Preparation method of high-nickel ternary positive electrode material, high-nickel ternary positive electrode material and electrochemical device thereof

Abstract

This application discloses a method for preparing a high-nickel ternary cathode material, the high-nickel ternary cathode material, and an electrochemical device thereof. The method involves mixing a high-nickel ternary precursor, a lithium source, Nb₂O₅, and NbOPO₄ to obtain a mixture, wherein the total molar amount of Nb element introduced by Nb₂O₅ and NbOPO₄ is N, and the molar amount of PO₄ introduced by NbOPO₄ is... 3‑ The molar amount is M, satisfying N:M = 1.25:1~3:1; and the mixture is sintered to allow Nb element to be doped into the bulk lattice of the high-nickel ternary precursor to form a matrix, and to allow PO4 to be doped into the bulk lattice of the precursor to form a matrix. 3‑ With the Li provided by the lithium source + An in-situ reaction generates a Li3PO4 coating layer on the substrate surface, yielding a ternary cathode material. This preparation method achieves a synergistic effect of bulk strengthening and interface protection, maintaining a high initial discharge capacity while simultaneously improving interface stability and cycle capacity retention. The process is simple and cost-effective.

Description

Technical Field

[0001] This application relates to the field of new energy technology, and more particularly to a method for preparing a high-nickel ternary cathode material, the high-nickel ternary cathode material and its electrochemical device. Background Technology

[0002] With the rapid development of new energy vehicles and energy storage, high-nickel ternary cathode materials have become a research hotspot due to their high specific capacity. However, high-nickel ternary cathode materials suffer from bulk structure degradation and interfacial chemical instability, resulting in poor interfacial stability and difficulty in improving cycle capacity retention.

[0003] To address these issues, doping or coating modifications are typically employed. However, single doping modification is insufficient to suppress interfacial side reactions, while single coating modification cannot inhibit the formation of bulk microcracks. It is difficult to achieve both simultaneously. Even when doping and coating are used together for modification, several problems remain, such as the tendency for multilayer coating structures to detach or fail during cycling, difficulty in maintaining interfacial stability, and complex process flows. Summary of the Invention

[0004] In view of this, in order to solve at least one of the above technical problems, this application provides a method for preparing a high-nickel ternary cathode material.

[0005] In addition, this application also provides a high-nickel ternary cathode material prepared by the aforementioned preparation method and an electrochemical device using the cathode material.

[0006] In one aspect, embodiments of this application provide a method for mixing a high-nickel ternary precursor, a lithium source, Nb₂O₅, and NbOPO₄ to obtain a mixture, wherein the total molar amount of Nb element introduced by Nb₂O₅ and NbOPO₄ is N, and the molar amount of PO₄ introduced by NbOPO₄ is... 3- The molar amount is M, satisfying N:M = 1.25:1~3:1; and the mixture is sintered to allow Nb element to be doped into the bulk lattice of the high-nickel ternary precursor to form a matrix, and to allow PO4 to be doped into the bulk lattice of the precursor to form a matrix. 3- With the Li provided by the lithium source + An in-situ reaction generates a Li3PO4 coating layer on the surface of the substrate, thereby obtaining the high-nickel ternary cathode material.

[0007] Based on the first aspect, in some embodiments of this application, the N:M ratio is 1.5:1 to 2.5:1.

[0008] Based on the first aspect, in some embodiments of this application, the molar ratio of Nb2O5 to NbOPO4 in the mixture is 0.25:1 to 0.75:1.

[0009] Based on the first aspect, in some embodiments of this application, the sintering temperature is 750℃~820℃ and the sintering time is 8h~15h.

[0010] Based on the first aspect, in some embodiments of this application, the heating rate of the sintering is 3.5 °C / min; and / or, the sintering is carried out in an oxygen atmosphere.

[0011] Based on the first aspect, in some embodiments of this application, the total Nb element accounts for 0.05% to 0.5% of the total molar amount of transition metals in the high-nickel ternary precursor.

[0012] Based on the first aspect, in some embodiments of this application, the general chemical formula of the high-nickel ternary precursor is Ni. x Co y Mn 1-x-y (OH)₂, where 0.85≤x≤0.9, 0.05≤y≤0.1.

[0013] Based on the first aspect, in some embodiments of this application, the mixing is carried out by dry solid-phase mixing, and the mixing time is 5 min to 50 min.

[0014] Based on the first aspect, in some embodiments of this application, the ratio of the molar amount of Li element in the lithium source to the total molar amount of transition metal in the high-nickel ternary precursor is 1.00~1.10:1.

[0015] Secondly, this application provides a high-nickel ternary cathode material, which is prepared by the aforementioned method for preparing high-nickel ternary cathode materials.

[0016] Thirdly, embodiments of this application provide an electrochemical device, the electrochemical device including a positive electrode sheet, the positive electrode sheet including a positive electrode material, the positive electrode material being the aforementioned high-nickel ternary positive electrode material.

[0017] The method for preparing high-nickel ternary cathode material provided in this application, by using Nb2O5 and NbOPO4 as composite niobium sources, allows for flexible control of the amount of Nb introduced and the amount of PO4. 3- The amount of Nb introduced is precisely controlled to balance the total molar amount of Nb and the total PO4. 3- The molar ratio is in the range of 1.25:1 to 3:1, which allows for the introduction of a specific amount of Nb into the bulk lattice of the matrix during one-step sintering, and the in-situ coating of a specific amount of Li3PO4 on the surface of the matrix. This achieves synergistic optimization of bulk strengthening and interface protection, enabling the cathode material to balance high capacity, long cycle life and interface stability.

[0018] Furthermore, the preparation method provided in this application sinters in one step, eliminating the need for multiple sintering processes for doping and coating, thereby simplifying the preparation process, reducing energy consumption and equipment investment, and offering advantages such as simple process flow, controllable cost, and ease of industrial production. Attached Figure Description

[0019] Figure 1 A process flow diagram of the preparation method of the high-nickel ternary cathode material provided in the embodiments of this application.

[0020] Figure 2 This is a scanning electron microscope (SEM) image of the high-nickel ternary cathode material provided in Example 1 of this application.

[0021] Figure 3 This is a comparison chart of the first discharge capacity and cycle capacity retention of the high-nickel ternary cathode materials provided in Examples 1 to 7 and Comparative Examples 1 to 8 of this application. Detailed Implementation

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of this application pertain. The terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the embodiments of this application. 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.

[0023] The following describes some embodiments of this application in detail. Unless otherwise specified, the embodiments and features described below can be combined with each other.

[0024] Please see Figure 1 As shown in the embodiments of this application, a method for preparing a high-nickel ternary cathode material is provided, comprising: Step S1: Mix the high-nickel ternary precursor, lithium source, Nb2O5, and NbOPO4 to obtain a mixture, wherein the total molar amount of Nb element introduced by Nb2O5 and NbOPO4 is N, and the molar amount of PO4 introduced by NbOPO4 is PO4. 3- The molar quantity is M, satisfying N:M = 1.25:1~3:1.

[0025] Step S2: Sinter the mixture to allow Nb element doping into the bulk lattice of the high-nickel ternary precursor to form a matrix, and to allow PO4 to... 3- Li provided by the lithium source + An in-situ reaction generates a Li3PO4 coating layer on the substrate surface, thereby obtaining the high-nickel ternary cathode material.

[0026] Among them, the high-nickel ternary precursor serves as the matrix raw material, determining the nickel content and layered structure of the final cathode material; the lithium source provides lithium ions to participate in the lithiation reaction to form the matrix, and reacts with the PO4 decomposed in step S2. 3- The reaction generates a Li3PO4 coating layer; Nb2O5 is used as a niobium source to achieve Nb doping into the bulk lattice; NbOPO4 is used as a composite niobium source, which can decompose Nb elements to participate in bulk doping and also provide PO4. 3- This material is used to form a Li3PO4 coating layer with lithium ions. By employing a combination of Nb2O5 and NbOPO4, the amount of Nb introduced and the PO4 content can be flexibly controlled. 3- The amount of Nb introduced is precisely controlled to balance the total molar amount of Nb and PO4. 3- With a molar ratio in the range of 1.25:1 to 3:1, sufficient Nb doping into the bulk lattice and in-situ coating of Li3PO4 on the substrate surface can be completed simultaneously in a one-step sintering process. This simplifies the multi-step doping and coating process in traditional processes into a single step. While maintaining a high initial discharge capacity, it also improves interface stability and cycle capacity retention. Furthermore, the process is simplified, cost is controllable, and it is easy to industrialize.

[0027] In some embodiments, the general chemical formula of the high-nickel ternary precursor is Ni x Co y Mn 1-x-y (OH)₂, where 0.85 ≤ x ≤ 0.9, 0.05 ≤ y < 0.1. The high-nickel ternary cathode material prepared using this high-nickel ternary precursor exhibits a high initial discharge capacity. Simultaneously, the transition metal ratio within this range contributes to the formation of a stable layered structure, providing excellent lattice support for subsequent lithiation reactions and bulk doping.

[0028] In some embodiments, the lithium source includes at least one of lithium hydroxide monohydrate and lithium carbonate. The lithium source is used to provide lithium ions to react with the high-nickel ternary precursor to form a matrix, and simultaneously, after sintering, to react with PO4 released from the decomposition of NbOPO4. 3- The reaction produces a Li3PO4 coating layer.

[0029] In step S2, Nb in Nb2O5 5+ Nb diffuses into the bulk lattice of the matrix material via solid-phase diffusion, replacing some transition metal sites. 5+ With its high valence state and strong Nb-O bond energy, NbOPO4 effectively strengthens the bulk structure, suppresses phase transitions and microcrack formation during charge and discharge processes, and thus improves the material's cycle stability. NbOPO4 decomposes during sintering, releasing PO4. 3- and Nb 5+ Nb5+ Similarly, it enters the bulk lattice to participate in doping, further supplementing the bulk strengthening effect; while PO4 3- Then with the remaining Li in the lithium source + The reaction generates Li3PO4, which is deposited in situ on the surface of the substrate material to form a coating layer. Since Li3PO4 is a fast ion conductor, it is beneficial for the rapid transport of lithium ions at the interface, thereby ensuring the realization of high initial discharge capacity. At the same time, the coating layer can effectively isolate the direct contact between the electrolyte and the substrate, suppress the occurrence of interfacial side reactions, and thus improve the chemical stability of the interface.

[0030] Therefore, the high-nickel ternary cathode material of this application incorporates Nb doping in the bulk phase and a Li3PO4 coating layer on the substrate surface. By precisely controlling the N:M ratio to 1.25:1~3:1, the amount of Nb doped in the bulk phase is appropriate, and the thickness of the Li3PO4 coating layer on the surface is suitable, achieving a good balance between bulk phase strengthening and interface protection. This results in a cathode material that maintains high initial discharge capacity while also improving interface stability and cycle capacity retention. When the N:M ratio is too high or too low, both the sample capacity and cycle capacity retention are low. Specifically, when the N:M ratio is too high, excessive electrochemically inert Nb occupies active sites, affecting capacity performance; when the N:M ratio is too low, the coating layer may be too thick, which can negatively impact lithium-ion interfacial transport.

[0031] For example, the N:M ratio can be 1.25:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 3:1, or any value within the range of any two of the above values.

[0032] In some embodiments, the N:M ratio is further 1.5:1 to 2.5:1. Controlling the N:M ratio within the above-mentioned preferred range allows for a better balance between Nb bulk doping and Li3PO4 in-situ coating, ensuring sufficient Nb elements enter the bulk lattice to strengthen the layered structure, suppress phase transitions and microcrack formation, while also guaranteeing an appropriate amount of PO4. 3- A dense and uniform Li3PO4 coating layer is generated to fully leverage the interfacial transport advantages of fast ion conductors, thereby achieving a good synergy between bulk phase enhancement and interfacial protection. While maintaining a high initial discharge capacity, it further improves interfacial stability and cycle capacity retention.

[0033] In some embodiments, the molar percentage of the total Nb element added relative to the total molar percentage of the transition metal in the high-nickel ternary precursor is 0.05% to 0.5%. This molar percentage can be, for example, 0.05%, 0.3%, 0.5%, or any value within the range of any two of these values. Controlling this molar percentage within the above range is beneficial for ensuring sufficient Nb element enters the bulk lattice to achieve enhanced doping, while reducing the impact of excessive doping on capacity due to the occupation of active sites, thereby achieving a good balance between bulk enhancement and capacity retention.

[0034] In some embodiments, the molar ratio of Nb₂O₅ to NbOPO₄ is 0.25:1 to 0.75:1. Controlling this ratio within this range allows for more precise control of the Nb and PO₄ content. 3- The amount. The molar percentage can be, for example, 0.25:1, 0.4:1, 0.6:1, 0.75:1, or any value within the range of any two of the above values.

[0035] In some embodiments, the sintering temperature is 750℃~820℃ to ensure sufficient growth of the matrix particles after the precursor reacts fully with the lithium salt, and the sintering time is 8h~15h. Controlling the sintering temperature and time within the aforementioned suitable range ensures that the following reactions are completed sequentially during the heating process: In the lower temperature range of 300℃~500℃, NbOPO4 decomposes and releases PO4. 3- With Li in the lithium source + The reaction proceeds fully, generating a dense and uniform Li3PO4 coating layer. This coating layer, acting as a fast ion conductor, facilitates rapid lithium-ion transport at the interface, ensuring a high initial discharge capacity. Simultaneously, it effectively isolates the electrolyte from direct contact with the substrate, suppressing interfacial side reactions and thus improving interfacial chemical stability. Furthermore, Li3PO4 does not undergo thermal decomposition or melting at 800°C, demonstrating sufficient stability for the high-temperature sintering process of the substrate material. Within the higher temperature range of 500°C to 800°C, Nb2O5 and NbOPO4 release Nb... 5+The material diffuses fully into the bulk lattice of the matrix, achieving deep doping and effectively strengthening the layered structure. This suppresses phase transitions and microcrack formation during charge and discharge, thereby improving the material's cycle stability. Simultaneously, the sintering temperature range matches the lithiation reaction temperature of the high-nickel ternary precursor, ensuring the formation of a stable layered structure in the matrix material and providing a structural basis for high capacity performance. This application utilizes a one-step sintering method to simultaneously optimize Nb bulk doping and in-situ Li3PO4 coating in the same heat treatment process. While maintaining high initial discharge capacity, it also improves interface stability and cycle capacity retention, and simplifies the process flow. The sintering temperature can be, for example, 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, 810℃, and 820℃, or any value within the range of any two of these values. The sintering time can be, for example, 8h, 9h, 10h, 11h, 12h, 13h, 14h, and 15h, or any value within the range of any two of the above values.

[0036] It should be noted that during the sintering process, the Li3PO4 coating layer preferentially forms in the lower temperature range, but as the temperature increases, Nb... 5+ It can penetrate the coating layer and enter the matrix lattice through atomic diffusion to achieve bulk doping.

[0037] Meanwhile, during the formation of the Li3PO4 coating, Nb 5+ It may also be partially distributed in the coating layer or at the interface between the coating layer and the substrate; therefore, during high-temperature stages, this portion of Nb... 5+ It can further penetrate into the matrix lattice through atomic diffusion, achieving a synergistic effect of interface modification and bulk doping.

[0038] In some embodiments, controlling the heating rate to 3.5 °C / min is beneficial for uniform heating and full reaction of each component during the heating process, ensuring that NbOPO4 decomposes uniformly in the lower temperature range and forms a dense and uniform Li3PO4 coating layer, while allowing Nb2O5 to release Nb stably in the higher temperature range. 5+ It diffuses uniformly into the bulk lattice of the matrix, thereby achieving synergistic optimization of bulk doping and surface coating, ensuring the consistency of material structure and performance.

[0039] It should be noted that the "high-temperature stage" mentioned here refers to the temperature conditions required for the various components of the material to react during the sintering process. Specifically, it refers to the temperature conditions that allow Nb₂O₅ and NbOPO₄ to fully participate in the reaction, allow Nb to effectively diffuse into the bulk crystal lattice, and allow PO₄ to react. 3- With Li +The temperature range within which the Li3PO4 coating layer is fully formed, such as the sintering temperature of 750℃~820℃ used in this application, is a specific implementation of the aforementioned "high temperature". Correspondingly, the "lower temperature range" mentioned in this application refers to the temperature range within which NbOPO4 decomposes to form the Li3PO4 coating layer; the "higher temperature range" refers to the temperature range within which Nb2O5 and NbOPO4 release Nb 5+ The diffusion into the bulk lattice of the matrix achieves doping within a temperature range, such as 500℃ to 800℃. By matching the above temperature window, the in-situ formation of the coating layer and bulk doping can be completed sequentially in a one-step heating process, thereby achieving synergistic modification.

[0040] In some embodiments, sintering is carried out in an oxygen atmosphere with an oxygen concentration ≥99%. This application employs a high-concentration oxygen atmosphere during high-temperature sintering, which provides sufficient oxygen partial pressure for the sintering process and effectively suppresses Ni oxidation caused by oxygen loss in high-nickel materials. 3+ Reduction and Li + / Ni 2+ The mixing of cations maintains the integrity and stability of the layered structure.

[0041] In some embodiments, the molar ratio of Li in the lithium source to the total molar ratio of transition metals in the high-nickel ternary precursor is controlled within the range of 1.00 to 1.10:1 to ensure that the lithiation reaction proceeds fully, forming a complete layered structure, and also helps to reduce residual alkaline lithium compounds on the surface, thereby obtaining a high-nickel ternary cathode material with excellent electrochemical performance. The total molar ratio of transition metals in the high-nickel ternary precursor refers to the sum of the molar ratios of nickel (Ni), cobalt (Co), and manganese (Mn), i.e., the sum of the molar ratios of the three elements Ni, Co, and Mn.

[0042] In some embodiments, the mixing is performed using dry solid-phase mixing. By employing dry solid-phase mixing during the batching stage, this application enables the high-nickel ternary precursor, lithium source, Nb2O5, and NbOPO4 components to fully contact and uniformly disperse in the solid state without the addition of solvents. This provides a good material basis for the subsequent sintering step to achieve the synergistic effect of bulk strengthening and interface protection.

[0043] In some embodiments, the mixing can be carried out using a plow mixer. The plow mixer uses high-speed rotating plow blades and flying blades to create convection, shearing and diffusion effects in the cylinder to achieve efficient and uniform mixing of the components.

[0044] In some embodiments, the mixing time is 5 min to 50 min, and the mixing rate is 700 rpm to 1400 rpm. Adjusting the mixing time within the above-mentioned suitable range is beneficial to ensure that the high-nickel ternary precursor, lithium source, Nb2O5 and NbOPO4 components are fully and uniformly mixed, and at the same time, it is beneficial to maintain the original morphology and structural integrity of the particles while ensuring sufficient mixing.

[0045] Compared with the prior art, the high-nickel ternary cathode material and preparation method provided in this application have the following beneficial effects: 1. This application employs Nb₂O₅ and NbOPO₄ as composite niobium sources and precisely controls the total molar amount of Nb introduced by both and the amount of PO₄ introduced by NbOPO₄. 3- The molar ratio of N:M is within the range of 1.25:1 to 3:1. This method achieves simultaneous Nb doping into the bulk lattice of the matrix and in-situ Li3PO4 coating on the matrix surface during a one-step sintering process. This approach effectively strengthens the bulk structure of the high-nickel ternary material through Nb doping, suppressing phase transitions and microcrack formation during charge and discharge. Simultaneously, the in-situ generated Li3PO4 coating effectively blocks interfacial side reactions between the electrolyte and the matrix, creating a synergistic effect between bulk strengthening and interfacial protection. This allows the high-nickel ternary cathode material to maintain high initial discharge capacity while simultaneously improving interfacial stability and cycle capacity retention.

[0046] 2. This application employs a one-step sintering method, achieving synergistic optimization of surface coating and bulk doping sequentially within the same heat treatment process: In the initial stage of heating, NbOPO4 decomposes and releases PO4. 3- With Li in the lithium source + The reaction generates a dense and uniform Li3PO4 coating layer, improving interfacial stability and lithium-ion transport efficiency; in the later stages of heating, Nb2O5 and NbOPO4 release Nb 5+ The coating fully diffuses into the matrix lattice to achieve bulk doping and strengthen the layered structure. This one-step process simplifies the preparation process, avoids the energy consumption and operational complexity caused by multiple sinterings, and ensures that coating and doping are completed synergistically in the same heat treatment process, maintaining the integrity and consistency of the material's layered structure, thereby achieving a balance between high initial discharge capacity and good cycle stability.

[0047] Secondly, this application provides a high-nickel ternary cathode material, which is prepared by the aforementioned preparation method. Due to the use of the above preparation method, the matrix lattice of this high-nickel ternary cathode material is uniformly doped with Nb element, and simultaneously coated with a Li3PO4 coating layer in situ on the surface, thus possessing both excellent bulk structural stability and interfacial chemical stability. While maintaining a high initial discharge capacity, it also improves interfacial stability and cycle capacity retention.

[0048] Thirdly, this application provides an electrochemical device comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode material, which is a positive electrode material prepared by the aforementioned preparation method or the aforementioned high-nickel ternary positive electrode material. Because this electrochemical device uses the aforementioned high-nickel ternary positive electrode material, it possesses good cycle stability and capacity retention, and its preparation process is simple and cost-controllable, which is beneficial for large-scale production.

[0049] The present application will be further described below with reference to specific embodiments and comparative examples.

[0050] Example 1 Step S1: React lithium hydroxide with high-nickel Ni 0.9 Co 0.05 Mn 0.05 The (OH)2 precursor is mixed in a ratio of 1.05:1 between the molar amount of Li in lithium hydroxide and the total molar amount of transition metals in the high-nickel ternary precursor (i.e., the sum of the molar amounts of Ni, Co, and Mn). Nb2O5 and NbOPO4 are added as dopants. The mixture is stirred evenly using a plow mixer to obtain a one-time dry-mixed product.

[0051] The mixing and stirring time in step S1 is 20 min, and the stirring speed is 1200 rpm. The molar percentage of Nb element in Nb₂O₅ relative to the total molar amount of transition metals in the high-nickel ternary precursor is 0.1 mol%. The molar percentage of P element in NbOPO₄ relative to the total molar amount of transition metals in the high-nickel ternary precursor is 0.1 mol%. The total molar amount of Nb element introduced by Nb₂O₅ and NbOPO₄, and the molar amount of PO₄ introduced by NbOPO₄... 3- The molar ratio of M to N:M is 2:1.

[0052] Step S2: The primary dry mix obtained in step S1 is sintered once in an oxygen atmosphere (oxygen concentration ≥99%) to obtain the matrix material. The primary sintering temperature in this step is 805℃, and the sintering time in the primary sintering temperature zone is 12h.

[0053] Step S3: After cooling the matrix material from step S2 in the furnace, the cathode material is obtained.

[0054] Example 2 The difference between this embodiment and Embodiment 1 is that in step S1, the molar percentage of Nb element in Nb2O5 relative to the total molar amount of transition metals in the high-nickel ternary precursor is 0.025 mol, and the molar percentage of P element in NbOPO4 relative to the total molar amount of transition metals in the high-nickel ternary precursor is 0.1 mol. The total molar amount of Nb element introduced by these two elements and the molar amount of PO4 introduced by NbOPO4 are...3- The molar ratio of M to N:M is 1.25:1. The remaining steps and parameters are the same as in Example 1.

[0055] Example 3 The difference between this embodiment and Embodiment 1 is that in step S1, the molar percentage of Nb element in Nb2O5 relative to the total molar amount of transition metals in the high-nickel ternary precursor is 0.05 mol%, and the molar percentage of P element in NbOPO4 relative to the total molar amount of transition metals in the high-nickel ternary precursor is 0.1 mol%. The total molar amount of Nb element introduced by these two elements and the molar amount of PO4 introduced by NbOPO4 are also related. 3- The molar ratio of M to N:M is 1.5:1. The remaining steps and parameters are the same as in Example 1.

[0056] Example 4 The difference between this embodiment and Embodiment 1 is that in step S1, the molar percentage of Nb element in Nb2O5 relative to the total molar amount of transition metals in the high-nickel ternary precursor is 0.15 mol, and the molar percentage of P element in NbOPO4 relative to the total molar amount of transition metals in the high-nickel ternary precursor is 0.1 mol. The total molar amount of Nb element introduced by these two elements and the molar amount of PO4 introduced by NbOPO4 are also related. 3- The molar ratio of M to N:M is 2.5:1. The remaining steps and parameters are the same as in Example 1.

[0057] Example 5 The difference between this embodiment and Embodiment 1 is that in step S1, the molar percentage of Nb element in Nb2O5 relative to the total molar amount of transition metals in the high-nickel ternary precursor is 0.2 mol%, and the molar percentage of P element in NbOPO4 relative to the total molar amount of transition metals in the high-nickel ternary precursor is 0.1 mol%. The total molar amount of Nb element introduced by these two elements and the molar amount of PO4 introduced by NbOPO4 are also related. 3- The molar ratio of M to N:M is 3:1. The remaining steps and parameters are the same as in Example 1.

[0058] Example 6 The difference between this embodiment and Embodiment 1 is that in step S1, the high-nickel ternary precursor is Ni. 0.8 Co 0.1 Mn 0.1 (OH)2. The remaining steps and parameters are the same as in Example 1.

[0059] Example 7 The difference between this embodiment and Embodiment 1 is that in step S1, the high-nickel ternary precursor is Ni. 0.85 Co 0.05 Mn 0.1 (OH)2. The remaining steps and parameters are the same as in Example 1.

[0060] Comparative Example 1 The difference between this comparative example and Example 1 is that Nb₂O₅ was not added in step S1, only NbOPO₄ was added. Specifically, the molar percentage of P element in NbOPO₄ relative to the total molar amount of transition metals in the high-nickel ternary precursor is 0.1 mol%. The total molar amount of Nb element introduced by NbOPO₄ and the molar amount of PO₄ introduced by NbOPO₄ are... 3- The molar ratio of M to N:M is 1:1. The remaining steps and parameters are the same as in Example 1.

[0061] Comparative Example 2 The difference between this comparative example and Example 1 is that NbOPO4 was not added in step S1, only Nb2O5 was added. The molar percentage of Nb element in Nb2O5 relative to the total molar amount of transition metals in the high-nickel ternary precursor is 0.2 mol%. The remaining steps and parameters are the same as in Example 1.

[0062] Comparative Example 3 The difference between this comparative example and Example 1 is that Nb2O5 and NbOPO4 were not added in step S1. The remaining steps and parameters are the same as in Example 1.

[0063] Comparative Example 4 The difference between this comparative example and Example 6 is that Nb2O5 and NbOPO4 were not added in step S1. The remaining steps and parameters are the same as in Example 6.

[0064] Comparative Example 5 The difference between this comparative example and Example 7 is that Nb2O5 and NbOPO4 were not added in step S1. The remaining steps and parameters are the same as in Example 7.

[0065] Comparative Example 6 The difference between this comparative example and Example 1 is that the dopants added in step S1 are LiNbO3 and Li3PO4, respectively. Specifically, the molar percentage of Nb in LiNbO3 relative to the total molar amount of transition metal in the high-nickel ternary precursor is 0.2 mol%, and the molar percentage of P in Li3PO4 relative to the total molar amount of transition metal in the high-nickel ternary precursor is 0.1 mol%. The remaining steps and parameters are the same as in Example 1.

[0066] Comparative Example 7 The difference between this comparative example and Example 1 is that the dopants added in step S1 are metallic Nb and NH4H2PO4, respectively. Specifically, the molar percentage of Nb in the high-nickel ternary precursor is 0.2 mol%, and the molar percentage of P in the high-nickel ternary precursor is 0.1 mol%. The remaining steps and parameters are the same as in Example 1.

[0067] Comparative Example 8 The difference between this embodiment and Embodiment 1 is that this comparative example uses a stepwise doping-coating process. The specific steps are as follows: Step S1: React lithium hydroxide with high-nickel Ni 0.9 Co 0.05 Mn 0.05 The (OH)₂ precursor was mixed with lithium in a total molar ratio of 1.05:1 to transition metals, and Nb₂O₅ was added as a dopant. The mixture was stirred evenly using a plow mixer to obtain a single dry-mix product, with a stirring time of 20 min. The molar percentage of Nb in Nb₂O₅ was 0.1 mol% of the total molar amount of transition metals in the high-nickel ternary precursor.

[0068] Step S2: The dry mixture obtained in step S1 is sintered once in an oxygen atmosphere (oxygen concentration ≥99%) to obtain the matrix material. The sintering temperature is 805℃, and the sintering time in the main temperature zone is 12h.

[0069] Step S3: The matrix material from step S2 is mixed and stirred evenly with NbOPO4 in a plow mixer to obtain a secondary mixture. The stirring time is 20 min and the stirring speed is 1200 rpm. The molar percentage of P element in NbOPO4 relative to the total molar amount of transition metals in the high-nickel ternary precursor is 0.1 mol%. This is achieved by combining the total molar amount of Nb element introduced in steps S1 and S3 with the molar amount of PO4 introduced from NbOPO4. 3- The molar ratio of M to N:M is 2:1.

[0070] Step S4: The secondary mixture from step S3 is subjected to secondary sintering in an oxygen atmosphere to obtain a stepwise doped-coated matrix material. The secondary sintering temperature is 650℃, and the sintering time in the main temperature zone is 10h.

[0071] The high-nickel ternary cathode materials obtained in Examples 1-8 and Comparative Examples 1-5, and the batteries prepared therefrom, were subjected to the following tests: Scanning electron microscopy (SEM) testing: The microstructure and structural features of the high-nickel ternary cathode material were observed using a JSM-IT210 scanning electron microscope. The testing conditions were: accelerating voltage 10.00 kV, magnification 5000x. This instrument has high-resolution imaging capabilities, clearly revealing the particle morphology, surface state, and structural features of the cathode material.

[0072] Average particle size test: Particle size distribution laser diffraction method, instrument model: Malvern, MasterSize 3000, pretreatment conditions: ultrasonic, particle refractive index: 2.42, dispersant: 2-3 drops of saturated sodium pyrophosphate, test cycle: 3 times, sample test time: 5 s, background test time: 5 s, stirrer / pump speed: 3200 rpm, internal ultrasonic power and time: 100% / 20s, keep single mode, turn on blue light.

[0073] D50 test: Particle size distribution laser diffraction method, instrument model: Malvern, Master Size 3000, pretreatment conditions: ultrasonic, particle refractive index: 2.42, dispersant: 2-3 drops of saturated sodium pyrophosphate, test cycle: 3 times, sample test time: 5 s, background test time: 5 s, stirrer / pump speed: 3200 rpm, internal ultrasonic power and time: 100% / 20s, keep single mode, turn on blue light.

[0074] Electrochemical performance testing: Battery preparation: High-nickel ternary cathode material, conductive carbon and binder PVDF are mixed evenly at a mass ratio of 90:5:5 to prepare a half cell.

[0075] First charge and discharge capacity test: The constant current charge and discharge test was performed using the Blue Battery Test System. The test voltage range was 2.8V~4.3V, the charge and discharge rate was +1C / -1C, the CV cutoff current was 0.01C, and the first discharge capacity was recorded.

[0076] First-time efficiency test: First-time efficiency = First discharge specific capacity / First charge specific capacity.

[0077] High-temperature cycle test: The constant current charge and discharge test was performed using the Blue Battery Test System. The test voltage range was 2.8V~4.3V, the test temperature was 45℃, the charge and discharge rate was +1C / 1C, the CV cutoff current was 0.01C, and the capacity retention rate was recorded after 100 cycles.

[0078] The test results of the examples and comparative examples are shown in Table 1 below.

[0079] Table 1 Results Analysis: Combining Table 1 and... Figure 2 and Figure 3It is evident that the high-nickel ternary cathode material prepared by the method of this application maintains a high initial discharge capacity while simultaneously improving interface stability and cycle capacity retention. Specifically, for Examples 2 to 5, when the N:M ratio is in the range of 1.25:1 to 3:1, the prepared high-nickel ternary cathode materials all exhibit good initial discharge capacity and cycle capacity retention. When the N:M ratio is in the range of 1.5:1 to 2.5:1, the cycle capacity retention of the material is at a relatively good level; when the N:M ratio is 2:1, the overall performance of the material reaches a relatively good state. Therefore, by controlling the N:M ratio within the range of 1.25:1 to 3:1, this application can achieve effective synergy between Nb bulk doping and Li3PO4 interface protection, maintaining a high initial discharge capacity while simultaneously improving interface stability and cycle capacity retention.

[0080] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 uses only NbOPO4 as a modifier, without adding Nb2O5, and its N:M ratio is 1:1; while Example 1 uses Nb2O5 and NbOPO4 as a composite niobium source, and the N:M ratio is 2:1. (Refer to Table 1 and...) Figure 2 The experimental results show that the cycling capacity retention rate of Comparative Example 1 is lower than that of Example 1. This demonstrates that by using a composite niobium source and optimizing the N:M ratio, the cycling stability of the material is improved, achieving the dual effects of bulk doping and interface protection.

[0081] The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 uses only Nb₂O₅ as a modifier and does not add NbOPO₄; while Example 1 uses a composite niobium source and the N:M ratio is 2:1. (Refer to Table 1 and...) Figure 2 The experimental results show that the cycling capacity retention rate of Comparative Example 2 is lower than that of Example 1. This demonstrates that the composite niobium source scheme can simultaneously address the dual modification requirements of bulk strengthening and interface protection, effectively improving interfacial chemical stability while enhancing the bulk structure.

[0082] The difference between Comparative Example 3 and Example 1 is that Comparative Example 3 did not add any modifiers; while Example 1 used a composite niobium source with an N:M ratio of 2:1. (Refer to Table 1 and...) Figure 2 The experimental results show that the cycle capacity retention rate of Comparative Example 3 is significantly lower than that of Example 1. Therefore, it is evident that this application, through modification with a composite niobium source, can effectively improve the cycle stability of high-nickel ternary cathode materials.

[0083] The difference between Comparative Example 4 and Example 6 is that Comparative Example 4 uses Ni. 0.8 Co 0.1 Mn 0.1Example 6 used an (OH)2 precursor without any modifiers; while Example 7 used a high-nickel ternary precursor with the same composition, and employed Nb2O5 and NbOPO4 as a composite niobium source with an N:M ratio of 2:1. Based on the experimental results in Table 1, Example 6 showed better cycle capacity retention than Comparative Example 4. Therefore, the composite niobium source modification scheme of this application has an improving effect on high-nickel ternary materials with different compositions, and can effectively improve the cycle stability of the materials.

[0084] The difference between Comparative Example 5 and Example 7 is that Comparative Example 5 uses Ni. 0.85 Co 0.05 Mn 0.1 Example 7 used an (OH)2 precursor without any modifiers; while Example 8 used a high-nickel ternary precursor with the same composition and employed Nb2O5 and NbOPO4 as a composite niobium source with an N:M ratio of 2:1. Based on the experimental results in Table 1, Example 7 showed better cycle capacity retention than Comparative Example 5. Therefore, the composite niobium source modification scheme of this application can achieve a synergistic effect of bulk strengthening and interface protection in high-nickel ternary materials with different nickel contents, which is beneficial to improving the overall electrochemical performance of the materials.

[0085] In Comparative Example 6, both LiNbO3 and Li3PO4 are stable crystals, and their Nb-O bonds and PO bonds are fully formed. They are difficult to break and recombine under conventional solid-state sintering conditions, making it difficult to achieve effective bulk doping and in-situ coating.

[0086] In Comparative Example 7, NH4H2PO4 decomposes to generate P2O5 and NH3 at 200℃-300℃, while niobium powder requires temperatures above 600℃ to begin oxidation and generate Nb2O5. The reaction temperature windows of the two are severely mismatched, leading to premature decomposition and volatilization of the phosphorus source and delayed oxidation of the niobium source, thus preventing a synergistic reaction. Therefore, the preparation method using Nb2O5 and NbOPO4 as the composite niobium source in Example 1 of this application is not obvious. Specifically, the unique synergistic effect achieved in this application is due to the following mechanisms: Firstly, the adjustable dosage ratio. Nb₂O₅ provides only Nb, focusing on bulk doping, while NbOPO₄ provides both Nb and P, with Nb used for supplementary doping and P used to form the Li₃PO₄ coating layer. By adjusting the ratio of the two, independent optimization of the doping and coating amounts is achieved, which is impossible with a single niobium source or other compounds with a fixed Nb / P ratio. Secondly, the matching of reaction timing. NbOPO₄ begins to decompose at 300℃-500℃, releasing PO₄⁻. 3- With excessive Li +The reaction generates a Li3PO4 coating layer in situ during the early stages of material lattice formation, while Nb2O5 gradually participates in the reaction between 500℃ and 800℃ to achieve bulk doping. The reaction temperature window of both covers the entire sintering process, ensuring that doping and coating occur simultaneously and synergistically. Based on the adjustability of the dosage ratio and the matching of the reaction timing, this application can achieve effective synergy between Nb bulk doping and Li3PO4 in situ coating in a one-step sintering process, thereby obtaining excellent electrochemical performance. As can be seen from Comparative Examples 6 and 7 and the examples, not any combination of Nb source and P source can achieve a good synergistic effect. Only by combining specific compounds Nb2O5 and NbOPO4 and utilizing the matching of their reaction temperature windows can effective synergy between Nb bulk doping and Li3PO4 in situ coating be achieved.

[0087] The difference between Comparative Example 8 and Example 1 is that Comparative Example 8 uses a step-by-step method to first perform Nb doping and sintering, and then mix NbOPO4 for a second sintering. Example 1, on the other hand, uses a one-step method to simultaneously complete doping and coating. Comparing Example 1 and Comparative Example 8, under the same final elemental ratio, the sample prepared using the step-by-step method exhibits significantly worse performance than that prepared using the one-step method. This is mainly because the secondary heat treatment causes secondary damage to the optimized bulk structure, and the subsequently introduced coating layer is difficult to grow in situ with high quality. Therefore, the one-step sintering method can avoid damage to the already formed bulk structure caused by secondary heat treatment and is conducive to the high-quality in-situ growth of the Li3PO4 coating layer, thus achieving a better synergistic effect. In terms of process, the one-step sintering process provided in this application has the following advantages: First, by directly sintering Nb2O5 and NbOPO4 with a high-nickel ternary precursor and a lithium source in a single mixing process, this application eliminates the need for intermediate cooling, crushing, sieving, and secondary mixing, simplifying the preparation process and reducing energy consumption and equipment investment. Second, the one-step sintering method avoids the potential adverse effects of secondary heat treatment on the formed bulk structure, which is beneficial for maintaining the integrity of the matrix layered structure. Simultaneously, the one-step sintering method utilizes the lower temperature decomposition of NbOPO4 to generate a Li3PO4 coating layer and the higher temperature of Nb2O5 to achieve temperature window matching for Nb bulk doping. This allows the coating layer to be generated in situ and uniformly covered in the early stages of lattice formation, while doping occurs fully in the subsequent high-temperature stage, thereby maximizing the synergistic effect of doping and coating. Therefore, the preparation method of this application simplifies the process while providing a reliable process guarantee for improving material performance.

[0088] In summary, this application achieves a synergistic effect between the bulk structure enhancement brought about by Nb doping and the interfacial chemical protection provided by Li3PO4 coating by adjusting the N:M ratio within the aforementioned suitable range. This optimizes the coating thickness and doping amount, ensuring that the Li3PO4 coating has a moderate thickness to facilitate rapid lithium-ion interfacial transport while ensuring that the Nb doping amount enhances the bulk structure without occupying excessive active sites. This results in a cathode material with high initial discharge capacity, good interfacial stability, and high cycle capacity retention. Compared with single modifiers, combinations of other niobium and phosphorus sources, and stepwise processes, this application maintains a high initial discharge capacity while improving interfacial stability and cycle capacity retention. Furthermore, this modification scheme is well-suited for high-nickel ternary materials with different compositions. Simultaneously, the one-step sintering process provided in this application simplifies the preparation process, reduces energy consumption and equipment investment, and avoids the adverse effects of secondary heat treatment on the bulk structure, providing a reliable process guarantee for improving material performance.

[0089] The above description describes some specific embodiments of this application, but in actual applications, the application should not be limited to these embodiments. For those skilled in the art, other modifications and alterations made based on the technical concept of this application should fall within the protection scope of this application.

Claims

1. A method for preparing a high-nickel ternary cathode material, characterized in that, include: A mixture of a high-nickel ternary precursor, a lithium source, Nb₂O₅, and NbOPO₄ was obtained. The total molar amount of Nb introduced by Nb₂O₅ and NbOPO₄ was N, and the amount of PO₄ introduced by NbOPO₄ was... 3- The molar quantity is M, satisfying N:M = 1.25:1 to 3:1; and The mixture is sintered to allow Nb element to be doped into the bulk lattice of the high-nickel ternary precursor to form a matrix, and PO4 is then incorporated into the matrix. 3- With the Li provided by the lithium source + An in-situ reaction generates a Li3PO4 coating layer on the surface of the substrate, thereby obtaining the high-nickel ternary cathode material.

2. The method for preparing the high-nickel ternary cathode material according to claim 1, characterized in that, The N:M ratio is 1.5:1 to 2.5:

1.

3. The method for preparing the high-nickel ternary cathode material according to claim 1, characterized in that, In the mixture, the molar ratio of Nb2O5 to NbOPO4 is 0.25:1 to 0.75:

1.

4. The method for preparing the high-nickel ternary cathode material according to claim 1, characterized in that, The sintering temperature is 750℃~820℃, and the sintering time is 8h~15h.

5. The method for preparing the high-nickel ternary cathode material according to claim 1, characterized in that, The total Nb element accounts for 0.05% to 0.5% of the total molar amount of transition metals in the high-nickel ternary precursor.

6. The method for preparing the high-nickel ternary cathode material according to claim 1, characterized in that, The general chemical formula of the high-nickel ternary precursor is Ni x Co y Mn 1-x-y (OH)₂, where 0.85≤x≤0.9, 0.05≤y<0.

1.

7. The method for preparing the high-nickel ternary cathode material according to claim 1, characterized in that, The mixing is performed using a dry solid-phase mixing method, and the mixing time is 5 min to 50 min.

8. The method for preparing the high-nickel ternary cathode material according to claim 1, characterized in that, The ratio of the molar amount of Li in the lithium source to the total molar amount of transition metals in the high-nickel ternary precursor is 1.00~1.10:

1.

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

10. An electrochemical device, characterized in that, The electrochemical device includes a positive electrode plate, the positive electrode plate includes a positive electrode material, and the positive electrode material is a positive electrode material prepared by the preparation method of high-nickel ternary positive electrode material as described in any one of claims 1 to 8.

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