Neodymium-copper-modified high-nickel ternary positive electrode material as well as preparation method and application thereof

Abstract

The invention discloses a neodymium-copper modified high-nickel ternary positive electrode material as well as a preparation method and application thereof, and belongs to the technical field of electrode materials and preparation thereof. Neodymium salt and copper salt are used as raw materials, the Nd2CuO4 coated and modified high-nickel ternary positive electrode material is obtained in a mode of secondary annealing after mixing, an Nd2CuO4 functional coating layer can physically isolate direct contact of an electrode electrolyte so as to further inhibit generation of interface side reaction, and the Nd2CuO4 functional coating layer has rich oxygen vacancies, so that the service life of the Nd2CuO4 ternary positive electrode material is prolonged. As a functional coating, the loss of interface lattice oxygen can be inhibited. Besides, Nd2CuO4 also has rigid constraining force, can inhibit expansion and contraction of the bulk phase layered structure, improves the stability of the bulk phase layered structure and an electrode electrolyte interface, and further greatly improves the lithium storage performance of the high-nickel ternary positive electrode material. A test result shows that the capacity retention ratio is 97.4% after circulation for 150 times under the high charging cut-off voltage of 4.5 V and the current density of 0.5 C.

Description

Technical Field

[0001] The invention relates to a neodymium-copper modified high-nickel ternary positive electrode material, a preparation method and application thereof, and belongs to the technical field of electrode materials and their preparation. Background Art

[0002] LiNi x Co y Mn 1-x-y O2 (NCM) ternary cathode materials have become the main choice for commercial cathodes due to their high output specific capacity and many other advantages. Especially when the nickel content is increased and the charge cut-off voltage is increased, the actual output specific capacity will be further increased, resulting in a lithium-ion battery with higher energy density. However, high voltage and high nickel mean deep lithium deintercalation and redox reactions, which poses greater challenges to the cycle life and safety of ternary cathode materials. For deep lithium deintercalation: a large number of lithium vacancies will promote the disordered migration of cations and form a greater degree of Li + / Ni 2+ Mixing, which will hinder the migration of lithium ions and form local lattice distortion. The accompanying local lattice internal stress will induce the formation of intracrystalline microcracks, causing the inactivation of limited active lithium and reducing the output capacity. In addition, a large number of lithium ion deintercalation is accompanied by a greater degree of volume expansion and contraction of the layered structure, which will form anisotropic internal stress inside the secondary agglomerate particles, causing intercrystalline microcracks and even particle crushing. After the particles are crushed, more new positive electrode material surfaces will be exposed, which will cause more electrolyte decomposition and cause a decrease in output capacity. For deep redox reactions: the positive electrode material will produce more highly active and unstable Ni 4+ , especially on the surface of the positive electrode particles, which will capture the electrons of the adjacent lattice oxygen and the electrolyte in contact with it and be reduced to stable Ni 2+ , then the lattice oxygen loses electrons and becomes active oxygen atoms. After combining with each other, they become oxygen molecules and overflow. Organic molecules in the electrolyte lose electrons and decompose and deposit on the surface of the particles. The loss of interfacial lattice oxygen will cause harmful interfacial phase transformations. At the same time, the overflowing oxygen will catalyze the decomposition of the oxidizing electrolyte and increase the risk of thermal runaway of the battery. The above hazards seriously reduce the cycle life and safety of high-voltage, high-nickel ternary cathode materials, restricting their practical commercial application.

[0003] In response to the above problems, the currently commonly used modification strategies include surface coating and bulk doping. Bulk doping can only affect the various parameters of the layered structure, while surface coating can not only constrain the volume change of the layered structure, but also physically isolate the direct contact between the electrode and the electrolyte, thereby directly improving the cycle stability of the high-voltage high-nickel ternary positive electrode material to the greatest extent. Patent CN119725462A discloses a modified ternary positive electrode material coated with a mixed layer of silicon monoxide and carbon. The coating layer effectively prevents the interaction between the ternary positive electrode material and the electrolyte, reduces side reactions, and improves the cycle stability of the battery. Patent CN119695096A discloses a high-nickel ternary positive electrode material coated and modified by barium zirconate, which exhibits higher charge and discharge efficiency and good cycle life. Patent CN119601649A discloses a high-nickel ternary cathode material with an aluminum-tantalum surface modification. A nanocoating containing aluminum-tantalum metal is constructed on the surface of the high-nickel ternary cathode material. Further high-temperature heat treatment is then performed to promote a chemical reaction between the cathode material and the surface coating, resulting in a surface structure with good stability and high charge transfer capability. This significantly improves the stability of the cathode material, resulting in a cathode material with high specific capacity and good cycle stability. However, the current role of the coating modification material is still insufficient to meet commercialization needs. It is necessary to develop coating material types with better performance to further enhance the lithium storage performance of high-voltage, high-nickel ternary cathode materials, thereby achieving the goal of manufacturing lithium-ion power batteries with high energy density, long cycle life, low cost, and high safety. Summary of the Invention

[0004] In order to solve the above problems existing in the existing lithium ion battery positive electrode materials, the present invention provides a neodymium copper modified high nickel ternary positive electrode material and its preparation method and application.

[0005] The technical solution of the present invention:

[0006] One of the purposes of the present invention is to provide a method for preparing a high-nickel ternary cathode material modified with neodymium copper, the method comprising the following steps:

[0007] (1) dissolving neodymium salt and copper salt in distilled water to form a mixed solution;

[0008] (2) adding high nickel ternary cathode material to the mixed solution, stirring evenly, heating in an oil bath, stirring and evaporating to dryness to obtain a mixed powder;

[0009] (3) The mixed powder is placed in a muffle furnace for annealing to obtain a neodymium-copper modified high-nickel ternary positive electrode material.

[0010] It is further defined that the neodymium salt in (1) is neodymium nitrate, neodymium sulfate or neodymium chlorate.

[0011] It is further defined that the copper salt in (1) is copper nitrate, copper sulfate or copper chlorate.

[0012] It is further limited that the mixed solution may also contain combinations of neodymium iron, neodymium aluminum, neodymium boron, lanthanum iron, lanthanum aluminum, lanthanum boron, etc.

[0013] It is further defined that the atomic ratio of neodymium to copper in the mixed solution of (1) is (1-2):1.

[0014] It is further defined that (2) the ratio of the amount of the added medium-high nickel ternary positive electrode material to the amount of copper in the mixed solution is 100:1.

[0015] Further definition, (2) the medium-high nickel ternary positive electrode material is LiNi x Co y Mn 1-x-y O2, where x ≥ 0.6.

[0016] It is further defined that (2) the heating temperature of the oil bath is 60-100°C.

[0017] It is further defined that the annealing temperature in (3) is 600-800°C and the time is 3-8h.

[0018] The second object of the present invention is to provide a neodymium-copper modified high-nickel ternary positive electrode material prepared by the above method.

[0019] The third object of the present invention is to provide an application of the above-mentioned neodymium-copper modified high-nickel ternary positive electrode material, specifically for lithium-ion battery positive electrode materials.

[0020] Beneficial effects of the present invention:

[0021] The present invention uses neodymium salt and copper salt as raw materials, and obtains a high-nickel ternary positive electrode material coated and modified by Nd2CuO4 by mixing and then performing secondary annealing. The Nd2CuO4 functional coating layer can not only physically isolate the direct contact between the electrode and the electrolyte, thereby inhibiting the occurrence of interfacial side reactions, but also has abundant oxygen vacancies. As a functional coating, it can inhibit the loss of interfacial lattice oxygen. In addition, Nd2CuO4 also has a rigid constraint force, which can inhibit the expansion and contraction of the bulk layered structure, improve the stability of the bulk layered structure and the electrode electrolyte interface, and thus greatly improve the lithium storage performance of the high-nickel ternary positive electrode material. The experimental results show that the capacity retention rate of the high-nickel ternary positive electrode material modified by neodymium copper can reach 97.4% after 150 cycles at a current density of 0.5C at a high charging cut-off voltage of 4.5V, while the unmodified original LiNi 0.70 Co 0.05 Mn 0.25The capacity retention rate of the O2 high-nickel ternary positive electrode material after 150 cycles at a current density of 0.5C was only 75.8%. This indicates that the neodymium-copper-modified high-nickel ternary positive electrode material prepared using the modification method provided by the present invention exhibits excellent charge-discharge cycle stability and can be widely used as a positive electrode material for lithium-ion batteries, making it suitable for widespread application. Furthermore, the modification method provided by the present invention offers advantages such as simple operation, energy conservation, and ease of industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the SEM image of the NCM prepared in Comparative Example 1;

[0023] Figure 2 This is the SEM image of NCM@Nd2CuO4 prepared in Example 1;

[0024] Figure 3 This is a graph showing the cycling stability test results of the lithium half-cell of the ternary cathode materials prepared in Example 1 and Comparative Example 1 in the voltage range of 3-4.5V and the current density of 0.5C. DETAILED DESCRIPTION

[0025] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0026] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0027] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0028] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods, and instruments used are conventional in the art and can be obtained commercially by those skilled in the art unless otherwise specified.

[0029] Comparative Example 1

[0030] (1) 3g of LiNi 0.70 Co 0.05 Mn 0.25The O2 high-nickel ternary cathode material was added to 30 mL of distilled water. The beaker was then placed in an 80°C oil bath and stirred continuously until the aqueous solution was completely evaporated.

[0031] (2) The above-mentioned evaporated LiNi 0.70 Co 0.05 Mn 0.25 The unmodified LiNi was obtained by secondary annealing of O2 powder at 700℃ in a muffle furnace for 5h. 0.70 Co 0.05 Mn 0.25 O2 high nickel ternary positive electrode material (denoted as NCM).

[0032] The SEM image of the NCM material obtained in Comparative Example 1 is shown in Figure 1 , which is a dense secondary sphere with a diameter of 10 μm formed by the accumulation of a large number of primary particles.

[0033] Example 1

[0034] (1) Dissolve 136 mg of Nd(NO3)3·6H2O and 75 mg of Cu(NO3)2·3H2O in 30 mL of distilled water.

[0035] (2) Add 3g of LiNi to the above solution 0.70 Co 0.05 Mn 0.25 O2 high nickel ternary positive electrode material, then place the beaker in an oil bath at 80 ° C and stir continuously until the aqueous solution is completely evaporated.

[0036] (3) The dried mixed powder was annealed for 5 h at 700 ° C in a muffle furnace to obtain LiNi modified with NdCu. 0.70 Co 0.05 Mn 0.25 O2 high nickel ternary positive electrode material (denoted as NCM@Nd2CuO4).

[0037] The SEM image of the NCM@Nd2CuO4 material obtained in Example 1 is shown in Figure 2 , which is a dense secondary sphere with a diameter of 10 μm formed by the accumulation of a large number of primary particles.

[0038] The NCM@Nd2CuO4 prepared in Example 1 and Comparative Example 1 and the unmodified NCM material were used as positive electrode active materials to test the electrochemical lithium storage performance of lithium half-cells. The specific steps are as follows:

[0039] The positive electrode active material, C45, KS-6, and PVDF were mixed in NMP solvent at a mass ratio of 90:4.5:3:2.5. The slurry solid content was designed to be 52%. After uniform mixing using a homogenizer, it was coated on aluminum foil and dried in an 80°C oven for 3 hours. After roller pressing and cutting, it was placed in a vacuum oven overnight. The active material loading of each electrode sheet was approximately 5.0 mg. The negative electrode used a metal lithium sheet, the separator was a polypropylene porous membrane, and the electrolyte was 1 mol L -1 LiPF6 was dissolved in a solvent system with a volume ratio of EC / EMC=3 / 7. The battery used a 2025 button cell and the lithium storage performance test was carried out in the voltage range of 3-4.5V.

[0040] The charge and discharge cycle stability of the batteries prepared from the NCM@Nd2CuO4 and NCM materials obtained in Example 1 and Comparative Example 1 at a current density of 0.5C in the voltage range of 3-4.5V is as follows: Figure 3 As shown, it can be seen that the cycle stability of the high-nickel ternary positive electrode material modified with neodymium copper is significantly better than that of the unmodified material. This fully demonstrates that the Nd2CuO4 coating modification with a perovskite structure plays a huge role in restricting the volume expansion of the layered structure, inhibiting the loss of interfacial lattice oxygen and stabilizing the electrode electrolyte interface, thereby effectively improving the lithium storage performance of the high-nickel ternary positive electrode material. Therefore, the present invention has more advantages in commercial promotion.

[0041] The above description is merely a preferred embodiment of the present invention. Given that those skilled in the art can make appropriate changes and modifications to the above embodiments, the present invention is not limited to the specific embodiments described above. Some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a high nickel ternary cathode material modified with neodymium copper, characterized in that: include: (1) dissolving neodymium salt and copper salt in distilled water to form a mixed solution; (2) adding high nickel ternary cathode material to the mixed solution, stirring evenly, heating in an oil bath, stirring and evaporating to dryness to obtain a mixed powder; (3) The mixed powder is placed in a muffle furnace for annealing to obtain a neodymium-copper modified high-nickel ternary positive electrode material.

2. The method according to claim 1, characterized in that (1) The neodymium salt is neodymium nitrate, neodymium sulfate or neodymium chlorate.

3. The method according to claim 1, characterized in that (1) The copper salt is copper nitrate, copper sulfate or copper chlorate.

4. The method according to claim 1, wherein The atomic ratio of neodymium to copper in the mixed solution of (1) is (1-2):

1.

5. The method according to claim 1, wherein (2) The ratio of the amount of the medium-high nickel ternary positive electrode material added to the amount of copper in the mixed solution is 100:

1.

6. The method according to claim 1, characterized in that (2) The medium-high nickel ternary positive electrode material is LiNi x Co y Mn 1-x- y O2, where x ≥ 0.

6.

7. The method according to claim 1, characterized in that (2) The heating temperature of the oil bath is 60-100℃.

8. The method according to claim 1, characterized in that (3) The annealing temperature is 600-800°C and the time is 3-8h.

9. A neodymium-copper modified high-nickel ternary positive electrode material prepared by the method according to any one of claims 1 to 8.

10. An application of the neodymium-copper modified high-nickel ternary cathode material according to claim 9, characterized in that: Used as positive electrode material for lithium-ion batteries.

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