Modified nickel-rich ternary positive electrode material and preparation method and application thereof

Abstract

The invention belongs to the technical field of lithium ion battery materials, and particularly relates to a modified nickel-rich ternary positive electrode material and a preparation method and application thereof. The modified nickel-rich ternary positive electrode material comprises a nickel-rich ternary positive electrode material and a hybrid coating layer (an Al2O3 coating layer and BaTiO3 nanoparticles anchored in the Al2O3 coating layer) coated on the surface of the nickel-rich ternary positive electrode material, the BaTiO3 nanoparticles and the nickel-rich ternary positive electrode material are bonded and connected through chemical bonds, the chemical formula of the nickel-rich ternary positive electrode material is LiNi < x > Co < y > Mn < 1-x-y > O < 2 >, x is greater than or equal to 0.90 and less than 0.95, and y is greater than or equal to 0.90 and less than 0.95. 0 < y < = 0.05. The modified nickel-rich ternary positive electrode material can meet the requirements of electron and ion transmission efficiency and interface protection, has high ionic conductivity, does not easily cause a local polarization phenomenon, and shows high specific discharge capacity, capacity retention ratio and cycling stability in a lithium ion battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery materials, and in particular relates to a modified nickel-rich ternary positive electrode material and a preparation method and application thereof. Background Art

[0002] With the continued growth in demand for energy density in energy storage systems for applications such as new energy vehicles, the development of high-capacity electrode materials has become a core research direction in the field of lithium-ion batteries. Nickel-rich layered oxide cathode materials (such as NCM) can significantly increase the specific capacity by increasing the nickel content, but the increase in nickel content also causes a decrease in the intrinsic stability of the material. For example, under high voltage or high temperature conditions, side reactions intensify, leading to microcrack formation, dissolution of transition metal ions, and the transformation of the layered structure to spinel or disordered phases, resulting in rapid capacity decay during electrode cycling. This inherent contradiction between capacity characteristics and structural stability has become a key bottleneck restricting the commercial application of nickel-rich ternary cathode materials.

[0003] Surface coating is the primary modification technology used to address the surface structural degradation and microcracks of nickel-rich ternary cathode materials. While traditional single-layer coatings can create a physical barrier to block electrolyte intrusion, a single coating cannot guarantee both efficient electron and ion transmission while also ensuring interface protection. For example, the non-uniformity and low ionic conductivity of the Al2O3 coating can easily lead to localized polarization. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a modified nickel-rich ternary positive electrode material and its preparation method and application. The modified nickel-rich ternary positive electrode material has uniform composition, high surface and interface structure stability, can take into account the electron and ion transmission efficiency and interface protection requirements, has high ionic conductivity, is not easy to cause local polarization, and exhibits high discharge specific capacity, capacity retention rate and cycle stability when applied to the positive electrode of a lithium-ion battery.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a modified nickel-rich ternary positive electrode material, comprising a nickel-rich ternary positive electrode material and a hybrid coating layer coated on the surface of the nickel-rich ternary positive electrode material; the hybrid coating layer comprises an Al2O3 coating layer and BaTiO3 nanoparticles anchored in the Al2O3 coating layer, the BaTiO3 nanoparticles are chemically bonded to the nickel-rich ternary positive electrode material; the chemical formula of the nickel-rich ternary positive electrode material is LiNi x Co y Mn 1-x-y O2, 0.90≤x<0.95, 0<y≤0.05.

[0007] Preferably, the chemical formula of the nickel-rich ternary cathode material is LiNi 0.90 Co 0.05 Mn 0.05 O2.

[0008] Preferably, the particle size of the modified nickel-rich ternary positive electrode material is 1 to 4 μm; the particle size of the BaTiO 3 nanoparticles is 40 to 60 nm; and the thickness of the Al 2 O 3 coating layer is 10 to 20 nm.

[0009] The present invention also provides a method for preparing the modified nickel-rich ternary cathode material described in the above technical solution, comprising the following steps:

[0010] After mixing a nickel-rich ternary positive electrode material, barium titanate and a first polar organic solvent for a first loading, the solvent is first removed to obtain a barium titanate-nickel-rich ternary positive electrode material precursor;

[0011] The barium titanate-nickel-rich ternary positive electrode material precursor, an aluminum source, and a second polar organic solvent are mixed for a second loading, and then the solvent is removed and dried in sequence to obtain an aluminum oxide-coated barium titanate-nickel-rich ternary positive electrode material precursor;

[0012] The aluminum oxide-coated barium titanate-nickel-rich ternary positive electrode material precursor is calcined in air to obtain the modified nickel-rich ternary positive electrode material.

[0013] Preferably, the amount of the barium titanate is 0.5-5% of the amount of the nickel-rich ternary positive electrode material.

[0014] Preferably, the aluminum source includes one or more of aluminum isopropoxide, aluminum nitrate and aluminum sulfate; the mass of the aluminum source is 0.5-2% of the mass of the nickel-rich ternary positive electrode material.

[0015] Preferably, the calcination temperature is 450-600° C., the holding time is 4-7 hours, and the heating rate to the calcination temperature is 1-10° C. / min.

[0016] The present invention also provides the use of the modified nickel-rich ternary positive electrode material described in the above technical solution or the modified nickel-rich ternary positive electrode material prepared by the preparation method described in the above technical solution in lithium-ion batteries.

[0017] The present invention also provides a positive electrode for a lithium ion battery, wherein the positive electrode active material of the positive electrode for a lithium ion battery is the modified nickel-rich ternary positive electrode material described in the above technical solution or the modified nickel-rich ternary positive electrode material prepared by the preparation method described in the above technical solution.

[0018] The present invention also provides a lithium ion battery, wherein the positive electrode is the positive electrode for the lithium ion battery described in the above technical solution.

[0019] The present invention provides a modified nickel-rich ternary positive electrode material comprising a nickel-rich ternary positive electrode material and a hybrid coating layer coated on the surface of the nickel-rich ternary positive electrode material; the hybrid coating layer comprises an Al2O3 coating layer and BaTiO3 nanoparticles anchored in the Al2O3 coating layer, the BaTiO3 nanoparticles are chemically bonded to the nickel-rich ternary positive electrode material; the chemical formula of the nickel-rich ternary positive electrode material is LiNi x Co y Mn 1-x-y O2, 0.90≤x<0.95, 0<y≤0.05. The present invention constructs a dual-functional Al2O3-BaTiO3 structure hybrid coating layer on the surface of the nickel-rich ternary positive electrode material. The dense and uniform aluminum oxide (Al2O3) coating layer is a chemically inert protective layer, forming a physical-chemical synergistic protection mechanism. On the one hand, the Al2O3 coating layer acts as a physical barrier to block the electrolyte and resist the corrosion of chemical substances in the electrolyte. On the other hand, it undergoes in-situ chemical conversion with the electrolyte during the circulation process, which can consume acidic substances (H + ), alleviate the structural degradation of the cathode material caused by proton embedding, stabilize the interface structure of the modified nickel-rich ternary cathode material, and make it less likely to degrade and produce microcracks; at the same time, the barium titanate (BaTiO3) nanoparticles anchored in the Al2O3 coating layer have high dielectric properties, which can regulate the interface electric field distribution of the modified nickel-rich ternary cathode material, promote the generation of lithium vacancies, and accelerate Li + Diffusion, with high ionic conductivity, the spontaneous polarization effect of barium titanate can reconstruct the interfacial charge distribution between the positive electrode and the electrolyte, reduce the interfacial migration activation energy of the lithium ion deintercalation process, and maintain the lithium ion transmission kinetics while suppressing the electrolyte decomposition side reaction and transition metal ion migration, significantly improving the stability of the interface structure, and not easily producing local polarization phenomena. Compared with the traditional single-layer coating technology, the modified nickel-rich ternary positive electrode material provided by the present invention has a coupling strategy of dielectric regulation and interface protection, which can simultaneously optimize the protection ability and the electron and ion transmission efficiency, improve the interface stability and structural integrity of the modified nickel-rich ternary positive electrode material, and achieve the coordinated optimization of transmission kinetics and positive electrode / electrolyte interface stability. When the modified nickel-rich ternary positive electrode material prepared by the present invention is applied to the positive electrode of a lithium-ion battery, it exhibits high discharge specific capacity, capacity retention rate and cycle stability.

[0020] The present invention also provides a method for preparing the modified nickel-rich ternary positive electrode material. The method is simple and easy to operate, has low cost, does not require complex equipment, and provides important reference significance for the large-scale preparation of high-stability nickel-rich ternary positive electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 XRD pattern of the modified nickel-rich ternary cathode material (AB@NCM90) prepared in Example 1;

[0022] Figure 2 This is an SEM image of the modified nickel-rich ternary cathode material (AB@NCM90) prepared in Example 1;

[0023] Figure 3 This is the EDS image of the modified nickel-rich ternary cathode material (AB@NCM90) prepared in Example 1;

[0024] Figure 4 HRTEM image of the modified nickel-rich ternary cathode material (AB@NCM90) prepared in Example 1;

[0025] Figure 5 This is a charge and discharge cycle performance diagram of a battery prepared using the modified nickel-rich ternary cathode material of Example 1 in Application Example 1;

[0026] Figure 6 This is a charge and discharge cycle performance diagram of a battery prepared using the NCM90 positive electrode material of Comparative Example 1 in Comparative Application Example 1;

[0027] Figure 7 This is a charge and discharge cycle performance diagram of a battery prepared using the Al2O3-coated NCM90 material prepared in Comparative Example 2 in Comparative Application Example 2;

[0028] Figure 8 This is a charge and discharge cycle performance diagram of a battery prepared using the BaTiO3-coated NCM90 material prepared in Comparative Example 3 in Comparative Example 3;

[0029] Figure 9 This is a rate performance comparison chart of a battery prepared using the modified nickel-rich ternary positive electrode material of Example 1 in Application Example 1 and a battery prepared using the NCM90 positive electrode material of Comparative Example 1 in Comparative Application Example 1. DETAILED DESCRIPTION

[0030] The present invention provides a modified nickel-rich ternary positive electrode material, comprising a nickel-rich ternary positive electrode material and a hybrid coating layer coated on the surface of the nickel-rich ternary positive electrode material; the hybrid coating layer comprises an Al2O3 coating layer and BaTiO3 nanoparticles anchored in the Al2O3 coating layer, the BaTiO3 nanoparticles are chemically bonded to the nickel-rich ternary positive electrode material; the chemical formula of the nickel-rich ternary positive electrode material is LiNi x Co y Mn 1-x-y O2, 0.90≤x<0.95, 0<y≤0.05.

[0031] As an embodiment, the chemical formula of the nickel-rich ternary cathode material is LiNi 0.90 Co 0.05 Mn 0.05 O2(NCM90).

[0032] As an embodiment, the particle size of the modified nickel-rich ternary positive electrode material is 1 to 4 μm, and in a specific embodiment, it is 1 to 3 μm; the particle size of the BaTiO3 nanoparticles is 40 to 60 nm, and in a specific embodiment, it is 45 to 50 nm; the thickness of the Al2O3 coating layer is 10 to 20 nm, and in a specific embodiment, it is 12 to 18 nm.

[0033] The present invention constructs an Al2O3-BaTiO3 structure hybrid coating layer on the surface of the nickel-rich ternary positive electrode material. The densely and uniformly coated aluminum oxide (Al2O3) is a chemically inert protective layer, forming a physical-chemical synergistic protection mechanism. On the one hand, the Al2O3 coating layer acts as a physical barrier to block the electrolyte and resist the corrosion of chemical substances in the electrolyte. On the other hand, it undergoes in-situ chemical conversion with the electrolyte during the circulation process, which can consume acidic substances (H + ), alleviate the structural degradation of the cathode material caused by proton embedding, stabilize the interface structure of the modified nickel-rich ternary cathode material, and make it less likely to degrade and produce microcracks; at the same time, the barium titanate (BaTiO3) nanoparticles anchored in the Al2O3 coating layer have high dielectric properties, which can regulate the interface electric field distribution of the modified nickel-rich ternary cathode material, promote the generation of lithium vacancies, and accelerate Li + Diffusion, with high ionic conductivity, the spontaneous polarization effect of barium titanate can reconstruct the interfacial charge distribution between the positive electrode and the electrolyte, reduce the interfacial migration activation energy of the lithium ion deintercalation process, and maintain the lithium ion transmission kinetics while suppressing the electrolyte decomposition side reaction and transition metal ion migration, significantly improving the stability of the interface structure, and not easily producing local polarization phenomena. Compared with the traditional single-layer coating technology, the modified nickel-rich ternary positive electrode material provided by the present invention has a coupling strategy of dielectric regulation and interface protection, which can simultaneously optimize the protection ability and the electron and ion transmission efficiency, improve the interface stability and structural integrity of the modified nickel-rich ternary positive electrode material, and achieve the coordinated optimization of transmission kinetics and positive electrode / electrolyte interface stability. When the modified nickel-rich ternary positive electrode material prepared by the present invention is applied to the positive electrode of a lithium-ion battery, it exhibits high discharge specific capacity, capacity retention rate and cycle stability.

[0034] The present invention also provides a method for preparing the modified nickel-rich ternary cathode material described in the above technical solution, comprising the following steps:

[0035] After mixing a nickel-rich ternary positive electrode material, barium titanate and a first polar organic solvent for a first loading, the solvent is first removed to obtain a barium titanate-nickel-rich ternary positive electrode material precursor;

[0036] The barium titanate-nickel-rich ternary positive electrode material precursor, an aluminum source, and a second polar organic solvent are mixed for a second loading, and then the solvent is removed and dried in sequence to obtain an aluminum oxide-coated barium titanate-nickel-rich ternary positive electrode material precursor;

[0037] The aluminum oxide-coated barium titanate-nickel-rich ternary positive electrode material precursor is calcined in air to obtain the modified nickel-rich ternary positive electrode material.

[0038] Unless otherwise specified, the present invention has no special requirements on the sources of the raw materials used, and commercially available products known to those skilled in the art can be used.

[0039] The present invention mixes nickel-rich ternary positive electrode material, barium titanate and a first polar organic solvent for first loading, and then removes the solvent to obtain a barium titanate-nickel-rich ternary positive electrode material precursor.

[0040] As an embodiment, the amount of the barium titanate is 0.5-5% of the amount of the nickel-rich ternary positive electrode material, and in a specific embodiment, it is 0.5-2%; the first polar organic solvent includes anhydrous ethanol and / or acetone, and in a specific embodiment, it is anhydrous ethanol; the ratio of the mass of the barium titanate to the volume of the first polar organic solvent is 1g: (650-1000) mL, and in a specific embodiment, it is 1g: (650-700) mL.

[0041] As an embodiment, the mixing of the nickel-rich ternary positive electrode material, barium titanate and the first polar organic solvent is as follows: barium titanate and the first polar organic solvent are mixed and ultrasonically dispersed, and the nickel-rich ternary positive electrode material is added to the obtained suspension; the temperature of the ultrasonic dispersion treatment is 10-20°C, 15-20°C in the specific embodiment, the power is 400-500W, 450-500W in the specific embodiment, the frequency is 20-30kHz, 25kHz in the specific embodiment, and the time is 60-90min, 60-80min in the specific embodiment.

[0042] As an embodiment, the first loading method is ultrasonic treatment; the ultrasonic treatment temperature is 10-20°C, specifically 15-20°C in a specific embodiment, the power is 400-500W, specifically 450-500W in a specific embodiment, the frequency is 20-30kHz, specifically 25kHz in a specific embodiment, and the time is 30-60min, specifically 30-45min in a specific embodiment. In the present invention, through ultrasonic treatment, barium titanate is loaded on the surface of the nickel-rich ternary cathode material by physical electrostatic adsorption.

[0043] As an embodiment, the first method of removing the solvent is to evaporate the solvent in a constant temperature oil bath; the temperature of the constant temperature oil bath is 80-90°C, and in a specific embodiment, it is 80-85°C; the time of the constant temperature oil bath is 3-4h, and in a specific embodiment, it is 3h; the constant temperature oil bath is carried out under stirring conditions; the stirring rate is 200-300rpm, and in a specific embodiment, it is 250rpm.

[0044] After obtaining the barium titanate-nickel-rich ternary positive electrode material precursor, the present invention mixes the barium titanate-nickel-rich ternary positive electrode material precursor, an aluminum source and a second polar organic solvent for a second loading, and then sequentially performs a second solvent removal and drying to obtain an aluminum oxide-coated barium titanate-nickel-rich ternary positive electrode material precursor.

[0045] As an embodiment, the aluminum source includes one or more of aluminum isopropoxide, aluminum nitrate and aluminum sulfate, and in a specific embodiment, it is aluminum isopropoxide; the aluminum nitrate is Al(NO3)3·9H2O; the mass of the aluminum source is 0.5-2% of the mass of the nickel-rich ternary positive electrode material, and in a specific embodiment, it is 0.5-1.5%.

[0046] As an embodiment, the second polar organic solvent includes anhydrous ethanol and / or acetone, and in a specific embodiment, it is anhydrous ethanol; the ratio of the mass of the aluminum source to the volume of the second polar organic solvent is 1g:(750~3000)mL, and in a specific embodiment, it is 1g:(1500~2000)mL.

[0047] As an embodiment, the barium titanate-nickel-rich ternary positive electrode material precursor, the aluminum source and the second polar organic solvent are mixed as follows: the aluminum source and the second polar organic solvent are mixed and stirred, and the barium titanate-nickel-rich ternary positive electrode material precursor is added to the obtained aluminum source solution; the stirring is magnetic stirring; the stirring temperature is 80-90°C, and in a specific embodiment, it is 80-85°C; the stirring rate is 700-800rpm, and in a specific embodiment, it is 750rpm; the stirring time is 4-5h, and in a specific embodiment, it is 4-4.5h.

[0048] As an embodiment, the second loading method is stirring; the stirring is magnetic stirring; the stirring temperature is 80-90°C, and in a specific embodiment, it is 80-85°C; the stirring rate is 700-800rpm, and in a specific embodiment, it is 750rpm; the stirring time is 2-3h, and in a specific embodiment, it is 2h.

[0049] In one embodiment, the second solvent removal step is to evaporate the solvent in a constant temperature oil bath; the temperature of the constant temperature oil bath is 80-100°C, and in a specific embodiment, 80-90°C; the temperature of the constant temperature oil bath is 4-6 hours, and in a specific embodiment, 5 hours; the constant temperature oil bath is stirred; the stirring rate is 200-300 rpm, and in a specific embodiment, 250 rpm. In the present invention, through stirring, the aluminum source is physically coated on the surface of the barium titanate-nickel-rich ternary cathode material precursor by electrostatic adsorption.

[0050] As an embodiment, the drying temperature is 80-120°C, and in a specific embodiment, it is 80-100°C; the drying time is 10-14 hours, and in a specific embodiment, it is 10-12 hours; the drying is vacuum drying; the vacuum degree of the vacuum drying is 0.7-1.0 bar, and in a specific embodiment, it is 0.8-1.0 bar.

[0051] After obtaining the aluminum oxide coated barium titanate-nickel-rich ternary positive electrode material precursor, the present invention calcines the aluminum oxide coated barium titanate-nickel-rich ternary positive electrode material precursor in air to obtain the modified nickel-rich ternary positive electrode material.

[0052] As an embodiment, the calcination temperature is 450-600°C, specifically 500-550°C, the holding time is 4-7h, specifically 5-6h; the heating rate to the calcination temperature is 1-10°C / min, specifically 3-5°C / min; the calcination equipment is a muffle furnace; after the calcination, the calcined product is naturally cooled.

[0053] During the calcination process, an Al2O3 coating is formed on the surface of the nickel-rich ternary cathode material through the thermal decomposition of the aluminum source. In the nickel-rich ternary cathode material, the high nickel content (>80%) reduces the stability of the lattice oxygen, which easily forms oxygen vacancies on the surface (especially when oxygen is released during charge and discharge). BaTiO3, as a perovskite structure material, is prone to oxygen vacancies in the distorted areas of the Ti-O octahedron on its surface. These vacancies act as highly active sites, preferentially adsorbing H2O molecules from the environment and generating surface hydroxyl groups through dissociation reactions. As a result, both the nickel-rich ternary cathode material and the BaTiO3 surface have hydroxyl groups. The nickel-rich ternary cathode material and the BaTiO3 are bonded together by the oxygen atoms after calcination, which have been dehydroxylated.

[0054] The present invention achieves the synergistic optimization of surface protection and charge transfer by modifying the surface of the nickel-rich ternary positive electrode material with an Al2O3-BaTiO3 structural hybrid coating layer, breaking through the technical bottleneck of the traditional single coating layer that is difficult to balance structural stability and dynamic performance.

[0055] In the prior art, the fast ion conductor coating layer requires the use of new coating technologies such as atomic layer deposition (ALD) or magnetron sputtering to achieve nanoscale uniform coating. Although these technologies can accurately control the coating thickness to achieve a uniform coating, they are expensive, time-consuming, and difficult to apply on a large scale. The preparation method provided by the present invention is simple to operate, low-cost, and easy to mass-produce, and the hybrid coating layer design strategy proposed is universal. The present invention provides a new technical path for the development of layered nickel-rich ternary positive electrode materials with high energy density and long cycle life, which is of great value in promoting the commercial application of next-generation lithium-ion batteries.

[0056] The present invention also provides the use of the modified nickel-rich ternary positive electrode material described in the above technical solution or the modified nickel-rich ternary positive electrode material prepared by the preparation method described in the above technical solution in lithium-ion batteries.

[0057] The present invention also provides a positive electrode for a lithium ion battery, wherein the positive electrode active material of the positive electrode for a lithium ion battery is the modified nickel-rich ternary positive electrode material described in the above technical solution or the modified nickel-rich ternary positive electrode material prepared by the preparation method described in the above technical solution.

[0058] As an embodiment, the preparation method of the positive electrode for lithium-ion batteries is as follows: a positive electrode active material, a conductive agent, a binder and a polar organic solvent are mixed, the resulting slurry is coated on a current collector, and after drying, slicing and pressing are performed in sequence.

[0059] As an embodiment, the conductive agent is a carbon material; the carbon material includes acetylene black and / or carboxylated carbon nanotubes, and in a specific embodiment, it is acetylene black and carboxylated carbon nanotubes; the mass ratio of acetylene black and carboxylated carbon nanotubes is 0-5:0-5, and the mass ratio of acetylene black and carboxylated carbon nanotubes is not 0 at the same time, and in a specific embodiment, it is 4:1; the mass ratio of the positive electrode active material and the conductive agent is 80-90:5-10, and in a specific embodiment, it is 90:5.

[0060] As an embodiment, the binder is polyvinylidene fluoride (PVDF); the mass ratio of the positive electrode active material to the binder is 80-90:5-10, and in a specific embodiment is 90:5.

[0061] As an embodiment, the polar organic solvent is N-methylpyrrolidone (NMP); the ratio of the volume of the polar organic solvent to the total mass of the positive electrode active material, the conductive agent and the binder is (2-2.5) mL:1.5 g, and in a specific embodiment it is (2-2.3) mL:1.5 g.

[0062] As an embodiment, the mixing is: after the positive electrode active material, the conductive agent and the binder are first mixed, a polar organic solvent is added and stirred; the stirring rate is 800 to 1000 rpm, and in a specific embodiment it is 850 to 950 rpm; the stirring time is 7 to 10 hours, and in a specific embodiment it is 8 to 9 hours.

[0063] As an embodiment, the coating is knife coating.

[0064] As an embodiment, the drying temperature is 80-120°C, and in a specific embodiment, it is 100-120°C; the drying time is 10-14 hours, and in a specific embodiment, it is 11-13 hours; the drying is vacuum drying; the vacuum degree of the vacuum drying is 0.7-1.0 bar, and in a specific embodiment, it is 0.8-1.0 bar.

[0065] As an embodiment, the pressing is punching; the equipment used for the punching is a manual punching machine.

[0066] As an embodiment, the positive electrode for lithium ion battery is a circular electrode sheet; the diameter of the positive electrode for lithium ion battery is 10 to 15 mm, and in a specific embodiment, it is 10 mm; the loading amount of the positive electrode active material in the positive electrode for lithium ion battery is 1.7 to 4.6 mg / cm 2 , in the specific embodiment, 3.8 to 4.6 mg / cm 2 .

[0067] The present invention also provides a lithium ion battery, wherein the positive electrode is the positive electrode for the lithium ion battery described in the above technical solution.

[0068] As an embodiment, the lithium-ion battery further includes: a negative electrode, a separator and an electrolyte; the negative electrode is metallic lithium; the separator is a polypropylene separator; the electrolyte includes a lithium salt and a non-polar organic solvent; the lithium salt is LiPF6; the concentration of the lithium salt in the electrolyte is 1 mol / L; the non-polar organic solvent includes ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC); the volume ratio of ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) is 1 to 3:1 to 5:1 to 2, and in a specific embodiment, it is 1:1:1.

[0069] As an embodiment, the lithium-ion battery is assembled in a glove box filled with argon.

[0070] The technical solutions of the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention, but they should not be understood as limiting the scope of protection of the present invention.

[0071] Example 1

[0072] Commercialized LiNi 0.90 Co 0.05 Mn 0.05 O2 (NCM90) is used as the matrix material, and the Al2O3-BaTiO3 double-layer coating structure is constructed step by step by wet chemical method:

[0073] First, based on the interface anchoring strategy, barium titanate (BaTiO3, BT) powder was mixed with anhydrous ethanol at a ratio of 1% of the amount of NCM90 substance, with the mass of barium titanate and the volume of anhydrous ethanol being 1g:650mL. The mixture was ultrasonically dispersed in an ultrasonic cell crusher at 20°C, 500W, and 25kHz for 1h to form a uniform suspension. NCM90 powder was then added and ultrasonicated for a second time for 30min to achieve uniform anchoring of BaTiO3 on the surface of NCM90. The mixture was then placed in an 80°C constant temperature oil bath with magnetic stirring at 250rpm for 3h, and the solvent was evaporated to complete the preliminary compounding, thus obtaining a BaTiO3-NCM90 precursor powder.

[0074] Subsequently, aluminum isopropoxide (C9H 21 AlO3) was dissolved in anhydrous ethanol at 1 wt% of the mass of NCM90, with the mass of aluminum isopropoxide and the volume ratio of anhydrous ethanol being 1 g:1500 mL. The mixture was stirred in a magnetic stirrer at a constant temperature of 80°C and 750 rpm for 4 h to form a transparent and uniform aluminum source solution. The BaTiO3-NCM90 precursor powder was added and stirred for 2 h to uniformly load the aluminum source on the surface of the BaTiO3-NCM90 precursor powder. After evaporating the solvent in an oil bath at a constant temperature of 90°C and magnetic stirring at 250 rpm for 5 h, the mixture was vacuum dried at 80°C and a vacuum degree of 0.8 bar for 12 h to obtain an alumina-coated BaTiO3-NCM90 precursor powder.

[0075] The alumina-coated BaTiO3-NCM90 precursor powder was placed in a muffle furnace, heated to 500°C at a heating rate of 5°C / min, and calcined for 5 hours in an air atmosphere. After natural cooling, a modified nickel-rich ternary positive electrode material was obtained, which was recorded as AB@NCM90.

[0076] Example 2

[0077] The difference from Example 1 is that the amount of barium titanate is 0.5% of the amount of NCM90. The rest of the contents are the same as Example 1.

[0078] Example 3

[0079] The difference from Example 1 is that the amount of barium titanate is 1.5% of the amount of NCM90. The rest of the contents are the same as Example 1.

[0080] Example 4

[0081] The difference from Example 1 is that the mass of aluminum isopropoxide is 0.5 wt % of the mass of NCM90, and the rest of the contents are the same as Example 1.

[0082] Example 5

[0083] The difference from Example 1 is that the mass of aluminum isopropoxide is 1.5 wt % of the mass of NCM90, and the rest of the contents are the same as Example 1.

[0084] Comparative Example 1

[0085] Using commercial LiNi 0.90 Co 0.05 Mn 0.05 O2 (NCM90) was used as a comparative example without modification of the coating layer.

[0086] Comparative Example 2

[0087] The difference from Example 1 is that no barium titanate is added, and NCM90 is directly mixed with aluminum isopropoxide and then calcined. The specific steps are as follows:

[0088] Commercialized LiNi 0.90 Co 0.05 Mn 0.05 O2 (NCM90) is the matrix material, and aluminum isopropoxide (C9H 21 AlO3) was dissolved in anhydrous ethanol at 1 wt% of the mass of NCM90, with the mass of aluminum isopropoxide and the volume ratio of anhydrous ethanol being 1 g:1500 mL. The solution was stirred continuously for 4 h in a magnetic stirrer at a constant temperature of 80°C and 750 rpm to form a transparent and uniform aluminum source solution. The NCM90 matrix material was added and stirred for 2 h to uniformly load the aluminum source on the surface of the NCM90. After evaporating the solvent in an oil bath at a constant temperature of 90°C and magnetic stirring at 250 rpm for 5 h, the solution was vacuum dried at 80°C and a vacuum degree of 0.8 bar for 12 h to obtain an alumina-coated NCM90 precursor powder.

[0089] The alumina-coated NCM90 precursor powder was placed in a muffle furnace, heated to 500°C at a heating rate of 5°C / min, and calcined for 5 hours in an air atmosphere. After natural cooling, an Al2O3-coated NCM90 material was obtained, which was recorded as A@NCM90.

[0090] Comparative Example 3

[0091] The difference from Example 1 is that no aluminum isopropoxide is added, and NCM90 and barium titanate are directly mixed and then calcined. The specific steps are as follows:

[0092] Commercialized LiNi 0.90 Co 0.05 Mn 0.05O2 (NCM90) was used as the matrix material, and barium titanate (BaTiO3, BT) powder was mixed with anhydrous ethanol at a ratio of 1 mol% of the mass of NCM90. The mass of barium titanate and the volume of anhydrous ethanol were 1 g:650 mL. The mixture was ultrasonically dispersed for 1 h in an ultrasonic cell crusher at 20 ° C, 500 W, and 25 kHz to form a uniform suspension. NCM90 powder was then added and ultrasonicated for a second time for 30 min to achieve uniform anchoring of BaTiO3 on the surface of NCM90. The mixture was then placed in an 80 ° C constant temperature oil bath and magnetically stirred at 250 rpm for 3 h until the solvent was completely evaporated. The mixture was then vacuum dried at 80 ° C and a vacuum degree of 0.8 bar for 12 h. The obtained powder was placed in a muffle furnace, heated to 500 ° C at a heating rate of 5 ° C / min, and calcined in an air atmosphere for 5 h. After natural cooling, BaTiO3-coated NCM90 material was obtained, which was recorded as B@NCM90.

[0093] Application Example 1

[0094] The modified nickel-rich ternary positive electrode material (AB@NCM90) prepared in Example 1 was mixed with acetylene black, carboxylated carbon nanotubes, and PVDF in a mass ratio of 90:4:1:5, and N-methylpyrrolidone (NMP, the volume of NMP and the total mass ratio of AB@NCM90, acetylene black, carboxylated carbon nanotubes and PVDF was 2.1 mL: 1.5 g) was added and stirred at 900 rpm for 8 h to prepare a slurry. The uniform slurry was then scraped onto the current collector and vacuum dried at 120 ° C and a vacuum degree of 0.8 bar for 12 h. The slices were punched out into circular electrode sheets with a diameter of 10 mm using a manual punching machine, which were used as the positive electrode, wherein the loading amount of the modified nickel-rich ternary positive electrode material was 4.0 mg / cm 2 A CR2025 button experimental battery was assembled in an argon-filled glove box using metallic lithium as the negative electrode, polypropylene as the separator, and 1 mol / L LiPF6 solution as the electrolyte (the solvent was a mixture of EC, DEC, and DMC in a volume ratio of 1:1:1).

[0095] Application Examples 2 to 5

[0096] The difference from Application Example 1 is that the modified nickel-rich ternary positive electrode material (AB@NCM90) prepared in Example 1 is replaced by the modified nickel-rich ternary positive electrode material (AB@NCM90) prepared in Examples 2 to 5, respectively.

[0097] Comparative Application Examples 1 to 3

[0098] The difference from Application Example 1 is that the modified nickel-rich ternary positive electrode material (AB@NCM90) prepared in Example 1 is replaced by the NCM90 of Comparative Example 1, the Al2O3-coated NCM90 material (A@NCM90) prepared in Comparative Example 2, and the BaTiO3-coated NCM90 material (B@NCM90) prepared in Comparative Example 3.

[0099] Performance Testing

[0100] (1) Figure 1 This is the XRD pattern of the modified nickel-rich ternary cathode material (AB@NCM90) prepared in Example 1. Figure 1 It can be seen from the XRD spectrum that the modified nickel-rich ternary cathode material exhibits a typical α-NaFeO2 layered structure (space group R3) at the characteristic diffraction peaks of (003), (101) and (104). _ m), indicating that the surface coating process has no significant impact on the crystal structure of the material itself.

[0101] (2) Figure 2 This is the SEM image of the modified nickel-rich ternary cathode material (AB@NCM90) prepared in Example 1. Figure 2 Analysis of the SEM images shows that the prepared modified nickel-rich ternary cathode material exhibits good structural integrity, with a rough, fuzzy surface, indicating successful coating and confirming that the coating does not affect the structure of the NCM90 cathode material. Further observation reveals that the BaTiO3 nanoparticles are uniformly anchored on the surface of the NCM90 matrix. The successful construction of this Al2O3-BaTiO3 hybrid coating structure provides favorable conditions for subsequent interfacial charge transfer.

[0102] (3) Figure 3 This is the EDS element distribution diagram of the modified nickel-rich ternary cathode material (AB@NCM90) prepared in Example 1. Figure 3 The EDS element surface distribution map found that the characteristic elements Al, Ba, Ti, and O showed a highly uniform two-dimensional distribution state on the surface of the modified nickel-rich ternary positive electrode material, further proving the successful construction of the hybrid coating layer on the surface of the NCM90 material.

[0103] (4) Figure 4 This is a high-resolution transmission electron microscopy (HRTEM) characterization image of the modified nickel-rich ternary positive electrode material (AB@NCM90) prepared in Example 1.

[0104] pass Figure 4High-resolution transmission electron microscopy analysis revealed the successful construction of an Al2O3-BaTiO3 composite coating on the NCM90 surface. The Al2O3 coating exhibited a continuous, dense, amorphous structure with a uniform thickness of approximately 18 nm, demonstrating excellent uniformity. BaTiO3 nanoparticles were then dispersed and anchored to the NCM90 surface. This synergistic coating structure not only inhibited electrolyte corrosion through the protective effect of Al2O3 but also leveraged the dielectric effect of BaTiO3 to regulate the interfacial potential, improving lithium-ion transport.

[0105] (5) The CR2025 button battery of Application Example 1 and Comparative Application Examples 1 to 3 was subjected to charge and discharge cycle tests, and the results were as follows: Figures 5 to 8 The specific operation is: at room temperature, the battery is at 2.75~4.3V (vs.Li + / Li) voltage range, at a rate of 0.1C (1C = 200mA g -1 ) for activation, and after activation, the charge-discharge cycle test was carried out at a 1C rate within the same voltage range.

[0106] Depend on Figure 5 It can be seen that the initial discharge capacity of the battery prepared with the modified nickel-rich ternary cathode material of Example 1 is 203.1 mAh·g -1 After 200 cycles at 1C, the capacity retention rate is 61.78%, which shows good charge and discharge capacity and cycle stability.

[0107] Depend on Figure 6 It can be seen that after the battery prepared with the NCM90 positive electrode material of Comparative Example 1 is cycled 200 times under 1C conditions, the capacity retention rate is 47.73%.

[0108] Depend on Figure 7 It can be seen that the battery prepared by using the Al2O3-coated NCM90 material of Comparative Example 2 has a capacity retention rate of 55.16% after 200 cycles under 1C conditions.

[0109] Depend on Figure 8 It can be seen that the battery prepared by coating NCM90 material with BaTiO3 in Comparative Example 3 has a capacity retention rate of 49.40% after 200 cycles under 1C conditions.

[0110] It can be seen that compared with Comparative Examples 1 to 3, the discharge specific capacity and cycle stability of the battery prepared using the modified nickel-rich ternary positive electrode material of Example 1 are significantly improved.

[0111] (6) The CR2025 button battery of Application Example 1 and Comparative Application Example 1 was subjected to rate performance test. The specific operation was as follows: at room temperature, the capacity retention ability of the battery prepared with the modified nickel-rich ternary positive electrode material (AB@NCM90) of Example 1 and the NCM90 positive electrode material of Comparative Example 1 at different charge and discharge rates was systematically investigated. The test program was set to a step-by-step rate change mode of 0.1C, 0.2C, 0.5C, 1C, 2C, 5C and 0.1C. The corresponding capacity-rate relationship curve is shown in detail. Figure 9 .

[0112] Depend on Figure 9 It can be seen that at a high rate (5C), the discharge capacity of the battery prepared with the NCM90 positive electrode material of Comparative Example 1 is 113.8 mAh g -1 The battery prepared with the modified nickel-rich ternary cathode material (AB@NCM90) of Example 1 has a higher discharge specific capacity of 128.0 mAh g -1 .

[0113] This invention innovatively proposes a "protective layer + functional layer" double coating collaborative design strategy. XRD phase analysis confirms that the constructed Al2O3-BaTiO3 double coating does not change the crystal structure of the NCM90 positive electrode material. Electrochemical performance studies have shown that the heterogeneous Al2O3-BaTiO3 double coating effectively suppresses the interfacial side reactions between the positive electrode / electrolyte through physical barrier effects and regulation of charge distribution, while optimizing the lithium ion diffusion kinetics. The synergistic effect of the two makes the modified nickel-rich layered positive electrode material exhibit excellent cycle stability and rate performance, and its capacity retention rate is improved by about 29% compared with the sample in Comparative Example 1.

[0114] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention rather than all the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A modified nickel-rich ternary cathode material, characterized in that: The invention comprises a nickel-rich ternary positive electrode material and a hybrid coating layer coated on the surface of the nickel-rich ternary positive electrode material; the hybrid coating layer comprises an Al2O3 coating layer and BaTiO3 nanoparticles anchored in the Al2O3 coating layer, and the BaTiO3 nanoparticles are chemically bonded to the nickel-rich ternary positive electrode material; the chemical formula of the nickel-rich ternary positive electrode material is LiNi x Co y Mn 1-x-y O2, 0.90≤x<0.95, 0<y≤0.

05.

2. The modified nickel-rich ternary cathode material according to claim 1, characterized in that The chemical formula of the nickel-rich ternary positive electrode material is LiNi 0.90 Co 0.05 Mn 0.05 O2.

3. The modified nickel-rich ternary cathode material according to claim 1 or 2, characterized in that: The particle size of the modified nickel-rich ternary positive electrode material is 1 to 4 μm; the particle size of the BaTiO 3 nanoparticles is 40 to 60 nm; and the thickness of the Al 2 O 3 coating layer is 10 to 20 nm.

4. The method for preparing the modified nickel-rich ternary cathode material according to any one of claims 1 to 3, characterized in that: The following steps are involved: After mixing a nickel-rich ternary positive electrode material, barium titanate and a first polar organic solvent for a first loading, the solvent is first removed to obtain a barium titanate-nickel-rich ternary positive electrode material precursor; The barium titanate-nickel-rich ternary positive electrode material precursor, an aluminum source, and a second polar organic solvent are mixed for a second loading, and then the solvent is removed and dried in sequence to obtain an aluminum oxide-coated barium titanate-nickel-rich ternary positive electrode material precursor; The aluminum oxide-coated barium titanate-nickel-rich ternary positive electrode material precursor is calcined in air to obtain the modified nickel-rich ternary positive electrode material.

5. The preparation method according to claim 4, characterized in that The amount of the barium titanate is 0.5-5% of the amount of the nickel-rich ternary positive electrode material.

6. The preparation method according to claim 4, characterized in that The aluminum source includes one or more of aluminum isopropoxide, aluminum nitrate and aluminum sulfate; the mass of the aluminum source is 0.5-2% of the mass of the nickel-rich ternary positive electrode material.

7. The preparation method according to claim 4, characterized in that The calcination temperature is 450-600° C., and the holding time is 4-7 hours; the heating rate to the calcination temperature is 1-10° C. / min.

8. Use of the modified nickel-rich ternary cathode material according to any one of claims 1 to 3 or the modified nickel-rich ternary cathode material prepared by the preparation method according to any one of claims 4 to 7 in lithium-ion batteries.

9. A positive electrode for a lithium ion battery, characterized in that The positive electrode active material of the positive electrode for lithium-ion batteries is the modified nickel-rich ternary positive electrode material according to any one of claims 1 to 3 or the modified nickel-rich ternary positive electrode material prepared by the preparation method according to any one of claims 4 to 7.

10. A lithium ion battery, characterized in that: The positive electrode is the positive electrode for a lithium ion battery according to claim 9.

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