Preparation method of ternary positive electrode material, ternary positive electrode material and application

Abstract

The invention discloses a preparation method of a ternary positive electrode material, the ternary positive electrode material and application, and relates to the technical field of lithium ion batteries. Through in-situ construction of a core-shell / gradient structure, surface side reactions are inhibited, high capacity characteristics are maintained, and energy density and cycling stability are both considered. Through nanopore channels are constructed in single crystal particles, particle cracking is inhibited, and the rate capability is improved; through plasma treatment, lithium ion de-intercalation active sites are increased, the wettability of an electrolyte is improved, interface contact is optimized, and the reaction kinetics performance is improved; boron / phosphorus-containing functional molecules are introduced to react with surface residual lithium, a stable CEI film containing components such as Li3PO4 and LiF is generated in situ, interface side reaction is inhibited, interface stability is improved, and metal impurities are not introduced. The energy density, the cycling stability and the rate capability of the material can be considered at the same time through the preparation processes of core-shell gradient structure construction, nanopore modification, surface defect regulation and control modification and surface coating modification.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a preparation method of a ternary positive electrode material, the ternary positive electrode material and application. BACKGROUND

[0002] With the wide application of lithium ion batteries in the fields of new energy vehicles, energy storage devices and the like, the market requirements for energy density, cycle stability and rate performance of the lithium ion batteries are continuously improved. Single-crystal 6-system ternary positive electrode materials (such as LiNi 0.6 Co 0.1 Mn 0.3 O2) have become one of the current mainstream positive electrode materials due to the high nickel content, excellent specific capacity and structural stability.

[0003] In the prior art, the modification of the single-crystal 6-system ternary positive electrode material mainly includes doping and coating: (1) Doping modification: by introducing metal elements such as Al, Zr and La to adjust the lattice structure of the material, the volume expansion in the charging and discharging process is inhibited, but the element doping uniformity is difficult to control, which may cause local lattice distortion, and the inhibition effect on the surface side reaction of the material is limited.

[0004] (2) Coating modification: coating an inert or ion conductive layer such as Al2O3 and WO3 on the surface of the material to reduce the direct contact between the material and the electrolyte, but the coating layer is prone to cracking and falling off, and cannot continuously play a protective role after long-term cycling, and meanwhile, some coating layers may hinder the diffusion of lithium ions, reducing the rate performance of the material.

[0005] In summary, the conventional modification methods are difficult to simultaneously consider the energy density, cycle stability and rate performance of the material, and the long-term effect of the modification effect is insufficient, which cannot meet the application requirements of high-power and long-life lithium ion batteries.

[0006] In view of this, the present application is proposed. SUMMARY

[0007] The present application aims to provide a preparation method of a ternary positive electrode material, the ternary positive electrode material and application, and aims to prepare a ternary positive electrode material considering the energy density, cycle stability and rate performance.

[0008] The present application is realized as follows: In a first aspect, the present application provides a preparation method of a ternary positive electrode material, comprising: Core-shell gradient structure construction: a core-shell structure precursor with a low-nickel shell layer and a high-nickel core layer is prepared by a co-precipitation method, and the core-shell structure precursor is calcined with a lithium source to obtain a core-shell structure ternary positive electrode material base material; Nanopore modification: Mix and calcine a core-shell structured ternary cathode material substrate with a pore-forming template agent to prepare a ternary cathode material containing nanopores; Surface defect regulation modification: Plasma treatment is performed on ternary cathode materials containing nanopores to obtain surface-modified ternary cathode materials; Surface coating modification: The surface-modified ternary cathode material, boron-phosphorus functional molecules and solvent are mixed to obtain a mixed slurry, which is then dried and calcined.

[0009] In an optional implementation, the preparation process of the core-shell structure precursor includes: A low-nickel shell precursor with a particle size of 5µm-10µm was prepared by reacting a low-nickel, high-manganese metal salt solution with a precipitant and a complexing agent. A high-nickel core precursor with a particle size of 15µm-20µm was prepared by reacting a high-nickel metal salt solution with a precipitant and a complexing agent. The high-nickel core precursor, water, and polyvinylpyrrolidone were mixed and stirred to obtain a high-nickel precursor mixture. The low-nickel shell precursor and water were mixed and stirred to obtain a low-nickel precursor mixture. The high-nickel precursor mixture was poured into the low-nickel precursor mixture, stirred, and then the solid and liquid were separated to obtain a core-shell structured precursor. The molar ratio of nickel, cobalt, and manganese in the low-nickel, high-manganese metal salt solution was (0.3-0.5):0.1:(0.2-0.4), and the molar ratio of nickel, cobalt, and manganese in the high-nickel metal salt solution was (0.7-0.9):0.1:(0.1-0.3). When preparing the core-shell structure precursor, the molar ratio of the low-nickel shell precursor to the high-nickel core precursor was controlled to be 1:(0.9-1.1). The concentration of polyvinylpyrrolidone in the system after mixing the high-nickel precursor mixture and the low-nickel precursor mixture was 0.01 mmol / L - 0.03 mmol / L.

[0010] In an optional embodiment, during the preparation of the low-nickel shell precursor, the reaction pH is controlled to be 10.4-10.8, the amount of ammonia solution added as a complexing agent is adjusted so that the ammonia concentration is 4-5 g / L, the reaction temperature is 50℃-60℃, and the reaction time is 1h-2h. And / or, in the process of preparing the core layer high nickel precursor, the reaction pH is controlled to be 11.6-12.0, the amount of complexing agent ammonia solution added is adjusted so that the ammonia concentration is 6-7 g / L, the reaction temperature is 50℃-60℃, and the reaction time is 2h-3h; And / or, when preparing a high-nickel precursor mixture, control the stirring speed at 900 rpm-1100 rpm and the stirring time at 40 min-100 min; when preparing a low-nickel precursor mixture, control the stirring speed at 400 rpm-800 rpm and the stirring time at 20 min-40 min; after the high-nickel precursor mixture is poured into the low-nickel precursor mixture, control the stirring speed at 700 rpm-900 rpm and the stirring time at 30 min-60 min.

[0011] In an optional embodiment, the core-shell structure precursor and the lithium source are mixed at a molar ratio of lithium to total nickel, cobalt and manganese of (1.05-1.10):1, and calcined in an oxygen-containing atmosphere, with the calcination temperature controlled at 750℃-850℃ and the calcination time at 10h-12h.

[0012] In an optional embodiment, the pore-forming template agent used in the nanopore modification process is selected from at least one of ammonium bicarbonate, magnesium carbonate, and sodium bicarbonate. And / or, the mass ratio of the core-shell structure ternary cathode material substrate to the pore-forming template agent is 1:(0.2-0.5); And / or, during the calcination process with the pore-forming template agent, the calcination temperature is controlled at 400℃-500℃ and the calcination time is 3h-5h. After calcination, the product is washed and dried.

[0013] In an optional implementation, during plasma treatment, the plasma power is controlled to be 100W-300W and the treatment time is 5min-15min. And / or, during plasma treatment, the gas introduced is an inert gas or a mixture of inert gas and oxygen, and the gas pressure is adjusted to 0.1 Pa - 0.5 Pa.

[0014] In an optional embodiment, the boron-containing phosphorus functional molecule used in the surface coating modification process is selected from at least one of 2,5-thiophene diboronic acid, hydroxypropyl distarch phosphoric acid, and 2,5-thiophene diphosphate. And / or, the mass ratio of surface-modified ternary cathode material to boron-phosphorus functional molecules is 1:(0.01-0.05). And / or, the mixed slurry is dried at 80℃-100℃ for 12h-24h, and then calcined at 300℃-400℃ in an inert atmosphere for 2h-4h.

[0015] Secondly, the present invention provides a ternary cathode material, which is prepared by any of the preparation methods described in the foregoing embodiments.

[0016] Thirdly, the present invention provides a positive electrode sheet comprising the ternary positive electrode material of the aforementioned embodiments.

[0017] Fourthly, the present invention provides a lithium-ion battery, including the positive electrode sheet of the aforementioned embodiments.

[0018] This invention has the following beneficial effects: Through a preparation process involving core-shell gradient structure construction, nanopore modification, surface defect regulation modification, and surface coating modification, this invention can simultaneously achieve optimal energy density, cycle stability, and rate performance of the material. Specifically: By constructing a core-shell / gradient structure in situ, elemental distribution can be regulated. The shell (low nickel and high manganese) provides structural stability and suppresses surface side reactions; the core (high nickel) maintains high capacity characteristics, balancing energy density and cycle stability; the elemental gradient transition structure facilitates lithium-ion diffusion and eliminates the risk of coating peeling.

[0019] By constructing interconnected nanopores within single-crystal particles, a buffer space for volume changes is provided, cyclic stress is alleviated, and particle cracking is inhibited; at the same time, the specific surface area is increased, the lithium-ion adsorption and diffusion capacity is enhanced, and the rate performance is improved.

[0020] By using plasma treatment, the type and density of surface defects can be precisely controlled, increasing the active sites for lithium ion insertion / extraction, improving electrolyte wettability, optimizing interfacial contact, and enhancing reaction kinetics.

[0021] Boron / phosphorus functional molecules are introduced to react with residual lithium on the surface (such as LiOH and Li2CO3) to generate a stable CEI film containing components such as Li3PO4 and LiF in situ. This suppresses interfacial side reactions, improves interfacial stability, and does not introduce metal impurities. Attached Figure Description

[0022] 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.

[0023] Figure 1 This provides a comparison of the cycle performance of the cathode materials for the embodiments and comparative examples of the present invention. Detailed Implementation

[0024] 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.

[0025] This invention provides a method for preparing a ternary cathode material. The preparation process, which involves core-shell gradient structure construction, nanopore modification, surface defect regulation modification, and surface coating modification, can simultaneously ensure the material's energy density, cycle stability, and rate performance.

[0026] The following sections explain each step: S1. Construction of core-shell gradient structure: A core-shell structure precursor with a low-nickel shell and a high-nickel core was prepared by co-precipitation. The core-shell structure precursor was then calcined with a lithium source to obtain a core-shell structure ternary cathode material substrate.

[0027] In some embodiments, the preparation process of the core-shell structure precursor includes: (1) using a low-nickel high-manganese metal salt solution to react with a precipitant and a complexing agent, and then filtering to prepare a low-nickel shell precursor with a particle size of 5µm-10µm; wherein the molar ratio of nickel, cobalt and manganese in the low-nickel high-manganese metal salt solution is (0.3-0.5):0.1:(0.2-0.4). (2) A high-nickel core precursor with a particle size of 15µm-20µm was prepared by mixing a high-nickel metal salt solution with a precipitant and a complexing agent. The molar ratio of nickel, cobalt and manganese in the high-nickel metal salt solution was (0.7-0.9):0.1:(0.1-0.3). (3) The high-nickel core precursor, water and polyvinylpyrrolidone were mixed and stirred to obtain a high-nickel precursor mixture. The low-nickel shell precursor and water were mixed and stirred to obtain a low-nickel precursor mixture. The high-nickel precursor mixture was poured into the low-nickel precursor mixture, and after stirring, the solid and liquid were separated to obtain a core-shell structure precursor. When preparing the core-shell structure precursor, the molar ratio of the low-nickel shell precursor and the high-nickel core precursor was controlled to be 1:(0.9-1.1). The concentration of polyvinylpyrrolidone in the system after mixing the high-nickel precursor mixture and the low-nickel precursor mixture was 0.01mmol / L-0.03mmol / L.

[0028] It should be noted that PVP is a polar polymer containing a highly polar pyrrolidone ring (C=O group), which can selectively adsorb onto different crystal faces of nanoparticles through coordination, serving as the basic template for constructing the core-shell structure. In addition, PVP has a long-chain structure, which can form a "polymer brush"-like protective layer on the particle surface in solution, preventing particle agglomeration. This stable colloidal environment is conducive to the uniform deposition of the subsequent second component (shell material) on its surface, achieving controllable coating.

[0029] Specifically, the particle size of the low-nickel shell precursor can be 5µm, 6µm, 7µm, 8µm, 9µm, 10µm, etc. The particle size of the high-nickel core precursor can be 15µm, 16µm, 17µm, 18µm, 19µm, 20µm, etc. The molar ratio of nickel, cobalt, and manganese in the low-nickel high-manganese metal salt solution is (0.3-0.5):0.1:(0.2-0.4), for example, 0.4:0.1:0.4; the molar ratio of nickel, cobalt, and manganese in the high-nickel metal salt solution is (0.7-0.9):0.1:(0.1-0.3), for example, 0.8:0.1:0.2. When the low-nickel shell precursor and the high-nickel core precursor are mixed, the molar ratio is controlled to be 1:(0.9-1.1), such as 1:1. By mixing the prepared low-nickel shell precursor and high-nickel core precursor in a specific molar ratio, a product with a nickel-cobalt-manganese molar ratio close to that of the 613 series can be obtained. The concentration of polyvinylpyrrolidone in the system after mixing the high-nickel precursor mixture and the low-nickel precursor mixture can be 0.01 mmol / L, 0.02 mmol / L, 0.03 mmol / L, etc.

[0030] Furthermore, in the preparation of the low-nickel shell precursor, a low-nickel high-manganese metal salt solution and a precipitant (sodium hydroxide solution) are introduced into the bottom liquid of the reactor for reaction, while a complexing agent (ammonia solution) is added to control the ammonia concentration to meet the requirements. During the reaction, the pH value is controlled at 10.4-10.8 (e.g., 10.4, 10.5, 10.6, 10.7, 10.8, etc.), the ammonia concentration is 4-5 g / L (e.g., 4.0 g / L, 4.3 g / L, 4.5 g / L, 4.8 g / L, 5.0 g / L, etc.), the reaction temperature is 50℃-60℃, and the reaction time is 1h-2h. The particle size of the precursor obtained after the reaction is controlled by adjusting the introduction rate. Specifically, the reaction temperature can be 50℃, 53℃, 55℃, 58℃, 60℃, etc.; the reaction time can be 1.0h, 1.3h, 1.5h, 1.8h, 2.0h, etc.

[0031] Furthermore, in the preparation of the high-nickel core precursor, a high-nickel metal salt solution and a precipitant (sodium hydroxide solution) are introduced into the bottom liquid of the reactor for reaction, while a complexing agent (ammonia solution) is added to control the ammonia concentration to meet the requirements. During the reaction, the pH value is controlled at 11.6-12.0 (e.g., 11.6, 11.7, 11.8, 11.9, 12.0, etc.), the ammonia concentration is 6-7 g / L (e.g., 6.0 g / L, 6.3 g / L, 6.5 g / L, 6.8 g / L, 7.0 g / L, etc.), the reaction temperature is 50℃-60℃, and the reaction time is 2h-3h. The particle size of the precursor obtained after the reaction is controlled by adjusting the introduction rate. Specifically, the reaction temperature can be 50℃, 53℃, 55℃, 58℃, 60℃, etc.; the reaction time can be 2.0h, 2.3h, 2.5h, 2.8h, 3.0h, etc.

[0032] Furthermore, when preparing the high-nickel precursor mixture, the stirring speed is controlled at 900 rpm-1100 rpm (e.g., 900 rpm, 1000 rpm, 1100 rpm, etc.), and the stirring time is 40 min-100 min (e.g., 40 min, 60 min, 80 min, 100 min, etc.); when preparing the low-nickel precursor mixture, the stirring speed is controlled at 400 rpm-800 rpm (e.g., 400 rpm, 600 rpm, 800 rpm, etc.), and the stirring time is 20 min-40 min (e.g., 20 min, 30 min, 40 min, etc.); after the high-nickel precursor mixture is poured into the low-nickel precursor mixture, the stirring speed is controlled at 700 rpm-900 rpm (e.g., 700 rpm, 800 rpm, 900 rpm, etc.), and the stirring time is 30 min-60 min (e.g., 30 min, 40 min, 50 min, 60 min, etc.).

[0033] Furthermore, the core-shell structure precursor and lithium source are mixed at a molar ratio of lithium to nickel, cobalt, and manganese of (1.05-1.10):1, and calcined in an oxygen-containing atmosphere. The calcination temperature is controlled at 750℃-850℃, and the calcination time is 10h-12h to obtain a gradient core-shell structured single-crystal 6-series ternary cathode material. The calcination atmosphere can be a pure oxygen atmosphere, but is not limited to this.

[0034] Specifically, the lithium source can be Li₂CO₃ or lithium hydroxide, etc. The molar ratio Li / (Ni+Co+Mn) can be 1.05:1, 1.06:1, 1.07:1, 1.08:1, 1.09:1, 1.10:1, etc. The calcination temperature can be 750℃, 780℃, 800℃, 820℃, 850℃, etc., and the calcination time can be 10h, 11h, 12h, etc.

[0035] It should be noted that traditional coatings are made of exogenous inert or conductive materials, which suffer from problems such as peeling, cracking, and hindered ion diffusion. This invention achieves elemental distribution control by constructing a core-shell / gradient structure in situ. The shell (low nickel, high manganese) provides structural stability and suppresses surface side reactions; the core (high nickel) maintains high capacity characteristics, balancing energy density and cycle stability. The elemental gradient transition structure facilitates lithium-ion diffusion and eliminates the risk of coating peeling.

[0036] S2, Nanopore Modification A ternary cathode material with a core-shell structure is mixed with a pore-forming template agent and calcined to decompose the template agent and generate gas, forming nanopores inside the material, thus preparing a ternary cathode material with nanopores.

[0037] In some embodiments, during the nanopore modification process, the pore-forming template agent used is selected from at least one of ammonium bicarbonate, magnesium carbonate, and sodium bicarbonate; the pore-forming template agent can be any one or more of the above. The mass ratio of the core-shell ternary cathode material substrate to the pore-forming template agent is 1:(0.2-0.5), such as 1:0.2, 1:0.3, 1:0.4, 1:0.5, etc. The mixing method of the core-shell ternary cathode material substrate and the pore-forming template agent is not limited; they can be mixed uniformly by grinding.

[0038] Furthermore, during the calcination process with the pore-forming template agent, the calcination temperature is controlled at 400℃-500℃, such as 400℃, 430℃, 450℃, 480℃, 500℃, etc.; the calcination time is 3h-5h, such as 3h, 4h, 5h, etc. The calcination atmosphere can be air. After calcination, the material is washed and dried. Washing can be done with deionized water to remove residual template agent; the drying method is not limited, and vacuum drying can be used to thoroughly remove moisture.

[0039] It should be noted that traditional modification methods do not consider the internal stress release mechanism of the material, making it prone to particle cracking during cycling. This invention constructs interconnected nanopores within single-crystal particles, providing a buffer space for volume changes, alleviating cyclic stress, and inhibiting particle cracking; simultaneously, it increases the specific surface area, enhances lithium-ion adsorption and diffusion capabilities, and improves rate performance.

[0040] S3, Surface Defect Control Modification The ternary cathode material containing nanopores is placed in a plasma treatment device and subjected to plasma treatment to obtain a surface-modified ternary cathode material.

[0041] In some embodiments, a gas is introduced into a plasma processing device, the gas pressure is adjusted to 0.1 Pa-0.5 Pa, the plasma power is set to 100 W-300 W, and the processing time is 5 min-15 min. The surface defect density of the material is controlled by plasma bombardment. After processing, the material is naturally cooled to room temperature to obtain a ternary cathode material with optimized surface defects. The introduced gas can be an inert gas or a mixture of inert gas and oxygen. The type of inert gas is not limited, such as argon.

[0042] Specifically, the gas pressure can be 0.1Pa, 0.2Pa, 0.3Pa, 0.4Pa, 0.5Pa, etc.; the plasma power can be 100W, 150W, 200W, 250W, 300W, etc.; and the processing time can be 5min, 8min, 10min, 12min, 15min, etc.

[0043] It should be noted that existing technologies do not pay enough attention to the regulation of surface defects, resulting in low utilization of active sites. This invention uses low-temperature plasma treatment to precisely regulate the type and density of surface defects, increase lithium-ion insertion / extraction active sites, improve electrolyte wettability, optimize interfacial contact (enhancing interfacial reactivity), and improve reaction kinetics performance.

[0044] S4, Surface coating modification The surface-modified ternary cathode material, boron-phosphorus functional molecules, and solvent are mixed and stirred to form a uniform slurry. The solvent is then removed by drying, allowing the boron-phosphorus functional molecules to be uniformly adsorbed on the surface of the cathode material. The dried material is then calcined to allow the boron-phosphorus functional molecules to react with residual lithium (LiOH, Li2CO3) on the surface, generating a stable CEI film containing components such as Li3PO4 and LiF in situ.

[0045] In some embodiments, during the surface coating modification process, the boron-containing phosphorus functional molecule used is selected from at least one of 2,5-thiophene diboronic acid, hydroxypropyl distarch phosphoric acid, and 2,5-thiophene diphosphate. The boron-containing phosphorus functional molecule used can be any one or more of these. Taking 2,5-thiophene diboronic acid as an example, after calcination, it reacts with residual lithium (LiOH, Li₂CO₃) on the surface to generate lithium 2,5-thiophene diboronic acid in situ.

[0046] The mass ratio of the surface-modified ternary cathode material to the boron-phosphorus functional molecule is 1:(0.01-0.05), such as 1:0.01, 1:0.02, 1:0.03, 1:0.04, 1:0.05, etc. The type of solvent is not limited; for example, N-methylpyrrolidone (NMP) can be used, and its amount is not limited, as long as a uniform slurry can be formed.

[0047] Further, the mixed slurry is dried at 80℃-100℃ for 12h-24h to fully remove the dispersant; then it is calcined at 300℃-400℃ in an inert atmosphere for 2h-4h to form a stable CEI film. Specifically, the drying temperature can be 80℃, 85℃, 90℃, 95℃, 100℃, etc.; the drying time can be 12h, 15h, 18h, 20h, 22h, 24h, etc.; the inert atmosphere can be argon, but is not limited to it. The calcination temperature can be 300℃, 330℃, 350℃, 380℃, 400℃, etc.; the calcination time can be 2h, 3h, 4h, etc.

[0048] It should be noted that existing technologies mostly employ metal doping, which primarily acts on the bulk structure and has limited ability to suppress surface side reactions. This invention introduces boron / phosphorus functional molecules that react with residual lithium on the surface (such as LiOH and Li2CO3) to generate a stable CEI film containing components such as Li3PO4 and LiF in situ, suppressing interfacial side reactions, improving interfacial stability, and without introducing metal impurities.

[0049] This invention provides a ternary cathode material, which is prepared by the preparation method provided in this invention. This ternary cathode material can balance the energy density, cycle stability and rate performance of the material, and the modification effect has a long-lasting effect, which can meet the application requirements of high-power and long-life lithium-ion batteries.

[0050] This invention provides a positive electrode sheet, including a ternary positive electrode material provided in this invention, with the ternary positive electrode material as the positive electrode active material, and a positive electrode active coating is formed on the positive electrode current collector.

[0051] This invention provides a lithium-ion battery, including the aforementioned positive electrode, and may also include a negative electrode, electrolyte, separator, etc., assembled into a lithium-ion battery product using conventional assembly methods. During the first charge and discharge process after assembly, lithium 2,5-thiophene dihydroboronic acid undergoes in-situ electrochemical oxidative decomposition to form a stable CEI film.

[0052] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0053] Example 1 This embodiment provides a method for preparing a ternary cathode material, the steps of which are as follows: 1. Core-shell / gradient structure construction (1) Preparation of low-nickel shell precursor Nickel nitrate, cobalt nitrate, and manganese nitrate were mixed in a nickel-cobalt-manganese molar ratio of 0.4:0.1:0.4 to obtain a low-nickel, high-manganese metal salt solution with a total nickel-cobalt-manganese concentration of 0.9 mol / L. A 4 mol / L sodium hydroxide aqueous solution was used as a precipitant, and a 0.4 mol / L ammonia aqueous solution was used as a complexing agent.

[0054] Water, precipitant, and complexing agent were mixed in a reactor to obtain a base solution with a pH of 10.7 and an ammonia concentration of 4.8 g / L. The mixture was heated to 55 °C, and a low-nickel, high-manganese metal salt solution, precipitant, and complexing agent were introduced into the base solution. The introduction rate of the low-nickel, high-manganese metal salt solution was controlled at 10 mL / s. The pH during the reaction was 10.6, and the ammonia concentration was 4.5 g / L. The reaction was carried out for 1.5 h, followed by filtration and aging at 50 °C for 3 h to obtain a shell-type low-nickel precursor with a particle size D50 of 8 µm.

[0055] (2) Preparation of high-nickel core precursor Nickel nitrate, cobalt nitrate, and manganese nitrate were mixed in a nickel-cobalt-manganese molar ratio of 0.8:0.1:0.2 to obtain a high-nickel metal salt solution with a total nickel-cobalt-manganese concentration of 1.1 mol / L. A 4 mol / L sodium hydroxide aqueous solution was used as a precipitant, and a 0.5 mol / L ammonia aqueous solution was used as a complexing agent.

[0056] Water, precipitant, and complexing agent were mixed in a reactor to obtain a base solution with a pH of 11.9 and an ammonia concentration of 6.8 g / L. The mixture was heated to 55 °C, and a high-nickel metal salt solution, precipitant, and complexing agent were introduced into the base solution. The introduction rate of the high-nickel metal salt solution was controlled at 10 mL / s. During the reaction, the pH was 11.8, the ammonia concentration was 6.5 g / L, and the reaction was carried out for 2.5 h. After filtration, the mixture was aged at 50 °C for 3 h to obtain a core-layer high-nickel precursor with a particle size D50 of 18 µm.

[0057] (3) Preparation of core-shell structure precursors Mix 1 mol of high-nickel precursor with 50 mL of deionized water, add 0.002 mmol of PVP (polyvinylpyrrolidone), and stir at 1000 rpm for 1 h to ensure that PVP is fully and uniformly distributed on the surface of the high-nickel ternary precursor, thus obtaining a high-nickel precursor mixture. Mix 1 mol of low-nickel precursor with 50 mL of deionized water, stir at 600 rpm for 30 min, and mix thoroughly to obtain a low-nickel precursor mixture. Then slowly pour the high-nickel precursor mixture into the low-nickel precursor mixture, stir at 800 rpm for 40 min, filter, and dry to obtain a core-shell structured ternary precursor.

[0058] (4) Roasting The core-shell structure precursor was mixed with Li2CO3 at a molar ratio of Li / (Ni+Co+Mn)=1.07 and calcined at 800℃ for 11 h in an oxygen atmosphere to obtain a gradient core-shell structured single crystal 6-system ternary cathode material.

[0059] 2. Nanopore modification The ternary cathode material obtained in step 1 was mixed with the template agent ammonium bicarbonate at a mass ratio of 1:0.3 and ground until homogeneous. The mixture was calcined in air at 450°C for 4 hours to decompose the template agent and generate gas, forming nanopores inside the material. The calcined material was washed with deionized water to remove residual template agent, and then vacuum dried to obtain a single-crystal 6-series ternary cathode material containing nanopores.

[0060] 3. Surface defect control and modification The ternary cathode material obtained in step 2 was placed in a plasma treatment device, argon gas was introduced, the gas pressure was adjusted to 0.3 Pa, the plasma power was set to 200 W, the treatment time was 10 min, and after the treatment was completed, it was naturally cooled to room temperature to obtain a ternary cathode material with optimized surface defects.

[0061] 4. Surface coating modification In step 3, the ternary cathode material, 2,5-thiophene diboronic acid, and N-methylpyrrolidone (NMP) were mixed at a mass ratio of 1:0.03:2 and stirred for 40 min to form a uniform slurry. The slurry was then vacuum dried at 90 °C for 20 h to remove the solvent, allowing 2,5-thiophene diboronic acid to be uniformly adsorbed onto the surface of the cathode material. The dried material was then calcined at 350 °C for 3 h in argon atmosphere to allow the 2,5-thiophene diboronic acid to react with residual lithium (LiOH, Li₂CO₃) on the surface to generate lithium 2,5-thiophene dihydroboronic acid.

[0062] Example 2 This embodiment provides a method for preparing a ternary cathode material, the steps of which are as follows: 1. Core-shell / gradient structure construction (1) Preparation of low-nickel shell precursor Nickel nitrate, cobalt nitrate, and manganese nitrate were mixed in a nickel-cobalt-manganese molar ratio of 0.3:0.1:0.4 to obtain a low-nickel, high-manganese metal salt solution with a total nickel-cobalt-manganese concentration of 0.8 mol / L. A 4 mol / L sodium hydroxide aqueous solution was used as a precipitant, and a 0.4 mol / L ammonia aqueous solution was used as a complexing agent.

[0063] Water, precipitant, and complexing agent were mixed in a reactor to obtain a base solution with a pH of 10.6 and an ammonia concentration of 4.4 g / L. The mixture was heated to 50°C, and a low-nickel, high-manganese metal salt solution, precipitant, and complexing agent were introduced into the base solution. The introduction rate of the low-nickel, high-manganese metal salt solution was controlled at 10 mL / s. During the reaction, the pH was 10.4 and the ammonia concentration was 4 g / L. After filtration, the mixture was aged at 45°C for 2 hours to obtain a shell-type low-nickel precursor with a particle size D50 of 5 µm.

[0064] (2) Preparation of high-nickel core precursor Nickel nitrate, cobalt nitrate, and manganese nitrate were mixed in a nickel-cobalt-manganese molar ratio of 0.9:0.1:0.2 to obtain a high-nickel metal salt solution with a total nickel-cobalt-manganese concentration of 1.2 mol / L. A 4 mol / L sodium hydroxide aqueous solution was used as a precipitant, and a 0.4 mol / L ammonia aqueous solution was used as a complexing agent.

[0065] Water, precipitant, and complexing agent were mixed in a reactor to obtain a base solution with a pH of 11.8 and an ammonia concentration of 6.5 g / L. The mixture was heated to 50 °C, and a high-nickel metal salt solution, precipitant, and complexing agent were introduced into the base solution. The introduction rate of the high-nickel metal salt solution was controlled at 10 mL / s. During the reaction, the pH was 11.6 and the ammonia concentration was 6 g / L. After filtration, the mixture was aged at 45 °C for 2 h to obtain a core-layer high-nickel precursor with a particle size D50 of 15 µm.

[0066] (3) Preparation of core-shell structure precursors Mix 0.9 mol of high-nickel precursor with 50 mL of deionized water, add 0.001 mmol of PVP (polyvinylpyrrolidone), and stir at 900 rpm for 100 min to ensure that PVP is fully and evenly distributed on the surface of the high-nickel ternary precursor, thus obtaining a high-nickel precursor mixture. Mix 1 mol of low-nickel precursor with 50 mL of deionized water, and stir at 400 rpm for 40 min until homogeneous, thus obtaining a low-nickel precursor mixture. Then, slowly pour the high-nickel precursor mixture into the low-nickel precursor mixture, stir at 700 rpm for 60 min, filter, and dry to obtain a core-shell structured ternary precursor.

[0067] (4) Roasting The core-shell precursor was mixed with Li2CO3 at a molar ratio of Li / (Ni+Co+Mn)=1.05 and calcined at 750℃ for 12h in an oxygen atmosphere.

[0068] 2. Nanopore modification The ternary cathode material obtained in step 1 was mixed with the template agent ammonium bicarbonate at a mass ratio of 1:0.2 and ground until homogeneous. The mixture was calcined in air at 400°C for 5 hours to decompose the template agent and generate gas, forming nanopores inside the material. The calcined material was washed with deionized water to remove residual template agent and then vacuum dried.

[0069] 3. Surface defect control and modification The ternary cathode material obtained in step 2 was placed in a plasma treatment device, argon gas was introduced, the gas pressure was adjusted to 0.1 Pa, the plasma power was set to 100 W, the treatment time was 15 min, and after the treatment was completed, it was naturally cooled to room temperature to obtain a ternary cathode material with optimized surface defects.

[0070] 4. Surface coating modification The ternary cathode material, 2,5-thiophene diboronic acid, and N-methylpyrrolidone (NMP) from step 3 were mixed at a mass ratio of 1:0.01:1.9 and stirred for 40 min to form a uniform slurry. The slurry was then vacuum dried at 80 °C for 24 h to remove the solvent, allowing 2,5-thiophene diboronic acid to be uniformly adsorbed onto the surface of the cathode material. The dried material was then calcined at 300 °C for 4 h in argon atmosphere to allow the 2,5-thiophene diboronic acid to react with residual lithium (LiOH, Li₂CO₃) on the surface to generate lithium 2,5-thiophene dihydroboronic acid.

[0071] Example 3 This embodiment provides a method for preparing a ternary cathode material, the steps of which are as follows: 1. Core-shell / gradient structure construction (1) Preparation of low-nickel shell precursor Nickel nitrate, cobalt nitrate, and manganese nitrate were mixed in a nickel-cobalt-manganese molar ratio of 0.5:0.1:0.3 to obtain a low-nickel, high-manganese metal salt solution with a total nickel-cobalt-manganese concentration of 0.9 mol / L. A 4 mol / L sodium hydroxide aqueous solution was used as a precipitant, and a 0.4 mol / L ammonia aqueous solution was used as a complexing agent.

[0072] Water, precipitant, and complexing agent were mixed in a reactor to obtain a base solution with a pH of 10.8 and an ammonia concentration of 5 g / L. The mixture was heated to 60°C, and a low-nickel, high-manganese metal salt solution, precipitant, and complexing agent were introduced into the base solution. The introduction rate of the low-nickel, high-manganese metal salt solution was controlled at 10 mL / s. The pH during the reaction was 10.7, and the ammonia concentration was 4.9 g / L. After filtration, the mixture was aged at 55°C for 4 h to obtain a shell-type low-nickel precursor with a particle size D50 of 10 µm.

[0073] (2) Preparation of high-nickel core precursor Nickel nitrate, cobalt nitrate, and manganese nitrate were mixed in a nickel-cobalt-manganese molar ratio of 0.7:0.1:0.3 to obtain a high-nickel metal salt solution with a total nickel-cobalt-manganese concentration of 1.1 mol / L. A 4 mol / L sodium hydroxide aqueous solution was used as a precipitant, and a 0.4 mol / L ammonia aqueous solution was used as a complexing agent.

[0074] Water, precipitant, and complexing agent were mixed in a reactor to obtain a base solution with a pH of 12 and an ammonia concentration of 7 g / L. The mixture was heated to 60°C, and a high-nickel metal salt solution, precipitant, and complexing agent were introduced into the base solution at a rate of 10 mL / s. The pH during the reaction was 11.9, and the ammonia concentration was 6.9 g / L. After filtration, the mixture was aged at 55°C for 4 hours to obtain a core-layer high-nickel precursor with a particle size D50 of 20 µm.

[0075] (3) Preparation of core-shell structure precursors Mix 1.1 mol of high-nickel precursor with 50 mL of deionized water, add 0.003 mmol of PVP (polyvinylpyrrolidone), and stir at 1100 rpm for 40 min to ensure that PVP is fully and evenly distributed on the surface of the high-nickel ternary precursor, thus obtaining a high-nickel precursor mixture. Mix 1 mol of low-nickel precursor with 50 mL of deionized water, stir at 800 rpm for 20 min to ensure uniform mixing, thus obtaining a low-nickel precursor mixture. Then slowly pour the high-nickel precursor mixture into the low-nickel precursor mixture, stir at 900 rpm for 30 min, filter, and dry to obtain a core-shell structured ternary precursor.

[0076] (4) Roasting The core-shell precursor was mixed with Li2CO3 at a molar ratio of Li / (Ni+Co+Mn)=1.10 and calcined at 850℃ for 10h in an oxygen atmosphere.

[0077] 2. Nanopore modification The ternary cathode material obtained in step 1 was mixed with the template agent ammonium bicarbonate at a mass ratio of 1:0.5 and ground until homogeneous. The mixture was calcined at 500°C for 3 hours in air to decompose the template agent and generate gas, forming nanopores inside the material. The calcined material was washed with deionized water to remove residual template agent and then vacuum dried.

[0078] 3. Surface defect control and modification The ternary cathode material obtained in step 2 was placed in a plasma treatment device, argon gas was introduced, the gas pressure was adjusted to 0.5 Pa, the plasma power was set to 300 W, the treatment time was 5 min, and after the treatment was completed, it was naturally cooled to room temperature to obtain a ternary cathode material with optimized surface defects.

[0079] 4. Surface coating modification In step 3, the ternary cathode material, 2,5-thiophene diboronic acid, and N-methylpyrrolidone (NMP) were mixed at a mass ratio of 1:0.05:2.2 and stirred for 40 min to form a uniform slurry. The slurry was then vacuum dried at 100 °C for 12 h to remove the solvent, allowing 2,5-thiophene diboronic acid to be uniformly adsorbed onto the surface of the cathode material. The dried material was then calcined at 400 °C for 2 h in argon atmosphere to allow the 2,5-thiophene diboronic acid to react with residual lithium (LiOH, Li₂CO₃) on the surface to generate lithium 2,5-thiophene dihydroboronic acid.

[0080] Example 4 The only difference from Example 1 is that in step 4, the boron-containing phosphorus functional molecule is replaced with hydroxypropyl distarch phosphoric acid.

[0081] Example 5 The only difference from Example 1 is that in step 4, the boron-phosphorus functional molecule is replaced with 2,5-thiophene diphosphate.

[0082] Example 6 The only difference from Example 1 is that in step 4, only the amount of 2,5-thiophene diboronic acid added is changed, and the mass ratio of the ternary cathode material to 2,5-thiophene diboronic acid is 1:0.005.

[0083] Example 7 The only difference from Example 1 is that in step 4, only the amount of 2,5-thiophene diboronic acid added is changed, and the mass ratio of the ternary cathode material to 2,5-thiophene diboronic acid is 1:0.10.

[0084] Comparative Example 1 This embodiment provides a single-crystal LiNi 6-series ternary cathode material prepared by a conventional coprecipitation method. 0.6 Co 0.1 Mn 0.3 O2.

[0085] Comparative Example 2 The only difference from Example 1 is that step 1 is omitted, and the conventional single-crystal 6-series ternary cathode material of Comparative Example 1 is used instead. Steps 2-4 are the same as in Example 1.

[0086] Comparative Example 3 The only difference from Example 1 is that step 2 is not performed.

[0087] Comparative Example 4 The only difference from Example 1 is that step 3 is omitted.

[0088] Comparative Example 5 The only difference from Example 1 is that step 4 is replaced by a conventional coating method, specifically as follows: the ternary cathode material from step 3 and 2,5-thiophene diboronic acid are mixed at a mass ratio of 1:0.03 and thoroughly ground in a quartz pot for 40 minutes. The mixed and ground material is then calcined at 350°C for 3 hours in argon atmosphere to allow the 2,5-thiophene diboronic acid to react with residual lithium (LiOH, Li2CO3) on the surface, generating lithium 2,5-thiophene dihydroronic acid.

[0089] Experimental Example 1 The performance of the cathode material products prepared by the test examples and comparative examples is shown in Table 1.

[0090] Test Method: Electrochemical tests were performed on a battery performance testing system, with a test voltage range of 3.0V~4.3V. The battery was subjected to charge-discharge cycle testing at a discharge efficiency of 0.2C. After two weeks of cycles, it was discharged once at 0.5C / 3C, representing the 3C discharge capacity. Subsequently, it underwent a small current recovery cycle at 0.1C / 0.1C for one week, and finally, a 1000-cycle test was performed at 0.5C / 1C. The average value of each group was taken. The test results for the average initial discharge specific capacity, 3C discharge capacity, and room temperature cycle retention rate (i.e., 1000-cycle retention rate) are shown in Table 1 and [Table data would be inserted here]. Figure 1 .

[0091] Table 1 Performance test results of the cathode materials prepared in the examples and comparative examples

[0092] This invention optimizes the preparation process of ternary cathode materials, achieving the following effects: (1) Significantly improved cycling stability: The CEI film generated by the molecular engineering strategy of this invention can effectively inhibit electrolyte decomposition and transition metal ion dissolution. The core-shell / gradient structure reduces surface phase transition, and the nanopores alleviate volume expansion stress. According to the test, the modified material of this invention can retain more than 90% of its capacity after 1000 cycles at 0.5C / 1C rate, which is 20-30 percentage points higher than that of conventional materials (capacity retention rate of 60-70%).

[0093] (2) Rate performance optimization: Nanopores increase lithium-ion diffusion channels, surface defects provide more active sites, and gradient structure promotes ion transport. At 3C high rate, the material's discharge specific capacity can reach more than 150mAh / g, which is 15-20% higher than conventional materials (120-130mAh / g).

[0094] (3) Excellent energy density: The high-nickel core of the core-shell / gradient structure retains the high specific capacity of the material. The first discharge specific capacity of the modified material can reach 180-190mAh / g, which is basically the same as that of the unmodified single crystal 6-series material, thus solving the capacity decay problem caused by conventional coating.

[0095] (4) The preparation process is simple and controllable: all modification steps are based on existing industrial equipment (such as calcination furnaces and plasma equipment), without the need for complex and precision instruments. The raw materials such as template agents and functional molecules are low in cost and easy to scale up production.

[0096] (5) The modification strategy has strong universality: it can be extended to ternary materials with different nickel contents and different crystal forms.

[0097] 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 ternary cathode material, characterized in that, include: Construction of core-shell gradient structure: A core-shell structure precursor with low nickel in the shell and high nickel in the core is prepared by co-precipitation method. The core-shell structure precursor is then calcined with a lithium source to obtain a core-shell structure ternary cathode material substrate. Nanopore modification: The core-shell structured ternary cathode material substrate and the pore-forming template agent are mixed and calcined to prepare a ternary cathode material containing nanopores; Surface defect regulation and modification: The ternary cathode material containing nanopores is subjected to plasma treatment to obtain a surface-modified ternary cathode material; Surface coating modification: The surface-modified ternary cathode material, boron-phosphorus functional molecules and solvent are mixed to obtain a mixed slurry, which is then dried and calcined.

2. The preparation method according to claim 1, characterized in that, The preparation process of the core-shell structure precursor includes: A low-nickel shell precursor with a particle size of 5µm-10µm was prepared by reacting a low-nickel, high-manganese metal salt solution with a precipitant and a complexing agent. A high-nickel core precursor with a particle size of 15µm-20µm was prepared by reacting a high-nickel metal salt solution with a precipitant and a complexing agent. The high-nickel core precursor, water, and polyvinylpyrrolidone were mixed and stirred to obtain a high-nickel precursor mixture. The low-nickel shell precursor and water were mixed and stirred to obtain a low-nickel precursor mixture. The high-nickel precursor mixture was poured into the low-nickel precursor mixture, stirred, and then subjected to solid-liquid separation to obtain a core-shell structured precursor. The molar ratio of nickel, cobalt, and manganese in the low-nickel, high-manganese metal salt solution is (0.3-0.5):0.1:(0.2-0.4), and the molar ratio of nickel, cobalt, and manganese in the high-nickel metal salt solution is (0.7-0.9):0.1:(0.1-0.3). When preparing the core-shell structure precursor, the molar ratio of the low-nickel shell precursor to the high-nickel core precursor is controlled to be 1:(0.9-1.1). The concentration of polyvinylpyrrolidone in the system after mixing the high-nickel precursor mixture and the low-nickel precursor mixture is 0.01 mmol / L - 0.03 mmol / L.

3. The preparation method according to claim 2, characterized in that, In the process of preparing the shell low-nickel precursor, the reaction pH is controlled at 10.4-10.8, the amount of complexing agent ammonia solution is adjusted so that the ammonia concentration is 4-5 g / L, the reaction temperature is 50℃-60℃, and the reaction time is 1h-2h. And / or, in the process of preparing the core layer high nickel precursor, the reaction pH is controlled to be 11.6-12.0, the amount of complexing agent ammonia solution added is adjusted so that the ammonia concentration is 6-7 g / L, the reaction temperature is 50℃-60℃, and the reaction time is 2h-3h; And / or, when preparing the high-nickel precursor mixture, the stirring speed is controlled at 900 rpm-1100 rpm and the stirring time is 40 min-100 min; when preparing the low-nickel precursor mixture, the stirring speed is controlled at 400 rpm-800 rpm and the stirring time is 20 min-40 min; after the high-nickel precursor mixture is poured into the low-nickel precursor mixture, the stirring speed is controlled at 700 rpm-900 rpm and the stirring time is 30 min-60 min.

4. The preparation method according to claim 1, characterized in that, The core-shell structure precursor and the lithium source are mixed at a molar ratio of lithium to total nickel, cobalt and manganese of (1.05-1.10):1, and calcined in an oxygen-containing atmosphere. The calcination temperature is controlled at 750℃-850℃ and the calcination time is 10h-12h.

5. The preparation method according to claim 1, characterized in that, In the process of nanopore modification, the pore-forming template agent used is selected from at least one of ammonium bicarbonate, magnesium carbonate and sodium bicarbonate; And / or, the mass ratio of the core-shell structured ternary cathode material substrate to the pore-forming template agent is 1:(0.2-0.5). And / or, during the calcination process with the pore-forming template agent, the calcination temperature is controlled at 400℃-500℃, the calcination time is 3h-5h, and after calcination is completed, the product is washed and dried.

6. The preparation method according to claim 1, characterized in that, During the plasma treatment process, the plasma power is controlled at 100W-300W and the treatment time is 5min-15min. And / or, during plasma treatment, the gas introduced is an inert gas or a mixture of inert gas and oxygen, and the gas pressure is adjusted to 0.1 Pa - 0.5 Pa.

7. The preparation method according to claim 1, characterized in that, In the process of surface coating modification, the boron-containing phosphorus functional molecule used is selected from at least one of 2,5-thiophene diboronic acid, hydroxypropyl distarch phosphoric acid, and 2,5-thiophene diphosphate. And / or, the mass ratio of the surface-modified ternary cathode material to the boron-phosphorus functional molecule is 1:(0.01-0.05). And / or, the mixed slurry is dried at 80℃-100℃ for 12h-24h, and then calcined at 300℃-400℃ in an inert atmosphere for 2h-4h.

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

9. A positive electrode sheet, characterized in that, Including the ternary cathode material as described in claim 8.

10. A lithium-ion battery, characterized in that, Includes the positive electrode sheet as described in claim 9.

Images