A ternary cathode material, its preparation method and its application

Abstract

This invention provides a ternary cathode material, its preparation method, and its application. The ternary cathode material includes a substrate and a coating layer covering the surface of the substrate; the substrate is a ternary material with the chemical formula LiNi. x Co y Mn z M (1‑x‑y‑z) O2, where 0.5 < x < 1, 0 < y < 0.3, 0 < z < 0.5, x + y + z < 1, and M is a dopant element selected from one or more of Zr, Mg, Sr, Al, W, Ti, Ta, Mo, N, B, Y, La, and Nb; the coating layer is a conductive polymer formed by modifying the matrix polymer with lithium salt; the matrix polymer is selected from one or more of polyethylene oxide, polypropylene oxide, and ethylene oxide-propylene oxide copolymer. By modifying the matrix polymer with lithium salt, a conductive polymer with high ionic conductivity is obtained, which is then used as a coating agent to coat the surface of the ternary material, thus solving the capacity and cycle life problems of the ternary cathode material in one step.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a ternary cathode material, its preparation method, and its application. Background Technology

[0002] In the field of power batteries, with the continuous improvement of the energy density of lithium-ion batteries in recent years, nickel-rich layered oxides have significantly improved the energy density of power batteries, resulting in a substantial increase in the driving range of electric vehicles. To meet the demands for higher energy density and lower cost in lithium-ion batteries, ternary cathode materials are an excellent solution.

[0003] To reduce costs, the cobalt content must be minimized, while increasing electrochemical capacity requires increasing the nickel content or improving the material's specific charge capacity and initial discharge efficiency. However, increasing the nickel content leads to drawbacks such as poor cycle performance, severe lithium-nickel mixing, and poor safety, which limit the industrialization of NCM battery systems. Moreover, conventional modification methods are unlikely to solve the capacity and cycle life issues in one go.

[0004] CN114212835A discloses a simple method for preparing an Al and Zr co-doped ultra-high nickel ternary single crystal material. This method involves a low-temperature combustion reaction of a mixed system consisting of lithium nitrate, nickel nitrate, cobalt nitrate, manganese nitrate, aluminum nitrate, zirconium nitrate, an organic complexing agent, and ammonium nitrate, thereby achieving the preparation of the ultra-high nickel ternary single crystal material and in-situ co-doping of Al and Zr elements. Although doping Al and Zr elements into the ultra-high nickel single crystal phase structure enhances the structural stability and improves the cycle performance of the material, the stable valence states of Al and Zr elements in the prepared ternary cathode material do not significantly increase its charging capacity, nor does it reduce the impedance of the ternary cathode material to improve its rate performance. Summary of the Invention

[0005] To address the shortcomings and defects of existing technologies, this invention aims to provide a ternary cathode material, its preparation method, and its application. This invention uses lithium salts to modify the matrix polymer, obtaining a conductive polymer with high ionic conductivity. This polymer is then used as a coating agent to coat the surface of the ternary material, which improves the ionic conductivity of the coated ternary cathode material, facilitates lithium-ion diffusion, increases the capacity of the cathode material, and reduces polarization during cycling, thus solving the capacity and cycling problems of ternary cathode materials in one step.

[0006] To achieve the above objectives, the first aspect of the present invention provides a ternary cathode material, which adopts the following technical solution:

[0007] A ternary cathode material includes: a substrate and a coating layer covering the surface of the substrate; the substrate is a ternary material with the chemical formula LiNi. x Co y Mn z M (1-x-y-z) O2, where 0.5 < x < 1 (e.g., x = 0.55, 0.6, 0.7, 0.8, 0.9, 0.95), 0 < y < 0.3 (e.g., y = 0.05, 0.1, 0.15, 0.2, 0.25, 0.28), 0 < z < 0.5 (e.g., z = 0.1, 0.2, 0.3, 0.4, 0.45, 0.48), x + y + z < 1, and M is a doping element selected from one or more of Zr, Mg, Sr, Al, W, Ti, Ta, Mo, N, B, Y, La, and Nb.

[0008] The coating layer is a conductive polymer formed from a lithium salt modified matrix polymer; the matrix polymer is selected from one or more of polyethylene oxide, polypropylene oxide, and ethylene oxide-propylene oxide copolymer.

[0009] In the above-mentioned ternary cathode material, as a preferred embodiment, the mass of the matrix polymer accounts for 0.2%-1.5% of the mass of the matrix (e.g., 0.3%, 0.5%, 0.8%, 1.0%, 1.2%, 1.3%, 1.4%); preferably, the mass ratio of the matrix polymer to the lithium salt is 2-18:1 (e.g., 3:1, 5:1, 7:1, 9:1, 10:1, 12:1, 15:1).

[0010] In the above-mentioned ternary cathode material, as a preferred embodiment, the molecular weight of the matrix polymer is 500-10000 (e.g., 800, 1000, 3000, 5000, 7000, 9000).

[0011] In the aforementioned ternary cathode materials, as a preferred embodiment, the lithium salt is selected from LiClO4, LiBF4, LiPF6, LiAlO2, Li2ZrO3, and Li4Ti5O. 12 One or more of them.

[0012] In the above-mentioned ternary materials, as a preferred embodiment, the microstructure of the ternary cathode material is a secondary microsphere composed of primary particles, and the D50 diameter of the secondary microsphere is 4-15μm (e.g., 5μm, 7μm, 9μm, 10μm, 12μm).

[0013] In this invention, conductive polymers formed from lithium salt-modified matrix polymers (such as PEO-LiClO4 composites, PEO-LiBF4 composites, PEO-LiPF6 composites, PEO-LiAlO2 composites, PPO-LiClO4 composites, EO / PO copolymer-LiClO4 composites, etc.) are used as coating agents to coat the surface of ternary materials. Because these conductive polymers formed from lithium salt-modified matrix polymers have high ionic conductivity at room temperature, especially at 10... -4 The conductivity of the coated ternary cathode material is around S / cm, which gives it high ionic conductivity, facilitating lithium-ion diffusion and thus increasing the capacity of the cathode material while reducing the problem of increased polarization during cycling. Furthermore, the conductive polymer formed by the lithium salt modified matrix polymer can uniformly coat the surface of the ternary material, forming a stable coating layer. This reduces side reactions at the electrode / electrolyte interface, stabilizes the surface structure of the material, and inhibits the dissolution of transition metal elements. Consequently, it reduces the deposition and reduction of transition metal elements at the negative electrode and the damage to the SEI of the negative electrode. It also reduces the consumption of active ions in the positive electrode during SEI repair, thereby improving the cycle performance and rate performance of the cathode material.

[0014] In this invention, the mass of the matrix polymer is limited to 0.2%-1.5% of the matrix mass. Within this range, it is beneficial to improve the specific capacity, cycle performance, and rate performance of the cathode material. If the mass of the matrix polymer is too small, the mass of the coating layer will be too small, and it will not play a role in improving the cycle performance and rate performance of the cathode material. If the mass of the matrix polymer is too large, the mass of the coating layer will be too large, which will reduce the specific capacity of the cathode material.

[0015] A second aspect of the present invention provides a method for preparing the above-mentioned ternary cathode material, comprising:

[0016] (1) A ternary material is obtained by mixing lithium source, ternary precursor material and M-containing compound, calcining and pulverizing.

[0017] (2) The ternary material is washed with water, filtered and dried to obtain dried material; then the matrix polymer and lithium salt are added to an organic solvent to obtain a polymer solution, and then the dried material is added for stirring and mixing, and then dried until the organic solvent is completely evaporated to obtain ternary cathode material.

[0018] This invention obtains a dried material by mixing, calcining, pulverizing, washing, filtering, and drying a lithium source, ternary precursor material, and a compound containing M. Then, a matrix polymer and lithium salt are added to an organic solvent to obtain a polymer solution. The dried material is then added and stirred, followed by drying until the organic solvent completely evaporates, resulting in a ternary cathode material. This drying process not only modifies the matrix polymer with lithium salt to form a conductive polymer but also uniformly coats the surface of the dried material. Specifically, a wet coating method is used to coat the surface of the dried material with the conductive polymer formed by the lithium salt-modified matrix polymer. This wet coating method results in a more uniform and better coating effect. The coated ternary cathode material reduces direct contact with the electrolyte, which is beneficial for improving cycle performance.

[0019] In the above preparation method, as a preferred embodiment, in step (1), the lithium source is lithium hydroxide or lithium carbonate; preferably, it is lithium hydroxide. More preferably, the ternary precursor material is nickel-cobalt-manganese hydroxide, with the chemical formula: Ni a Co b Mn c (OH)2, wherein 0.5 < a < 1 (e.g., a = 0.55, 0.6, 0.7, 0.8, 0.9, 0.95), 0 < b < 0.3 (e.g., b = 0.05, 0.1, 0.15, 0.2, 0.25, 0.28), 0 < c < 0.5 (e.g., c = 0.1, 0.2, 0.3, 0.4, 0.45, 0.48), a + b + c = 1; preferably, the molar ratio of lithium in the lithium source to the total amount of nickel, cobalt and manganese in the ternary precursor material is 1.0-1.1:1 (e.g., 1.01:1, 1.02:1, 1.05:1, 1.08:1, 1.09:1).

[0020] In the above preparation method, as a preferred embodiment, in step (1), the M-containing compound is selected from one or more compounds including Zr, Mg, Sr, Al, W, Ti, Ta, Mo, N, B, Y, La, and Nb; more preferably, the M-containing compound is selected from one or more salts or oxides including Zr, Mg, Sr, Al, W, Ti, Ta, Mo, N, B, Y, La, and Nb; preferably, the molar ratio of the M element in the M-containing compound to the nickel, cobalt, and manganese elements in the ternary precursor material is (1-xyz):x:y:z, 0.5 < x < 1 (ratio For example, x = 0.55, 0.6, 0.7, 0.8, 0.9, 0.95), 0 < y < 0.3 (e.g., y = 0.05, 0.1, 0.15, 0.2, 0.25, 0.28), 0 < z < 0.5 (e.g., z = 0.1, 0.2, 0.3, 0.4, 0.45, 0.48), x + y + z < 1; more preferably, the molar ratio of element M in the M-containing compound to the total amount of nickel, cobalt, and manganese in the ternary precursor material is 0.001-0.01:1 (e.g., 0.002:1, 0.004:1, 0.005:1, 0.007:1, 0.009:1).

[0021] In the above preparation method, as a preferred embodiment, in step (1), the mixing process is carried out in a high-speed mixer with a mixing speed of 100-800 rpm (e.g., 200 rpm, 500 rpm, 700 rpm) and a mixing time of 5-60 min (e.g., 10 min, 20 min, 30 min, 40 min, 50 min); the calcination process is carried out in a kiln under an air or oxygen atmosphere with a calcination temperature of 700-1100℃ (e.g., 750℃, 800℃, 900℃, 1000℃) and a time of 8-15 h (e.g., 10 h, 11 h, 12 h, 13 h, 14 h).

[0022] In the above preparation method, as a preferred embodiment, in step (2), the organic solvent is one of acetonitrile, toluene, and chloroform; preferably, the matrix polymer is selected from one or more of polyethylene oxide, polypropylene oxide, and ethylene oxide-propylene oxide copolymer; preferably, the lithium salt is selected from LiClO4, LiBF4, LiPF6, LiAlO2, Li2ZrO3, and Li4Ti5O. 12 One or more of the following; preferably, in the polymer solution, the sum of the mass of the matrix polymer and the lithium salt is 1%-5% (e.g., 1.2%, 1.5%, 2%, 3%, 4%) of the mass of the polymer solution.

[0023] In the above preparation method, as a preferred embodiment, in step (2), the mass of the matrix polymer accounts for 0.2%-1.5% of the mass of the dried material (e.g., 0.3%, 0.5%, 0.8%, 1.0%, 1.2%, 1.3%, 1.4%); preferably, the mass ratio of the matrix polymer to the lithium salt is 2-18:1 (e.g., 3:1, 5:1, 7:1, 9:1, 10:1, 12:1, 15:1).

[0024] In the above preparation method, as a preferred embodiment, in step (2), the drying temperature is 100-150℃ (e.g., 110℃, 120℃, 130℃, 140℃), and the time is 4-8h (e.g., 4.5h, 5h, 6h, 7h).

[0025] In this invention, the drying temperature is limited to 100-150℃. Within this temperature range, not only is the evaporation of organic solvents beneficial, but the uniform coating of conductive polymers onto the surface of the ternary material is also beneficial. If the drying temperature is too low, it will affect the evaporation of organic solvents, resulting in an excessively long drying process. If the drying temperature is too high, it will cause the organic solvents to evaporate too quickly, preventing the conductive polymers from uniformly coating the surface of the ternary material.

[0026] The third aspect of the present invention provides an application of the above-described ternary cathode material or the ternary cathode material prepared by the above-described preparation method in lithium-ion batteries.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) The present invention utilizes a conductive polymer formed by lithium salt modified matrix polymer as a coating agent to coat the surface of ternary material, which can improve the ionic conductivity of the coated ternary cathode material, facilitate lithium ion diffusion, improve the capacity of the cathode material, and reduce the increase of polarization during cycling, thus solving the capacity and cycling problems of ternary cathode material in one go.

[0029] (2) In this invention, the matrix polymer and lithium salt are added to an organic solvent to obtain a polymer solution. Then, the dried material is added and stirred and mixed. After drying, the organic solvent is completely evaporated to obtain a ternary cathode material. The drying process not only modifies the matrix polymer with lithium salt to form a conductive polymer, but also uniformly coats it on the surface of the dried material. That is, the conductive polymer formed by lithium salt-modified matrix polymer is coated on the surface of the dried material by a wet coating method. The wet coating effect is more uniform and better. The coated ternary cathode material can reduce direct contact with the electrolyte, which is more conducive to improving cycle performance. Attached Figure Description

[0030] Figure 1This is a SEM image of the ternary cathode material prepared in Example 1 of the present invention;

[0031] Figure 2 This is a SEM image of the ternary cathode material prepared in Comparative Example 1 of this invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0033] The embodiments of the present invention are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and processes are given. However, the protection scope of the present invention is not limited to the following embodiments. The process parameters in the following embodiments that do not specify specific conditions are generally in accordance with conventional conditions.

[0034] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0035] In this invention, unless otherwise specified and / or stated, all values ​​relating to component amounts are in parts by weight. Process parameters in the following examples, unless otherwise specified, are generally performed under conventional conditions. The raw materials described in the following examples are all available from publicly available commercial sources; the chemical formula of the ternary precursor material in this invention is: Ni a Co b Mn c (OH)2, wherein 0.5 < a < 1, 0 < b < 0.3, 0 < c < 0.5, a + b + c = 1. The method of the present invention is applicable to any nickel-cobalt-manganese ternary precursor material that meets the above conditions. Here, for the convenience of comparing the effects of each embodiment and the prepared cathode material, the molar ratio of Ni:Co:Mn in the ternary precursor materials used in the following embodiments and comparative examples is 83:12:5; the particle size of nano-zirconia is 50-500 nm; the molecular weight of polyethylene oxide is 800, and the Tg is -67℃; the molecular weight of polyethylene oxide is 1100, and the Tg is -73℃; the molecular weight of ethylene oxide-propylene oxide copolymer is 1000, and the Tg is -69℃.

[0036] The present invention will now be described in further detail with reference to specific embodiments.

[0037] Example 1: A method for preparing a ternary cathode material modified by PEO-LiClO4 composite material coating, comprising:

[0038] (1) Lithium hydroxide, ternary precursor material and nano-zirconia are added to a high-speed mixer for mixing. The molar ratio of lithium in lithium hydroxide to the total amount of nickel, cobalt and manganese in ternary precursor material is 1.04:1. The mass of nano-zirconia added is 0.5% of the mass of ternary precursor material. The mixing speed is 500 rpm and the mixing time is 20 min to obtain the mixture.

[0039] (2) The mixture obtained in step (1) is calcined in an oxygen atmosphere in a kiln. The calcination temperature is 750℃ and the time is 12h. After the calcination is completed, the temperature is lowered to room temperature. The material is crushed by mechanical mill and passed through a 325-mesh sieve to obtain ternary material. The ternary material is then mixed with deionized water and washed, filtered, and dried to obtain dried material.

[0040] (3) Polyethylene oxide and LiClO4 were added to acetonitrile and dissolved completely to obtain a colorless and transparent solution. The mass of acetonitrile was 20 times the sum of the masses of polyethylene oxide and LiClO4. Then, dried material was added and stirred. Polyethylene oxide accounted for 0.7% of the mass of the dried material, and LiClO4 accounted for 0.17% of the mass of the dried material. The mixture was then dried at 120℃ for 5 hours until the acetonitrile completely evaporated. The resulting material was passed through a 325-mesh sieve to obtain a ternary cathode material coated and modified with PEO-LiClO4 composite material (its SEM image is shown below). Figure 1 (As shown).

[0041] Example 2: A method for preparing a ternary cathode material modified by PEO-LiClO4 composite material coating, comprising:

[0042] (1) Lithium hydroxide, ternary precursor material and nano-zirconia are added to a high-speed mixer for mixing. The molar ratio of lithium in lithium hydroxide to the total amount of nickel, cobalt and manganese in ternary precursor material is 1.04:1. The mass of nano-zirconia added is 0.5% of the mass of ternary precursor material. The mixing speed is 500 rpm and the mixing time is 20 min to obtain the mixture.

[0043] (2) The mixture obtained in step (1) is calcined in an oxygen atmosphere in a kiln. The calcination temperature is 750℃ and the time is 12h. After the calcination is completed, the temperature is lowered to room temperature. The material is crushed by mechanical mill and passed through a 325-mesh sieve to obtain ternary material. The ternary material is then mixed with deionized water and washed, filtered, and dried to obtain dried material.

[0044] (3) Polyethylene oxide and LiClO4 were added to acetonitrile and dissolved completely to obtain a colorless and transparent solution. The mass of acetonitrile was 20 times the sum of the masses of polyethylene oxide and LiClO4. Then, dried material was added and stirred and mixed. Polyethylene oxide accounted for 1.5% of the mass of dried material and LiClO4 accounted for 0.364% of the mass of dried material. The mixture was then dried at 120°C for 5 hours until the acetonitrile was completely volatilized. The mixture was then passed through a 325-mesh sieve to obtain a ternary cathode material coated and modified with PEO-LiClO4 composite material.

[0045] Example 3: A method for preparing a ternary cathode material modified by PEO-LiClO4 composite material coating, comprising:

[0046] (1) Lithium hydroxide, ternary precursor material and nano-zirconia are added to a high-speed mixer for mixing. The molar ratio of lithium in lithium hydroxide to the total amount of nickel, cobalt and manganese in ternary precursor material is 1.04:1. The mass of nano-zirconia added is 0.5% of the mass of ternary precursor material. The mixing speed is 500 rpm and the mixing time is 20 min to obtain the mixture.

[0047] (2) The mixture obtained in step (1) is calcined in an oxygen atmosphere in a kiln. The calcination temperature is 750℃ and the time is 12h. After the calcination is completed, the temperature is lowered to room temperature. The material is crushed by mechanical mill and passed through a 325-mesh sieve to obtain ternary material. The ternary material is then mixed with deionized water and washed, filtered, and dried to obtain dried material.

[0048] (3) Polyethylene oxide and LiClO4 were added to acetonitrile and completely dissolved to obtain a colorless and transparent solution. The mass of acetonitrile was 20 times the sum of the masses of polyethylene oxide and LiClO4. Then, dried material was added and stirred and mixed. Polyethylene oxide accounted for 0.2% of the mass of dried material, and LiClO4 accounted for 0.049% of the mass of dried material. The mixture was then dried at 120°C for 5 hours until the acetonitrile was completely volatilized. The mixture was then passed through a 325-mesh sieve to obtain a ternary cathode material coated and modified with PEO-LiClO4 composite material.

[0049] Example 4: A method for preparing a ternary cathode material modified by PEO-LiClO4 composite material coating, comprising:

[0050] (1) Lithium hydroxide, ternary precursor material and nano-zirconia are added to a high-speed mixer for mixing. The molar ratio of lithium in lithium hydroxide to the total amount of nickel, cobalt and manganese in ternary precursor material is 1.04:1. The mass of nano-zirconia added is 0.5% of the mass of ternary precursor material. The mixing speed is 500 rpm and the mixing time is 20 min to obtain the mixture.

[0051] (2) The mixture obtained in step (1) is calcined once in an oxygen atmosphere in a kiln. The temperature of the first calcination is 750°C and the time is 12h. After the calcination is completed, the temperature is lowered to room temperature. The material is crushed by mechanical mill and passed through a 325-mesh sieve to obtain ternary material. The ternary material is then mixed with deionized water and stirred for washing, filtration and drying to obtain dried material.

[0052] (3) Polyethylene oxide and LiClO4 were added to acetonitrile to completely dissolve the polymer and obtain a colorless and transparent solution. The mass of acetonitrile was 20 times the sum of the masses of polyethylene oxide and LiClO4. Then, drying material was added. Polyethylene oxide accounted for 0.7% of the mass of the drying material, and LiClO4 accounted for 0.35% of the mass of the drying material. The material was then dried at 120°C for 5 hours until the acetonitrile was completely volatilized. The material was then passed through a 325-mesh sieve to obtain a ternary cathode material coated and modified with PEO-LiClO4 composite material.

[0053] Example 5: A method for preparing a ternary cathode material modified by PEO-LiClO4 composite material coating, comprising:

[0054] (1) Lithium hydroxide, ternary precursor material and nano-zirconia are added to a high-speed mixer for mixing. The molar ratio of lithium in lithium hydroxide to the total amount of nickel, cobalt and manganese in ternary precursor material is 1.04:1. The mass of nano-zirconia added is 0.5% of the mass of ternary precursor material. The mixing speed is 500 rpm and the mixing time is 20 min to obtain the mixture.

[0055] (2) The mixture obtained in step (1) is calcined once in an oxygen atmosphere in a kiln. The temperature of the first calcination is 750°C and the time is 12h. After the calcination is completed, the temperature is lowered to room temperature. The material is crushed by mechanical mill and passed through a 325-mesh sieve to obtain ternary cathode material. Then, the ternary cathode material is mixed with deionized water and stirred for washing, filtration and drying to obtain dried material.

[0056] (3) Polyethylene oxide and LiClO4 were added to acetonitrile to completely dissolve the polymer and obtain a colorless and transparent solution. The mass of acetonitrile was 20 times the sum of the masses of polyethylene oxide and LiClO4. Then, drying material was added. The weight ratio of polyethylene oxide to drying material was 0.7%, and LiClO4 accounted for 0.039% of the mass of drying material. The mixture was then dried at 120°C for 5 hours until the acetonitrile was completely volatilized. The mixture was then passed through a 325-mesh sieve to obtain a ternary cathode material coated and modified with PEO-LiClO4 composite material.

[0057] Example 6: A method for preparing a ternary cathode material modified by PPO-LiAlO2 composite material coating, comprising:

[0058] (1) Lithium hydroxide, ternary precursor material and nano-zirconia are added to a high-speed mixer for mixing. The molar ratio of lithium in lithium hydroxide to the total amount of nickel, cobalt and manganese in ternary precursor material is 1.04:1. The mass of nano-zirconia added is 0.5% of the mass of ternary precursor material. The mixing speed is 500 rpm and the mixing time is 20 min to obtain the mixture.

[0059] (2) The mixture obtained in step (1) is calcined in an oxygen atmosphere in a kiln. The calcination temperature is 750℃ and the time is 12h. After the calcination is completed, the temperature is lowered to room temperature. The material is crushed by mechanical mill and passed through a 325-mesh sieve to obtain ternary material. The ternary material is then mixed with deionized water and washed, filtered, and dried to obtain dried material.

[0060] (3) Polypropylene oxide and LiAlO2 are added to acetonitrile and completely dissolved to obtain a colorless and transparent solution. The mass of acetonitrile is 20 times the sum of the masses of polypropylene oxide and LiAlO2. Then, dried material is added and stirred and mixed. Polypropylene oxide accounts for 0.7% of the mass of dried material and LiAlO2 accounts for 0.17% of the mass of dried material. Then, it is dried at 120℃ for 5 hours until the acetonitrile is completely volatilized. The PPO-LiAlO2 composite material-coated modified ternary cathode material is obtained by passing it through a 325-mesh sieve.

[0061] Example 7: A method for preparing a ternary cathode material modified by coating with an EO / PO copolymer-LiAlO2 composite material, comprising:

[0062] (1) Lithium hydroxide, ternary precursor material and nano-zirconia are added to a high-speed mixer for mixing. The molar ratio of lithium in lithium hydroxide to the total amount of nickel, cobalt and manganese in ternary precursor material is 1.04:1. The mass of nano-zirconia added is 0.5% of the mass of ternary precursor material. The mixing speed is 500 rpm and the mixing time is 20 min to obtain the mixture.

[0063] (2) The mixture obtained in step (1) is calcined in an oxygen atmosphere in a kiln. The calcination temperature is 750℃ and the time is 12h. After the calcination is completed, the temperature is lowered to room temperature. The material is crushed by mechanical mill and passed through a 325-mesh sieve to obtain ternary material. The ternary material is then mixed with deionized water and washed, filtered, and dried to obtain dried material.

[0064] (3) Ethylene oxide-propylene oxide copolymer and LiAlO2 were added to acetonitrile and dissolved completely to obtain a colorless and transparent solution. The mass of acetonitrile was 20 times the sum of the masses of ethylene oxide-propylene oxide copolymer and LiAlO2. Then, dried material was added and stirred and mixed. The ethylene oxide-propylene oxide copolymer accounted for 0.7% of the mass of dried material and LiAlO2 accounted for 0.17% of the mass of dried material. The mixture was then dried at 120°C for 5 hours until the acetonitrile was completely volatilized. The ternary cathode material coated and modified with EO / PO copolymer-LiAlO2 composite material was obtained by passing the mixture through a 325-mesh sieve.

[0065] Comparative Example 1: A method for preparing a ternary cathode material, comprising:

[0066] (1) Lithium hydroxide, ternary precursor material and nano-zirconia are added to a high-speed mixer for mixing. The molar ratio of lithium in lithium hydroxide to the total amount of nickel, cobalt and manganese in ternary precursor material is 1.04:1. The mass of nano-zirconia added is 0.5% of the mass of ternary precursor material. The mixing speed is 500 rpm and the mixing time is 20 min to obtain the mixture.

[0067] (2) The mixture obtained in step (1) was calcined in a kiln under an oxygen atmosphere at a temperature of 750°C for 12 hours. After calcination, the mixture was cooled to room temperature, and the material was crushed using a mechanical mill and passed through a 325-mesh sieve to obtain the ternary cathode material (its SEM image is shown below). Figure 2 (As shown).

[0068] Comparative Example 2: A method for preparing a PEO-coated modified ternary cathode material, comprising:

[0069] (1) Lithium hydroxide, ternary precursor material and nano-zirconia are added to a high-speed mixer for mixing. The molar ratio of lithium in lithium hydroxide to the total amount of nickel, cobalt and manganese in ternary precursor material is 1.04:1. The mass of nano-zirconia added is 0.5% of the mass of ternary precursor material. The mixing speed is 500 rpm and the mixing time is 20 min to obtain the mixture.

[0070] (2) The mixture obtained in step (1) is calcined once in an oxygen atmosphere in a kiln. The temperature of the first calcination is 750°C and the time is 12h. After the calcination is completed, the temperature is lowered to room temperature. The material is crushed by mechanical mill and passed through 325 mesh to obtain ternary cathode material. Then, the ternary cathode material is mixed with deionized water and stirred for water washing, filtration and drying to obtain dried material.

[0071] (3) Polyethylene oxide is added to acetonitrile and completely dissolved to obtain a colorless and transparent solution, wherein the mass of acetonitrile is 20 times the mass of polyethylene oxide. Then, dried material is added, with polyethylene oxide accounting for 0.7% of the mass of the dried material. The material is dried at 120°C for 5 hours until the acetonitrile is completely volatilized. The material is then passed through a 325-mesh sieve to obtain a PEO-coated modified ternary cathode material.

[0072] Comparative Example 3: A method for preparing a LiClO4-coated modified ternary cathode material, comprising:

[0073] (1) Lithium hydroxide, ternary precursor material and nano-zirconia are added to a high-speed mixer for mixing. The molar ratio of lithium in lithium hydroxide to the total amount of nickel, cobalt and manganese in ternary precursor material is 1.04:1. The mass of nano-zirconia added is 0.5% of the mass of ternary precursor material. The mixing speed is 500 rpm and the mixing time is 20 min to obtain the mixture.

[0074] (2) The mixture obtained in step (1) is calcined once in an oxygen atmosphere in a kiln. The temperature of the first calcination is 750°C and the time is 12h. After the calcination is completed, the temperature is lowered to room temperature. The material is crushed by mechanical mill and passed through 325 mesh to obtain ternary cathode material. Then, the ternary cathode material is mixed with deionized water and stirred for water washing, filtration and drying to obtain dried material.

[0075] (3) LiClO4 was added to acetonitrile and dissolved completely to obtain a colorless and transparent solution. The mass of acetonitrile was 20 times that of LiClO4. Then, drying material was added, with LiClO4 accounting for 0.17% of the mass of the drying material. The mixture was dried at 120°C for 5 hours until the acetonitrile was completely volatilized. The solution was then passed through a 325-mesh sieve to obtain the LiClO4-coated modified ternary cathode material.

[0076] Comparative Example 4: A method for preparing a ternary cathode material modified by PEO-LiClO4 composite material coating, comprising:

[0077] (1) Lithium hydroxide, ternary precursor material and nano-zirconia are added to a high-speed mixer for mixing. The molar ratio of lithium in lithium hydroxide to the total amount of nickel, cobalt and manganese in ternary precursor material is 1.04:1. The mass of nano-zirconia added is 0.5% of the mass of ternary precursor material. The mixing speed is 500 rpm and the mixing time is 20 min to obtain the mixture.

[0078] (2) The mixture obtained in step (1) is calcined once in an oxygen atmosphere in a kiln. The temperature of the first calcination is 750°C and the time is 12h. After the calcination is completed, the temperature is lowered to room temperature. The material is crushed by mechanical mill and passed through a 325-mesh sieve to obtain ternary cathode material. Then, the ternary cathode material is mixed with deionized water and stirred for washing, filtration and drying to obtain dried material.

[0079] (3) Polyethylene oxide and LiClO4 were added to acetonitrile to completely dissolve the polymer and obtain a colorless and transparent solution. The mass of acetonitrile was 20 times the sum of the masses of polyethylene oxide and LiClO4. Then, drying material was added. Polyethylene oxide accounted for 2% of the mass of the drying material, and LiClO4 accounted for 0.486% of the mass of the drying material. The material was dried at 120°C for 5 hours until the acetonitrile was completely volatilized. The material was then passed through a 325-mesh sieve to obtain a ternary cathode material coated and modified with PEO-LiClO4 composite material.

[0080] Comparative Example 5: A method for preparing a ternary cathode material modified with PEO-LiClO4 composite material, comprising:

[0081] (1) Lithium hydroxide, ternary precursor material and nano-zirconia are added to a high-speed mixer for mixing. The molar ratio of lithium in lithium hydroxide to the total amount of nickel, cobalt and manganese in ternary precursor material is 1.04:1. The mass of nano-zirconia added is 0.5% of the mass of ternary precursor material. The mixing speed is 500 rpm and the mixing time is 20 min to obtain the mixture.

[0082] (2) The mixture obtained in step (1) is calcined once in an oxygen atmosphere in a kiln. The temperature of the first calcination is 750°C and the time is 12h. After the calcination is completed, the temperature is lowered to room temperature. The material is crushed by mechanical mill and passed through a 325-mesh sieve to obtain ternary cathode material. Then, the ternary cathode material is mixed with deionized water and stirred for washing, filtration and drying to obtain dried material.

[0083] (3) Polyethylene oxide and LiClO4 were added to acetonitrile and dissolved completely to obtain a colorless and transparent solution. The mass of acetonitrile was 20 times the sum of the masses of polyethylene oxide and LiClO4. Then, drying material was added. Polyethylene oxide accounted for 0.1% of the mass of the drying material, and LiClO4 accounted for 0.024% of the mass of the drying material. The material was dried at 120°C for 5 hours until the acetonitrile was completely volatilized. The material was then passed through a 325-mesh sieve to obtain a ternary cathode material coated and modified with PEO-LiClO4 composite material.

[0084] Performance testing

[0085] The ternary cathode materials prepared in Examples 1-7 and the ternary cathode materials prepared in Comparative Examples 1-5 were used as active materials and mixed with PVDF and SP at a mass ratio of 90:5:5. The mixture was ball-milled for 60 min using NMP as solvent. The slurry was then uniformly coated onto aluminum foil and vacuum dried at 80°C for 2 h. Finally, it was cut into circular electrode sheets with a diameter of 11 mm using a punch as working electrodes. In a clean glove box filled with Ar (O2 content less than 0.1 ppm, H2O content less than 0.1 ppm), a coin cell (cell model CR2032) was prepared according to a certain assembly process, using a lithium metal sheet as the counter electrode, a Celgard 2400 porous propylene membrane as the separator, a 1 mol / L lithium hexafluorophosphide (LiPF6) solution as the electrolyte, and a volume ratio of ethylene carbonate (EC): ethyl carbonate (DMC) of 1:1 as the solvent. After completion, the cell was allowed to stand for 3 h to allow the electrolyte and electrode materials to be fully wetted. The first discharge specific capacitance and cycle performance were tested at room temperature (25℃±1) and 60℃, with a voltage range of 3.0-4.3V. The impedance test was performed as follows: after the coin cell completed the first charge-discharge cycle at 0.1C at room temperature, it was fully charged at 1C and then the electrochemical impedance was measured at the electrochemical workstation as Rct (mΩ) before cycling. After cycling for 100 cycles at 1C, the electrochemical impedance was measured as Rct (mΩ) after cycling. The test results are shown in Table 1.

[0086] Table 1

[0087]

[0088]

[0089] Note: The 100-cycle capacity retention rate at 25℃-1C is the ratio of the discharge capacity at 1C at 25℃ for 100 cycles to the discharge capacity in the first cycle.

[0090] The capacity retention rate after 100 cycles at 60℃-1C is the ratio of the discharge capacity after 100 cycles at 60℃ and 1C to the discharge capacity after the first cycle.

[0091] The ionic conductivity of the PEO-LiClO4 composite material is 10. -4The coated ternary cathode material exhibits high ionic conductivity (S / cm), which is beneficial for lithium-ion diffusion. With increasing coating thickness, the impedance decreases both before and after cycling. However, after reaching 1.5%, the impedance slightly increases, mainly because the overly dense coating of the PEO-LiClO4 composite hinders contact between the material and the electrolyte, leading to increased polarization. However, the dense coating layer reduces side reactions at the electrode / electrolyte interface, stabilizes the material surface structure, and inhibits the dissolution of transition metal elements. This reduces the deposition and reduction of transition metal elements at the negative electrode and their damage to the SEI (Sediment Ion Exchange), thus minimizing the consumption of active ions at the cathode during SEI repair. The cycling rate and impedance data of Example 4 were significantly worse, mainly because the mass ratio of lithium salt to matrix polymer was too large. The coordination of ether oxygen atoms in the composite material with lithium ions gradually became saturated, and the number of freely moving ions gradually approached a constant. Moreover, as the mass ratio of lithium salt to matrix polymer increased, the glass transition temperature of the polymer (PEO-LiClO4 composite material) increased, which limited the mobility of polymer chain segments and hindered lithium ion transport.

[0092] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention shall be within the scope of protection of the pending claims of the present invention.

Claims

1. A ternary cathode material, characterized in that, include: The substrate and the coating layer covering the surface of the substrate; The matrix is ​​a ternary material with the chemical formula LiNi. x Co y Mn z M (1-x-y-z) O2, where 0.5 < x < 1, 0 < y < 0.3, 0 < z < 0.5, x + y + z < 1, and M is a doping element selected from one or more of Zr, Mg, Sr, Al, W, Ti, Ta, Mo, N, B, Y, La, and Nb; The coating layer is a conductive polymer formed from a lithium salt modified matrix polymer; the matrix polymer is selected from one or more of polyethylene oxide (PEO), polypropylene oxide (PPO), and ethylene oxide-propylene oxide copolymer. The matrix polymer accounts for 0.2%-0.8% of the mass of the matrix, and the mass ratio of the matrix polymer to the lithium salt is 5-18:1; The preparation method of the ternary cathode material includes: (1) The lithium source, ternary precursor material and M-containing compound are mixed, calcined and pulverized to obtain ternary material; (2) The ternary material is washed with water, filtered and dried to obtain dried material; then the matrix polymer and lithium salt are added to an organic solvent to obtain a polymer solution, and then the dried material is added for stirring and mixing, and then dried until the organic solvent is completely evaporated to obtain ternary cathode material; The lithium salt is selected from LiClO4, LiBF4, LiPF6, LiAlO2, Li2ZrO3, and Li4Ti5O. 12 One or more of them.

2. The ternary cathode material according to claim 1, characterized in that, The molecular weight of the matrix polymer is 500-10000.

3. The ternary cathode material according to claim 1, characterized in that, The microstructure of the ternary cathode material is a secondary microsphere composed of primary particles, and the D50 diameter of the secondary microsphere is 4-15 μm.

4. The ternary cathode material according to claim 1, characterized in that, In step (1), the lithium source is lithium hydroxide and / or lithium carbonate; And / or, the ternary precursor material is nickel-cobalt-manganese hydroxide, with the chemical formula: Ni a Co b Mn c (OH)2, where 0.5 < a < 1, 0 < b < 0.3, 0 < c < 0.5, and a + b + c = 1; And / or, the molar ratio of lithium in the lithium source to the total amount of nickel, cobalt and manganese in the ternary precursor material is 1.0-1.1:

1.

5. The ternary cathode material according to claim 1, characterized in that, In step (1), the molar ratio of element M in the M-containing compound to nickel, cobalt and manganese in the ternary precursor material is (1-xyz): x:y:z, 0.5<x<1, 0<y<0.3, 0<z<0.5, x+y+z<1.

6. The ternary cathode material according to claim 5, characterized in that, The molar ratio of element M in the M-containing compound to the total amount of nickel, cobalt, and manganese in the ternary precursor material is 0.001-0.01:

1.

7. The ternary cathode material according to claim 1, characterized in that, The M-containing compound is a salt or oxide of one or more of the elements Zr, Mg, Sr, Al, W, Ti, Ta, Mo, N, B, Y, La, and Nb.

8. The ternary cathode material according to claim 1, characterized in that, In step (1), the mixing process is carried out in a high-speed mixer with a mixing speed of 100-800 rpm and a mixing time of 5-60 min; the calcination process is carried out in a kiln under an air or oxygen atmosphere with a calcination temperature of 700-1100℃ and a time of 8-15 h. And / or, in step (2), the drying process is carried out at a temperature of 100-150°C for 4-8 hours.

9. The ternary cathode material according to claim 1, characterized in that, In step (2), the organic solvent is one of acetonitrile, toluene, and chloroform; And / or, in the polymer solution, the sum of the mass of the matrix polymer and the lithium salt is 1%-5% of the mass of the polymer solution.

10. The application of a ternary cathode material as described in any one of claims 1-9 in a lithium-ion battery.

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