Lanthanum and niobium co-doped high-nickel ternary cathode materials and their preparation methods, cathode sheets, and batteries

Abstract

This invention relates to the field of battery materials technology, and particularly to lanthanum and niobium co-doped high-nickel ternary cathode materials, their preparation methods, cathode sheets, and batteries. The preparation method involves weighing and uniformly mixing a high-nickel NCM9055 precursor, a lithium source, a lanthanum source, and a niobium source. The resulting mixture is placed in an oxygen-containing atmosphere and pre-calcined at 450–550°C for 3–7 hours, followed by high-temperature calcination at 700–800°C for 10–17 hours, and then cooled to obtain the lanthanum and niobium co-doped high-nickel ternary cathode material. This invention, by introducing lanthanum and niobium doping into a high-nickel ternary layered material system, can effectively control the crystal structure and local electronic environment. The synergistic effect of these two elements can significantly suppress lattice oxygen release and unfavorable phase transitions during charging and discharging, reduce the generation of internal cracks in the particles, and thus further improve the structural stability and cycle durability of the material.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to lanthanum and niobium co-doped high-nickel ternary cathode materials, their preparation methods, cathode sheets, and batteries. Background Technology

[0002] With the rapid development of new energy vehicles and energy storage technologies, lithium-ion batteries have been widely used due to their high energy density and long cycle life. Among them, high-nickel ternary layered cathode materials (such as LiNi) are particularly important. 0.90 Co 0.05 Mn 0.05 O2 (NCM9055) is considered an important candidate material for high-energy-density power batteries due to its high specific capacity and low cost. However, with the increase of nickel content, the structural stability of the material decreases significantly, making it prone to structural defects during charge-discharge cycles. / Problems such as cation mixing, lattice oxygen escape, and the transformation of layered structures into spinel or rock salt phases, along with the generation of microcracks inside the particles and the intensification of interfacial side reactions, lead to increased charge transport impedance, rapid capacity decay, and reduced cycle life, severely restricting the further application of high-nickel ternary cathode materials.

[0003] To address the aforementioned issues, elemental doping is considered a crucial method for enhancing the structural stability of materials. By introducing exogenous elements, crystal structure can be modulated, transition metal-oxygen bond strength enhanced, and harmful phase transitions suppressed. However, single-element doping often fails to simultaneously achieve a synergistic improvement in both structural stability and electrochemical performance. In contrast, dual-element synergistic doping can produce synergistic effects in lattice modulation, electronic structure optimization, and defect regulation, effectively suppressing cation mixing and structural degradation, thereby improving the cycle stability and lifespan of high-nickel ternary cathode materials.

[0004] Therefore, it is particularly important to develop a high-nickel ternary cathode material based on dual-doping modification to improve its structural stability and thus enhance its specific capacity and cycle stability. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide lanthanum and niobium co-doped high-nickel ternary cathode materials, their preparation methods, cathode sheets, and batteries, so as to solve the problems of structural degradation, cation mixing, and insufficient cycle stability that existing high-nickel ternary cathode materials are prone to during long-term charge and discharge.

[0006] The following is a summary of this disclosure to provide a basic understanding of some aspects. This summary is not intended to identify key or important elements, nor is it intended to limit the implementation or any aspects of the claims. Furthermore, this summary provides a simplified overview of some aspects that can be described in more detail in other parts of this disclosure.

[0007] The present invention solves the above-mentioned technical problems through the following technical means:

[0008] In a first aspect, embodiments of the present invention provide a method for preparing a lanthanum-niobium co-doped high-nickel ternary cathode material, comprising the following steps:

[0009] NiSO4·6H2O, MnSO4·H2O and CoSO4·7H2O were weighed and added to deionized water to prepare a transition metal salt solution. Then, ammonia water was added as a complexing agent while sodium hydroxide solution was added dropwise to form a precipitate. The solid obtained by filtration was washed and dried to obtain a high-nickel NCM9055 precursor.

[0010] Weigh out the high-nickel NCM9055 precursor, lithium source, lanthanum source and niobium source and mix them evenly to obtain a mixture. Place the mixture in an oxygen-containing atmosphere, first heat it to 450-550℃ for pre-calcination for 3-7 hours, then heat it to 700-800℃ for high-temperature calcination for 10-17 hours, and then cool it down to obtain lanthanum and niobium co-doped high-nickel ternary cathode material.

[0011] In conjunction with the first aspect, in some embodiments, the molar ratio of the high-nickel NCM9055 precursor to the lithium source is 1:(1 to 1.1).

[0012] In conjunction with the first aspect, in some embodiments, the lithium source is at least one of lithium hydroxide, lithium carbonate, or lithium nitrate.

[0013] In conjunction with the first aspect, in some embodiments, the total molar number of nickel, cobalt, and manganese in the high-nickel NCM9055 precursor is related to the molar number of lanthanum source. niobium source The molar ratio between them is 99.5:0.25:0.25, or 99:0.5:0.5, or 98.5:0.75:0.75, or 98:1:1.

[0014] In conjunction with the first aspect, in some embodiments, the lanthanum source is lanthanum oxide, and the niobium source is niobium oxide.

[0015] In conjunction with the first aspect, in some embodiments, the pre-calcination is to pre-calcine at 450-550°C by heating at 1-10°C / min for 3-7 hours; the high-temperature calcination is to pre-calcine at 700-800°C by heating at 1-10°C / min for 10-17 hours; and the cooling is to cool to room temperature at 1-5°C / min.

[0016] In conjunction with the first aspect, in some embodiments, the preparation method of the high-nickel NCM9055 precursor is as follows: NiSO4·6H2O, MnSO4·H2O and CoSO4·7H2O are weighed according to the molar ratio of Ni:Co:Mn=90:5:5 and added to deionized water to prepare a transition metal salt solution. Then, a complexing agent ammonia water is added while stirring, and sodium hydroxide solution is added dropwise to form a precipitate. The obtained solid is filtered, washed and dried to obtain the high-nickel NCM9055 precursor.

[0017] Secondly, embodiments of the present invention provide a lanthanum and niobium co-doped high-nickel ternary cathode material, which is prepared using the preparation method described in the first aspect.

[0018] Thirdly, embodiments of the present invention provide a positive electrode sheet, wherein the raw materials for preparing the positive electrode sheet include the lanthanum and niobium co-doped high-nickel ternary positive electrode material described in the second aspect.

[0019] Fourthly, embodiments of the present invention provide a battery, the battery comprising the positive electrode sheet described in the third aspect.

[0020] The present invention discloses a method for preparing lanthanum and niobium co-doped high-nickel ternary cathode materials. This method combines a precursor co-precipitation process with a solid-state heat treatment process. By rationally controlling the doping ratio and heat treatment conditions, it achieves a uniform distribution of lanthanum and niobium elements in the material lattice, thereby optimizing the material's microstructure and enhancing its structural stability. The preparation method of this invention is simple in process, easy to control in parameters, and uses widely available raw materials. It has good reproducibility and promising prospects for industrial application, providing a feasible technical solution for the large-scale preparation of high-nickel ternary cathode materials.

[0021] The lanthanum-niobium co-doped high-nickel ternary cathode material of this invention effectively modulates the crystal structure and local electronic environment by introducing lanthanum and niobium synergistically into a high-nickel ternary layered material system. The introduction of lanthanum helps stabilize the layered structure and alleviate lattice stress during cycling, while niobium enhances the bonding strength of the transition metal-oxygen bond and reduces the degree of Li / Ni cation mixing. The synergistic effect of these two elements significantly suppresses lattice oxygen release and unfavorable phase transitions during charge and discharge, while reducing the generation of internal cracks in the particles, thereby further improving the structural stability and cycle durability of the material. This provides an effective modification strategy for the development of high-energy-density lithium-ion power battery cathode materials.

[0022] Tests showed that the lithium-ion battery assembled from the electrode sheet prepared by the lanthanum and niobium co-doped high-nickel ternary cathode material of the present invention exhibited a high first-cycle discharge capacity (218.3 mAh / g) at 0.1C, with a first-cycle coulombic efficiency as high as 93.7%, and maintained a high capacity retention rate (94.7%) during long-term cycling at 1C rate, indicating that it has excellent rate performance and cycle stability. Attached Figure Description

[0023] Figure 1 Here is a SEM image of the cathode material prepared in Example 1;

[0024] Figure 2 These are the XRD patterns of the cathode material prepared in Example 1 and the cathode material prepared in Comparative Example 1;

[0025] Figure 3 These are the 0.1C first-cycle charge-discharge diagrams of batteries assembled with electrodes prepared from the positive electrode material of Example 1.

[0026] Figure 4 The diagram shows the first charge-discharge cycle at 0.1C for batteries assembled with electrodes made from the positive electrode material of Comparative Example 1.

[0027] Figure 5 The diagram shows the first charge-discharge cycle at 0.1C for batteries assembled with electrodes made from the cathode material of Comparative Example 2.

[0028] Figure 6 The diagram shows the first charge-discharge cycle at 0.1C for batteries assembled with electrodes made from the cathode material of Comparative Example 3.

[0029] Figure 7 The graphs show the cycle performance of batteries assembled with electrodes made from the cathode materials of Comparative Examples 1, 2, and 3 at a 1C rate.

[0030] Figure 8 These are cycle performance graphs of batteries assembled with electrodes prepared from the positive electrode materials of Examples 1, 2, and 3 at a 1C rate.

[0031] Figure 9 The graphs show the rate performance of batteries assembled with electrodes made from the cathode materials of Example 1 and Comparative Example 1, respectively. Detailed Implementation

[0032] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0033] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0034] To address the issues of structural degradation, cation mixing, and insufficient cycle stability that easily occur in high-nickel ternary cathode materials during long-term charge-discharge processes, this invention proposes a method for preparing high-nickel ternary cathode materials through synergistic doping of lanthanum and niobium to achieve structural control. This is achieved by introducing appropriate amounts of lanthanum and niobium into the material lattice. and Elements that modulate the transition metal layer structure and local electronic environment enhance the stability of the material's crystal structure and improve its cycling performance.

[0035] The preparation method of the lanthanum and niobium co-doped high-nickel ternary cathode material of the present invention includes the following steps:

[0036] (1) Using NiSO4·6H2O, MnSO4·H2O, and CoSO4·7H2O as transition metal sources, ammonia as a complexing agent, and NaOH as a precipitant, a high-nickel NCM9055 precursor was prepared by continuous hydroxide co-precipitation. Specifically, according to the molar ratio of Ni:Co:Mn = 90:5:5, NiSO4·6H2O, MnSO4·H2O, and CoSO4·7H2O were weighed and added to deionized water to prepare a transition metal salt solution. Then, the complexing agent ammonia was added while stirring, and sodium hydroxide solution was added dropwise to form a precipitate. The obtained solid was filtered, washed, and dried to obtain the high-nickel NCM9055 precursor. This step uses an existing conventional process, and the process conditions can be set with reference to existing conventional processes, as long as the co-precipitation method is used to prepare the high-nickel NCM9055 precursor.

[0037] (2) Weigh out the high-nickel NCM9055 precursor, lithium source, lanthanum source, and niobium source, mix them evenly to obtain a mixture, place the mixture in an oxygen-containing atmosphere, first heat to 450-550℃ for pre-calcination for 3-7 hours, then heat to 700-800℃ for high-temperature calcination for 10-17 hours, and then cool down to obtain lanthanum and niobium co-doped high-nickel ternary cathode material. In this step, the molar ratio of high-nickel NCM9055 precursor to lithium source is 1:(1-1.1), and the lithium source is at least one of lithium hydroxide, lithium carbonate, or lithium nitrate; the total molar number of nickel, cobalt, and manganese in the high-nickel NCM9055 precursor is 1:(1-1.1). , The molar ratio between them is 99.5:0.25:0.25, or 99:0.5:0.5, or 98.5:0.75:0.75, or 98:1:1; the pre-calcination is to pre-calcine at 450-550℃ for 3-7 hours by heating at 1-10℃ / min; the high-temperature calcination is to pre-calcine at 700-800℃ for 10-17 hours by heating at 1-10℃ / min; the cooling is to cool to room temperature at 1-5℃ / min.

[0038] The preparation method of the lanthanum and niobium co-doped high-nickel ternary cathode material of the present invention will be described below through specific embodiments:

[0039] Example 1

[0040] The preparation method of the lanthanum and niobium co-doped high-nickel ternary cathode material in this embodiment is as follows:

[0041] High-nickel Ni 0.90 Co 0.05 Mn 0.05 (OH)₂ precursor, LiOH·H₂O, La₂O₃, and Nb₂O₅ were ball-milled for 30 min, and then dry-milled until homogeneous to obtain a mixture. The molar ratio of high-nickel NCM9055 precursor to lithium source was 1:1.03, and the high-nickel Ni... 0.90 Co 0.05 Mn 0.05 Transition metal ions (TM=Ni+Co+Mn) in the (OH)2 precursor and , The molar ratio of the materials was 99:0.5:0.5. The mixture was placed in an oxygen-containing tube furnace for two-step calcination: first, it was pre-calcined at 480℃ with a heating rate of 5℃ / min and held for 5 h; then, it was further heated at 760℃ with a heating rate of 5℃ / min and held for 15 h for high-temperature calcination; finally, it was cooled to room temperature at a cooling rate of 2.5℃ / min to obtain lanthanum and niobium co-doped high-nickel ternary cathode material.

[0042] Example 2

[0043] The preparation method of the lanthanum and niobium co-doped high-nickel ternary cathode material in this embodiment is as follows:

[0044] High-nickel Ni 0.90 Co 0.05 Mn 0.05 The (OH)2 precursor, lithium source, La2O3, and Nb2O5 were ball-milled for 30 min, and then dry-milled until homogeneous to obtain a mixture. The molar ratio of high-nickel NCM9055 precursor to lithium source was 1:1.03, with the lithium source being LiOH·H2O or lithium carbonate, and the high-nickel Ni... 0.90 Co 0.05 Mn0.05 Transition metal ions (TM=Ni+Co+Mn) in the (OH)2 precursor and , The molar ratio was 99.5:0.25:0.25. The mixture was placed in an oxygen-containing tube furnace for two-step calcination: first, it was pre-calcined at 480℃ with a heating rate of 5℃ / min and held for 5h; then, it was further heated at 760℃ with a heating rate of 5℃ / min and held for 15h for high-temperature calcination; finally, it was cooled to room temperature at a cooling rate of 2.5℃ / min to obtain lanthanum and niobium co-doped high-nickel ternary cathode material.

[0045] Example 3

[0046] The preparation method of the lanthanum and niobium co-doped high-nickel ternary cathode material in this embodiment is as follows:

[0047] High-nickel Ni 0.90 Co 0.05 Mn 0.05 (OH)₂ precursor, LiOH·H₂O, La₂O₃, and Nb₂O₅ were ball-milled for 30 min, and then dry-milled until homogeneous to obtain a mixture. The molar ratio of high-nickel NCM9055 precursor to lithium source was 1:1.03, and the high-nickel Ni... 0.90 Co 0.05 Mn 0.05 Transition metal ions (TM=Ni+Co+Mn) in the (OH)2 precursor and , The molar ratio was 98.5:0.75:0.75. The mixture was placed in an oxygen-containing tube furnace for two-step calcination: first, it was pre-calcined at 480℃ with a heating rate of 5℃ / min and held for 5h; then, it was calcined at 760℃ with a heating rate of 5℃ / min and held for 15h; finally, it was cooled to room temperature at a cooling rate of 2.5℃ / min to obtain lanthanum and niobium co-doped high-nickel ternary cathode material.

[0048] Example 4

[0049] The preparation method of the lanthanum and niobium co-doped high-nickel ternary cathode material in this embodiment is as follows:

[0050] High-nickel Ni 0.90 Co 0.05 Mn 0.05 (OH)₂ precursor, LiOH·H₂O, La₂O₃, and Nb₂O₅ were ball-milled for 30 min, and then dry-milled until homogeneous to obtain a mixture. The molar ratio of high-nickel NCM9055 precursor to lithium source was 1:1.1, and the high-nickel Ni... 0.90 Co 0.05 Mn 0.05Transition metal ions (TM=Ni+Co+Mn) in the (OH)2 precursor and , The molar ratio was 98:1:1. The mixture was placed in an oxygen-containing tube furnace for two-step calcination: first, it was pre-calcined at 450℃ with a heating rate of 1℃ / min and held for 3 hours; then, it was calcined at 700℃ with a heating rate of 1℃ / min and held for 10 hours; finally, it was cooled to room temperature at a cooling rate of 1℃ / min to obtain lanthanum and niobium co-doped high-nickel ternary cathode material.

[0051] Example 5

[0052] The preparation method of the lanthanum and niobium co-doped high-nickel ternary cathode material in this embodiment is as follows:

[0053] High-nickel Ni 0.90 Co 0.05 Mn 0.05 (OH)₂ precursor, LiOH·H₂O, La₂O₃, and Nb₂O₅ were ball-milled for 30 min, and then dry-milled until homogeneous to obtain a mixture. The molar ratio of high-nickel NCM9055 precursor to lithium source was 1:1.05, and the high-nickel Ni... 0.90 Co 0.05 Mn 0.05 Transition metal ions (TM=Ni+Co+Mn) in the (OH)2 precursor and , The molar ratio was 99:0.5:0.5. The mixture was placed in an oxygen-containing tube furnace for two-step calcination: first, it was pre-calcined at 550℃ with a heating rate of 10℃ / min and held for 7 hours; then, it was calcined at 800℃ with a heating rate of 10℃ / min and held for 17 hours; finally, it was cooled to room temperature at a cooling rate of 5℃ / min to obtain lanthanum and niobium co-doped high-nickel ternary cathode material.

[0054] Comparative Example 1

[0055] The preparation method of the cathode material in this comparative example is as follows:

[0056] High-nickel Ni 0.90 Co 0.05 Mn 0.05 The (OH)2 precursor was ball-milled with LiOH·H2O (TM: Li = 1: 1.03) for 30 min. The uniformly mixed powder was heated to 480℃ in oxygen at a heating rate of 5℃ / min and held at that temperature for 5 h. Then, the temperature was raised to 750℃ and held for 15 h. After that, the temperature was lowered to 200℃ at a cooling rate of 2.5℃ / min and then allowed to cool naturally to room temperature to obtain the original LiNi. 0.90 Co 0.05 Mn0.05 O2.

[0057] Comparative Example 2

[0058] The preparation method of the cathode material in this comparative example is as follows:

[0059] High-nickel Ni 0.90 Co 0.05 Mn 0.05 (OH)2 precursor, LiOH·H2O, and La2O3 were ball-milled for 30 min, and then dry-milled until homogeneous to obtain a mixture. Among them, high-nickel Ni... 0.90 Co 0.05 Mn 0.05 The molar ratio of (OH)₂ precursor to LiOH·H₂O is 1:1.03, and the transition metal ions (TM=Ni+Co+Mn) and The molar ratio was 99.5:0.5. The resulting mixture was placed in an oxygen-containing tube furnace for two-step calcination: first, the temperature was increased to 480℃ at 5℃ / min for pre-calcination and held for 5h; then, the temperature was increased to 760℃ and held for 15h for high-temperature calcination; finally, the temperature was cooled to room temperature at a rate of 2.5℃ / min to obtain lanthanum and niobium co-doped high-nickel ternary cathode material.

[0060] Comparative Example 3

[0061] The preparation method of the cathode material in this comparative example is as follows:

[0062] High-nickel Ni 0.90 Co 0.05 Mn 0.05 (OH)₂ precursor, LiOH·H₂O, and Nb₂O₅ were ball-milled for 30 min, and then dry-milled until homogeneous to obtain a mixture. High-nickel Ni was also present. 0.90 Co 0.05 Mn 0.05 The molar ratio of (OH)₂ precursor to LiOH·H₂O is 1:1.03, and the transition metal ions (TM=Ni+Co+Mn) and The molar ratio was 99.5:0.5. The resulting mixture was placed in an oxygen-containing tube furnace for two-step calcination: first, the temperature was increased to 480℃ at 5℃ / min for pre-calcination and held for 5h; then, the temperature was increased to 760℃ and held for 15h for high-temperature calcination; finally, the temperature was cooled to room temperature at a rate of 2.5℃ / min to obtain lanthanum and niobium co-doped high-nickel ternary cathode material.

[0063] The cathode materials prepared in Examples 1-3 and Comparative Examples 1-3 were used as samples for specific capacity and cycle performance testing, as detailed below:

[0064] The electrochemical performance testing procedure is as follows: A positive electrode slurry is prepared by weighing each positive electrode material sample, carbon black (SP), and polyvinylidene fluoride (PVDF) at a mass ratio of 80:13:7, where the PVDF is a 3 wt% solution prepared using N-methylpyrrolidone (NMP) as the solvent. The slurry is then uniformly coated onto aluminum foil (density 2.5 mg / cm³). 2 After drying in a 120 ℃ forced-air drying oven for 12 hours, the material was sliced ​​to a diameter of 14 mm and weighed to obtain the NCM positive electrode for lithium-ion batteries. Using lithium metal sheets as the negative electrode and a 1 mol / L LiPF6 solution of ethylene carbonate (EC) and diethyl carbonate (DEC) mixed solution (volume ratio 1:1) as the electrolyte, CR2025 button batteries were assembled in an argon-atmospheric glove box. Finally, the batteries were tested for electrical performance using the Xinwei testing system.

[0065] The electrical performance test parameters were set as follows: voltage range 2.7V~4.3V; specific capacity was tested in the first cycle with 0.1C charge / 0.1C discharge; 100 cycles (cycles 3 to 102) were performed with 1C charge / 1C discharge to test its cycle performance; its rate performance was tested at 0.1C, 0.3C, 0.5C, 1C, 3C, and 5C rates. The test results are as follows. Figure 1-9 As shown.

[0066] Figure 1 These are SEM images of the cathode material prepared in Example 1. Figure 1 It can be seen that the high-nickel ternary cathode material exhibits a typical secondary spherical particle morphology, composed of a large number of well-crystallized, uniformly sized primary particles with excellent sphericity. This indicates that the La and Nb co-doping and the two-step calcination process did not destroy the spherical structure of the ternary precursor, while ensuring good crystallization of the primary particles. The complete spherical structure facilitates sufficient electrolyte wetting, and the uniform primary particles shorten the lithium-ion diffusion path, providing a structural basis for excellent electrochemical performance.

[0067] Figure 2 These are the XRD patterns of the cathode material prepared in Example 1 and the cathode material prepared in Comparative Example 1. Figure 2 It can be seen that the samples of Example 1 and Comparative Example 1 both exhibit The characteristic diffraction peaks of the layered structure (R-3m space group) indicate that La and Nb co-doping did not change the main crystal structure of the material, and also formed the La4NiLiO8 perovskite phase. In comparison, the diffraction peaks of Example 1 are sharper, with a smaller full width at half maximum (FWHM), and the characteristic splitting peaks of (006) / (012) and (018) / (110) are more obvious, indicating that the crystallinity of the material is higher after La and Nb co-doping, and the order of the layered structure is significantly improved. In the high-nickel ternary cathode material, the peak intensity ratio of I(003) / I(104) is higher than that of the other two sets of characteristic splitting peaks. / The degree of cation mixing is negatively correlated; the ratio in Example 1 is much higher than that in Comparative Example 1, indicating that La and Nb co-doping effectively suppresses the severe cation mixing problem in the high-nickel system and reduces the lithium site being... Structural instability and loss of active lithium due to occupation.

[0068] Figure 3 These are the 0.1C first-cycle charge-discharge diagrams of batteries assembled with electrodes prepared from the positive electrode material of Example 1. Figure 4 The diagram shows the first charge-discharge cycle at 0.1C for batteries assembled with electrodes made from the positive electrode material of Comparative Example 1. Figure 5 The diagram shows the first charge-discharge cycle at 0.1C for batteries assembled with electrodes made from the cathode material of Comparative Example 2. Figure 6 These are the 0.1C first-cycle charge-discharge diagrams of batteries assembled with electrodes made from the positive electrode material of Comparative Example 3. From... Figures 3 to 6 It can be seen that lanthanum and niobium co-doping significantly improves the initial electrochemical performance: the initial discharge specific capacity and initial coulombic efficiency of all doped samples are much higher than those of the undoped comparative example 1, indicating that La and Nb doping can reduce the initial irreversible capacity loss of high-nickel ternary lithium and improve the utilization rate of active lithium. The specific capacity and coulombic efficiency of Example 1 are better than those of the La and Nb single-doped samples, and the mechanism is: large radius It can widen the lithium interlayer spacing, lower the lithium-ion diffusion barrier, and activate more electrochemical active sites; high valence state It can stabilize the transition metal valence state and suppress oxygen evolution and interfacial side reactions during charge and discharge. The two work synergistically to reduce the first irreversible reaction and improve the specific capacity of the material. The sample in Example 1 has a more stable charge and discharge voltage plateau and less polarization in the charge and discharge curve, indicating that the electrochemical reaction kinetics of the electrode after co-doping are better.

[0069] Figure 7 The graphs show the cycle performance of batteries assembled with electrodes made from the cathode materials of Comparative Examples 1, 2, and 3 at a 1C rate. Figure 8 These are cycle performance graphs of batteries assembled with electrodes prepared from the positive electrode materials of Examples 1, 2, and 3, at a 1C rate. From... Figure 7 and Figure 8It can be seen that the capacity retention of Comparative Example 1 (undoped sample) after 100 cycles is only 74.8%, which is due to the severe layered-spinel / rock salt phase transformation, transition metal dissolution, microcrack initiation, and structural collapse during the high-nickel ternary cycling process. The capacity retention of the La-doped sample (Comparative Example 2) and the Nb-doped sample (Comparative Example 3) after 100 cycles increased to 87.4% and 92.4%, respectively, proving that both elements have the function of stabilizing the crystal lattice and inhibiting structural decay. The capacity retention of Example 1 after 100 cycles is as high as 94.7%, which is much higher than that of the single-doped sample, showing extremely strong structural stability. The synergistic mechanism is: It can pin the crystal lattice, suppressing volume deformation and microcrack formation during charging and discharging; It can stabilize the valence state of transition metals and suppress transition metal dissolution and electrolyte side reactions. Both of these factors, from the perspectives of bulk structure and interfacial stability, jointly suppress capacity decay during cycling.

[0070] Figure 9 These are rate performance graphs of batteries assembled with electrodes prepared from the positive electrode materials of Example 1 and Comparative Example 1, respectively. Figure 9 It can be seen that the discharge specific capacity of Example 1 is significantly higher than that of Comparative Example 1 across the entire rate range, with a particularly pronounced advantage at high rates: after a 5C high-current charge-discharge cycle, Example 1 still maintains a specific capacity of approximately 180 mAh / g, while Comparative Example 1 only has approximately 140 mAh / g; when the rate recovers from 5C to 0.1C, the specific capacity of Example 1 is almost completely recovered, while Comparative Example 1 shows a significant irreversible capacity loss. La doping widens the lithium interlayer spacing, significantly reduces the lithium-ion diffusion barrier, and improves the specific capacity. The solid-phase diffusion rate is improved; Nb doping enhances the electronic conductivity of the material and stabilizes the electrode-electrolyte interface, reducing interfacial side reactions during high-current charging and discharging. Lanthanum and niobium synergistically optimize the ion / electron transport dynamics of the material, ultimately achieving excellent rate performance and structural resistance to high-current impacts.

[0071] In summary, the lanthanum and niobium co-doped high-nickel ternary cathode material of this invention can simultaneously optimize the crystal structure, interface stability, and ion / electron transport kinetics of high-nickel ternary materials, achieving comprehensive improvements in specific capacity, initial coulombic efficiency, cycle stability, and rate performance. Therefore, the lanthanum and niobium co-doped high-nickel ternary cathode material of this invention can be prepared as a cathode active material and used in the preparation of cathode sheets for lithium-ion batteries, and the prepared cathode sheets can be used to assemble batteries.

[0072] The foregoing description includes examples from this specification. Of course, for the purposes of describing this specification, it is impossible to describe every conceivable combination of components or methods; however, those skilled in the art will understand that many other combinations and arrangements are possible. Therefore, this specification is intended to cover all such changes, modifications, and variations that fall within the spirit and scope of the appended claims. Furthermore, with regard to the use of the term "comprising" in the detailed description or claims, the term is intended to be inclusive in a manner similar to the term "including," as interpreted when "comprising" is used as a transitional word in the claims.

[0073] 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 claims of the present invention.

Claims

1. A method for preparing lanthanum and niobium co-doped high-nickel ternary cathode material, characterized in that, Includes the following steps: Weigh out the high-nickel NCM9055 precursor prepared by co-precipitation method, lithium source, lanthanum source and niobium source, mix them evenly to obtain a mixture, place the mixture in an oxygen-containing atmosphere, first heat to 450-550℃ for pre-calcination for 3-7 hours, then heat to 700-800℃ for high-temperature calcination for 10-17 hours, and then cool down to obtain lanthanum and niobium co-doped high-nickel ternary cathode material.

2. The preparation method according to claim 1, wherein, The molar ratio of the high-nickel NCM9055 precursor to the lithium source is 1:(1~1.1).

3. The preparation method according to claim 2, wherein, The lithium source is at least one of lithium hydroxide, lithium carbonate, or lithium nitrate.

4. The preparation method according to claim 1, wherein, The total molar number of nickel, cobalt, and manganese in the high-nickel NCM9055 precursor is similar to that in the lanthanum source. niobium source The molar ratio between them is 99.5:0.25:0.25, or 99:0.5:0.5, or 98.5:0.75:0.75, or 98:1:

1.

5. The preparation method according to claim 4, wherein, The lanthanum source is lanthanum oxide, and the niobium source is niobium oxide.

6. The preparation method according to claim 1, wherein, The pre-calcination is performed by heating to 450-550℃ at a rate of 1-10℃ / min for 3-7 hours; the high-temperature calcination is performed by heating to 700-800℃ at a rate of 1-10℃ / min for 10-17 hours; and the cooling is performed by cooling to room temperature at a rate of 1-5℃ / min.

7. The preparation method according to claim 1, wherein, The preparation method of the high-nickel NCM9055 precursor is as follows: According to the molar ratio of Ni:Co:Mn=90:5:5, NiSO4·6H2O, MnSO4·H2O and CoSO4·7H2O were weighed and added to deionized water to prepare a transition metal salt solution. Then, ammonia water as a complexing agent was added while stirring, and sodium hydroxide solution was added dropwise to form a precipitate. The solid obtained by filtration was washed and dried to obtain the high-nickel NCM9055 precursor.

8. A lanthanum and niobium co-doped high-nickel ternary cathode material, characterized in that, It is prepared by the preparation method described in any one of claims 1-7.

9. A positive electrode sheet, characterized in that, The raw materials for preparing the positive electrode sheet include the lanthanum and niobium co-doped high-nickel ternary positive electrode material as described in claim 8.

10. A battery, characterized in that, The battery includes the positive electrode as described in claim 9.

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