Gradient-doped lithium-ion battery high-nickel cathode material, preparation method and application thereof

Abstract

The application discloses a gradient-doped lithium ion battery high-nickel positive electrode material and a preparation method and application thereof. w Ni x Co y M z J a Q b O2, wherein 0.9<=w<=1.1, 0.5<=x<1, 0

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a high-nickel cathode material for lithium-ion batteries with multi-mechanism synergistic regulation of gradient doping, its preparation method, and its application. Background Technology

[0002] With the widespread application of high-energy-density lithium-ion batteries in electric vehicles and energy storage, high-nickel cathode materials (such as LiNi) are becoming increasingly important. 0.8 Co 0.1 Mn 0.1 O2 has attracted widespread attention due to its high specific capacity and cost advantages. However, when the nickel content in the material reaches more than 80%, its layered structure exhibits inherent instability, specifically manifested as a violent H2-H3 phase transition, lattice oxygen precipitation, and instability due to Ni. 2+ With Li + The close proximity of radii leads to severe cation mixing, resulting in a decline in the material's cycling performance. Typically, this manifests as a capacity decay exceeding 30% after 300 cycles, which has become a key bottleneck restricting its large-scale application. To improve the overall performance of the material, it is urgent to address this through multi-scale structural defect repair and synergistic regulation of surface and interface stability. However, existing single-element doping methods suffer from limitations in modification dimensionality and insufficient synergistic effects. These methods not only fail to balance structural stability and lithium-ion conduction, but excessive doping can even block lithium-ion migration channels. Summary of the Invention

[0003] In view of this, the present invention proposes a high-nickel cathode material for lithium-ion batteries with multi-mechanism synergistic regulation of gradient doping, its preparation method and application, in order to solve the fundamental technical problem that existing high-nickel cathode materials are difficult to improve in a synergistic way due to the instability of the bulk structure and the mixing of ions at the surface and interface.

[0004] To address the above problems, one aspect of the present invention proposes the following technical solution:

[0005] A gradient-doped high-nickel cathode material for lithium-ion batteries, with the general chemical formula Li. w Ni x Co y M z J a Q bO2, where 0.9 ≤ w ≤ 1.1, 0.5 ≤ x < 1, 0 < y < 0.6, 0 < z < 0.6, 0 < a < 0.4, 0 < b < 0.4, and w + a + b = 1, x + y + z = 1; where M is selected from one of the elements Al, Mg, Ti, Zr, and Mn, J is selected from one of the elements La, Ce, Gd, Y, Mg, Ca, and Zr, Q is selected from one of the elements Mg, Ca, La, Ce, Nd, and Zr, and M, J, and Q are different elements from each other.

[0006] Furthermore, its c-axis lattice constant is between 14.1960 Å and 14.2093 Å.

[0007] Furthermore, its Li + -Ni 2+ mixing degree is lower than 2.1%.

[0008] Furthermore, it has a spherical secondary particle structure with uniform distribution, where the primary particle size range is 0.3 μm to 0.7 μm, and the secondary particle size range is 2.8 μm to 5.5 μm.

[0009] Furthermore, the J element is doped into the precursor material prior to the Q element, so that the high-nickel cathode material of the lithium-ion battery has a gradient doping structure with the J element enriched in the core of the material particles and the Q element enriched in the surface layer of the material particles.

[0010] Furthermore, the J element forms a strong J-O bond with oxygen to inhibit the phase transformation and collapse of the layered structure during deep de-lithiation, reduce the generation of microcracks, ensure the structural integrity inside the particles, and improve the cycle life from the root cause; after the Q element occupies the Li site on the surface layer, it greatly reduces the interfacial impedance of lithium ions entering and leaving the active particles, improves the rate performance and charge acceptance ability; at the same time, the strong pillar effect of the Q element can effectively delay the transformation of the surface layer from the layered structure to the inert rock salt phase and maintain the surface reaction activity.

[0011] On the other hand, the present invention proposes a preparation method of the aforementioned high-nickel cathode material for lithium-ion batteries, including the following steps: S1. Using LiNi β Co γ M α O2 as the precursor material, introducing the oxide of J, and mixing and calcining according to the first preset molar ratio to obtain the first doped material; where 0 < α < 0.6, 0.5 ≤ β < 1, 0 < γ < 0.6, and α + β + γ = 1; S2. Introducing the oxide of Q, and mixing and calcining with the first doped material according to the second preset molar ratio to obtain the gradient-doped high-nickel cathode material for lithium-ion batteries.

[0012] Furthermore, using LiNi 0.8 Co 0.1 Mn 0.1O2 is used as the precursor material, and Y2O3 is introduced as the yttrium source, following the LiNi... 0.8 Co 0.1 Mn 0.1 The mixture of O2 and Y2O3 in a molar ratio of 1:0.01 was calcined to obtain the first doped material, Li. 0.98 Ni 0.8 Co 0.1 Mn 0.1 Y 0.02 O2; Step S2 specifically includes: in Li 0.98 Ni 0.8 Co 0.1 Mn 0.1 Y 0.02 Based on O2, Nd2O3 is introduced as the neodymium source, according to Li 0.98 Ni 0.8 Co 0.1 Mn 0.1 Y 0.02 The high-nickel cathode material Li2 for lithium-ion batteries is obtained by calcining a mixture of O2 and Nd2O3 in a molar ratio of 1:0.005. 0.97 Ni 0.8 Co 0.1 Mn 0.1 Y 0.02 Nd 0.01 O2.

[0013] Furthermore, the calcination in steps S1 and S2 both adopt a two-stage gradient calcination method, which includes: a first stage, calcining the mixture in an oxygen atmosphere at a first temperature; and a second stage, calcining the material obtained in the first stage at a second temperature; the second temperature is lower than the first temperature.

[0014] Another aspect of the present invention proposes the application of the aforementioned high-nickel cathode material for lithium-ion batteries, used as the cathode of lithium-ion batteries.

[0015] The beneficial effects of this invention are reflected in the following: The gradient-doped high-nickel cathode material for lithium-ion batteries provided by this invention achieves a dual improvement in bulk structural stability and surface / interface stability through the synergistic effect of multiple doping elements. Strongly bonding elements J selected from La, Ce, Gd, Y, Mg, Ca, or Zr can form stable JO bonds (such as YO bonds) with oxygen, effectively suppressing the layered phase transition and collapse during deep delithiation and reducing microcrack generation. Meanwhile, large-radius elements Q selected from Mg, Ca, La, Ce, Nd, or Zr (such as metallic Nd) occupying Li sites significantly reduce the interfacial resistance of lithium ions entering and exiting active particles, improving rate performance and charge acceptance. The strong pillaring effect of large-radius elements Q (such as metallic Nd) effectively delays the transformation of the surface layer from a layered structure to an inert rock salt phase, maintaining surface reactivity; simultaneously, it generates a steric hindrance effect, physically blocking Ni… 2+ Migrating to the Li layer significantly reduces the degree of cation mixing. Through a gradient doping structure of "J stable inside, Q solid outside", a synergistic effect of bulk structural stability and interface ion migration suppression is achieved at the molecular scale, ultimately resulting in a synergistic improvement in specific capacity and ultra-long cycle life.

[0016] The gradient introduction strategy of multiple dopants avoids the lithium-ion migration channel blockage problem that may be caused by excessive doping of a single element. By optimizing the doping order and ratio, uniform distribution and functional complementarity of each element in the material are achieved. The appropriate increase of the c-axis lattice constant expands the interlayer spacing, providing a more optimized channel for lithium-ion diffusion, thereby improving the electrochemical kinetic performance of the material.

[0017] Ultimately, the material of this invention exhibits a synergistic improvement in high specific capacity (≥239mAh / g@0.2C) and ultra-long cycle stability (capacity retention ≥82.8% after 300 cycles), effectively solving the technical problem of rapid cycle decay of high-nickel cathode materials and providing an important material foundation for the development of high-energy-density lithium-ion batteries.

[0018] Furthermore, the gradient doping process employed in the preparation method of this invention has a core advantage in achieving functional synergy and spatial positioning of multiple dopant elements through precise timing control, thereby overcoming the performance bottleneck of homogeneous doping. If multiple dopant elements are mixed and calcined together, the uniform distribution of elements can easily lead to functional competition and mutual inhibition. The gradient doping method of this invention, however, is implemented step-by-step: firstly, a J-cation (such as Y-) is introduced at high temperature. 3+ This allows it to preferentially enter the bulk phase via extremely strong JO bonds, constructing a stable "skeleton" and effectively suppressing the H2-H3 phase transition and the generation of bulk microcracks from an energy perspective; subsequently, larger radius Q cations (such as Nd) are introduced. 3+ This makes it easier for Ni to accumulate near the surface and grain boundaries of particles, and utilizes its huge steric hindrance effect to physically block Ni.2+ Migration towards the lithium layer suppresses surface cation mixing and the formation of rock salt phases at the source. This strategy cleverly forms a gradient protection structure of "J stable inside, Q solid outside," achieving a synergistic enhancement of bulk structural stability and interfacial ion mixing suppression, addressing both the symptoms and the root cause. Ultimately, this approach yields a more complete crystal structure and stronger grain boundaries at the microscopic level, and synergistically improves the material's cycling stability and capacity retention at the macroscopic level, achieving a modification effect of "1+1>2." Attached Figure Description

[0019] Figure 1 This is a process diagram of the preparation of high-nickel cathode material for lithium-ion batteries with gradient doping according to an embodiment of the present invention.

[0020] Figure 2 This is a comparison of the XRD patterns of Embodiment 1 of the present invention with those of Comparative Examples 1 and 2.

[0021] Figure 3 This is a scanning electron microscope image of Comparative Example 1 (NCM) of the present invention.

[0022] Figure 4 This is a scanning electron microscope image of Comparative Example 2 (NCM-Y) of the present invention.

[0023] Figure 5 This is a scanning electron microscope image of Embodiment 1 (NCM-YNd) of the present invention.

[0024] Figure 6 This is a transmission electron microscope image of Example 1 (NCM-YNd) of the present invention.

[0025] Figure 7 This is a comparison chart of the long-cycle performance of Embodiment 1 of the present invention and Comparative Examples 1 and 2.

[0026] Figure 8 This is a comparison chart of the rate performance of Embodiment 1 of the present invention and Comparative Examples 1 and 2.

[0027] Figure 9 This is a comparison diagram of the electrochemical impedance spectroscopy of Example 1 of the present invention with Comparative Examples 1 and 2. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments, but the implementation of the present invention is not limited thereto. It should be understood that the embodiments provided are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0029] This invention targets existing high-nickel cathode materials (such as LiMn). 0.1 Ni 0.8 Co 0.1In view of the problems of poor structural stability and rapid decline in cycling performance of O2), a strategy of gradient doping with multiple elements is proposed to achieve a synergistic enhancement effect by utilizing the characteristics of different elements. Specifically, a strong-bonding element is first introduced to stabilize the crystal structure, and then a large-radius element is introduced to inhibit cation mixing, ultimately obtaining a gradient-doped high-nickel cathode material with high capacity and long cycle life.

[0030] The gradient-doped high-nickel cathode material of the embodiment of the present invention uses an existing high-nickel cathode material (such as LiMn 0.1 Ni 0.8 Co 0.1 O2) as a precursor, and two elements are introduced successively for site-selective doping. Specifically, a first element J that can combine with O element to form a strong-bonding structure is first introduced for doping, replacing some sites of Li. On the basis of forming a strong-bonding structure as a stable "skeleton" of the material, a second element Q with a larger radius that can inhibit cation mixing (cation mixing caused by the close radii of Ni 2+ and Li + ) is introduced for doping, ultimately obtaining a gradient-doped high-nickel cathode material, whose chemical general formula is: Li w Ni x Co y M z J a Q b O2, where 0.9 ≤ w ≤ 1.1, 0.5 ≤ x < 1, 0 < y < 0.6, 0 < z < 0.6, 0 < a < 0.4, 0 < b < 0.4, and w + a + b = 1, x + y + z = 1; where M is selected from one of the elements Al, Mg, Ti, Zr, and Mn, J is selected from one of the elements La, Ce, Gd, Y, Mg, Ca, and Zr, Q is selected from one of the elements Mg, Ca, La, Ce, Nd, and Zr, and M, J, and Q are mutually different elements. The obtained high-nickel cathode material Li w Ni x Co y M z J a Q b O2 has an expanded c-axis lattice constant compared to the traditional high-nickel cathode material LiMn 0.1 Ni 0.8 Co 0.1 O2, and it is between 14.1960 Å and 14.2093 Å.

[0031] Example 1

[0032] This example provides a Y, Nd gradient-doped lithium-ion battery high-nickel cathode material Li 0.97 Ni 0.8 Co 0.1 Mn0. 1Y 0.02 Nd 0.01 O2, or Li w Ni x Co y M z J a Q b In O2, M represents Mn, J represents Y, and Q represents Nd. The high-nickel cathode material in this embodiment is Li. 0.97 Ni 0.8 Co 0.1 Mn 0.1 Y 0.02 Nd 0.01 O2 uses LiNi, a traditional high-nickel cathode material 0.8 Co 0.1 Mn 0.1 O2 is used as the precursor material, and yttrium and neodymium sources are sequentially introduced, followed by gradient sintering. For example... Figure 1 As shown, its preparation process is as follows:

[0033] Step S1: Provide precursor material LiNi 0.8 Co 0.1 Mn 0.1 O2, introducing Y2O3 as the yttrium source, according to LiNi 0.8 Co 0.1 Mn 0.1 The mixture of O2 and Y2O3 in a molar ratio of 1:0.01 was calcined using a two-stage gradient calcination method. First, the mixture was calcined at approximately 800°C for about 12 hours in an oxygen atmosphere, followed by a further calcination at approximately 500°C for about 5 hours. Cooling then yielded the doped material Li. 0.98 Ni 0.8 Co 0.1 Mn 0.1 Y 0.02 O2 (denoted as NCM-Y);

[0034] Step S2, in Li 0.98 Ni 0.8 Co 0.1 Mn 0.1 Y 0.02 Based on O2, Nd2O3 is introduced as the neodymium source, according to Li 0.98 Ni 0.8 Co 0.1 Mn 0.1 Y 0.02 The final material Li in this embodiment was obtained by calcining a mixture of O2 and Nd2O3 in a molar ratio of 1:0.005. 0.97 Ni 0.8 Co 0.1 Mn 0.1 Y0.02 Nd 0.01 O2 (denoted as NCM-YNd). The calcination in this step still adopts the two-stage gradient calcination method. The specific temperature and calcination time can be the same as or different from step S1. For example, the NCM-Y material and Nd2O3 mixture can be calcined at about 900℃ for 11 hours in an oxygen atmosphere, and then calcined at 500℃ for 3 hours.

[0035] In this embodiment, Y is first introduced. 3+ It forms extremely strong YO bonds with oxygen ions, significantly inhibiting the shrinkage and collapse of the layered structure towards a salt-like facies (H2-H3 phase transition) during deep delithiation, thereby reducing the generation of microcracks. The replaced Li... + In addition, during the high-temperature calcination process, excess lithium occupies the normal lithium sites that are not occupied by dopants, ensuring that the final product contains active Li₂ capable of chemically cycling and deintercalating. + The quantity is sufficient to ensure that the reversible capacity of the material does not decrease significantly due to doping. Then, Nd with a larger radius is introduced. 3+ This makes it easier for Ni to accumulate near the surface and grain boundaries of the particles, utilizing its huge steric hindrance effect to physically block Ni. 2+ Migration to the lithium layer suppresses surface cation mixing and the formation of rock salt phase from the source. Ultimately, it achieves a synergistic improvement in high specific capacity (≥239mAh / g@0.2C) and ultra-long cycling stability (capacity retention ≥82.8% after 300 cycles), overcoming the core defects of rapid cycle decay and functional conflicts of dopant elements in existing technologies.

[0036] Example 2

[0037] This embodiment provides another Y, Nd-doped high-nickel cathode material, Li. 0.94 Ni 0.8 Co 0.1 Mn 0.1 Y 0.05 Nd 0.01 O2, which is based on the traditional high-nickel cathode material LiNi 0.8 Co 0.1 Mn 0.1 O2 is used as the precursor material, and yttrium and neodymium sources are introduced sequentially, followed by gradient sintering. Unlike Example 1, the doping ratios of metallic Y and Nd are slightly different, as reflected in:

[0038] First, Y₂O₃ is introduced as the yttrium source, according to LiNi 0.8 Co 0.1 Mn 0.1 The mixture of O2 and Y2O3 in a molar ratio of 1:0.025 was calcined. The mixture was first calcined at 750°C for 15 hours in an oxygen atmosphere, then calcined at 400°C for 3 hours. After cooling, the doped material Li was obtained.0.95 Ni 0.8 Co 0.1 Mn 0.1 Y 0.05 O2;

[0039] Then, Nd₂O₃ is introduced as the neodymium source, and it is reacted with the doped material Li obtained in the previous step. 0.95 Ni 0.8 Co 0.1 Mn 0.1 Y 0.05 O2 according to Li 0.95 Ni 0.8 Co 0.1 Mn 0.1 Y 0.05 The mixture of O2 and Nd2O3 in a molar ratio of 1:0.005 was calcined. The mixture was first calcined at 850°C for 12 hours in an oxygen atmosphere, then calcined at 500°C for 5 hours. After cooling, the gradient-doped high-nickel cathode material Li2 of this embodiment was obtained. 0.94 Ni 0.8 Co 0.1 Mn 0.1 Y 0.05 Nd 0.01 O2.

[0040] Comparative Example 1

[0041] This comparative example provides a high-nickel cathode material, LiNi. 0.8 Co 0.1 Mn 0.1 O2, which is composed of LiOH and Ni 0.8 Co 0.1 Mn 0.1 Using (OH)₂ as a raw material, the molar ratio of Li:Mn:Ni:Co was controlled at 1:0.1:0.8:0.1, and the mixture was calcined to synthesize the precursor material LiNi. 0.8 Co 0.1 Mn 0.1 O2 (denoted as NCM).

[0042] Comparative Example 2

[0043] This comparative example is based on Comparative Example 1, introducing Y2O3 as the yttrium source, and following the LiNi... 0.8 Co 0.1 Mn 0.1 The materials were mixed in a molar ratio of O2:Y2O3 = 1:0.01, and then subjected to a two-stage gradient calcination to obtain the doped material Li. 0.98 Ni 0.8 Co 0.1 Mn 0.1 Y 0.02 O2 (denoted as NCM-Y).

[0044] It should be noted that the calcination method used in the preparation of each sample in the embodiments and comparative examples of this invention is a two-stage gradient calcination method. The temperature of the first stage is not limited to the temperatures mentioned in the aforementioned embodiments and comparative examples, and can be adjusted within the range of 500℃ to 1200℃, with a heating rate of 2-10℃ / min. The calcination time is also not limited to the aforementioned time and can be 10-18 hours. The temperature of the second stage is also not limited to the temperatures mentioned in the aforementioned embodiments and comparative examples, and can be appropriately adjusted within the range of 300℃ to 800℃, as long as the temperature of the second stage is lower than that of the first stage. The heating rate can be 2-10℃ / min, and the calcination time is also not limited to the times mentioned in the aforementioned examples and can be 3-8 hours.

[0045] The effectiveness of the present invention will be verified by comparing the performance of Comparative Example 1 (NCM), Comparative Example 2 (NCM-Y) with the material (NCM-YNd) of Example 1 of the present invention.

[0046] The crystal structures of the three samples were characterized by X-ray diffraction (XRD) using a Bruker D8 Advance diffractometer with Cu Kα rays (λ = 0.15406 nm) as the radiation source. The operating conditions were a tube voltage of 45 kV and a tube current of 40 mA. The scan rate was 10° / min within the 2θ range of 10°–90°. The XRD patterns of the three samples are shown below. Figure 2 As shown, the results indicate that all samples exhibit an α-NaFeO2 structure, belonging to the R-3m space group, proving that Y and Nd doping did not alter the crystal structure of the material.

[0047] Detailed crystal structure information was obtained through refinement using GSAS II software, and the relevant refinement results are summarized in Table 1. XRD refinement results show that after Y and Nd co-doping, Li… + / Ni 2+ The degree of Li / Ni mixing was reduced from 4.3% in the original material (NCM) to 2.1%, significantly suppressing the Li / Ni mixing phenomenon. Furthermore, the doping modification increased the c-axis lattice constant of the material, indicating an expansion of the interlayer spacing, which is beneficial for optimizing lithium-ion diffusion channels and thus improving the electrochemical performance of the material.

[0048] Table 1 Summary of XRD Refinement Data

[0049]

[0050] The morphology of the materials was characterized using field emission scanning electron microscopy (HITACHI S-4800, SU 8010). The relevant results for the three sample materials are as follows: Figure 3 , Figure 4 and Figure 5 As shown in the scanning electron microscopy (SEM) images, the synthesized NCM materials exhibit aggregated secondary particles. Compared to NCM materials, the secondary particles in NCM-Y materials are more uniformly distributed. NCM-YNd materials, on the other hand, possess a more uniformly distributed spherical secondary particle structure, with the secondary particles ranging in size from 2.8 to 5.5 micrometers and the primary particles ranging in size from 0.3 to 0.7 micrometers.

[0051] Transmission electron microscopy (TEM) images were acquired using FEI Tecnai T12 and FEI Tecnai G2 F30 instruments, and samples were prepared using focused ion beam systems (FIB, Scios, FEI). Figure 6 As shown, the NCM-YNd sample surface of this embodiment exhibits a layered structure. Combining the characterization results from XRD, SEM, and TEM, it can be concluded that this invention, based on the theory of lattice defect repair in high-nickel materials, employs a gradient doping strategy to improve the Y... 3+ With Nd 3+ Uniform doping in the bulk phase enhances the stability of the crystal structure through strong YO and Nd-O bonds, thereby improving the structural integrity and electrochemical performance of the material.

[0052] The above three samples were used to prepare electrode slurries for lithium-ion battery cathodes, and the prepared cathodes were used to further assemble lithium-ion batteries to verify the advantages of the high-nickel cathode material of the present invention.

[0053] Using the above three sample materials (NCM, NCM-Y, and NCM-YNd) as positive electrode active materials, electrodes were fabricated according to the following steps:

[0054] The positive electrode active material, acetylene black, and polyvinylidene fluoride (PVDF, Solef 5130) were mixed in N-methylpyrrolidone (NMP) solvent at a mass ratio of 8:1:1 and stirred until homogeneous. The resulting slurry was uniformly coated onto an aluminum foil current collector, with an active material mass loading of 1–2 mg·cm⁻². The coated electrode was dried in a vacuum oven at 120 °C for 12 hours, then punched into circular electrode sheets with a diameter of 12 mm and transferred to an argon-filled glove box.

[0055] The battery assembly adopts a CR2032 coin cell structure, with the prepared positive electrode as the positive electrode, lithium metal as the negative electrode, and a Celgard PP2400 membrane as the separator. Each battery is injected with 70 μL of electrolyte, which is 1 M LiPF6 dissolved in a solvent mixture prepared by ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and fluoroethylene carbonate (FEC) in a volume ratio of 1:1:1.

[0056] Electrochemical performance testing of coin cells was conducted on a multi-channel cell testing system (LAND CT 2001 A) with a voltage range of 2.8–4.3 V (relative to Li). + / Li). For example Figure 7 As shown, after three activation cycles at a current density of 0.2 C, the battery underwent long-term cycling testing at 1 C. The results show that the NCM-YNd material maintained 82.8% capacity retention after 300 cycles, significantly better than the 72.0% retention of the undoped NCM sample, indicating that the dual-doping strategy has significant advantages in improving structural stability and cycle life. Furthermore, as... Figure 8 As shown, the NCM-YNd samples exhibited excellent rate performance under different rate (C-rate) conditions, further verifying their good electrochemical kinetics and lithium-ion diffusion capabilities. The charge-discharge specific capacities of the samples at different current densities are presented in Table 2. The NCM-YNd material achieved an initial discharge specific capacity of 239 mAh / g at a current density of 0.2C, significantly higher than the undoped NCM material (158 mAh / g), indicating that the dual-doping strategy effectively improved the reversible capacity and lithium-ion storage capability of the material.

[0057] Table 2 Comparison of specific capacity of different samples at different current densities

[0058]

[0059] Electrochemical impedance spectroscopy (EIS) measurements were performed on a multichannel electrochemical workstation (VMP3, Biologic), with a frequency range of 100 kHz to 10 MHz. Figure 9 As shown, compared with the undoped NCM material, the impedance of the NCM-YNd sample is significantly reduced, indicating that the dual-doping strategy effectively reduces the interfacial resistance and enhances the migration ability of lithium ions in the electrode material, thereby helping to improve the electrochemical reaction kinetics performance of the material.

[0060] The gradient dual-doping modification scheme of the present invention: The first step is to introduce Y 3+ Y 3+ Driven by its powerful reaction force, YO bonds are formed, allowing it to preferentially and fully penetrate the crystal lattice, establishing a stable "crystal framework." At this stage, there is no competition, and Y... 3+ This maximizes its ability to suppress phase transitions. Once a stable framework is formed, the second step involves introducing Nd. 3+ At this time, Nd 3+ It can suppress cation mixing without being affected by Y 3+ It can maximize its spatial steric hindrance effect by resisting interference.

[0061] In summary, by constructing a Y-Nd dual-gradient doping system, a specific capacity of up to 230 mAh / g (0.2C) and a capacity retention of ≥82.8% after 300 cycles were achieved, significantly outperforming existing high-nickel single-doped systems. The advancement of this technology lies in the proposed "synergistic bulk doping" enhancement mechanism, effectively overcoming the technical bottleneck of the single modification dimension of traditional doping strategies. It establishes a highly competitive new paradigm for material design, possessing significant technological barriers and widespread application value.

Claims

1. A gradient-doped high-nickel cathode material for lithium-ion batteries, characterized in that: Its chemical general formula is Li w Ni x Co y Mn z Y a Nd b O2, where 0.9 ≤ w ≤ 1.1, 0.5 ≤ x < 1, 0 < y < 0.6, 0 < z < 0.6, 0 < a < 0.4, 0 < b < 0.4, and w + a + b = 1, x + y + z = 1; Y element is doped into the precursor material before Nd element, so that the high-nickel cathode material of the lithium-ion battery has a gradient doping structure in which Y element is enriched in the core of the material particles and Nd element is enriched in the surface of the material particles.

2. The high-nickel cathode material for lithium-ion batteries as described in claim 1, characterized in that: Its c-axis lattice constant is between 14.1960 Å and 14.2093 Å.

3. The high-nickel cathode material for lithium-ion batteries as described in claim 1, characterized in that: Its Li + -Ni 2+ The degree of mixing is less than 2.1%.

4. The high-nickel cathode material for lithium-ion batteries as described in claim 1, characterized in that: It has a uniformly distributed spherical secondary particle structure, wherein the size of the primary particles ranges from 0.3μm to 0.7μm, and the size of the secondary particles ranges from 2.8μm to 5.5μm.

5. The high-nickel cathode material for lithium-ion batteries as described in claim 1, characterized in that: Y forms strong YO bonds with oxygen to suppress the layered structure phase transition and collapse during deep delithiation, reduce the generation of microcracks, and ensure the structural integrity of the particles, thereby improving cycle life from the root. After Nd occupies Li sites on the surface, it greatly reduces the interfacial resistance of lithium ions entering and leaving the active particles, improving rate performance and charge acceptance. At the same time, the strong pillaring effect of Nd can effectively delay the transformation of the surface from a layered structure to an inert rock salt phase, maintaining surface reactivity.

6. The method for preparing the high-nickel cathode material for lithium-ion batteries according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1, with LiNi β Co γ Mn α O2 is used as a precursor material. Oxide of Y is introduced and mixed and calcined according to a first preset molar ratio to obtain the first doped material; wherein, 0 < α < 0.6, 0.5 ≤ β < 1, 0 < γ < 0.6, and α + β + γ = 1; S2. Introduce Nd oxide and mix it with the first doped material according to a second preset molar ratio and calcine to obtain the gradient-doped high-nickel cathode material for lithium-ion batteries.

7. The preparation method according to claim 6, characterized in that, Step S1 specifically includes: using LiNi 0.8 Co 0.1 Mn 0.1 O2 is used as the precursor material, and Y2O3 is introduced as the yttrium source, following the LiNi... 0.8 Co 0.1 Mn 0.1 The mixture of O2 and Y2O3 in a molar ratio of 1:0.01 was calcined to obtain the first doped material, Li. 0.98 Ni 0.8 Co 0.1 Mn 0.1 Y 0.02 O2; Step S2 specifically includes: in Li 0.98 Ni 0.8 Co 0.1 Mn 0.1 Y 0.02 Based on O2, Nd2O3 is introduced as the neodymium source, according to Li 0.98 Ni 0.8 Co 0.1 Mn 0.1 Y 0.02 The high-nickel cathode material Li2 for lithium-ion batteries is obtained by calcining a mixture of O2 and Nd2O3 in a molar ratio of 1:0.

005. 0.97 Ni 0.8 Co 0.1 Mn 0.1 Y 0.02 Nd 0.01 O2.

8. The preparation method according to claim 6, characterized in that, Both steps S1 and S2 employ a two-stage gradient calcination method, which includes: a first stage, calcining the mixture in an oxygen atmosphere at a first temperature; and a second stage, calcining the material obtained in the first stage at a second temperature, wherein the second temperature is lower than the first temperature.

9. The application of the high-nickel cathode material for lithium-ion batteries as described in any one of claims 1 to 5, characterized in that, Used as the positive electrode in lithium-ion batteries.

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