscale additives and then sintering them. The chemical formula of the precursor is Ni x Co y Mn 1-x-y (OH)2, where 0.90≤x≤0.98, 0<y<0.9, 0<1-xy<0.9; The lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium acetate, and lithium oxalate; The element M contained in the M-source nanoscale additive includes at least two of the following: Co, Mn, Ti, Zr, Sr, Al, Mg, Sb, V, Ta, Ce, Sn, Nb, B, Sc, Y, Mo, Hf, La, and W.

[0009] In an optional embodiment, the preparation of the nickel-cobalt-manganese cathode material to be coated in one step further includes at least one of the following features: Feature 1: The molar ratio of Li in the lithium source to the transition metal element in the precursor is 1.04:1 to 1.07:1; Feature 2: By mass percentage, M in the M-source nanoscale additive accounts for 1000ppm~10000ppm of the precursor; Feature 3: The mixing speed of the precursor, lithium source and M source nanoscale additive is 900 rpm to 1200 rpm, and the mixing time is 40 min to 60 min; Feature 4: Sintering includes: first heat treatment at 450℃~650℃ for 2h~3h, then heating to 650℃~780℃ and holding for 10h~15h; Feature 5: The heating rate during the sintering process is 2℃ / min~10℃ / min; Feature 6: Sintering is carried out in an oxygen atmosphere.

[0010] In an optional implementation, the first coating includes mixing a primary coating source with the nickel-cobalt-manganese cathode material to be coated, followed by sintering.

[0011] In an optional implementation, the first coating includes at least one of the following features: Feature 7: By mass percentage, bimetallic acid salt compounds account for 500 ppm to 10000 ppm of the total amount of nickel-cobalt-manganese cathode material to be coated in one step; Feature 8: Bimetallic acid salts include at least one of cobalt aluminate, cobalt molybdate, cobalt tungstate, cobalt stannate, and cobalt titanate; Feature 9: The mixing speed of the primary coating source and the nickel-cobalt-manganese cathode material to be coated is 800 rpm to 1200 rpm, and the mixing time is 20 min to 40 min; Feature 10: The sintering temperature of the primary coating source and the nickel-cobalt-manganese cathode material to be coated is 400℃~700℃, and the sintering time is 5h~12h; Feature 11: The sintering atmosphere of the primary coating source and the nickel-cobalt-manganese cathode material to be coated includes at least one of oxygen and air; Feature 12: The heating rate during the sintering process of the primary coating source and the nickel-cobalt-manganese cathode material to be coated is 2℃ / min~10℃ / min.

[0012] In an optional implementation, the second coating includes mixing the secondary coating source with the cathode material to be coated, followed by sintering.

[0013] In an optional implementation, the second coating includes at least one of the following features: Feature 13: The mass percentage of nano-sized alumina is 50ppm to 2000ppm of the cathode material to be coated. Feature 14: The mass percentage of boric acid micro powder is 50ppm to 2000ppm of the cathode material to be secondary coated; Feature 15: The mixing speed of the secondary coating source and the cathode material to be secondary coated is 800 rpm to 1000 ppm, and the mixing time is 20 min to 40 min; Feature 16: The sintering temperature of the secondary coating source and the cathode material to be secondary coated is 270℃~350℃, and the sintering time is 5h~12h; Feature 17: The sintering atmosphere of the secondary coating source and the cathode material to be secondary coated includes at least one of oxygen and air; Feature 18: The heating rate during the sintering process of the secondary coating source and the cathode material to be secondary coated is 2℃ / min~10℃ / min.

[0014] Secondly, the present invention provides a composite coated modified nickel-cobalt-manganese ternary cathode material, which is prepared by any of the preparation methods described in the foregoing embodiments.

[0015] In an optional embodiment, the composite-coated modified nickel-cobalt-manganese ternary cathode material includes an inner substrate, an intermediate layer, and an outer layer; wherein the inner substrate is LiNi doped with an M source. x Co y Mn 1-x-y O2, where 0.90≤x≤0.98, 0<y<0.9, 0<1-xy<0.9, the middle layer is a coating layer formed by bimetallic acid salts, and the outer layer is a coating layer formed by nano-sized alumina and boric acid powder.

[0016] Thirdly, the present invention provides a lithium-ion battery comprising the composite-coated modified nickel-cobalt-manganese ternary cathode material of the aforementioned embodiments.

[0017] The beneficial effects of this invention include: This invention involves a primary coating of a bimetallic acid salt compound containing at least cobalt, followed by a secondary coating of nano-sized alumina and boric acid powder. This dual coating effectively reduces interfacial side reactions, improves interfacial kinetics, interfacial stability, and structural stability, resulting in a composite-coated modified nickel-cobalt-manganese ternary cathode material with excellent ion diffusion capabilities. Furthermore, it avoids direct contact between the composite-coated modified nickel-cobalt-manganese ternary cathode material and the electrolyte, further reducing side reactions between the two. In other words, the preparation method provided by this invention effectively improves the problems of low structural stability, high residual lithium, low capacity after coating, and poor rate and cycle performance of nickel-cobalt-manganese ternary cathode materials.

[0018] The resulting composite-coated modified nickel-cobalt-manganese ternary cathode material has high conductivity and Li + It has the advantages of high diffusion rate, high stability, low residual lithium, high discharge capacity after coating, and better rate and cycle performance. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a SEM image of the composite-coated modified nickel-cobalt-manganese ternary cathode material prepared in Example 1 of this invention; Figure 2 The image shows the XRD pattern of the composite-coated modified nickel-cobalt-manganese ternary cathode material prepared in Example 1 of this invention. Figure 3The first charge-discharge performance diagrams of the composite-coated modified nickel-cobalt-manganese ternary cathode material of Example 1 and the final ternary cathode material of Comparative Example 1 after being prepared into button batteries are shown. Figure 4 The graphs show the charge-discharge cycle performance of button batteries prepared from the composite-coated modified nickel-cobalt-manganese ternary cathode material of Example 1 and the final ternary cathode material of Comparative Example 1 at 45°C. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0022] The following is a detailed description of the composite-coated modified nickel-cobalt-manganese ternary cathode material, its preparation method, and its application provided by the present invention.

[0023] This invention provides a method for preparing a composite-coated modified nickel-cobalt-manganese ternary cathode material, comprising the following steps: applying a primary coating source to the nickel-cobalt-manganese cathode material to be coated for the first time to obtain a cathode material to be coated for the second time; applying a secondary coating source to the cathode material to be coated for the second time. The primary coating source is a bimetallic acid salt compound containing at least cobalt; the secondary coating source includes nano-sized alumina and boric acid micropowder (i.e., micron-sized boric acid powder).

[0024] In some alternative embodiments, the preparation of the nickel-cobalt-manganese cathode material to be coated in one step includes: mixing the precursor, lithium source and M-source nanoscale additives and then sintering them.

[0025] The precursor has the chemical formula Ni x Co y Mn 1-x-y (OH)2, 0.90≤x≤0.98, 0<y<0.9, 0<1-xy<0.9.

[0026] The lithium source may, by way of example, include at least one of lithium carbonate, lithium hydroxide, lithium acetate, and lithium oxalate, preferably lithium hydroxide.

[0027] The molar ratio of Li in the lithium source to the transition metal element in the precursor can be from 1.04:1 to 1.07:1, such as 1.04:1, 1.05:1, 1.06:1 or 1.07:1, or other values ​​within the range of 1.04:1 to 1.07:1.

[0028] The element M contained in the M-source nanoscale additive may, exemplarily, include at least two of the following: Co, Mn, Ti, Zr, Sr, Al, Mg, Sb, V, Ta, Ce, Sn, Nb, B, Sc, Y, Mo, Hf, La, and W. In some preferred embodiments, the M-source includes both Zr and Sr.

[0029] It should be emphasized that when the M source includes both Zr and Sr, it can play a role in structure-interface synergistic reinforcement. Specifically, through Zr... 4+ Strengthening the lattice to suppress phase transformation cracks, Sr 2+ Increasing interlayer spacing reduces cation mixing, thereby improving structural stability. Zr induces fast lithium-ion channels, while Sr enhances electronic conductivity, synergistically achieving high-rate performance. Zr-O bonds suppress oxygen loss, and Sr surface modification reduces side reactions, improving cycle retention. The M in the M-source nanoscale additive can be 1000 ppm to 10000 ppm of the precursor, such as 1000 ppm, 2000 ppm, 5000 ppm, 8000 ppm, or 10000 ppm, or other values ​​within the range of 1000 ppm to 10000 ppm. In some preferred embodiments, the M in the M-source nanoscale additive can be 2500 ppm to 6000 ppm of the precursor.

[0030] If the amount of M in the M-source nanoscale additive is less than 2500 ppm of the precursor, it is not conducive to improving the structural stability of the material, and the structural stability of the matrix material cannot be guaranteed; if the amount of M in the M-source nanoscale additive is higher than 6000 ppm of the precursor, although it can improve the structural performance of the material, it will reduce the capacity utilization of the material.

[0031] The mixing speed of the precursor, lithium source, and M-source nanoscale additive can be from 900 rpm to 1200 rpm, such as 900 rpm, 1000 rpm, 1100 rpm, or 1200 rpm, or other values ​​within the range of 900 rpm to 1200 rpm. The mixing time of the precursor, lithium source, and M-source nanoscale additive can be from 40 min to 60 min, such as 40 min, 50 min, or 60 min, or other values ​​within the range of 40 min to 60 min. The mixing temperature can be from 25℃ to 45℃, such as 25℃, 30℃, 35℃, 40℃, or 45℃.

[0032] In some optional embodiments, the sintering of the mixture of precursor, lithium source, and M-source nanoscale additive may include: first, heat treatment at 450℃~650℃ (e.g., 450℃, 500℃, 550℃, 600℃, or 650℃, etc.) for 2h~3h (e.g., 2h, 2.5h, or 3h, etc.), then heating to 650℃~780℃ (e.g., 670℃, 680℃, 700℃, 720℃, 750℃, or 780℃, etc.) and holding at that temperature for 10h~15h (e.g., 10h, 11h, 12h, 13h, 14h, or 15h, etc.). The heating rate during the above sintering process can be 2℃ / min~10℃ / min, such as 2℃ / min, 5℃ / min, 8℃ / min, or 10℃ / min, etc. The above sintering process can be carried out in an oxygen atmosphere.

[0033] Furthermore, the sintered material can be cooled, crushed, and sieved to obtain the nickel-cobalt-manganese cathode material to be coated once.

[0034] Continuing from the above, taking the M source, which simultaneously includes Zr and Sr, as an example, the nickel-cobalt-manganese cathode material to be coated is modified by incorporating nanoscale additives from the M source during the preparation process. Among these, the high-valence Zr... 4+ It can improve the bulk stability of materials, Sr 2+ It can provide interface protection; doping with the aforementioned M source not only lowers the sintering temperature of the material, but also utilizes the steric hindrance effect of the large ionic radius to suppress Ni. 2+ Migration also reduces the anisotropic volume change caused by the H2-H3 phase transition in the material and suppresses the loss of lattice oxygen, ensuring the structural stability of the inner layer matrix of the invented cathode material.

[0035] In some alternative implementations, the first coating may include mixing a primary coating source with the nickel-cobalt-manganese cathode material to be coated, followed by sintering.

[0036] By mass percentage, the bimetallic acid salt compound can account for 500 ppm to 10000 ppm of the total amount of the nickel-cobalt-manganese cathode material to be coated, such as 500 ppm, 1000 ppm, 2000 ppm, 5000 ppm, 8000 ppm, or 10000 ppm, or other values ​​within the range of 500 ppm to 10000 ppm. In some preferred embodiments, the bimetallic acid salt compound can account for 2000 ppm to 6000 ppm of the total amount of the primary coating source and the nickel-cobalt-manganese cathode material to be coated.

[0037] If the amount of bimetallic acid salt compound is less than 500 ppm of the total amount of nickel-cobalt-manganese cathode material to be coated, the coating modification effect will not be achieved; if the amount of bimetallic acid salt compound is more than 6000 ppm of the total amount of nickel-cobalt-manganese cathode material to be coated, the coating layer will be too thick, affecting the diffusion of lithium ions and reducing the capacity utilization and rate performance of the cathode material.

[0038] Bimetallic acid salt compounds may, by way of example, include at least one of cobalt aluminate, cobalt molybdate, cobalt tungstate, cobalt stannate, and cobalt titanate, preferably cobalt molybdate.

[0039] The aforementioned bimetallic acid salt compounds possess certain electrical conductivity, ion transport properties, catalytic activity, thermal conductivity, hydrophobicity, thermal stability, and chemical stability against acid and alkali corrosion.

[0040] The mixing speed of the primary coating source and the nickel-cobalt-manganese cathode material to be coated can be 800 rpm to 1200 rpm, such as 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, or 1200 rpm, or other values ​​within the range of 800 rpm to 1200 rpm. The mixing time of the primary coating source and the nickel-cobalt-manganese cathode material to be coated can be 20 min to 40 min, such as 20 min, 25 min, 30 min, 35 min, or 40 min, or other values ​​within the range of 20 min to 40 min. The mixing temperature can be 20℃ to 45℃, such as 20℃, 30℃, 35℃, 40℃, or 45℃.

[0041] The sintering temperature of the primary coating source and the nickel-cobalt-manganese cathode material to be coated can be 400℃~700℃, such as 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, or 700℃, or other values ​​within the range of 400℃~700℃. The sintering time of the primary coating source and the nickel-cobalt-manganese cathode material to be coated can be 5h~12h, such as 5h, 6h, 7h, 8h, 9h, 10h, 11h, or 12h, or other values ​​within the range of 5h~12h. The sintering atmosphere can include at least one of oxygen and air. The heating rate during the sintering process can be 2℃ / min~10℃ / min, such as 2℃ / min, 5℃ / min, 8℃ / min, or 10℃ / min.

[0042] Furthermore, the sintered material can be cooled, washed and filtered with water, and vacuum dried to obtain the cathode material to be coated a second time.

[0043] Continuing from the above, taking cobalt molybdate as an example of a bimetallic acid salt compound, sintering cobalt molybdate with the nickel-cobalt-manganese cathode material to be coated at a specific temperature consumes residual lithium while forming a mixed fast-ion conductor composite coating layer of lithium cobalt oxide and lithium molybdate. This significantly reduces residual lithium on the material surface, improves the interfacial transport kinetics of Li, and suppresses parasitic side reactions, thus improving the electrochemical performance of the material. After sintering, the cobalt molybdate coating effectively inhibits the dissolution of Ni in the coated cathode material, prevents direct contact between the electrolyte and the material surface, effectively protects the cathode from parasitic reactions between high-nickel content materials and organic electrolytes, improves the cycle stability of the material, and reduces capacity loss. In addition, cobalt molybdate can also capture some of the active oxygen in the material, further reducing subsequent side reactions between the material and the electrolyte. Its hydrophobicity also reduces the conversion of lithium deposition into residual alkali on the material surface. The coating layer formed can also protect the material surface from further damage during water washing to reduce alkali loss, ultimately reducing capacity loss and improving cycle stability. On the other hand, after sintering, Co and Mo can form a "pillar effect" to stabilize the surface structure of the material while reducing the bond energy of the Li-O bond. The formed Li vacancies can also accelerate the Li-O bond formation process. + Transport rate. Furthermore, Co can be injected into the grain boundaries of the material during sintering, further constructing Li... + A fast channel for transmission; in addition, Mo 6+ Strong oxidation ability can reduce Ni on the material surface 2+ Oxidized to Ni 3+ This reduces the formation of surface salt rock phases, further maintaining the integrity and stability of the crystal structure.

[0044] In some alternative implementations, the second coating includes mixing the secondary coating source with the cathode material to be coated, followed by sintering.

[0045] The mass percentage of nano-sized alumina can be 50ppm to 2000ppm of the cathode material to be secondary coated, such as 500ppm, 1000ppm, 1500ppm, or 2000ppm. Similarly, the mass percentage of boric acid micropowder can also be 50ppm to 2000ppm of the cathode material to be secondary coated, such as 500ppm, 1000ppm, 1500ppm, or 2000ppm.

[0046] If the amount of nano-sized alumina is too low, it can easily lead to uneven outer coating, which is not conducive to further improving the material's cycle life, thermal stability, and other properties. If the amount of nano-sized alumina is too high, it will reduce the capacity of the cathode material. If the amount of boric acid powder is too low, it will not be conducive to improving the material's capacity. If the amount of boric acid powder is too high, it will consume more active lithium, leading to a decrease in the capacity of the cathode material.

[0047] In this invention, nano-sized alumina can further improve the material's cycle life and thermal stability, while boric acid micro powder can improve the capacity of the cathode material. By combining the two as a secondary coating source, the material's capacity can be improved while its cycle performance is also increased.

[0048] The mixing speed between the secondary coating source and the cathode material to be secondary coated can be 800 rpm to 1000 ppm, such as 800 rpm, 850 rpm, 900 rpm, 950 rpm, or 1000 rpm, or other values ​​within the range of 800 rpm to 1000 rpm. The mixing time between the secondary coating source and the cathode material to be secondary coated can be 20 min to 40 min, such as 20 min, 25 min, 30 min, 35 min, or 40 min, or other values ​​within the range of 20 min to 40 min. The mixing temperature can be 20℃ to 45℃, such as 20℃, 30℃, 35℃, 40℃, or 45℃.

[0049] The sintering temperature of the secondary coating source and the cathode material to be secondary coated can be 270℃~350℃, such as 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃, or 350℃, or other values ​​within the range of 270℃~350℃. The sintering time of the secondary coating source and the cathode material to be secondary coated can be 5h~12h, such as 5h, 6h, 7h, 8h, 9h, 10h, 11h, or 12h, or other values ​​within the range of 5h~12h. The sintering atmosphere can include at least one of oxygen and air. The heating rate during the sintering process can be 2℃ / min~10℃ / min, such as 2℃ / min, 5℃ / min, 8℃ / min, or 10℃ / min.

[0050] Furthermore, the sintered material can be cooled and sieved to remove iron, thereby obtaining a composite-coated modified nickel-cobalt-manganese ternary cathode material.

[0051] Building upon the above, this invention employs a primary coating of a bimetallic acid salt compound containing at least cobalt, followed by a secondary coating of nano-sized alumina and boric acid powder. This dual coating effectively reduces interfacial side reactions, improves interfacial kinetics, interfacial stability, and structural stability, resulting in a composite-coated modified nickel-cobalt-manganese ternary cathode material with excellent ion diffusion capabilities. Furthermore, it avoids direct contact between the composite-coated modified nickel-cobalt-manganese ternary cathode material and the electrolyte, further reducing side reactions between the composite-coated modified nickel-cobalt-manganese ternary cathode material and the electrolyte. In other words, the preparation method provided by this invention effectively improves the problems of low structural stability, high residual lithium, low capacity after coating, and poor rate and cycle performance of nickel-cobalt-manganese ternary cathode materials. Moreover, the preparation method provided by this invention is simple, highly operable, and the sintering conditions can be adjusted on existing mature production line processes, making it suitable for large-scale production. It provides a feasible strategy for preparing lithium-ion battery cathode materials with high energy density and superior safety performance.

[0052] Accordingly, the present invention also provides a composite-coated modified nickel-cobalt-manganese ternary cathode material, which is prepared by the above-described preparation method.

[0053] In some optional embodiments, the composite-coated modified nickel-cobalt-manganese ternary cathode material includes an inner substrate, an intermediate layer, and an outer layer; wherein the inner substrate is LiNi doped with an M source. x Co y Mn 1-x-y O2, where 0.90≤x≤0.98, 0<y<0.9, 0<1-xy<0.9, the middle layer is a coating layer formed by bimetallic acid salts, and the outer layer is a coating layer formed by nano-sized alumina and boric acid powder.

[0054] In some alternative embodiments, the composite-coated modified nickel-cobalt-manganese ternary cathode material contains 6.6wt% to 7.4wt% (e.g., 6.6wt%, 6.7wt%, 6.8wt%, 6.9wt%, 7.0wt%, 7.1wt%, 7.2wt%, 7.3wt%, or 7.4wt%) of Li element.

[0055] The composite-coated modified nickel-cobalt-manganese ternary cathode material provided by this invention has high conductivity and Li + It has the advantages of high diffusion rate, high stability, low residual lithium, high discharge capacity after coating, and better rate and cycle performance.

[0056] In addition, the present invention also provides a lithium-ion battery comprising the above-mentioned composite-coated modified nickel-cobalt-manganese ternary cathode material.

[0057] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0058] Example 1 This embodiment provides a composite-coated modified nickel-cobalt-manganese ternary cathode material, the preparation method of which includes: S1: Prepare the nickel-cobalt-manganese cathode material to be coated once.

[0059] S11: The precursor, lithium source and M source nanoscale additives are mixed in a high-speed mixer to obtain the first mixture.

[0060] The precursor is Ni 0.935 Co 0.045 Mn 0.02 (OH)2, the lithium source is battery-grade lithium hydroxide, and the M source nanoscale additives are nanoscale zirconium oxide, nanoscale aluminum hydroxide, and nanoscale magnesium hydroxide. The molar ratio of Li in the lithium source to the transition metal element in the precursor is 1.06:1; by mass percentage, nanoscale zirconium oxide accounts for 3000 ppm of the precursor, aluminum hydroxide accounts for 1000 ppm of the precursor, and magnesium hydroxide accounts for 500 ppm of the precursor.

[0061] The mixing speed was 1000 rpm, the mixing time was 45 min, and the mixing temperature was 25℃~45℃.

[0062] S12: Sinter the first mixture.

[0063] The first mixture is placed in a box furnace and heated to 500°C at a rate of 3°C / min under an oxygen atmosphere. After heat treatment for 3 hours, the temperature is further increased to 720°C and sintered for 12 hours. Then, the mixture is cooled, crushed, and sieved to obtain the nickel-cobalt-manganese cathode material to be coated once.

[0064] S2: Perform the first coating on the nickel-cobalt-manganese cathode material to be coated once.

[0065] S21: The primary coating source and the nickel-cobalt-manganese cathode material to be coated are mixed in a high-speed mixer to obtain a second mixture.

[0066] The primary coating source is nano-sized cobalt molybdate; by mass percentage, the cobalt molybdate is 5000 ppm of the total amount of cobalt molybdate and the nickel-cobalt-manganese cathode material to be coated.

[0067] The high-speed mixer operates at 1000 rpm, with a mixing time of 30 minutes and a mixing temperature of 20℃~45℃.

[0068] S22: The second mixture is placed in a box furnace and heated to 650°C at a rate of 3°C / min under an oxygen atmosphere. It is then sintered at this temperature for 8 hours, followed by cooling, washing and filtering with water, and vacuum drying to obtain the cathode material to be coated a second time.

[0069] S3: Perform a second coating on the nickel-cobalt-manganese cathode material to be coated.

[0070] S31: The secondary coating source and the cathode material to be secondary coated are mixed in a high-speed mixer to obtain a third mixture; The secondary coating source is nano-sized alumina and boric acid micro powder; by mass percentage, the nano-sized alumina is 1000 ppm of the cathode material to be secondary coated, and the boric acid micro powder is 1000 ppm of the cathode material to be secondary coated.

[0071] The high-speed mixer operates at 1000 rpm, with a mixing time of 30 minutes and a mixing temperature of 20℃~45℃.

[0072] S32: The third mixture is placed in a box furnace and heated to 320°C at a rate of 3°C / min under an oxygen atmosphere. It is then held at this temperature for 8 hours and sintered. After cooling and sieving to remove iron, the composite-coated modified nickel-cobalt-manganese ternary cathode material is obtained.

[0073] Example 2 The difference between this embodiment and Embodiment 1 is that the primary coating source is replaced by an equal amount of nano-sized cobalt molybdate with nano-sized cobalt tungstate.

[0074] Example 3 The difference between this embodiment and Embodiment 1 is that the primary coating source is replaced by an equal amount of nano-sized cobalt molybdate with nano-sized cobalt titanate.

[0075] Example 4 The difference between this embodiment and Embodiment 1 is that the primary coating source is replaced by an equal amount of nano-sized cobalt molybdate with nano-sized cobalt aluminate.

[0076] Example 5 The difference between this embodiment and Embodiment 1 is that the primary coating source is replaced by an equal amount of nano-sized cobalt molybdate with nano-sized cobalt stannate.

[0077] Example 6 The difference between this embodiment and Embodiment 1 is that the M element in the M-source nanoscale additive is composed of Zr and Sr, and by mass percentage, Zr is 3000 ppm of the precursor and Sr is 1500 ppm of the precursor.

[0078] Example 7 This embodiment provides a composite-coated modified nickel-cobalt-manganese ternary cathode material, the preparation method of which includes: S1: Prepare the nickel-cobalt-manganese cathode material to be coated once.

[0079] S11: The precursor, lithium source and M source nanoscale additives are mixed in a high-speed mixer to obtain the first mixture.

[0080] The precursor is Ni 0.90 Co 0.055 Mn 0.045 (OH)2, the lithium source is battery-grade lithium carbonate, and the M element in the M source nanoscale additive is composed of Mn, Co and Ti. The molar ratio of Li in the lithium source to the transition metal element in the precursor is 1.04:1; by mass percentage, Mn is 500 ppm of the precursor, Co is 250 ppm of the precursor, and Ti is 250 ppm of the precursor.

[0081] The mixing speed was 900 rpm, the mixing time was 60 min, and the mixing temperature was 25℃~45℃.

[0082] S12: Sinter the first mixture.

[0083] The first mixture was placed in a box furnace and heated to 450°C at a rate of 2°C / min under an oxygen atmosphere. After heat treatment for 3 hours, the temperature was increased to 740°C and sintered for 15 hours. Then, the mixture was cooled, crushed, and sieved to obtain the nickel-cobalt-manganese cathode material to be coated once.

[0084] S2: Perform the first coating on the nickel-cobalt-manganese cathode material to be coated once.

[0085] S21: The primary coating source and the nickel-cobalt-manganese cathode material to be coated are mixed in a high-speed mixer to obtain a second mixture.

[0086] The primary coating source is nano-sized cobalt molybdate; by mass percentage, the cobalt molybdate is 500 ppm of the total amount of cobalt molybdate and the nickel-cobalt-manganese cathode material to be coated.

[0087] The high-speed mixer operates at 800 rpm, with a mixing time of 40 minutes and a mixing temperature of 20℃~45℃.

[0088] S22: The second mixture is placed in a box furnace and heated to 400°C at a rate of 2°C / min under an oxygen atmosphere. It is then sintered at this temperature for 12 hours, followed by cooling, washing and filtering with water, and vacuum drying to obtain the cathode material to be coated a second time.

[0089] S3: Perform a second coating on the nickel-cobalt-manganese cathode material to be coated.

[0090] S31: The secondary coating source and the cathode material to be secondary coated are mixed in a high-speed mixer to obtain a third mixture; The secondary coating source is nano-sized alumina and boric acid micro powder; by mass percentage, the nano-sized alumina is 1000 ppm of the cathode material to be secondary coated, and the boric acid micro powder is 1000 ppm of the cathode material to be secondary coated.

[0091] The high-speed mixer operates at 800 rpm, with a mixing time of 40 minutes and a mixing temperature of 20℃~45℃.

[0092] S32: The third mixture is placed in a box furnace and heated to 270°C at a rate of 2°C / min under an oxygen atmosphere. It is then sintered at this temperature for 12 hours, followed by cooling and sieving to remove iron, thus obtaining the composite-coated modified nickel-cobalt-manganese ternary cathode material.

[0093] Example 8 This embodiment provides a composite-coated modified nickel-cobalt-manganese ternary cathode material, the preparation method of which includes: S1: Prepare the nickel-cobalt-manganese cathode material to be coated once.

[0094] S11: The precursor, lithium source and M source nanoscale additives are mixed in a high-speed mixer to obtain the first mixture.

[0095] The precursor is Ni 0.98 Co 0.015 Mn 0.005 (OH)2, the lithium source is battery-grade lithium acetate, and the M element in the M source nanoscale additive is composed of Ce, Mo and Zr. The molar ratio of Li in the lithium source to the transition metal element in the precursor is 1.07:1; in terms of mass percentage, Ce is 5000 ppm of the precursor, Mo is 3000 ppm of the precursor, and Zr is 2000 ppm of the precursor.

[0096] The mixing speed was 1200 rpm, the mixing time was 40 min, and the mixing temperature was 25℃~45℃.

[0097] S12: Sinter the first mixture.

[0098] The first mixture is placed in a box furnace and heated to 650°C at a rate of 10°C / min under an oxygen atmosphere. After heat treatment for 3 hours, the temperature is further increased to 750°C and sintered for 10 hours. Then, the mixture is cooled, crushed, and sieved to obtain the nickel-cobalt-manganese cathode material to be coated once.

[0099] S2: Perform the first coating on the nickel-cobalt-manganese cathode material to be coated once.

[0100] S21: The primary coating source and the nickel-cobalt-manganese cathode material to be coated are mixed in a high-speed mixer to obtain a second mixture.

[0101] The primary coating source is nano-sized cobalt molybdate; by mass percentage, cobalt molybdate is 10,000 ppm of the total amount of cobalt molybdate and the nickel-cobalt-manganese cathode material to be coated.

[0102] The high-speed mixer has a rotation speed of 1200 rpm, a mixing time of 20 min, and a mixing temperature of 20℃~45℃.

[0103] S22: The second mixture is placed in a box furnace and heated to 700°C at a rate of 10°C / min under an oxygen atmosphere. It is then sintered at this temperature for 5 hours, followed by cooling, washing and filtering with water, and vacuum drying to obtain the cathode material to be coated a second time.

[0104] S3: Perform a second coating on the nickel-cobalt-manganese cathode material to be coated.

[0105] S31: The secondary coating source and the cathode material to be secondary coated are mixed in a high-speed mixer to obtain a third mixture; The secondary coating source is nano-sized alumina and boric acid micro powder; by mass percentage, the nano-sized alumina is 1000 ppm of the cathode material to be secondary coated, and the boric acid micro powder is 1000 ppm of the cathode material to be secondary coated.

[0106] The high-speed mixer operates at 1000 rpm, with a mixing time of 20 min and a mixing temperature of 20℃~45℃.

[0107] S32: The third mixture is placed in a box furnace and heated to 350°C at a rate of 10°C / min under an oxygen atmosphere. It is then held at this temperature for sintering for 5 hours, followed by cooling and sieving to remove iron, thus obtaining the composite-coated modified nickel-cobalt-manganese ternary cathode material.

[0108] Comparative Example 1 The difference between this comparative example and Example 1 is that no M-source nanoscale additives, bimetallic acid salts, nanoscale alumina, or boric acid micropowder were used in the preparation process.

[0109] Comparative Example 2 The difference between this comparative example and Example 1 is that bimetallic acid salts, nano-sized alumina, and boric acid powder were not used in the preparation process.

[0110] Comparative Example 3 The difference between this comparative example and Example 1 is that nano-sized alumina and boric acid powder were not used in the preparation process.

[0111] Comparative Example 4 The difference between this comparative example and Example 1 is that no bimetallic acid salt compounds were used in the preparation process.

[0112] Comparative Example 5 The difference between this comparative example and Example 1 is that no M-source nanoscale additives were used in the preparation process.

[0113] Comparative Example 6 The difference between this comparative example and Example 1 is that the M-source nanoscale additive is only nanoscale zirconia, and the nanoscale zirconia precursor is 4500 ppm by mass percentage.

[0114] Comparative Example 7 The difference between this comparative example and Example 1 is that the M-source nanoscale additive is only nanoscale strontium oxide, and the nanoscale strontium oxide is 4500 ppm of the precursor by mass percentage.

[0115] Comparative Example 8 The difference between this comparative example and Example 1 is that cobalt molybdate is replaced with an equal amount of cobalt sulfate.

[0116] Comparative Example 9 The difference between this comparative example and Example 1 is that the secondary coating source is only nano-sized alumina, and the nano-sized alumina is 2000 ppm of the cathode material to be secondary coated by mass percentage.

[0117] Comparative Example 10 The difference between this comparative example and Example 1 is that the secondary coating source is only boric acid micro powder, which is 2000 ppm of the positive electrode material to be secondary coated by mass percentage.

[0118] Test case (1) The structure of the composite-coated modified nickel-cobalt-manganese ternary cathode material prepared in Example 1 was observed, and its SEM image is shown below. Figure 1 As shown, the XRD pattern is as follows Figure 2 As shown.

[0119] Depend on Figure 1 It can be seen that the surface of the composite-coated modified nickel-cobalt-manganese ternary cathode material is relatively uniformly coated, and there is no obvious additive agglomeration on the material surface.

[0120] Depend on Figure 2 It can be seen that the composite-coated modified nickel-cobalt-manganese ternary cathode material has no other impurity peaks, indicating that the coating layer does not affect the material's structure. (2) The final ternary cathode materials obtained in Examples 1-8 and Comparative Examples 1-10 were used as battery cathode materials to make coin cells and their electrochemical performance was tested.

[0121] The production method is as follows: a. The final ternary cathode materials are stirred in a ratio of cathode material powder: conductive agent (SP): adhesive (PVDF) = 90:5:5 to form a uniformly dispersed cathode slurry. The slurry is then coated, punched, and vacuum dried. A lithium metal sheet is used as the negative electrode material for the counter electrode, and a polypropylene film with micropores is used as the battery separator. Ethylene carbonate (EC) / dimethyl carbonate (DMC) with a solvent volume ratio of 1:1 and 1 mol / L LiPF6 are used as the electrolyte. The cells are assembled into 2032 button cells in a glove box filled with dry high-purity argon gas and left to stand for 8 hours. b. After the button batteries have been left to stand, charge and discharge them at an ambient temperature of 25°C, at a voltage of 3.0V~4.3V, and at a current rate of 0.1C. Perform electrochemical performance tests on Examples 1~8 and Comparative Examples 1~10, and calculate their first discharge efficiency, i.e.: first efficiency = first discharge specific capacity / first charge specific capacity × 100%.

[0122] c. At 45°C, charge / discharge at 3.0V~4.3V with 1C, and perform cycle performance tests on Examples 1~8 and Comparative Examples 1~10. Calculate the capacity retention rate after 50 cycles using the following formula: Capacity retention rate = Specific capacity at 50th discharge / Specific capacity at first discharge × 100%.

[0123] The results are shown in Table 1 and Figure 3 and Figure 4 As shown.

[0124] Table 1 Electrical performance test results

[0125] As shown in Table 1 above, compared with Comparative Example 1, the battery performance (such as initial efficiency, discharge specific capacity, and high-temperature cycle stability) of the composite-coated modified nickel-cobalt-manganese ternary cathode materials prepared in each embodiment of the present invention has been significantly improved. This indicates that the preparation method provided by the present invention effectively improves the initial efficiency of the material and enhances its charge-discharge performance; at the same time, it also exhibits good cycle performance at a high temperature of 45°C and a 1C rate, further demonstrating that its rate performance has also been improved. Specifically, after double coating, interfacial side reactions are effectively reduced, the interfacial kinetics, interfacial stability, and structural stability of the material are improved, giving the composite material good ion diffusion ability. It also avoids direct contact between the material and the electrolyte, reducing side reactions between the material and the electrolyte, resulting in the excellent electrochemical performance of this composite cathode material.

[0126] The comparative examples demonstrate that the composite coating of cobalt molybdate inner layer and alumina and boric acid outer layer can effectively prevent direct contact reaction between the cathode material surface and the electrolyte, prevent electrolyte decomposition side reactions, improve the cycle stability of the cathode material, and greatly improve the cycle life of the battery.

[0127] In summary, the method provided by this invention can improve problems such as low material structural stability, high residual lithium, low capacity after coating, and poor rate and cycle performance. The resulting composite-coated modified nickel-cobalt-manganese ternary cathode material has high conductivity and Li... + It has the advantages of high diffusion rate, high stability, low residual lithium, high discharge capacity after coating, and better rate and cycle performance.

[0128] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a composite-coated modified nickel-cobalt-manganese ternary cathode material, characterized in that, Includes the following steps: The primary coating source is used to perform a first coating on the nickel-cobalt-manganese cathode material to be coated, resulting in a cathode material to be coated a second time. The secondary coating source is used to perform a second coating on the cathode material to be coated. The primary coating source is a bimetallic acid salt compound containing at least cobalt, including at least one of cobalt aluminate, cobalt molybdate, cobalt tungstate, cobalt stannate, and cobalt titanate; the bimetallic acid salt compound accounts for 500 ppm to 10000 ppm of the total amount of the nickel-cobalt-manganese cathode material to be primary coated by mass percentage; the secondary coating source includes nano-sized alumina and boric acid micropowder; the mass percentage of the nano-sized alumina is 50 ppm to 2000 ppm of the cathode material to be secondary coated by mass percentage; the mass percentage of the boric acid micropowder is 50 ppm to 2000 ppm of the cathode material to be secondary coated by mass percentage.

2. The preparation method according to claim 1, characterized in that, The preparation of the nickel-cobalt-manganese cathode material to be coated in one step includes: mixing the precursor, lithium source and M source nanoscale additives and then sintering them. The precursor has the chemical formula Ni x Co y Mn 1-x-y (OH)2, where 0.90≤x≤0.98, 0<y<0.9, 0<1-xy<0.9; The lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium acetate, and lithium oxalate; The element M contained in the M-source nanoscale additive includes at least two of the following: Co, Mn, Ti, Zr, Sr, Al, Mg, Sb, V, Ta, Ce, Sn, Nb, B, Sc, Y, Mo, Hf, La, and W.

3. The preparation method according to claim 2, characterized in that, The preparation of the nickel-cobalt-manganese cathode material to be coated in one step also includes at least one of the following features: Feature 1: The molar ratio of Li in the lithium source to the transition metal element in the precursor is 1.04:1 to 1.07:1; Feature 2: By mass percentage, M in the M-source nanoscale additive accounts for 1000ppm~10000ppm of the precursor; Feature 3: The mixing speed of the precursor, the lithium source and the M source nanoscale additive is 900 rpm to 1200 rpm, and the mixing time is 40 min to 60 min; Feature 4: Sintering includes: first heat treatment at 450℃~650℃ for 2h~3h, then heating to 650℃~780℃ and holding for 10h~15h; Feature 5: The heating rate during the sintering process is 2℃ / min~10℃ / min; Feature 6: Sintering is carried out in an oxygen atmosphere.

4. The preparation method according to claim 1, characterized in that, The first coating process includes mixing the primary coating source with the nickel-cobalt-manganese cathode material to be coated, followed by sintering.

5. The preparation method according to claim 4, characterized in that, The first coating includes at least one of the following features: Feature 7: The mixing speed of the primary coating source and the nickel-cobalt-manganese cathode material to be coated is 800 rpm to 1200 rpm, and the mixing time is 20 min to 40 min; Feature 8: The sintering temperature of the primary coating source and the nickel-cobalt-manganese cathode material to be coated is 400℃~700℃, and the sintering time is 5h~12h; Feature 9: The sintering atmosphere of the primary coating source and the nickel-cobalt-manganese cathode material to be coated includes at least one of oxygen and air; Feature 10: The heating rate during the sintering process of the primary coating source and the nickel-cobalt-manganese cathode material to be coated is 2℃ / min~10℃ / min.

6. The preparation method according to claim 1, characterized in that, The second coating process includes mixing the secondary coating source with the cathode material to be coated, followed by sintering.

7. The preparation method according to claim 6, characterized in that, The second coating includes at least one of the following features: Feature 11: The mixing speed of the secondary coating source and the positive electrode material to be secondary coated is 800 rpm to 1000 rpm, and the mixing time is 20 min to 40 min; Feature 12: The sintering temperature of the secondary coating source and the positive electrode material to be secondary coated is 270℃~350℃, and the sintering time is 5h~12h; Feature 13: The sintering atmosphere of the secondary coating source and the positive electrode material to be secondary coated includes at least one of oxygen and air; Feature 14: The heating rate during the sintering process of the secondary coating source and the positive electrode material to be secondary coated is 2℃ / min~10℃ / min.

8. A composite-coated modified nickel-cobalt-manganese ternary cathode material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. The composite-coated modified nickel-cobalt-manganese ternary cathode material according to claim 8, characterized in that, The composite-coated modified nickel-cobalt-manganese ternary cathode material comprises an inner substrate, an intermediate layer, and an outer layer; wherein the inner substrate is LiNi doped with an M source. x Co y Mn 1-x-y O2, wherein 0.90≤x≤0.98, 0<y<0.9, 0<1-xy<0.9, the intermediate layer is a coating layer formed by bimetallic acid salt compounds, and the outer layer is a coating layer formed by nano-sized alumina and boric acid micro powder.

10. A lithium-ion battery, characterized in that, Including the composite-coated modified nickel-cobalt-manganese ternary cathode material as described in claim 9.

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