A dual-element co-doped modified ternary positive electrode material, a preparation method and application thereof

Abstract

This invention provides a dual-element co-doped modified ternary cathode material, its preparation method, and its application. The dual-element co-doped modified ternary cathode material comprises the following raw materials: a ternary cathode material precursor, zirconium dioxide, niobium pentoxide, and a lithium source; the mass ratio of the ternary cathode material precursor, zirconium dioxide, and niobium pentoxide is 1:0.002-0.003:0.001-0.005; the particle size D50 of the zirconium dioxide is 0.5-2 μm; and the particle size D50 of the niobium pentoxide is 3-5 μm. The dual-element co-doped modified ternary cathode material provided by this invention, by employing zirconium and niobium as bulk co-dopersive elements and controlling the amount and particle size of the doping raw materials zirconium dioxide and niobium pentoxide, significantly improves the specific capacity and cycle stability of the prepared ternary cathode material under fast-charging conditions.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery materials technology, specifically to a dual-element co-doped modified ternary cathode material, its preparation method, and its application. Background Technology

[0002] The energy density, cycle life, and safety performance of lithium-ion batteries are determined by the performance of the cathode material. High-nickel ternary layered oxides, due to their significant advantages of high specific capacity and low cost, have become the mainstream research and development direction for lithium-ion battery cathode materials in fields such as new energy vehicles and energy storage devices. Compared with conventional low- and medium-nickel ternary materials, high-nickel systems can significantly improve the energy density of individual battery cells, meeting the needs of devices for long-range operation and high-current charging and discharging, and have broad prospects for industrial application.

[0003] However, high-nickel ternary materials inherently possess structural defects that severely limit their performance under high-rate conditions. The increased nickel content in high-nickel ternary materials exacerbates lithium-nickel mixing, disrupting the integrity of the layered crystal structure and hindering the rapid insertion and extraction of lithium ions. During high-rate charge and discharge, repeated lithium ion insertion and extraction cause drastic expansion and contraction of the material lattice, leading to crystal structure collapse, microcrack initiation and propagation, and ultimately electrode failure. Simultaneously, the strong catalytic activity of the high-nickel component accelerates electrolyte decomposition, continuously generating a thick and unstable interfacial film on the material surface, significantly increasing interfacial impedance. This ultimately results in a sharp decline in specific capacity at high rates and low capacity retention during long-cycle operation, failing to meet the practical application requirements of high power and long lifespan.

[0004] Currently, existing technologies commonly employ modification methods such as elemental doping and surface coating to optimize the performance of high-nickel materials, but all have certain drawbacks. Existing elemental doping methods have limited effectiveness; the dopant components cannot be uniformly dispersed, resulting in an inability to effectively suppress the Li content in the material. + / Ni 2+ Due to cation mixing, the electrochemical performance of cathode materials is difficult to improve. While surface coating can reduce electrolyte erosion to some extent, it cannot solve the performance degradation caused by bulk structure distortion and intensified cation mixing at high rates. Therefore, developing a ternary cathode material that can maintain high capacity and excellent cycle performance at high rates is of great significance. Summary of the Invention

[0005] This invention provides a dual-element co-doped modified ternary cathode material, its preparation method, and its application, in order to solve the problems of reduced specific capacity and poor cycle performance caused by intensified cation mixing and structural distortion in existing ternary cathode materials at high rates.

[0006] In a first aspect, the present invention provides a dual-element co-doped modified ternary cathode material, comprising the following raw materials: a ternary cathode material precursor, zirconia, niobium pentoxide, and a lithium source; the chemical formula of the ternary cathode material precursor is Ni x Co y Mn 1-x-y (OH)2, where 0.8 ≤ x ≤ 0.95, 0.05 ≤ y < 0.2, and 0 < x + y < 1; the mass ratio of the ternary cathode material precursor, zirconia, and niobium pentoxide is 1:0.002 - 0.003:0.001 - 0.005; the particle size D50 of the zirconia is 0.5 - 2 μm; the particle size D50 of the niobium pentoxide is 3 - 5 μm.

[0007] In an optional embodiment, the lithium source includes lithium hydroxide and / or lithium carbonate.

[0008] In an optional embodiment, the molar ratio of the total metal elements in the ternary cathode material precursor to the lithium element in the lithium source is 1:1.03 - 1.08.

[0009] In an optional embodiment, the method for preparing the ternary cathode material precursor includes the following steps: mixing a nickel source, a cobalt source, a manganese source with water to obtain a mixed solution, adding a precipitating agent and a chelating agent for coprecipitation reaction, and subjecting the obtained product to aging and drying to obtain the ternary cathode material precursor.

[0010] In an optional embodiment, the nickel source includes at least one of nickel sulfate, nickel acetate, and nickel nitrate.

[0011] In an optional embodiment, the cobalt source includes at least one of cobalt sulfate, cobalt acetate, and cobalt nitrate.

[0012] In an optional embodiment, the manganese source includes at least one of manganese sulfate, manganese acetate, and manganese nitrate.

[0013] In an optional embodiment, the precipitating agent includes at least one of sodium hydroxide, potassium hydroxide, and sodium carbonate. <​​​​​​​​

[0017] In one alternative implementation, the aging process involves allowing the sample to stand for 12-16 hours.

[0018] In one optional embodiment, the drying temperature is 80-90°C and the time is 14-18 hours.

[0019] Secondly, this invention provides a method for preparing the above-mentioned dual-element co-doped modified ternary cathode material, comprising the following steps: The ternary cathode material precursor, zirconium dioxide, niobium pentoxide and dispersant are first mixed, dried and then mixed with lithium source, and sintered to obtain a dual-element doped modified ternary cathode material.

[0020] In one alternative embodiment, the dispersant includes at least one of ethanol, methanol, and isopropanol.

[0021] In one optional embodiment, the total mass ratio of the ternary cathode material precursor, zirconium dioxide, and niobium pentoxide to the volume ratio of the dispersant is 1 g: 0.5-3 mL.

[0022] In one alternative embodiment, the first mixing speed is 2000-3000 r / min and the time is 30-40 min.

[0023] In one optional embodiment, the drying temperature is 85-95°C and the time is 6-8 hours.

[0024] In one alternative embodiment, the second mixing speed is 200-400 rpm and the time is 2-3 hours.

[0025] In one optional embodiment, the sintering operation is to raise the temperature from room temperature to 475-485°C at a rate of 3-4°C / min under an oxygen atmosphere, hold the temperature for 4-6 hours, and then continue to raise the temperature to 730-740°C at a rate of 2-3°C / min and hold the temperature for 11-13 hours.

[0026] Thirdly, the present invention provides a positive electrode sheet, comprising: Positive current collector, and A positive electrode active material layer disposed on at least one side of the positive electrode current collector, the positive electrode active material layer comprising the above-mentioned dual-element co-doped modified ternary positive electrode material or the dual-element co-doped modified ternary positive electrode material prepared by the above-mentioned preparation method.

[0027] Fourthly, the present invention provides a secondary battery comprising the aforementioned positive electrode sheet. Fifthly, the present invention provides an electrical device comprising the aforementioned secondary battery.

[0028] Compared with the prior art, the present invention has the following beneficial effects: 1. The dual-element co-doped modified ternary cathode material provided by this invention, through the use of zirconium and niobium dual-element bulk co-doping, fully combines the structural stabilizing effect of the strong metal-oxygen bond of Zr with that of Nb. 5+ Inhibit Li + / Ni 2+ Leveraging the advantages of mixed arrangement and enhanced lattice structure, synergistic modification of Nb-12 ions is achieved. 5+ The high-bond-energy Nb-O bonds formed can replace some of the Ni-O bonds in the crystal, enhancing the structural integrity of the high-nickel ternary cathode material during charge and discharge processes and reducing Li... + / Ni 2+ Cation mixing enhances lithium-ion diffusion rate and effectively prevents lattice collapse. Furthermore, controlling the amount and particle size of the raw materials zirconium dioxide and niobium pentoxide within a specific range can achieve uniform dispersion of the doping components, ensuring stable synergistic modification effects of the two elements. If the particle size is too large, it can easily cause agglomeration and uneven distribution of the doping components; if the particle size is too small, it can easily lead to excessive surface enrichment of the particles, failing to achieve the modification effect. Precise control of particle size and amount can ensure uniform dispersion of the doping components, resulting in a significant improvement in the specific capacity and cycle stability of the two-element co-doped ternary cathode material at high rates.

[0029] 2. The preparation method of the dual-element co-doped modified ternary cathode material provided by the present invention is simple, controllable, and reproducible, enabling the prepared dual-element co-doped modified ternary cathode material to have high specific capacity and cycle stability at high rates, making it suitable for high-rate, long-life power battery applications and possessing good industrialization value. Detailed Implementation

[0030] The following embodiments are provided to better understand the present invention, but the following embodiments 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 scope of protection of the present invention.

[0031] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0032] Example 1 This embodiment provides a method for preparing a dual-element co-doped modified ternary cathode material, including the following steps: (1) Nickel sulfate, cobalt sulfate, and manganese sulfate were mixed with water at a molar ratio of 90:5:5 to obtain a mixed solution with a total metal ion concentration of 2.0 mol / L. Ammonia solution with 6.0 mol / L was used as a chelating agent and NaOH solution with 5.0 mol / L was used as a precipitant. The three solutions were pumped into a continuous co-precipitation reactor at a constant rate of 20 mL / min. The reaction temperature was controlled at 70℃, pH at 11.0, and stirring speed at 350 rpm. After reacting at a constant temperature for 13 h, the mixture was allowed to stand for aging for 14 h. The precipitate was repeatedly washed with deionized water until the filtrate was neutral. The precipitate was then dried in a vacuum drying oven at 85℃ for 16 h to obtain the ternary cathode material precursor Ni. 0.9 Co 0.05 Mn 0.05 (OH)2; (2) Weigh 10g of ternary cathode material precursor, 0.025g of zirconium dioxide (particle size D50 of 1μm) and 0.01g of niobium pentoxide (particle size D50 of 4μm) and 5.1mL of anhydrous ethanol dispersant, and stir them in a high-speed homogenizer at 2500r / min for 35min until a viscous slurry without solid-liquid separation is formed; after drying the slurry at 90℃ for 7h, place it in a planetary ball mill, continue to add lithium hydroxide and grind at a speed of 300rpm. The mixture was heated for 2.5 hours, wherein the ratio of the molar number of lithium element in lithium hydroxide to the total molar number of metal elements in the ternary cathode material precursor was 1.05:1. The mixture was then placed in a tube furnace and sintered in a pure oxygen atmosphere. The sintering procedure was as follows: the temperature was increased from room temperature to 480℃ at a rate of 3.5℃ / min and held for 5 hours, then increased to 735℃ at a rate of 2.5℃ / min and held for 12 hours, and then naturally cooled to room temperature to obtain the bi-element co-doped modified ternary cathode material.

[0033] Example 2 This embodiment provides a method for preparing a dual-element co-doped modified ternary cathode material, including the following steps: (1) Nickel sulfate, cobalt sulfate, and manganese sulfate were mixed with water at a molar ratio of 90:5:5 to obtain a mixed solution with a total metal ion concentration of 1.8 mol / L. A chelating agent of 6.0 mol / L ammonia solution and a precipitating agent of 5.0 mol / L NaOH solution were used. The three solutions were pumped into a continuous co-precipitation reactor at a constant rate of 20 mL / min. The reaction temperature was controlled at 65℃, the pH at 10.8, and the stirring speed at 300 rpm. After reacting at a constant temperature for 12 h, the mixture was allowed to stand for aging for 16 h. The precipitate was repeatedly washed with deionized water until the filtrate was neutral. The precipitate was then dried in a vacuum drying oven at 80℃ for 18 h to obtain the ternary cathode material precursor Ni. 0.9 Co 0.05 Mn 0.05 (OH)2; (2) Weigh 10g of ternary cathode material precursor, 0.025g of zirconium dioxide (particle size D50 of 0.5μm) and 0.025g of niobium pentoxide (particle size D50 of 5μm) and 20.1mL of anhydrous ethanol dispersant, and stir at 2000r / min for 40min using a high-speed homogenizer until a viscous slurry without solid-liquid separation is formed; dry the slurry at 85℃ for 8h and then place it in a planetary ball mill, and continue to add lithium hydroxide at 400rpm. The mixture was ground at a certain speed for 2 hours, wherein the ratio of the number of moles of lithium element in lithium hydroxide to the total number of moles of metal elements in the ternary cathode material precursor was 1.03:1. The mixture was then placed in a tube furnace and sintered in a pure oxygen atmosphere. The sintering procedure was as follows: the temperature was increased from room temperature to 485℃ at a rate of 3℃ / min and held for 4 hours, then increased to 740℃ at a rate of 2℃ / min and held for 11 hours, and then naturally cooled to room temperature to obtain the dual-element co-doped modified ternary cathode material.

[0034] Example 3 This embodiment provides a method for preparing a dual-element co-doped modified ternary cathode material, including the following steps: (1) Nickel sulfate, cobalt sulfate, and manganese sulfate were mixed with water at a molar ratio of 90:5:5 to obtain a mixed solution with a total metal ion concentration of 2.2 mol / L. A 6.0 mol / L citric acid solution was used as a chelating agent, and a 5.0 mol / L NaOH solution was used as a precipitating agent. The three solutions were pumped into a continuous co-precipitation reactor at a constant rate of 20 mL / min. The reaction temperature was controlled at 75℃, the pH at 11.2, and the stirring speed at 400 rpm. After reacting at a constant temperature for 24 h, the mixture was allowed to stand for 12 h. The precipitate was repeatedly washed with deionized water until the filtrate was neutral. The precipitate was then dried in a vacuum drying oven at 90℃ for 14 h to obtain the ternary cathode material precursor Ni. 0.9 Co 0.05 Mn 0.05 (OH)2; (2) Weigh 10g of ternary cathode material precursor, 0.025g of zirconium dioxide (particle size D50 of 2μm) and 0.05g of niobium pentoxide (particle size D50 of 3μm) and 30mL of anhydrous ethanol dispersant, and stir them in a high-speed homogenizer at 3000r / min for 30min until a viscous slurry without solid-liquid separation is formed; after drying the slurry at 95℃ for 7h, place it in a planetary ball mill, and continue to add lithium hydroxide at a speed of 200rpm. After grinding for 3 hours, the ratio of the number of moles of lithium in the lithium hydroxide to the total number of moles of metal elements in the ternary cathode material precursor was 1.08:1. The mixture was then placed in a tube furnace and sintered in a pure oxygen atmosphere. The sintering procedure was as follows: the temperature was increased from room temperature to 475℃ at a rate of 4℃ / min and held for 6 hours, then increased to 730℃ at a rate of 3℃ / min and held for 13 hours, and then naturally cooled to room temperature to obtain the dual-element co-doped modified ternary cathode material.

[0035] Example 4 This embodiment provides a method for preparing a dual-element co-doped modified ternary cathode material, which is basically the same as that in Example 1, except that the amount of zirconium dioxide in step (2) is adjusted to 0.02g and the amount of niobium pentoxide is adjusted to 0.05g.

[0036] Example 5 This embodiment provides a method for preparing a dual-element co-doped modified ternary cathode material, which is basically the same as that in Example 1, except that the amount of zirconium dioxide in step (2) is adjusted to 0.03g and the amount of niobium pentoxide is adjusted to 0.05g.

[0037] Comparative Example 1 This comparative example provides a method for preparing a ternary cathode material, which is basically the same as that in Example 1, except that the addition of zirconium dioxide and niobium pentoxide in step (2) is omitted.

[0038] Comparative Example 2 This comparative example provides a method for preparing a ternary cathode material, which is basically the same as that in Example 1, except that the particle size D50 of zirconium dioxide is adjusted to 3 μm and the particle size D50 of niobium pentoxide is adjusted to 5.2 μm.

[0039] Comparative Example 3 This comparative example provides a method for preparing a ternary cathode material, which is basically the same as that in Example 1, except that the addition of niobium pentoxide in step (2) is omitted and the amount of zirconium dioxide is adjusted to 0.035g.

[0040] Comparative Example 4 This comparative example provides a method for preparing a ternary cathode material, which is basically the same as that in Example 1, except that the addition of zirconium dioxide in step (2) is omitted and the amount of niobium pentoxide is adjusted to 0.035g.

[0041] Experimental Example 1 1. The positive electrode materials obtained in each embodiment and comparative example are assembled into coin cells. The preparation method of the coin cells is as follows: (1) Preparation of positive electrode sheet: The positive electrode material, conductive carbon black, and polyvinylidene fluoride binder obtained from each example and comparative example were mixed in a mass ratio of 8:1:1. N-methylpyrrolidone (NMP) was used as solvent, and the mixture was stirred in a vacuum mixer for 3 hours to form a uniform and viscous slurry. The slurry was uniformly coated onto an aluminum foil current collector with a thickness of 20 μm using an automatic coating machine. The coated electrode sheet was then placed in a vacuum oven at 100°C and dried for 14 hours. After that, it was compacted with a roller press and cut into round sheets with a diameter of 12 mm. The mass loading of the positive electrode material on each electrode sheet was precisely controlled to be 3 mg / cm³. 2 ; (2) Button cell assembly: All battery assembly steps were carried out in a glove box filled with high-purity argon (H2O<0.1ppm, O2<0.1ppm). The negative electrode was a lithium metal sheet, the separator was Celgard 2400, and the electrolyte was 1M LiPF6 (the solvent was ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1). The negative electrode shell, negative electrode sheet (lithium sheet), electrolyte were added, separator was laid, positive electrode sheet was added, electrolyte was added, positive electrode shell was covered, and the sealing machine was used to press and seal the battery to obtain a button cell. The assembled battery was left to stand for 14 hours before testing.

[0042] 2. Perform performance tests on the button cells prepared above. 1) Charge and discharge test: Under 25℃ conditions, the coin cell is charged at 0.1C and discharged at 0.1C, with a voltage range of 2.75V-4.3V, to obtain the first charge specific capacity and the first discharge specific capacity. Then, the first coulombic efficiency is calculated according to (first discharge specific capacity / first charge specific capacity) × 100%.

[0043] 2) Cyclic performance test: Under 25℃ conditions, the button cell is cycled 300 times at 5C, with a voltage range of 2.75V-4.3V; the capacity retention rate after 300 cycles at 5C = (discharge specific capacity of the 300th cycle at 5C / discharge specific capacity of the 1st cycle at 5C) × 100%.

[0044] 3. Test Results Table 1 Test Results

[0045] As shown in Table 1, the dual-element co-doped modified ternary cathode materials prepared in Examples 1-5 of the present invention, through modification by doping with dual elements of specific particle size, not only have a high specific capacity, but also significantly optimize the long-cycle capacity retention rate of the material, exhibiting excellent structural stability and cycle life; while the cathode materials prepared in Comparative Examples 1-4 have significantly worse cycle performance because they did not undergo dual-element doping or the particle size of the dopant source was not within a specific range.

[0046] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A dual-element co-doped modified ternary cathode material, characterized in that, It includes the following raw materials: ternary cathode material precursor, zirconia, niobium pentoxide, and lithium source; the chemical formula of the ternary cathode material precursor is Ni x Co y Mn 1-x-y (OH)2, where 0.8 ≤ x ≤ 0.95, 0.05 ≤ y < 0.2, 0 < x + y < 1; the mass ratio of the ternary cathode material precursor, zirconia, and niobium pentoxide is 1:0.002 - 0.003:0.001 - 0.005; the particle size D50 of the zirconia is 0.5 - 2 μm; the particle size D50 of the niobium pentoxide is 3 - 5 μm.

2. The dual-element co-doped modified ternary cathode material according to claim 1, characterized in that, The lithium source includes lithium hydroxide and / or lithium carbonate; And / or, the ratio of the total number of moles of metal elements in the ternary cathode material precursor to the number of moles of lithium elements in the lithium source is 1:1.03-1.

08.

3. The dual-element co-doped modified ternary cathode material according to claim 1 or 2, characterized in that, The preparation method of the ternary cathode material precursor includes the following steps: mixing a nickel source, a cobalt source, a manganese source, and water to obtain a mixed solution, adding a precipitant and a chelating agent to carry out a co-precipitation reaction, and aging and drying the obtained product to obtain the ternary cathode material precursor.

4. The dual-element co-doped modified ternary cathode material according to claim 3, characterized in that, The nickel source includes at least one of nickel sulfate, nickel acetate, and nickel nitrate; And / or, the cobalt source includes at least one of cobalt sulfate, cobalt acetate, and cobalt nitrate; And / or, the manganese source includes at least one of manganese sulfate, manganese acetate, and manganese nitrate; And / or, the precipitant includes at least one of sodium hydroxide, potassium hydroxide, and sodium carbonate; And / or, the chelating agent includes at least one of ammonia, ethylenediaminetetraacetic acid, and citric acid; And / or, the total metal ion concentration in the mixed solution is 1.8-2.2 mol / L; And / or, the coprecipitation reaction is carried out at a rotation speed of 300-400 rpm, a temperature of 65-75℃, a time of 12-24 h, and a pH of 10.8-11.

2. And / or, the aging process involves standing for 12-16 hours; And / or, the drying temperature is 80-90℃ and the time is 14-18h.

5. The method for preparing the dual-element co-doped modified ternary cathode material according to any one of claims 1-4, characterized in that, Includes the following steps: The ternary cathode material precursor, zirconium dioxide, niobium pentoxide and dispersant are first mixed, dried and then mixed with lithium source, and sintered to obtain a dual-element doped modified ternary cathode material.

6. The preparation method according to claim 5, characterized in that, The dispersant includes at least one of ethanol, methanol, and isopropanol; And / or, the ratio of the total mass of the ternary cathode material precursor, zirconium dioxide, and niobium pentoxide to the volume of the dispersant is 1g:0.5-3mL.

7. The preparation method according to claim 5, characterized in that, The first mixing speed is 2000-3000 r / min, and the time is 30-40 min; And / or, the drying temperature is 85-95℃ and the time is 6-8h; And / or, the second mixing speed is 200-400 rpm, and the time is 2-3 h; And / or, the sintering operation is to raise the temperature from room temperature to 475-485°C at a rate of 3-4°C / min under an oxygen atmosphere, hold the temperature for 4-6 hours, and then continue to raise the temperature to 730-740°C at a rate of 2-3°C / min and hold the temperature for 11-13 hours.

8. A positive electrode sheet, characterized in that, include: Positive current collector, and A positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises the dual-element co-doped modified ternary positive electrode material as described in any one of claims 1-4 or the dual-element co-doped modified ternary positive electrode material prepared by the preparation method described in any one of claims 5-7.

9. A secondary battery, characterized in that, Includes the positive electrode sheet as described in claim 8.

10. An electrical device, characterized in that, Includes the secondary battery as described in claim 9.

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