A high-nickel positive electrode material based on a zirconium-based organic metal framework UiO-66 dynamic protection mechanism and a preparation method and application thereof

Abstract

The application discloses a high-nickel positive electrode material based on a zirconium-based organic metal skeleton UiO-66 dynamic protection mechanism and a preparation method and application thereof. 4+ In the process of battery electrochemical cycle, the porous structure of UiO-66 is used to in-situ adsorb electrolyte corrosion components and capture dissolved transition metal ions, and Zr 4+ is released to in-situ dope into the positive electrode surface layer lattice, so that the dual dynamic synergistic protection of interface passivation and lattice pinning is simultaneously realized. The method effectively inhibits lithium-nickel cation mixing, lattice oxygen precipitation, micro-crack expansion and transition metal dissolution of the high-nickel positive electrode, and significantly improves the structural stability and long cycle life of the material. The application has a simple process, is compatible with the existing battery manufacturing process, and has a good industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of cathode material technology for chemical power sources lithium-ion batteries, specifically involving a high-nickel cathode material based on the dynamic protection mechanism of zirconium-based organometallic framework UiO-66, its preparation method, and its application. Background Technology

[0002] With the rapid development of new energy electric vehicles, smart energy storage grids, and other fields, the market demand for lithium-ion batteries with high energy density, long cycle life, and high safety and stability is becoming increasingly urgent. The energy density of lithium-ion batteries is mainly determined by the cathode material. Among existing layered cathode material systems, high-nickel layered oxides like LiNi0 are particularly important. 0.9 Co 0.05 Mn 0.05 O2 (NCM90) has high specific capacity and a relatively high operating voltage platform, making it a core candidate cathode material for next-generation high-energy-density lithium-ion batteries.

[0003] However, increased nickel content leads to a significant decrease in the cycle stability of high-nickel cathode materials, severely restricting their large-scale commercial application. Research indicates that the performance degradation of high-nickel cathodes mainly stems from two core issues: lattice structure degradation and interfacial chemical failure. On the one hand, the lattice structure is prone to irreversible degradation. During the charging and delithiation process, Ni... 2+ Ionic radius (0.69 Å) and Li + With similar ionic radii (0.76 Å), Ni 2+ It readily migrates from the transition metal layer to the lithium layer, causing severe lithium-nickel cation mixing, destroying the original layered crystal structure, and undergoing irreversible phase transitions to electrochemically inert spinel and rock salt phases, resulting in rapid capacity decay. Simultaneously, deep delithiation is easily accompanied by lattice oxygen precipitation, further exacerbating crystal structure collapse. On the other hand, the electrode interface is prone to chemical failure. Alkaline impurities such as LiOH and Li₂CO₃ remaining on the surface of the high-nickel cathode can catalyze the decomposition of the electrolyte to generate corrosive HF. HF continuously erodes the surface lattice of the cathode, inducing the dissolution, migration, and deposition of transition metal ions such as Ni, Co, and Mn on the negative electrode surface, damaging the stability of the negative electrode SEI film structure, causing a continuous increase in battery internal resistance and irreversible capacity decay. The aforementioned lattice degradation and interface failure are not independent effects; they are coupled and form a vicious cycle, greatly hindering the industrial application of high-nickel layered cathode materials.

[0004] Current modification methods mainly include elemental doping and surface coating: metal ions such as Al, Mg, and Zr are doped during the synthesis process to stabilize the crystal lattice, or oxides such as Al2O3 and TiO2 are used to coat the electrolyte and isolate it from direct contact with the positive electrode. However, existing modification methods are all static and passive protection, involving only one-time modification during battery fabrication. During long-term electrochemical cycling, the pre-coated layer is prone to detachment, the doped active sites gradually fail, and the material experiences structural fatigue. This makes it impossible to continuously stabilize the crystal lattice and interface environment, and it is difficult to fundamentally sever the coupling degradation effect between lattice instability and interface failure.

[0005] Therefore, developing a modification technology that can continuously regulate and dynamically stabilize the high-nickel cathode lattice structure and interfacial chemical environment during long-term battery cycling, and suppress structural degradation and interfacial side reactions from both bulk and interfacial dimensions, is a key technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0007] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0008] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a high-nickel cathode material based on the dynamic protection mechanism of zirconium-based organometallic framework UiO-66.

[0009] To solve the above technical problems, the present invention provides the following technical solution: a high-nickel cathode material based on the dynamic protection mechanism of zirconium-based organometallic framework UiO-66, characterized in that: it includes a high-nickel layered oxide cathode active material, and a zirconium-based organometallic framework composite with the high-nickel layered oxide cathode active material, wherein the zirconium-based organometallic framework provides dynamic protection for the high-nickel layered oxide cathode active material during electrochemical cycling. The high-nickel layered oxide positive electrode active material is NCM90, and the zirconium-based organometallic framework is UiO-66, with UiO-66 added at a rate of 0.1 wt% to 1 wt% compared to NCM90. The UiO-66 is used to provide dynamic protection for the positive electrode active material during electrochemical cycling.

[0010] As a preferred embodiment of the high-nickel cathode material of the present invention, the UiO-66 is obtained by heating and refluxing 4-fluoroterephthalic acid and ZrCl4 in a mixed solution of acetic acid and deionized water, followed by washing and drying.

[0011] As a preferred embodiment of the high-nickel cathode material of the present invention, the heating and reflow temperature is 100~120℃ and the time is 12~15 h.

[0012] As a preferred embodiment of the high-nickel cathode material of the present invention, the amount of UiO-66 added is 0.5 wt% of the mass of NCM90.

[0013] As a preferred embodiment of the high-nickel cathode material of the present invention, the high-nickel cathode material further includes a conductive agent and a binder.

[0014] Another objective of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a high-nickel cathode material based on the zirconium-based organometallic framework UiO-66 dynamic protection mechanism, characterized in that it includes: A modified positive electrode sheet is obtained by mixing high-nickel layered oxide positive electrode active material, conductive agent, binder and UiO-66 powder in a certain proportion, and then grinding, slurrying, coating and drying.

[0015] In a preferred embodiment of the preparation method described in this invention, the mass ratio of the high-nickel layered oxide positive electrode active material, the conductive agent, and the binder is 8:1:1.

[0016] Another object of the present invention is to overcome the shortcomings of the prior art and provide a lithium-ion battery, characterized in that it comprises the above-mentioned high-nickel cathode material.

[0017] As a preferred embodiment of the lithium-ion battery of the present invention, the lithium-ion battery retains a capacity of not less than 86.25% after 150 cycles at a voltage range of 3.0-4.8 V and a rate of 0.2 C; and retains a capacity of not less than 81.58% after 500 cycles.

[0018] Another objective of this invention is to overcome the shortcomings of the prior art and provide an application of a high-nickel cathode material in the fields of electric vehicles or energy storage grids.

[0019] Another objective of this invention is to overcome the shortcomings of the prior art and provide a method for dynamically protecting high-nickel cathode materials, characterized by: introducing UiO-66 into the high-nickel cathode system so that it can simultaneously perform the following functions during battery cycling: It adsorbs acidic corrosive components in the electrolyte and captures dissolved transition metal ions through its porous framework and surface sites; it also slowly releases Zr.4+ This allows it to be doped in situ into the positive electrode surface lattice, thereby suppressing lithium-nickel cation mixing and lattice oxygen evolution.

[0020] Beneficial effects of this invention: (1) Construct a dynamic self-optimizing protection mechanism to overcome the limitations of traditional static modification: This invention relies on UiO-66 to target Zr 4+ The controllable slow-release properties of Zr can be achieved during battery cycling. 4+ Progressive in-situ doping pins and repairs the lattice structure in real time, effectively suppressing lithium-nickel cation mixing, lattice oxygen evolution, and microcrack propagation, thus completely overcoming the drawbacks of traditional one-time doping and coating modification in the later stages of cycling.

[0021] (2) The dual synergistic stabilization of the surface lattice and interface breaks the vicious cycle of performance degradation: The UiO-66 porous framework can adsorb HF in situ, capture dissolved transition metal ions, passivate electrode interfaces, and suppress side reactions; it can also slowly release Zr. 4+ By strengthening the crystal lattice structure from the inside of the crystal and bidirectionally coupling interface protection and surface lattice stability, the vicious cycle of "lattice degradation-interface corrosion" is broken from the root, significantly improving structural integrity and capacity retention under long-term cycling.

[0022] (3) The preparation process is simple and compatible with existing industrial production lines: This invention can synthesize UiO-66 powder through a simple reflux method. It only requires physical mixing and slurry preparation with cathode material, conductive agent and binder. There is no need to modify the existing mature processes such as electrode coating, drying and battery assembly. It has strong adaptability, controllable cost and good prospects for industrial application.

[0023] (4) Significantly improved overall electrochemical performance: The modified NCM90-Zr0.5 high-nickel cathode material obtained by this invention has a significantly reduced cycle capacity decay rate and a greatly improved crystal structure integrity. It can effectively suppress lithium-nickel cation mixing and irreversible phase transitions in the crystal lattice, while significantly reducing the dissolution and loss of transition metal ions during cycling. The above multiple advantages fully demonstrate that the dynamic protection mechanism constructed by UiO-66 can be synergistically optimized from multiple dimensions such as crystal structure, cation order, and interface stability, substantially improving the structural stability and long cycle life of the high-nickel cathode. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 The image shown is the XRD pattern of UIO-66 obtained in Embodiment 1 of the present invention.

[0025] Figure 2 This is a SEM image of UIO-66 obtained in Embodiment 1 of the present invention.

[0026] Figure 3 The image shows the pore size distribution curve of UiO-66 obtained in Example 1 of this invention.

[0027] Figure 4 The EDS elemental distribution of NCM90-Zr0.5 before cycling is shown in the embodiment of the present invention.

[0028] Figure 5 The diagram shows the cycle performance of NCM90 with different amounts of Zr added, obtained according to an embodiment of the present invention.

[0029] Figure 6 This is a cross-sectional SEM image of NCM90-Zr0.5 particles after cycling, obtained according to an embodiment of the present invention. The blue arrow indicates the EDS line scan path.

[0030] Figure 7 EDS line scan distribution curves of Ni, Co, Mn and Zr elements collected along the arrow path.

[0031] Figure 8 The cyclic performance diagrams are for NCM90 and NCM90-Zr0.5.

[0032] Figure 9 The XRD patterns of NCM90 and NCM90-Zr0.5 after 50, 100, and 150 cycles are shown.

[0033] Figure 10 The electron paramagnetic resonance (EPR) spectra of NCM90 and NCM90-Zr0.5 after cycling are shown.

[0034] Figure 11 Cross-sectional SEM images of unmodified NCM90(a) and NCM90-Zr0.5(b) cathode particles after cycling.

[0035] Figure 12 Digital photographs of the lithium metal anode obtained after disassembly from a full cell assembled with (a) NCM90 and (b) NCM90-Zr0.5 positive electrodes.

[0036] Figure 13 The results are obtained from ICP-OES testing of the deposition of transition metals (Ni, Co, Mn) in the lithium anodes of NCM90 and NCM90-Zr0.5 batteries after cycling. Detailed Implementation

[0037] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0038] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0039] Secondly, the term "one embodiment" or "embodiment" as used 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 different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0040] The raw materials used in this invention are shown in Table 1.

[0041] Table 1

[0042] The instruments used in the embodiments of this invention are shown in Table 2.

[0043] Table 2

[0044] Test method in this embodiment of the invention: (1) X-ray diffraction (XRD) reveals the crystal structure of a material by analyzing the diffraction pattern generated by the coherent scattering of X-rays by the crystal, based on the Bragg equation. It can not only accurately identify the crystal phase composition of a substance, but also be used to determine fine structural information such as grain size, lattice parameters, and stress state. In this study, we used the X'Pert PRO MPO instrument (Cu Kα radiation, λ = 1.5418 Å) from Panaco, with a scan rate of 10 o min⁻¹, a tube voltage of 40 kV, and a tube current of 40 mA.

[0045] (2) Scanning Electron Microscope (SEM) uses a focused electron beam to scan the sample surface point by point, generating high-resolution images by detecting signals such as excited secondary electrons. It can present microscopic morphologies at the micrometer and nanometer scales with extremely high depth of field, allowing the observed surface to reveal clear three-dimensional structural details. In this study, a SU8010 scanning electron microscope was used, with an accelerating voltage of 5 kV and a working distance of 5 mm during testing.

[0046] (3) The pore structure of the samples was tested by the nitrogen static adsorption method under liquid nitrogen conditions at 77 K using a fully automated CANTA iQ surface area analyzer. The samples were pretreated and degassed in a vacuum environment at 120℃ to remove adsorbed moisture and impurity gases from the surface. The nitrogen adsorption-desorption isotherm curves were obtained by testing. The specific surface area was calculated using the BET model and the mesopore size distribution was analyzed using the BJH model to characterize the pore size of the UiO-66 material.

[0047] (4) Transmission Electron Microscope (TEM) uses a high-energy electron beam to penetrate ultrathin samples. The transmitted and diffracted electron signals are focused, magnified, and imaged using an electromagnetic lens system, allowing for direct observation of the atomic-scale internal microstructure of materials. This characterization technique can simultaneously analyze sample morphology, crystal structure, and elemental composition. It is an indispensable visualization tool for analyzing the microstructure of materials and a core standard method in the field of material microscopic characterization. In this study, a Thermo Fisher Talos F200X transmission electron microscope coupled with energy dispersive spectroscopy (EDS) was used to characterize the elemental distribution characteristics of the UiO-66 and NCM90 composite particles.

[0048] (5) A constant current charge-discharge test was conducted. The Li / / NCM90 coin cells were assembled and placed in a 30 ℃ constant temperature oven for 8 hours. Then, a long-cycle performance test was carried out using the Xinwei Battery Test System. The test voltage range was set to 3~4.8 V. The cells were first activated at a rate of 0.1 C for 3 cycles, and the subsequent cycle rate was adjusted to 0.2 C.

[0049] (6) Stress-free ion beam polishing was performed on the sample cross-section using a Leica EM TIC 3X argon ion polisher. The sample was first mechanically pre-ground, fixed on a rotating sample stage, and then placed in the vacuum chamber of the instrument. The chamber was evacuated to a pressure not exceeding 10⁻⁶ mbar, and the argon ion gun was turned on. The accelerating voltage was set to 5~7.5 kV, the ion beam current to 2~3 mA, and the ion beam incident angle to 3~15°. The sample was rotated at 5~10 rpm and moved laterally synchronously, and was bombarded with argon ion beams for polishing for 1~3 h to eliminate surface mechanical damage and impurities, and to prepare a smooth and undamaged fresh cross-section for observing the microcrack morphology of the cathode material after cycling.

[0050] (7) Inductively coupled plasma mass spectrometry (ICP-MS) is a highly sensitive technique for quantitative analysis of trace elements, widely used in materials science, environmental chemistry, and electrochemical energy storage. Its basic principle is as follows: after atomization, the sample is introduced into a high-temperature inductively coupled plasma (ICP), where elements are atomized and ionized. The resulting ions are separated and detected by a mass spectrometer according to their mass-to-charge ratio (m / z), thus achieving rapid and accurate determination of multiple elements. This paper uses ICP-MS to quantitatively analyze the content of residual transition metals (Ni, Co, Mn) in the cathode material after cycling, in order to assess the degree of dissolution of transition metals in the cathode material under different modification conditions. The ICP-MS instrument used in this experiment is an Agilent 7900 ICP-MS.

[0051] (8) Electron paramagnetic resonance (EPR), also known as electron spin resonance (ESR), is a magnetic resonance technique based on the characteristics of unpaired electron magnetic moments in materials. It is used to detect the unpaired electron properties in atoms or molecules and explore the structural characteristics of their surrounding environment. It has unique advantages in studying free radicals, transition metals, and defects. The EPR instrument used in this study is the EPR200M instrument from QuantumCTek Inc., used to analyze the lattice oxygen loss in the cathode structure after cycling.

[0052] Example 1 This embodiment provides a high-nickel cathode material based on the dynamic protection mechanism of zirconium-based organometallic framework UiO-66, its preparation method, and its application, specifically including the following steps: (1) Synthesis of UiO-66 powder: Prepare a diluted acetic acid solution by mixing 30 mL of deionized water with 20 mL of acetic acid. Then, add 0.12 g of 4-fluoroterephthalic acid and 0.116 g of zirconium chloride (ZrCl4) sequentially, stirring until evenly dispersed. Transfer the mixture to a round-bottom flask and heat under reflux at 100 °C for 12 hours. After the reaction is complete, cool to room temperature and wash the product twice each with deionized water and anhydrous ethanol. Finally, dry under vacuum overnight at 60 °C to obtain UiO-66 powder.

[0053] Figure 1 The XRD pattern of the synthesized UiO-66 sample is shown, which is in high agreement with the standard spectrum of simulated UiO-66. The positions of the characteristic diffraction peaks are not significantly shifted, and the peaks are sharp and free of impurities, confirming the successful preparation of UiO-66 material with high crystallinity and high purity.

[0054] Figure 2 SEM images of synthesized UiO-66 show that the sample exhibits a uniform nanoscale octahedral particle morphology, with individual particle sizes ranging from approximately 50 to 100 nm. A certain degree of soft agglomeration exists between the particles, a typical characteristic of nano-MOF powders. The particles have smooth surfaces, regular morphologies, and no obvious amorphous impurities, indicating that the prepared UiO-66 possesses good crystallinity and uniformity.

[0055] Figure 3 The pore size distribution curve of UiO-66 shows a single-peak characteristic, with pore sizes of approximately 0.6–0.7 nm, which is highly consistent with the theoretical micropore size of UiO-66. The overall pore size distribution is narrow and concentrated, with no obvious mesopore or macropore signals, indicating that the material has a uniform microporous structure and good pore regularity.

[0056] (2) Preparation of modified positive electrode sheet: NCM90 cathode powder, conductive carbon black and PVDF binder were uniformly mixed at a mass ratio of 8:1:1, and UiO-66 powder with a mass fraction of 0.5 wt% of NCM90 was added to the mixture.

[0057] The mixture was ground in a dry environment for 0.5 h, and then NMP solvent was added and stirred continuously for 24 h to prepare a uniform electrode slurry.

[0058] The slurry was uniformly coated onto the surface of the aluminum current collector using a coating machine, and the coating thickness was controlled to be 7–10 μm. The coated electrode was then dried in a vacuum drying oven at 80°C and allowed to cool naturally to room temperature to obtain the NCM90-Zr0.5 positive electrode. The electrode was then cut into circular positive electrodes with a diameter of 1.4 cm, and the loading of the active material NCM90 was controlled to be 1–2 mg.

[0059] Figure 4The energy dispersive spectroscopy (EDS) surface scanning analysis of NCM90-Zr0.5 before cycling showed that the main elements Ni, Co, Mn and O were highly uniformly distributed within the particles, with no obvious segregation or local enrichment. Zr was also uniformly dispersed throughout the entire particle range, indicating that UIO-66 and NCM90 achieved good homogeneous composite.

[0060] (3) Battery assembly: Inside an argon-atmospheric glove box, coin cells are assembled and sealed in the following order: negative electrode shell, lithium metal sheet, electrolyte, separator, positive electrode sheet, gasket, carbon sheet, and positive electrode shell.

[0061] Electrochemical cycle performance tests were conducted on the assembled battery. During the test, UiO-66 could slowly release Zr. 4+ In-situ doping is incorporated into the surface lattice of NCM90 to achieve lattice self-modification and structural pinning, thereby effectively stabilizing the high-nickel cathode crystal structure.

[0062] Comparative Example 1 The difference between this comparative example and Example 1 is that the UiO-66 powder in step (2) is omitted, while the remaining steps are the same as in Example 1, and pure NCM90 positive electrode sheet and battery are obtained.

[0063] Example 2 The difference between this embodiment and embodiment 1 is that the mass fraction of UiO-66 powder in step (2) is adjusted to 0.1wt%, while the remaining steps are the same as in embodiment 1, to obtain NCM90-Zr0.1 positive electrode sheet and battery.

[0064] Example 3 The difference between this embodiment and embodiment 1 is that the mass fraction of UiO-66 powder in step (2) is adjusted to 0.2wt%, while the remaining steps are the same as in embodiment 1, to obtain NCM90-Zr0.2 positive electrode sheet and battery.

[0065] Example 4 The difference between this embodiment and embodiment 1 is that the mass fraction of UiO-66 powder in step (2) is adjusted to 1wt%, while the remaining steps are the same as in embodiment 1, and NCM90-Zr1 positive electrode sheet and battery are obtained.

[0066] Table 1. Capacity retention of NCM90 and NCM90 cathodes modified with different Zr contents after cycling.

[0067] To screen for the optimal UiO-66 composite doping amount, this invention sets four UiO-66 composite ratios of 0.1 wt%, 0.2 wt%, 0.5 wt%, and 1 wt% to prepare NCM90-Zr0.1, NCM90-Zr0.2, NCM90-Zr0.5, and NCM90-Zr1 modified cathode materials, respectively. The prepared samples were assembled into half-cells, and their electrochemical performance was characterized using a Newway battery testing system within the voltage range of 3.0–4.8 V.

[0068] Combination Figure 5 The half-cell cycle test results of NCM90 cathodes modified with different UiO-66 composite ratios in Table 1 show that 0.5wt% is the optimal composite ratio. This modified sample exhibits the best cycle stability, with a capacity retention of 86.65% after 150 cycles. In contrast, the capacity retention of the unmodified pure NCM90 cathode is only 67.97%.

[0069] Figure 6 The SEM images of the NCM90-Zr0.5 cathode particles after cycling are shown, clearly revealing the radial grain aggregation structure of typical spherical secondary particles with a particle size of approximately 8~10 μm. The blue arrows indicate the path of the EDS line scan analysis, which runs through the complete cross-section of the particle from the left edge to the right edge.

[0070] The EDS linear scan distribution curves of Ni, Co, Mn and Zr elements collected along this path are shown below. Figure 7 As shown, the main elements Ni, Co, and Mn are uniformly distributed throughout the particles, while the modified element Zr exhibits significant surface enrichment characteristics: the Zr content in the bulk phase of the particles is extremely low and the distribution is stable, with obvious Zr element signal peaks only appearing in the edge regions on both sides of the particles, confirming that Zr is mainly enriched in the surface layer of NCM90-Zr0.5 particles, and confirming that Zr has been successfully doped on the NCM90 surface.

[0071] Further long-cycle performance tests were conducted on the optimal sample NCM90-Zr0.5. The long-cycle performance of pure NCM90 and NCM90-Zr0.5 cathodes was compared within the voltage range of 3.0–4.8 V. The results are as follows: Figure 8 As shown, under test conditions of 0.2 C and 30 ℃, the cycling performance of each sample differed significantly: the pure NCM90 sample retained only 65.91% of its capacity after 200 cycles; while the sample with 0.5 wt% Zr... 4+ The composite modified NCM90-Zr0.5 cathode still retains a capacity of 81.58% after 500 long cycles.

[0072] The X-ray diffraction patterns of NCM90 and NCM90-Zr0.5 electrodes after 50, 100, and 150 cycles are as follows: Figure 9As shown in a and b, the diffraction peaks of both the unmodified and doped samples are highly consistent with the LiNiO2 standard phase in the R-3m space group, and there are no obvious impurity diffraction peaks. Local magnification of the (0 0 3) characteristic diffraction peak revealed that the characteristic peak of the undoped NCM90 after 150 cycles shifted significantly to a lower angle, indicating an irreversible increase in the c-axis interlayer spacing and an irreversible phase transition. Notably, the intensity ratio of the (0 0 3) to (1 0 4) diffraction peaks can preliminarily characterize the degree of lithium-nickel cation mixing in the nickel-rich cathode material.

[0073] Table 2. Intensity ratio of (003) / (104) diffraction peaks of NCM90 and NCM90-Zr0.5 cathodes at different cycle numbers.

[0074] As shown in Table 2, under different cycle numbers, the intensity ratio of (0 0 3) / (1 0 4) of NCM90-Zr0.5 is greater than that of NCM90, indicating that zirconium ion doping can effectively reduce the degree of lithium nickel cation mixing.

[0075] Figure 10 Electron paramagnetic resonance (EPR) spectroscopy revealed a significant decrease in the signal intensity corresponding to oxygen vacancies in the zirconium-doped NCM90-Zr0.5 material compared to the original NCM90 material. This result directly confirms that zirconium ion doping can suppress the formation of oxygen vacancies. This suppression effect stems from the higher bond energy of the zirconium oxide chemical bonds after zirconium ion doping. These chemical bonds can firmly fix adjacent oxygen ions, hindering the loss of lattice oxygen and thus reducing the formation of oxygen vacancies.

[0076] Figure 11 Images a and b illustrate the particle morphology of the two cathode materials after cycling, with clear structural changes. The NCM90 material exhibits numerous microcracks, resulting from anisotropic volume changes during cycling. These microcracks cause particle pulverization and fragmentation, a major cause of the rapid performance degradation of the NCM90 cathode. In contrast, the spherical secondary particles of the NCM90-Zr0.5 cathode show only a few microcracks, clearly demonstrating that zirconium doping effectively suppresses internal stress and maintains structural integrity under high-voltage operating conditions.

[0077] The cycled battery was disassembled and characterized (see...). Figure 12 The study found that, compared to the modified NCM90-Zr0.5, the unmodified cathode system exhibited a higher concentration of black material on the surface of the lithium metal anode. Inductively coupled plasma atomic emission spectrometry (ICP-AES) results were also presented. Figure 13 Further confirmation showed that the content of transition metals on the surface of the modified lithium anode was significantly reduced, indicating that UiO-66 can effectively inhibit the dissolution of transition metals in the cathode.

[0078] Comparative Example 2 This comparative example utilizes traditional modification methods to prepare niobium-doped modified high-nickel layered NCM90 cathode material, specifically including the following steps: First, 1.0% molar fraction of niobium pentoxide was added to NCM90, and after thorough mixing, the mixture was placed in a ball mill and milled for 2 hours at a speed of 300 r / min. The resulting mixture was then calcined at 550℃ for 12 hours under an oxygen protective atmosphere to obtain the niobium-modified composite cathode material, labeled as Nb-NCM90.

[0079] Electrochemical test results show that, under the conditions of 25 ℃, charge / discharge rate of 0.2 C, and voltage range of 2.7~4.3V, Nb-NCM90 retains 82.42% of its capacity after 200 charge / discharge cycles.

[0080] Comparative Example 3 This comparative example provides a conventional modification method for preparing high-nickel layered cathode materials, specifically including the following steps: First, NCM90 and 1.0% ammonium fluoride were dispersed in anhydrous ethanol, stirred at 350 r / min, evaporated in an oil bath at 60℃, dried at 80℃ for 12 h, ground, and then calcined at 550℃ for 12 h in an oxygen atmosphere (heating and cooling rate 2 ℃ / min) to obtain the single fluorine doped material F-NCM90.

[0081] Keeping the process conditions unchanged, 1.0% molar fraction of nano-gadolinium oxide was further composited on the surface of F-NCM90, and the same post-treatment and calcination process was followed to obtain the fluorine-doped gadolinium oxide-coated composite modified material F-NCM90@Gd2O3.

[0082] Electrochemical tests (2.7~4.3 V, 0.2 C) showed that the modified composite sample had limited cycling performance, with a capacity retention of only 78.5% after 200 cycles. The overall performance of the modified sample was poor and significantly inferior to the product obtained by the technical solution of this invention.

[0083] The above results indicate that although traditional static modification methods can improve the structural stability and cycle performance of high-nickel cathode materials to a certain extent, their mechanism of action mainly relies on pre-formed fixed doping sites or surface protective layers, making it difficult to achieve continuous and adaptive interface repair and structural regulation during long cycles.

[0084] In contrast, the "dynamic protection" mechanism proposed in this invention can continuously participate in interface repair, active species capture, and structural stability regulation during electrode charge-discharge cycles, thus distinguishing it from traditional static doping or coating modification methods. Compared with existing reports, the NCM90-Zr0.5 material modified by this invention still exhibits excellent long-term cycling stability under higher cutoff voltage conditions: at 3.0–4.8 V, 0.2 C, and 30 ℃, the capacity retention rate reaches 88.81% after 200 cycles, and remains at 81.58% after 500 cycles. This result shows that this invention can not only effectively alleviate interfacial side reactions and structural degradation of NCM90 materials under harsh high-voltage conditions, but also its dynamic protection effect has a more durable stabilizing effect during long cycles, which has a significant advantage over traditional static modification strategies.

[0085] In summary, this invention uses a zirconium-based organometallic framework, UiO-66, as the modifying medium and introduces it into the NCM90 high-nickel cathode system through a simple physical composite method. This is achieved by leveraging the unique porous structure, surface coordination sites, and Zr content of UiO-66. 4+ The sustained-release properties construct a dynamic synergistic protection mechanism that combines interfacial adsorption passivation and in-situ lattice pinning. The NCM90-Zr0.5 modified material prepared with an optimal 0.5 wt% UiO-66 composite ratio can adsorb electrolyte corrosion components and capture dissolved transition metal ions through framework pores and active sites, thus weakening interfacial side reactions. Furthermore, it can continuously release Zr during electrochemical cycling. 4+ In-situ doping into the cathode lattice effectively suppresses lithium-nickel cation mixing, lattice oxygen evolution, and the initiation and propagation of secondary particle microcracks. Microstructure characterization, crystal phase analysis, and long-cycle electrochemical testing results all confirm that UiO-66 modification can simultaneously stabilize the high-nickel cathode structure from both interfacial chemistry and surface lattice dimensions. This breaks through the limitations of traditional static coating and elemental doping, which can only provide passive protection and are prone to failure in the later stages of cycling, significantly improving the structural reversibility and long cycle life of high-nickel cathode materials. Furthermore, the preparation process of this invention is simple and easy to implement, has good compatibility with existing electrode manufacturing processes, and possesses good practical application and industrialization promotion value.

[0086] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A high-nickel cathode material based on a zirconium-based organometallic framework UiO-66 dynamic protection mechanism, characterized in that: This includes a high-nickel layered oxide cathode active material and a zirconium-based organometallic framework combined with the high-nickel layered oxide cathode active material, wherein the zirconium-based organometallic framework provides dynamic protection for the high-nickel layered oxide cathode active material during electrochemical cycling. The high-nickel layered oxide positive electrode active material is NCM90, and the zirconium-based organometallic framework is UiO-66, with UiO-66 added at a rate of 0.1 wt% to 1 wt% compared to NCM90.

2. The high-nickel cathode material as described in claim 1, characterized in that: The UiO-66 is obtained by heating 4-fluoroterephthalic acid and ZrCl4 in a mixed solution of acetic acid and deionized water under reflux, followed by washing and drying.

3. The high-nickel cathode material as described in claim 2, characterized in that: The heating reflux temperature is 100~120℃, and the time is 12~15 h.

4. The high-nickel cathode material as described in claim 1, characterized in that: The amount of UiO-66 added is 0.5 wt% of the mass of NCM90.

5. The high-nickel cathode material as described in any one of claims 1 to 4, characterized in that: The high-nickel cathode material also includes a conductive agent and a binder.

6. The method for preparing high-nickel cathode material based on the zirconium-based organometallic framework UiO-66 dynamic protection mechanism as described in claim 5, characterized in that: include, A modified positive electrode sheet is obtained by mixing high-nickel layered oxide positive electrode active material, conductive agent, binder and UiO-66 powder in a certain proportion, and then grinding, slurrying, coating and drying.

7. A lithium-ion battery, characterized in that: It includes the high-nickel cathode material as described in any one of claims 1 to 4.

8. The lithium-ion battery as described in claim 7, characterized in that: The lithium-ion battery retains a capacity of no less than 86.25% after 150 cycles at a voltage range of 3.0-4.8 V and a rate of 0.2 C; and a capacity retention of no less than 81.58% after 500 cycles.

9. The application of the high-nickel cathode material as described in any one of claims 1 to 5 in the field of electric vehicles or energy storage grids.

10. A method for dynamically protecting high-nickel cathode materials, characterized in that: By introducing UiO-66 into the high-nickel cathode system, it can simultaneously perform the following functions during battery cycling: It adsorbs acidic corrosive components in the electrolyte and captures dissolved transition metal ions through its porous framework and surface sites; it also slowly releases Zr. 4+ This allows it to be doped in situ into the positive electrode surface lattice, thereby suppressing lithium-nickel cation mixing and lattice oxygen evolution.

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