Preparation and application of a multi-doped and coated composite layered cathode material

Abstract

The application provides preparation and application of a multiple-doped and coated composite layered positive electrode material. The high-nickel positive electrode material is modified internally by aluminum titanium cations and sulfur anions, and the surface is coated with lithium sulfate to isolate electrolyte and reduce side reactions. The multiple doping and coating synergistically improve the specific capacity and cycle stability of the layered positive electrode material at a high charge cut-off voltage. Meanwhile, the method is simple and effective, low in cost, and suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the preparation and application of a composite layered cathode material with multiple doping and coating, belonging to the lithium-ion battery technology field within electrochemistry. Background Technology

[0002] Lithium-ion batteries are widely used in consumer electronics, but they still cannot meet the demands for grid energy storage and the daily performance of electric vehicles. Currently, most commercially available lithium-ion batteries still use lithium iron phosphate as the cathode, which has a relatively low energy density. Therefore, developing high-energy-density lithium-ion batteries is urgently needed, and finding high-capacity cathode materials is key to achieving high-energy-density lithium-ion batteries. High-nickel layered oxides exhibit higher specific capacity at higher cutoff voltages and are low in cost, making them a promising cathode material for high-energy-density lithium batteries.

[0003] However, due to the overlap of electron orbitals, lithium-ion extraction from high-nickel layered oxides at high cutoff voltages is often accompanied by oxygen anion redox reactions. Irreversible oxygen evolution accelerates electrolyte decomposition and structural phase transitions in the cathode material, inevitably leading to undesirable transition metal migration and structural distortion during cycling. This results in rapid capacity loss and voltage decay in the cathode material. Therefore, improving the high-voltage structural stability of the cathode material and suppressing irreversible oxygen-related reactions are crucial for achieving high-voltage, long-cycle stability of high-nickel materials.

[0004] Doping and coating are common modification methods for layered oxide cathode materials. It has been found that both doping and surface coating can improve the performance of layered cathode materials under high-voltage conditions in different ways. Specifically, Al doping can effectively suppress cation mixing and prevent structural phase transitions caused by excessive delithiation. Ti doping can alter internal defects and increase structural stability. S anion doping can stabilize the oxygen layer and reduce O2. 2- Lithium sulfate coating on the surface of layered materials can both isolate the electrode material from the electrolyte, reducing side reactions, and improve lithium-ion transport efficiency. However, these individual modifications can only play a limited role in high-nickel cathode materials, and the overall improvement in high-voltage performance is insufficient, failing to meet the demands for high-nickel cathode material performance. Furthermore, composite modification methods are mostly complex, costly, and difficult to commercialize, and the resulting materials often exhibit poor morphological uniformity. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a method for preparing and applying a composite layered cathode material with multiple doping and coating.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A composite layered cathode material with multiple doping and coating is prepared by the following method, the steps of which are as follows:

[0008] (1) The layered cathode material precursor powder, lithium source, aluminum source, titanium source and sulfate are ground and mixed evenly in anhydrous ethanol to obtain a mixed powder;

[0009] (2) The mixed powder is placed in a crucible, and then the crucible is placed in a heating device. First, the temperature is raised to 480℃~520℃ for pre-calcination for 4h~6h, and then the temperature is raised to 600℃~1000℃ for calcination for 8h~15h. After calcination, the temperature is lowered and cooled to obtain a composite layered cathode material with multiple doping and coating in the crucible.

[0010] The molar ratio of the layered cathode precursor sample material to the lithium source sample material is 1:1.05 to 1.2. The amount of aluminum source is 0.2% to 5% of the amount of the layered cathode precursor powder, more preferably 0.5% to 1.5%. The amount of titanium source is 0.2% to 5% of the amount of the layered cathode precursor powder, more preferably 0.5% to 2%. The amount of sulfate is 0.7% to 10% of the amount of the layered cathode precursor powder, more preferably 1% to 3%.

[0011] The sulfate ions are derived from lithium sulfate, aluminum sulfate, and titanium sulfate.

[0012] Preferably, in step (1), the layered cathode material precursor powder is (Ni x A y M 1-x-y (OH)2、(Ni) x A y M 1-x-y CO3 or (Ni x A y M 1-x-y C2O4, where A is Co or Fe, M is Mn or W, and 0 <x<1,0≤y<1,0≤1-x-y<1。

[0013] Preferably, in step (1), the lithium source sample can be lithium sulfate, lithium carbonate, lithium hydroxide or lithium oxalate.

[0014] Preferably, in step (1), the aluminum source sample can be aluminum sulfate, aluminum acetate, aluminum carbonate, or aluminum oxalate.

[0015] Preferably, in step (1), the titanium source sample can be titanium dioxide, tetrabutyl titanate, or titanium sulfate.

[0016] Preferably, in step (1), the relative humidity is 5% to 20%, the temperature is 30°C to 60°C, and the grinding time is 0.5h to 2h. When the lithium source or titanium is a moisture-sensitive material such as lithium hydroxide or tetrabutyl titanate, water absorption of the material can be effectively avoided by controlling the grinding conditions.

[0017] Preferably, in step (2), during the heating process, the temperature increase rate is 2℃ / min to 15℃ / min, and during the cooling process, the temperature decrease rate is 1℃ / min to 10℃ / min.

[0018] Preferably, when the nickel content in the layered cathode material precursor powder is greater than 0.8% in step (1), the high-temperature heating device in step (2) is a tube furnace with an oxygen atmosphere and a gas flow rate of 50 cfm to 300 cfm. Otherwise, a muffle furnace is used with an air atmosphere.

[0019] Preferably, the particle diameter of the multi-doped and coated composite layered cathode material is 1 μm to 15 μm, wherein the Al doping is 0.2% to 5% of the mass of the layered cathode material, the Ti doping is 0.2% to 5% of the mass of the layered cathode material, the sulfur anion doping is 0.2% to 5% of the mass of the layered cathode material, and the Li2SO4 coating is 0.5% to 5% of the mass of the layered cathode material.

[0020] A lithium-ion battery, wherein the positive electrode material of the battery is a composite layered positive electrode material with multiple doping and coating as described in this invention.

[0021] Beneficial effects

[0022] This invention provides a multi-doped and coated composite layered cathode material, which is obtained in a one-step process using a lithium-ion source, an aluminum source, a titanium source, and a sulfate to achieve both cation and anion doping and fast ion conductor coating. The three doped ions play different roles in the material structure, synergistically enhancing the high-voltage performance of the high-nickel material. Ti 4+ The doping of Ni will make Ni 2+ / Ni 3+ As the proportion increases, some sulfate ions are reduced to S2. 2- This will make Ni 2+ / Ni 3+As the ratio decreases, a balance is reached between the two. In addition, the decomposition of sulfate ions to synthesize a Li₂SO₄ fast ion conductor coating layer on the material surface also exhibits its rigid protective mechanism and rapid ion diffusion performance. Ultimately, through the synergistic effect of multiple doping and coating, side reactions such as oxygen production in high-voltage cathodes can be reduced, while the lithium-ion transport rate can be increased, stabilizing the internal lattice structure of the cathode in the high delithiation state, thereby significantly improving the specific capacity and cycle stability of the layered cathode material at high charging cutoff voltages.

[0023] This invention provides a composite layered cathode material with multiple doping and coating. By adding a modifying substance during the lithium mixing process, the effect of multiple anion and cation doping and coating is achieved in one step. The method is simple, effective, and low in cost. The prepared material has good morphological uniformity and is suitable for large-scale production. Attached Figure Description

[0024] Figure 1 The image shows the energy dispersive spectroscopy (EDS) spectrum of the cross-section of the composite layered cathode material prepared in Example 1.

[0025] Figure 2 XPS data for the composite layered cathode material prepared in Example 1.

[0026] Figure 3 The graph shows the electrochemical cycle performance of batteries assembled with the cathode materials prepared in Example 1, Comparative Example 1, and Comparative Example 2. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to specific embodiments.

[0028] In the following embodiments or comparative examples:

[0029] Assembly of button batteries: At room temperature, the working electrode is first prepared by mixing the material prepared in the examples or comparative examples with a conductive agent and a binder in a ratio of 8:1:1 to form a uniform slurry; then, the slurry is uniformly coated onto aluminum foil with a scraper and dried under vacuum at 100°C for 12 hours to obtain the working electrode; finally, the aluminum foil coated with the sample is pressed into small discs with a diameter of 1.1 cm using a punching machine as the positive electrode, lithium foil as the negative electrode material, and 1.0 M LiPF6 carbonate electrolyte to prepare the button battery.

[0030] Electrochemical performance tests were performed using the Blue Electric system, with a test voltage range of 3.0-4.6V, a test temperature of 30℃, and a current density of 1C (1C = 200mA / g).

[0031] Example 1

[0032] Precursor (Ni) 0.9 Co 0.05 Mn0.05 (OH)₂, LiOH, (CH₃COO)₃Al, TiO₂, and Li₂SO₄ were mixed in a molar ratio of 0.98:1.00:0.01:0.01:0.02 and ground for 0.5 h at a relative humidity of 10% and a temperature of 45°C to obtain a mixed powder. The mixed powder was loosely spread in a crucible, which was then placed in a tube furnace. The temperature was increased to 500°C at a rate of 5°C / min and pre-calcined for 5 h. The temperature was then increased to 750°C and calcined for 10 h in an oxygen atmosphere with a flow rate of 200 cfm. Finally, the temperature was decreased at a rate of 2°C / min to obtain a multi-doped and coated composite layered cathode material, denoted as Al. 0.01 Ti 0.01 S 0.01 -Li(Ni 0.9 Co 0.05 Mn 0.05 )O2@Li2SO4.

[0033] The cross-sectional EDS test results of the composite layered cathode material are as follows: Figure 1 As shown, the results indicate that Al, Ti, and S elements are uniformly distributed inside the composite material.

[0034] The XPS test results of the composite layered cathode material are as follows: Figure 2 As shown, the results indicate that Al exists in the composite material in a +3 valence state, Ti in a +4 valence state, and S in a SO42- valence state. 2- and S2 2- It exists in the form of.

[0035] The electrochemical cycling results of the assembled battery are as follows: Figure 3 As shown in the figure, Example 1 still has a specific capacity of 183.1 mAh / g after 300 cycles, with a capacity retention rate of 91.0%.

[0036] Comparative Example 1

[0037] Precursor (Ni) 0.9 Co 0.05 Mn 0.05 Li(Ni)₂ and LiOH were mixed at a molar ratio of 1.00:1.07. Anhydrous ethanol was added and the mixture was ground for 0.5 hours at a relative humidity of 10% and a temperature of 45°C to obtain a mixed powder. The mixed powder was loosely spread in a crucible, which was then placed in a tube furnace. The furnace was pre-calcined at 500°C for 5 hours at a heating rate of 5°C / min, followed by calcination at 750°C for 10 hours in an oxygen atmosphere with a flow rate of 200 cfm. Finally, the temperature was lowered at a rate of 2°C / min to obtain a layered cathode material, denoted as Li(Ni)₂. 0.9 Co 0.05Mn 0.05 )O2.

[0038] The electrochemical cycling results of the assembled battery are as follows: Figure 3 As shown in the figure, Comparative Example 1 has a specific capacity of only 106.8 mAh / g after 300 cycles, with a capacity retention of 54.1%.

[0039] Comparative Example 2

[0040] Precursor (Ni) 0.9 Co 0.05 Mn 0.05 (OH)₂, LiOH, (CH₃COO)₃Al, and TiO₂ were mixed in a molar ratio of 0.98:1.07:0.01:0.01%. Anhydrous ethanol was added and the mixture was ground for 0.5 h at a relative humidity of 10% and a temperature of 45°C to obtain a mixed powder. The mixed powder was loosely spread in a crucible, which was then placed in a tube furnace. The temperature was increased to 500°C at a rate of 5°C / min and pre-calcined for 5 h. The temperature was then increased to 750°C and calcined for 10 h in an oxygen atmosphere with a flow rate of 200 cfm. Finally, the temperature was decreased at a rate of 2°C / min to obtain an aluminum-titanium co-doped composite material, denoted as Al. 0.01 Ti 0.01 -Li(Ni 0.9 Co 0.05 Mn 0.05 )O2.

[0041] The electrochemical cycling results of the assembled battery are as follows: Figure 3 As shown in the figure, Comparative Example 2 has a specific capacity of 155.6 mAh / g after 300 cycles, with a capacity retention of 79.8%.

[0042] In summary, the invention includes, but is not limited to, the above embodiments. Any equivalent substitutions or partial improvements made under the spirit and principles of this invention shall be considered to be within the protection scope of this invention.

Claims

1. A composite layered cathode material with multiple doping and coating, characterized in that: The material is prepared by the following method, the steps of which are as follows: (1) The layered cathode material precursor powder, lithium source, aluminum source, titanium source and sulfate are ground and mixed evenly in anhydrous ethanol to obtain a mixed powder; (2) The mixed powder is placed in a crucible, and then the crucible is placed in a heating device. First, the temperature is raised to 480℃~520℃ for pre-calcination for 4h~6h, and then the temperature is raised to 600℃~1000℃ for calcination for 8h~15h. After calcination, the temperature is lowered and cooled to obtain a composite layered cathode material with multiple doping and coating in the crucible. The molar ratio of the layered cathode precursor sample material to the lithium source sample material is 1:1.05~1.2; the amount of aluminum source is 0.2%~5% of the amount of layered cathode precursor powder; the amount of titanium source is 0.2%~5% of the amount of layered cathode precursor powder; and the amount of sulfate is 0.7%~10% of the amount of layered cathode precursor powder. The sulfate ions are derived from lithium sulfate, aluminum sulfate, and titanium sulfate.

2. The composite layered cathode material with multiple doping and coating as described in claim 1, characterized in that: In step (1), the layered cathode material precursor powder is (Ni x A y M 1-x-y (OH)2、(Ni) x A y M 1-x-y CO3 or (Ni x A y M 1-x-y C2O4, where A is Co or Fe, M is Mn or W, and 0 <x<1,0≤y<1,0<1-x-y<1。 3. The composite layered cathode material with multiple doping and coating as described in claim 1, characterized in that: In step (1), the lithium source sample is lithium sulfate, lithium oxalate, lithium carbonate, or lithium hydroxide; the aluminum source sample is aluminum sulfate, aluminum carbonate, aluminum oxalate, or aluminum acetate; and the titanium source sample is titanium dioxide, tetrabutyl titanate, or titanium sulfate.

4. The composite layered cathode material with multiple doping and coating as described in claim 1, characterized in that: In step (1), the relative humidity is 5%~20%, the temperature is 30℃~60℃, and the grinding time is 0.5h~2h. When the lithium source or titanium source is a moisture-sensitive material such as lithium hydroxide or tetrabutyl titanate, the material can be effectively prevented from absorbing water by controlling the grinding conditions.

5. The composite layered cathode material with multiple doping and coating as described in claim 1, characterized in that: In step (2), during the heating process, the temperature increase rate is 2℃ / min~15℃ / min, and during the cooling process, the temperature decrease rate is 1℃ / min~10℃ / min.

6. The composite layered cathode material with multiple doping and coating as described in claim 1, characterized in that: When the nickel content in the layered cathode material precursor powder is greater than 0.8 in step (1), the heating device in step (2) is a tube furnace with an oxygen atmosphere and a gas flow rate of 50cfm~300cfm; otherwise, a muffle furnace is used with an air atmosphere.

7. The composite layered cathode material with multiple doping and coating as described in claim 1, characterized in that: The particle diameter of the multi-doped and coated composite layered cathode material is 1μm~15μm, wherein the Al element doping amount is 0.2%~5% of the mass of the layered cathode material, the Ti element doping amount is 0.2%~5% of the mass of the layered cathode material, the sulfur dimer anion doping amount is 0.2%~5% of the mass of the layered cathode material, and the Li2SO4 coating amount is 0.5%~5% of the mass of the layered cathode material.

8. A lithium-ion battery, characterized in that: The positive electrode of the lithium-ion battery is a composite layered positive electrode material with multiple doping and coating as described in any one of claims 1 to 7.

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