A core-shell structured ternary cathode material, its preparation method and application

Abstract

This invention provides a core-shell ternary cathode material, its preparation method, and its application. The preparation method of the core-shell ternary cathode material includes the following steps: S1, mixing a first nickel source, a first cobalt source, a first manganese source, and a first solvent to obtain a core solution; adding a precipitant and a complexing agent, and performing a first reaction to obtain a core-containing system; S2, mixing a second nickel source, a second cobalt source, a second manganese source, and a second solvent to obtain a shell solution; mixing the core-containing system and the shell solution, and performing a second reaction to obtain a core-shell precursor; S3, mixing the core-shell precursor and a lithium source, adding a tantalum source for mixing i, adding a cesium source for mixing ii, and performing a first sintering to obtain a matrix; S4, mixing the matrix, LiF, NbF5, and a third solvent, and performing a second sintering to obtain a core-shell ternary cathode material. The obtained core-shell ternary cathode material has excellent structural stability, ion conductivity, and interfacial compatibility.

Description

Technical Field

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

[0002] Low-nickel ternary cathode materials typically refer to layered oxide cathode materials with a nickel molar ratio of less than 60%, exhibiting excellent structural stability, thermal stability, and safety. However, current low-nickel ternary cathode materials still face numerous insurmountable technical bottlenecks in energy density and long cycle life under high-voltage applications, and their overall electrochemical performance is insufficient to meet the demands of high-end batteries.

[0003] Traditional homogeneous doping modification methods can only improve the stability of the material's crystal structure to a limited extent. A single doping element system has a limited function and cannot simultaneously achieve multiple objectives such as stable bulk structure, optimized interfacial impedance, and rapid lithium-ion transport. Therefore, its effect on improving the material's discharge specific capacity and coulombic efficiency is limited. Ternary cathode materials prepared by conventional high-temperature sintering processes tend to have a uniform elemental distribution within the particles. Under high-voltage charging conditions of 4.5V and above, the material surface is highly susceptible to lattice phase transitions, transition metal dissolution, and electrolyte oxidation and decomposition, leading to uncontrolled interfacial side reactions and structural collapse, ultimately causing rapid capacity decay.

[0004] Existing technologies generally lack precise and differentiated control strategies for the bulk and surface structures of ternary cathode materials, making it difficult to synergistically address key issues such as poor stability of the surface lithium-rich layer and limited bulk lithium-ion migration rate under high voltage. This prevents a fundamental improvement in the material's capacity and cycle retention capabilities. Furthermore, traditional coating modifications are mostly simple physical coatings, resulting in low interfacial bonding strength and poor interfacial compatibility between the coating layer and the substrate material. During long-term high-voltage charge-discharge cycles, these coatings are prone to cracking, peeling, and detachment, failing to provide sustained interfacial protection. Consequently, the overall performance of ternary cathode materials cannot be significantly improved, severely limiting their large-scale application in high-voltage, long-cycle power batteries. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects of existing ternary cathode materials, such as small discharge specific capacity, poor coulombic efficiency and low capacity retention, so as to provide a core-shell structured ternary cathode material, its preparation method and application.

[0006] Therefore, the present invention provides the following technical solution: The first aspect of this invention protects a method for preparing a core-shell structured ternary cathode material, wherein the preparation method includes the following steps: S1, the first nickel source, the first cobalt source, the first manganese source and the first solvent are mixed to obtain a core solution; a precipitant and a complexing agent are added to carry out the first reaction to obtain a core-containing system; S2, the second nickel source, the second cobalt source, the second manganese source, and the second solvent are mixed to obtain a shell solution; the core-containing system and the shell solution are mixed to carry out a second reaction to obtain a core-shell precursor; S3, mix the core-shell precursor and lithium source, add tantalum source for mixing i, add cesium source for mixing ii, and perform the first sintering to obtain the matrix; S4, the matrix, LiF, NbF5 and the third solvent are mixed and sintered for a second time to obtain a core-shell structured ternary cathode material.

[0007] In one optional embodiment, the Ni in the first nickel source, the Co in the first cobalt source, and the Mn in the first manganese source satisfy Ni:Co:Mn=60:(5-30):(10-35); optionally, Ni:Co:Mn=60:(10-20):(20-30).

[0008] In one optional embodiment, the total concentration of metal ions in the nucleus solution is 1-5 mol / L.

[0009] In this invention, the types of precipitant and complexing agent are conventional in the art. Typically, but not limited to, the precipitant includes at least one of sodium hydroxide, potassium hydroxide, and sodium carbonate; the complexing agent includes at least one of ammonia (25% by mass), ethylenediamine, and citric acid.

[0010] In one optional embodiment, the precipitant is prepared by adding water to form a precipitant solution with a concentration of 1-5 mol / L; optionally, the flow rate of the precipitant solution is 1-10 mL / min.

[0011] In one optional embodiment, the complexing agent is prepared by adding water to form a complexing agent solution with a concentration of 0.5-5 mol / L; optionally, the flow rate of the complexing agent solution is 1-10 mL / min.

[0012] Optionally, the precipitant solution and the complexing agent solution are added in parallel flow.

[0013] In one optional embodiment, the conditions for the first reaction include: a temperature of 50-60°C, a pH of 10-12, a stirring speed of 100-500 rpm, and a time of 5-10 hours.

[0014] In one optional embodiment, the Ni in the second nickel source, the Co in the second cobalt source, and the Mn in the second manganese source satisfy Ni:Co:Mn=60:(5-30):(10-35); optionally, Ni:Co:Mn=60:(10-20):(20-30).

[0015] In this invention, the first nickel source and the second nickel source each independently include at least one of nickel sulfate, nickel nitrate, and nickel acetate; the first cobalt source and the second cobalt source each independently include at least one of cobalt sulfate, cobalt nitrate, and cobalt acetate; the first manganese source and the second manganese source each independently include at least one of manganese sulfate, manganese nitrate, and manganese acetate; and the first solvent and the second solvent each independently include at least one of water, ethanol, methanol, and ethylene glycol.

[0016] In one optional embodiment, the total concentration of metal ions in the shell solution is 1-5 mol / L.

[0017] In one alternative embodiment, a shell solution is added to the nucleus-containing system, the flow rate of which is 1-10 mL / min.

[0018] In one optional embodiment, the conditions for the second reaction include: a temperature of 50-60°C, a pH of 10-12, a stirring speed of 100-500 rpm, and a time of 5-10 hours.

[0019] In this invention, a laser particle size analyzer is used to determine the D50 (median particle size). The D50 of the core-shell precursor is 3.8-4.2 μm, which facilitates subsequent preparation steps.

[0020] In one optional embodiment, the total molar amount of metal elements in the core-shell precursor and the molar ratio of lithium elements in the lithium source are 1:(1-1.1).

[0021] In this invention, the lithium source is conventional in the art, and typically, without limitation, includes at least one of lithium hydroxide (LiOH·H2O), lithium carbonate, lithium nitrate, and lithium acetate.

[0022] In one optional embodiment, the total molar amount of metal elements in the core-shell precursor and the molar ratio of tantalum elements in the tantalum source are 1:(0.0003-0.0008), and can be optionally 1:(0.0004-0.0006).

[0023] In one optional embodiment, the tantalum source includes at least one of tantalum pentachloride (TaCl5), tantalum pentoxide, lithium tantalate, tantalum ethoxide, tantalum isopropoxide, tantalum oxalate, tantalum fluoride, and tantalum nitrate.

[0024] In one alternative implementation, the conditions for mixing i include mixing at a speed of 300-500 rpm for 10-20 minutes.

[0025] In one optional embodiment, the total molar amount of metal elements in the core-shell precursor and the molar ratio of cesium elements in the cesium source are 1:(0.0004-0.001), and can be optionally 1:(0.0006-0.0008).

[0026] In one optional embodiment, the cesium source includes at least one of cesium nitrate (CsNO3), cesium carbonate, cesium chloride, cesium hydroxide, cesium acetate, cesium sulfate, and cesium oxalate.

[0027] In one alternative implementation, the conditions for mixing ii include mixing at a speed of 300-500 rpm for 30-120 minutes.

[0028] In one alternative embodiment, the first sintering includes a primary sintering and a secondary sintering; the primary sintering is carried out in an oxygen atmosphere.

[0029] Optionally, the conditions for the first sintering include: heating to 500-650°C at a rate of 1-5°C / min and holding for 6-8 hours; or, optionally, heating to 600-620°C. Optionally, the conditions for the secondary sintering include: heating to 900-1100℃ at a rate of 6-10℃ / min and holding for 10-12 hours; or, optionally, heating to 900-1000℃.

[0030] The first sintering stage of this invention is a low-temperature pre-sintering stage, which is carried out at a lower temperature and a slower heating rate. This allows the lithium source, tantalum source, cesium source and core-shell precursor to fully undergo solid-state reaction, achieving uniform dispersion of dopant elements and preliminary lattice solidification, avoiding incomplete local reactions or element segregation, and effectively reducing the residual alkali content of the material and improving interface stability. The second sintering stage is a high-temperature crystallization stage, which raises the temperature to a higher level through a faster heating rate and holds it at that temperature for a long time. This promotes the formation of a complete layered crystal structure in the material, improves crystallinity and lattice order, enhances the structural stability of the material, and suppresses lattice phase transitions and transition metal dissolution under high voltage. This, in turn, improves the material's discharge specific capacity, initial coulombic efficiency and long-cycle capacity retention.

[0031] In one optional embodiment, the mass ratio of the matrix to LiF is 100:(0.5-1.5), optionally 100:(0.6-0.8).

[0032] In one optional embodiment, the mass ratio of the matrix to NbF5 is 100:(0.5-1.5), optionally 100:(0.8-1.0).

[0033] In one optional embodiment, the ratio of the matrix to the third solvent is 100g:(300-800)mL.

[0034] In this invention, the third solvent includes water and / or anhydrous ethanol.

[0035] In step S4 of this invention, ultrasound is used for mixing; optionally, the conditions for ultrasound are: power of 400-500W and frequency of 30-50kHz.

[0036] In step S4 of this invention, the mixture is further dried; moreover, spray drying is adopted, and the conditions include: inlet temperature of 150-200℃, outlet temperature of 90-120℃, atomizing disc rotation speed of 20000-30000rpm, feed rate of 40-60mL / min, nitrogen as drying medium, and oxygen concentration controlled below 5%.

[0037] In one optional embodiment, the second sintering is carried out in an inert gas (nitrogen) protective environment, and the conditions for the second sintering include: heating to 300-600°C at a rate of 1-3°C / min and holding for 4-6 hours; optionally, heating to 400-500°C.

[0038] The second aspect of this invention protects a core-shell structured ternary cathode material prepared by the aforementioned method for preparing core-shell structured ternary cathode materials.

[0039] In this invention, the D50 of the core-shell structured ternary cathode material is 3.5-4.5 μm.

[0040] A third aspect of this invention protects a secondary battery, wherein the secondary battery comprises a core-shell ternary cathode material prepared by the aforementioned preparation method or the aforementioned core-shell ternary cathode material.

[0041] Compared with the prior art, the present invention has the following beneficial effects: The preparation method of core-shell ternary cathode material provided by this invention controls the process from precursor morphology, bulk doping, interface coating to sintering and crystallization, significantly improving the structural stability, ion conductivity and interface compatibility of core-shell ternary cathode material, and effectively solving the defects of low discharge specific capacity, poor initial coulombic efficiency and low capacity retention rate in existing technologies.

[0042] The present invention provides a method for preparing a core-shell ternary cathode material. Steps S1 and S2 construct the core-shell precursor in separate steps, achieving precise control of the bulk structure. Through a two-step co-precipitation method of first preparing the core and then growing the shell, the core provides a high-structure framework, while the shell improves interfacial compatibility, avoiding surface phase transitions and electrolyte erosion under high voltage, as is common in traditional homogeneous materials, thus fundamentally improving cycle stability and capacity retention. Step S3 uses tantalum and cesium sources for stepwise doping, ensuring uniform dispersion and non-agglomeration of dopants. Tantalum source doping strengthens the lattice framework and suppresses phase transitions; cesium source doping widens lithium site channels and improves lithium-ion migration rate, resulting in high crystallinity, complete lattice, and low residual alkali, significantly improving discharge specific capacity and initial coulombic efficiency. Step S4 uses LiF and NbF5 dual fluorine sources for synergistic coating. LiF optimizes interfacial impedance and improves initial efficiency; NbF5 suppresses side reactions and protects the material surface, solving the problems of weak adhesion and easy peeling failure of traditional coating layers.

[0043] Furthermore, the process of this invention is highly controllable, has good batch consistency, is suitable for industrial scale-up, requires no complex equipment, has high feasibility for mass production, and produces materials with uniform particle size, moderate specific surface area, and excellent processing performance. Detailed Implementation

[0044] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0045] In the description of the embodiments of the present invention, the technical terms "first", "second", etc. are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0046] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0047] The "range" disclosed in this invention is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This range can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. In this invention, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers from a to b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein; "0-5" is merely a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that the parameter can be, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0048] In the description of the embodiments of the present invention, the term "and / or" is merely a description of the relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0049] In the description of the embodiments of the present invention, the term "at least one" refers to one or more (including two).

[0050] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0051] Example 1 This embodiment provides a core-shell structured ternary cathode material, the preparation method of which includes the following steps: S1, 315.2 g of NiSO4·6H2O, 67.4 g of CoSO4·7H2O, and 94.6 g of MnSO4·H2O were weighed and dissolved in 2 L of water to obtain a nucleus solution, wherein the total concentration of metal ions was 2.0 mol / L, and the Ni:Co:Mn ratio was 60:12:28; 320 g of NaOH was mixed with water to obtain a 2 L precipitant solution, wherein the NaOH concentration in the precipitant solution was 4.0 mol / L; 25% ammonia water was mixed with water to obtain a 2 L complexing agent solution, wherein the NH3·H2O concentration in the complexing agent solution was 0.8 mol / L; the precipitant solution and the complexing agent solution were added to the reactor in parallel at a flow rate of 5 mL / min, the temperature was 55℃, the pH was 11.0, the stirring speed was 400 rpm, and the reaction time was 8 hours to obtain a nucleus-containing system; S2, 315.2 g of NiSO4·6H2O, 45.0 g of CoSO4·7H2O, and 108.2 g of MnSO4·H2O were weighed and dissolved in 2 L of water to obtain a shell solution, wherein the total concentration of metal ions was 2.0 mol / L and Ni:Co:Mn = 60:8:32; the shell solution was added to the core-containing system at a flow rate of 5 mL / min and the reaction was carried out for 6 hours; the product was obtained, washed with deionized water (2 L each time) until pH < 7.5, and dried under vacuum at 120 °C for 12 hours to obtain the core-shell precursor, wherein Ni:Co:Mn = 60:10:30; S3, 100g of core-shell precursor and LiOH·H2O were mixed, wherein the molar ratio of the total molar amount of metal elements in the core-shell precursor to the molar ratio of lithium element in LiOH·H2O was 1:1.05; TaCl5 was added and premixed at 500rpm for 15 minutes, wherein the molar ratio of the total molar amount of metal elements in the core-shell precursor to the molar ratio of tantalum element in TaCl5 was 1:0.000489; then CsNO3 was added and mixed at 500rpm for 55 minutes, wherein the molar ratio of the total molar amount of metal elements in the core-shell precursor to the molar ratio of cesium element in CsNO3 was 1:0.000744; the mixture was placed in a corundum crucible and placed in an oxygen atmosphere furnace, heated to 600℃ at a rate of 5℃ / min and held for 6 hours, then heated to 960℃ at a rate of 8℃ / min and held for 12 hours, and cooled with the furnace; the mixture was then pulverized by air jet and passed through a 400-mesh sieve to obtain the matrix; S4. 100g of matrix, 0.8g of LiF, 0.8g of NbF5, and 500mL of anhydrous ethanol were mixed and ultrasonically dispersed at 400W and 40kHz for 60 minutes. Spray drying was then carried out with an inlet temperature of 180℃, an outlet temperature of 100℃, an atomizing disc rotation speed of 25000rpm, a feed rate of 50mL / min, nitrogen as the drying medium, and an oxygen concentration controlled below 5%. The mixture was placed in a corundum crucible and then in a tube furnace. Under nitrogen protection, the temperature was increased to 400℃ at a rate of 3℃ / min and held for 5 hours. The mixture was then cooled with the furnace to obtain a core-shell structured ternary cathode material.

[0052] Example 2 This embodiment provides a core-shell structured ternary cathode material, the preparation method of which includes the following steps: S1, the same as S1 in Example 1, except that the amounts of NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O are adjusted so that the total concentration of metal ions in the nucleus solution is 2.0 mol / L and Ni:Co:Mn=60:14:26; S2, following the method in Example 1, except that the amounts of NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O are adjusted so that the total concentration of metal ions in the shell solution is 2.0 mol / L and Ni:Co:Mn=60:6:34; the resulting core-shell precursor has Ni:Co:Mn=60:10:30. S3, the method is the same as S3 in Example 1, except that the total molar amount of metal elements in the core-shell precursor and the molar ratio of tantalum element are 1:0.000405, and the total molar amount of metal elements in the core-shell precursor and the molar ratio of cesium element are 1:0.000892. S4. Following the method in S4 of Example 1, a core-shell structured ternary cathode material is obtained.

[0053] Example 3 This embodiment provides a core-shell structured ternary cathode material, the preparation method of which includes the following steps: S1, as in S1 of Example 2; S2, in accordance with the method of S2 in Example 2; S3, in accordance with the method of S3 in Example 2; S4. 100g of matrix, 0.6g of LiF, 1.0g of NbF5, and 500mL of anhydrous ethanol were mixed and ultrasonically dispersed at 400W and 40kHz for 60 minutes. Spray drying was then carried out with an inlet temperature of 180℃, an outlet temperature of 100℃, an atomizing disc rotation speed of 25000rpm, a feed rate of 50mL / min, nitrogen as the drying medium, and an oxygen concentration controlled below 5%. The mixture was placed in a corundum crucible and then in a tube furnace. Under nitrogen protection, the temperature was increased to 420℃ at a rate of 3℃ / min and held for 5 hours. The mixture was then cooled with the furnace to obtain a core-shell structured ternary cathode material.

[0054] Example 4 This embodiment provides a core-shell structured ternary cathode material, the preparation method of which includes the following steps: S1, the same as S1 in Example 1, except that the amounts of NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O are adjusted so that the total concentration of metal ions in the nucleus solution is 2.0 mol / L and Ni:Co:Mn=60:8:34; S2, following the method in Example 1, except that the amounts of NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O are adjusted so that the total concentration of metal ions in the shell solution is 2.0 mol / L, and Ni:Co:Mn = 60:12:26; the resulting core-shell precursor has Ni:Co:Mn = 60:10:30. S3, in accordance with the method of S3 in Example 1; S4. Following the method in S4 of Example 1, a core-shell structured ternary cathode material is obtained.

[0055] Example 5 This embodiment provides a core-shell structured ternary cathode material, the preparation method of which includes the following steps: S1, as described in S1 of Example 1; S2, in accordance with the method of S2 in Example 1; S3, the method is the same as S3 in Example 1, except that the total molar amount of metal elements in the core-shell precursor and the molar ratio of tantalum element are 1:0.0003, and the total molar amount of metal elements in the core-shell precursor and the molar ratio of cesium element are 1:0.0004. S4. Following the method in S4 of Example 1, a core-shell structured ternary cathode material is obtained.

[0056] Example 6 This embodiment provides a core-shell structured ternary cathode material, the preparation method of which includes the following steps: S1, as described in S1 of Example 1; S2, in accordance with the method of S2 in Example 1; S3, following the method in Example 1, except that it is placed in an oxygen atmosphere furnace, heated to 580°C at a rate of 3°C / min and held for 8 hours, then heated to 1100°C at a rate of 10°C / min and held for 10 hours, and cooled with the furnace; after being pulverized by airflow and passed through a 400-mesh sieve, the matrix is ​​obtained. S4. Following the method in S4 of Example 1, a core-shell structured ternary cathode material is obtained.

[0057] Example 7 This embodiment provides a core-shell structured ternary cathode material, the preparation method of which includes the following steps: S1, as described in S1 of Example 1; S2, in accordance with the method of S2 in Example 1; S3, in accordance with the method of S3 in Example 1; S4 follows the same procedure as S4 in Example 1, except that 100g of the matrix, 1.2g of LiF, 0.6g of NbF5, and 500mL of anhydrous ethanol are mixed to obtain a core-shell structured ternary cathode material.

[0058] Example 8 This embodiment provides a core-shell structured ternary cathode material, the preparation method of which includes the following steps: S1, as in S1 of Example 2; S2, in accordance with the method of S2 in Example 2; S3, in accordance with the method of S3 in Example 2; S4 follows the same procedure as S4 in Example 1, except that under nitrogen protection, the temperature is increased to 350°C at a rate of 2°C / min and held for 5 hours, followed by furnace cooling to obtain a core-shell structured ternary cathode material.

[0059] Comparative Example 1 This comparative example provides a ternary cathode material, the preparation method of which includes the following steps: S1, NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O were weighed and dissolved in 2L of water to obtain a base solution, wherein the total concentration of metal ions was 2.0 mol / L and the Ni:Co:Mn ratio was 60:10:30; 320g of NaOH was mixed with water to obtain a 2L precipitant solution, wherein the NaOH concentration in the precipitant solution was 4.0 mol / L; 25% ammonia water was mixed with water to obtain a 2L complexing agent solution, wherein the NH3·H2O concentration in the complexing agent solution was 0.8 mol / L; the precipitant solution and the complexing agent solution were added to the reactor in parallel at a rate of 5 mL / min, the temperature was 55℃, the pH was 11.0, the stirring speed was 400 rpm, and the reaction time was 14 hours to obtain the precursor; S2, 100g of core-shell precursor and LiOH·H2O were mixed, wherein the molar ratio of the total molar amount of metal elements in the core-shell precursor to that of lithium was 1:1.05; TaCl5 was added and premixed at 500rpm for 15 minutes, wherein the molar ratio of the total molar amount of metal elements in the core-shell precursor to that of tantalum in TaCl5 was 1:0.000489; then CsNO3 was added and mixed at 500rpm for 55 minutes, wherein the molar ratio of the total molar amount of metal elements in the core-shell precursor to that of cesium in CsNO3 was 1:0.000744; the mixture was placed in a corundum crucible and placed in an oxygen atmosphere furnace, heated to 600℃ at a rate of 5℃ / min and held for 6 hours, then heated to 960℃ at a rate of 8℃ / min and held for 12 hours, and cooled with the furnace; the mixture was then pulverized by air jet milling and passed through a 400-mesh sieve to obtain the matrix; S3. Mix 100g of matrix, 0.8g of LiF, 0.8g of NbF5, and 500mL of anhydrous ethanol. Disperse the mixture ultrasonically at 400W and 40kHz for 60 minutes. Spray dry the mixture at an inlet temperature of 180℃ and an outlet temperature of 100℃. Place the mixture in a corundum crucible and in a tube furnace. Under nitrogen protection, heat the mixture to 400℃ at a rate of 3℃ / min and hold for 5 hours. Cool the mixture with the furnace to obtain a core-shell structured ternary cathode material.

[0060] Comparative Example 2 This comparative example provides a core-shell structured ternary cathode material, the preparation method of which includes the following steps: S1, as in S1 of Example 2; S2, in accordance with the method of S2 in Example 2; S3. Mix 100g of core-shell precursor with LiOH·H2O, wherein the molar ratio of the total molar amount of metal elements in the core-shell precursor to the molar amount of lithium is 1:1.05; add Al2O3 and MgO, wherein the molar ratio of the total molar amount of metal elements in the core-shell precursor to the molar amount of aluminum in Al2O3 is 1:0.00152, and the molar ratio of the total molar amount of metal elements in the core-shell precursor to the molar amount of magnesium in MgO is 1:0.00149. Mix at 500rpm for 70 minutes, place in a corundum crucible, and place in an oxygen atmosphere furnace. Heat to 600℃ at a rate of 5℃ / min and hold for 6 hours, then heat to 960℃ at a rate of 8℃ / min and hold for 12 hours. Cool with the furnace. Pulverize by air jet and pass through a 400-mesh sieve to obtain the matrix. S4, following the method in S4 of Example 2, a core-shell structured ternary cathode material is obtained.

[0061] Comparative Example 3 This comparative example provides a core-shell structured ternary cathode material, the preparation method of which includes the following steps: S1, as described in S1 of Example 1; S2, in accordance with the method of S2 in Example 1; S3, in accordance with the method of S3 in Example 1; S4. 100g of the substrate was placed in a corundum crucible and placed in a tube furnace. Under nitrogen protection, the temperature was increased to 400℃ at a rate of 3℃ / min and held for 5 hours. The furnace was then cooled to obtain a core-shell structured ternary cathode material.

[0062] Comparative Example 4 This comparative example provides a core-shell structured ternary cathode material, the preparation method of which includes the following steps: S1, as described in S1 of Example 1; S2, in accordance with the method of S2 in Example 1; S3, in accordance with the method of S3 in Example 1; S4 follows the same procedure as S4 in Example 1, except that 100g of the matrix, 1.8g of NbF5, and 500mL of anhydrous ethanol are mixed to obtain a core-shell structured ternary cathode material.

[0063] Test case The compaction density was determined using a powder compactor under a pressure of 17 kN. The residual alkali content was determined using an automatic titrator; Specific surface area was determined using the BET nitrogen adsorption method; The test results are shown in Table 1; Table 1

[0064] Preparation method of CR2032 button cell: The materials (core-shell structure ternary cathode material or ternary cathode material) obtained in the examples and comparative examples are used as cathode active materials. Cathode active materials, conductive carbon black, and polyvinylidene fluoride are weighed at a mass ratio of 96:2:2. Polyvinylidene fluoride and 3.5 mL of N-methylpyrrolidone (NMP) are stirred for 30 minutes. Cathode active materials and conductive carbon black are added, and the mixture is stirred at 800 rpm for 240 minutes to obtain a cathode slurry with a solid content of 48%. The slurry is coated on a 20 μm aluminum foil (wet film 150 μm) and vacuum dried at 110℃ for 12 hours. It is then compacted to 3.55 g / cm³ using a roller mill at 120 MPa. 3 Punch-cut discs with a diameter of 14mm (active ingredient loading 9mg / cm³) 2 Using lithium metal sheets as the counter electrode and Celgard 2400 as the separator, the electrolyte was a 1 mol / L LiPF6 mixed solution of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), with a volume ratio of EC, EMC, and DEC of 1:1:1 and an injection volume of 80 μL. The CR2032 coin cell was assembled in an argon glove box, and after standing for 24 hours, it was tested in the Blue Electric CT3001 system. Test method for charge and discharge capacity: At 25℃, charge the battery to 4.5V at a rate of 0.1C to obtain the initial charge specific capacity at 0.1C; then discharge it to 3.0V at a rate of 0.1C to obtain the initial discharge specific capacity at 0.1C. Initial coulombic efficiency = (initial discharge capacity / initial charge capacity) × 100%; The capacity retention rate test method is as follows: At 25℃, the battery is charged to 4.5V at a rate of 1C, and then discharged to 3.0V at a rate of 1C, for 500 cycles. The capacity retention rate on the 500th cycle is calculated as (500th discharge capacity / 1st discharge capacity) × 100%. The test results are shown in Table 2; Table 2

[0065] Comparing Example 1 and Comparative Example 1, it can be seen that Comparative Example 1 uses a traditional homogeneous precursor without a core-shell differentiated design, while Example 1 constructs a core-shell structure through two-step co-precipitation. The core provides structural support, and the shell optimizes interface compatibility, effectively suppressing lattice phase transitions and electrolyte erosion under high voltage. The core-shell structure precursor can significantly improve the overall performance of ternary cathode materials.

[0066] A comparison of Example 1 and Comparative Example 2 shows that stepwise doping with tantalum and cesium is superior to traditional homogeneous doping with aluminum and magnesium. Comparative Example 2, which uses aluminum and magnesium doping, cannot simultaneously achieve lattice strengthening and ion conduction; Example 1, which uses stepwise doping with tantalum and cesium, demonstrates that tantalum doping stabilizes the lattice framework and suppresses phase transitions, while cesium doping widens lithium diffusion channels and increases migration rate, resulting in more uniform doping dispersion and significantly improved discharge specific capacity and cycle stability.

[0067] A comparison of Example 1 and Comparative Example 3 shows that the LiF and NbF5 dual-fluorine source coating can significantly reduce interfacial side reactions and improve cycle retention. Comparative Example 3 did not undergo coating treatment, and the material surface had no protective layer; Example 1, through dual-fluorine source synergistic coating, LiF optimizes interfacial impedance and improves initial coulombic efficiency, while NbF5 inhibits transition metal dissolution and electrolyte decomposition. The coating layer is firmly bonded and not easily peeled off, resulting in a significant reduction in residual alkali and a substantial improvement in cycle life; a comparison of Example 1 and Comparative Example 4 shows that the LiF and NbF5 dual-fluorine coating effect is better than NbF5 coating alone.

[0068] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a core-shell structured ternary cathode material, characterized in that, The preparation method includes the following steps: S1, the first nickel source, the first cobalt source, the first manganese source and the first solvent are mixed to obtain a core solution; a precipitant and a complexing agent are added to carry out the first reaction to obtain a core-containing system; S2, the second nickel source, the second cobalt source, the second manganese source, and the second solvent are mixed to obtain a shell solution; the core-containing system and the shell solution are mixed to carry out a second reaction to obtain a core-shell precursor; S3, mix the core-shell precursor and lithium source, add tantalum source for mixing i, add cesium source for mixing ii, and perform the first sintering to obtain the matrix; S4, the matrix, LiF, NbF5 and the third solvent are mixed and sintered for a second time to obtain a core-shell structured ternary cathode material.

2. The preparation method according to claim 1, characterized in that, The first nickel source contains Ni, the first cobalt source contains Co, and the first manganese source contains Mn, satisfying Ni:Co:Mn=60:(5-30):(10-35); optionally, Ni:Co:Mn=60:(10-20):(20-30); And / or, the total concentration of metal ions in the nucleus solution is 1-5 mol / L; And / or, prepare a precipitant solution with a concentration of 1-5 mol / L by adding water to the precipitant; Optionally, the flow rate of the precipitant solution is 1-10 mL / min; And / or, prepare a complexing agent solution with a concentration of 0.5-5 mol / L by adding water to the complexing agent; Optionally, the flow rate of the complexing agent solution is 1-10 mL / min; Optionally, the precipitant solution and the complexing agent solution are added in parallel flow.

3. The preparation method according to claim 1 or 2, characterized in that, The Ni in the second nickel source, the Co in the second cobalt source, and the Mn in the second manganese source satisfy the condition Ni:Co:Mn=60:(5-30):(10-35); optionally, Ni:Co:Mn=60:(10-20):(20-30); And / or, the total concentration of metal ions in the shell solution is 1-5 mol / L; And / or, add a shell solution to the nucleus-containing system, wherein the flow rate of the shell solution is 1-10 mL / min.

4. The preparation method according to any one of claims 1-3, characterized in that, The total molar amount of metal elements in the core-shell precursor and the molar ratio of lithium elements in the lithium source are 1:(1-1.1). And / or, the total molar amount of metal elements in the core-shell precursor and the molar ratio of tantalum elements in the tantalum source are 1:(0.0003-0.0008), or optionally 1:(0.0004-0.0006); And / or, the tantalum source includes at least one of tantalum pentachloride, tantalum pentoxide, lithium tantalate, tantalum ethoxide, tantalum isopropoxide, tantalum oxalate, tantalum fluoride, and tantalum nitrate; And / or, the total molar amount of metal elements in the core-shell precursor and the molar ratio of cesium elements in the cesium source are 1:(0.0004-0.001), or optionally 1:(0.0006-0.0008); And / or, the cesium source includes at least one of cesium nitrate, cesium carbonate, cesium chloride, cesium hydroxide, cesium acetate, cesium sulfate, and cesium oxalate.

5. The preparation method according to any one of claims 1-4, characterized in that, The mass ratio of the matrix to LiF is 100:(0.5-1.5), and can be optionally 100:(0.6-0.8); And / or, the mass ratio of the matrix to NbF5 is 100:(0.5-1.5), optionally 100:(0.8-1.0); And / or, the ratio of the matrix to the third solvent is 100g:(300-800)mL.

6. The preparation method according to any one of claims 1-5, characterized in that, The conditions for the first reaction include: a temperature of 50-60℃, a pH of 10-12, a stirring speed of 100-500 rpm, and a time of 5-10 hours. And / or, the conditions for the second reaction include: a temperature of 50-60°C, a pH of 10-12, a stirring speed of 100-500 rpm, and a time of 5-10 hours; And / or, the conditions for mixing i include: mixing at a speed of 300-500 rpm for 10-20 minutes; And / or, the conditions for mixing ii include: mixing at a speed of 300-500 rpm for 30-120 minutes.

7. The preparation method according to any one of claims 1-6, characterized in that, The first sintering includes primary sintering and secondary sintering; Optionally, the conditions for the first sintering include: heating to 500-650°C at a rate of 1-5°C / min and holding for 6-8 hours; or, optionally, heating to 600-620°C. Optionally, the conditions for the secondary sintering include: heating to 900-1100℃ at a rate of 6-10℃ / min and holding for 10-12 hours; or, optionally, heating to 900-1000℃.

8. The preparation method according to any one of claims 1-7, characterized in that, The conditions for the second sintering include: heating to 300-600℃ at a rate of 1-3℃ / min and holding for 4-6 hours; optionally, heating to 400-500℃.

9. A core-shell structured ternary cathode material prepared by the preparation method of the core-shell structured ternary cathode material according to any one of claims 1-8.

10. A secondary battery, characterized in that, The secondary battery includes a core-shell ternary cathode material prepared by any one of the preparation methods of claims 1-8 or the core-shell ternary cathode material of claim 9.

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