A multi-element doped p2 phase sodium-ion battery layered oxide cathode material and a preparation method thereof

Abstract

This invention provides a multi-element doped P2 phase sodium-ion battery layered oxide cathode material and its preparation method. The chemical formula of the cathode material is Na. 0.67 Ni 0.33‑x‑y Mn 0.67 Zn x Cu y O 2‑ z F z Where 0 < x ≤ 0.09, 0 < y ≤ 0.09, and 0 < z ≤ 0.06. This invention synthesizes a cathode material with a multilayered stacked hexagonal structure via a simple solvothermal method. Through Zn / Cu / F doping and material structure regulation, phase transitions are suppressed, and solid solution reactions are synergistically promoted, resulting in excellent Na... + The diffusion kinetics exhibit excellent rate performance and cycle performance within the high-voltage window. The multi-component doping method of this invention is simple, controllable, has a short process, and low cost, making it suitable for large-scale production of sodium-ion battery cathode materials.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery cathode materials, specifically relating to a multi-element doped P2 phase sodium-ion battery layered oxide cathode material and its preparation method. Background Technology

[0002] With the rapid development of new energy technologies and the increasing demand for large-scale energy storage, sodium-ion batteries, with their advantages of abundant sodium resources, low cost, and excellent low-temperature performance, have become a highly promising next-generation energy storage system to replace traditional lithium-ion batteries. Among the many cathode materials for sodium-ion batteries, the P2-type layered transition metal oxide Na... 0.67 Ni 0.33 Mn 0.67 O2(NNMO) possesses a wide two-dimensional sodium ion transport channel and a high theoretical specific capacity (173 mAh g⁻¹). -1 The NNMO electrode has attracted much attention from academia and industry due to its excellent rate performance. However, in actual charge and discharge processes, the irreversible P2-O2 phase transition of the NNMO electrode in the high-voltage range, and the Na... + The vacancy ordering, Mn dissolution, and Jahn-Teller effect lead to poor cycle performance and severe high-voltage capacity decay in this type of cathode material, which greatly limits its commercial application in long-life, high-energy-density energy storage devices.

[0003] To overcome the aforementioned structural defects and improve electrochemical performance, elemental doping is one of the most feasible modification strategies. While single-element doping can alleviate lattice stress to some extent, it is difficult to completely suppress complex high-pressure phase transitions. Multi-element doping, by introducing various heteroatoms to occupy different positions in the lattice, forms a stable crystal structure, widens the interlayer spacing, and reduces Na+ stress. + The diffusion barrier enhances the reversible capacity and energy density of the cathode material. Therefore, the multi-element co-doping strategy optimizes material performance through multi-atom synergistic effects, providing a new research approach for the application and development of sodium-ion battery cathode material technology. Summary of the Invention

[0004] Based on the problems existing in the prior art, the present invention provides a multi-doped P2 phase sodium-ion battery layered oxide cathode material and its preparation method, aiming to improve the conductivity of NNMO cathode material and enhance cycle stability and rate performance.

[0005] To achieve its objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a multi-element doped P2 phase sodium-ion battery layered oxide cathode material, the chemical formula of which is: Na 0.67 Ni 0.33-x-y Mn 0.67 Znx Cu y O 2-z F z , where 0 < x ≤ 0.09, 0 < y ≤ 0.09, and 0 < z ≤ 0.06; The sodium-ion battery layered oxide cathode material has a multi-layered stacked hexagonal morphology; In the sodium-ion battery layered oxide cathode material, some Ni sites are replaced by Zn and Cu elements, and some O sites are replaced by F elements.

[0006] Secondly, the present invention provides a method for preparing the multi-element doped P2 phase sodium-ion battery layered oxide cathode material, comprising the following steps: (1) Dissolve soluble sodium source, soluble nickel salt, soluble manganese salt, soluble zinc salt, soluble copper salt and soluble fluoride source in deionized water according to stoichiometric ratio to obtain solution A; (2) Dissolve the chelating agent in deionized water to obtain solution B; (3) Mix solution A and solution B; after the treatment, dry the mixture, collect the solid product and grind it to obtain precursor powder; (4) The precursor is sintered at 450~550℃ for 4~6h in the first stage and then sintered at 850~950℃ for 12~16h in the second stage to obtain a multi-element doped P2 phase sodium-ion battery layered oxide cathode material.

[0007] Furthermore, in the above preparation method, the chelating agent is selected from at least one of citric acid, oxalic acid, and ammonia water.

[0008] Further, in the above preparation method: the soluble nickel salt is selected from at least one of nickel carbonate, nickel acetate, and nickel nitrate; the soluble manganese salt is selected from at least one of manganese carbonate, manganese acetate, and manganese nitrate; the soluble zinc salt is selected from at least one of zinc carbonate, zinc acetate, and zinc nitrate; the soluble copper salt is selected from at least one of copper carbonate, copper acetate, and copper nitrate; the soluble sodium source is selected from at least one of sodium carbonate, sodium bicarbonate, sodium nitrate, sodium acetate, and trisodium citrate; and the soluble fluorine source is selected from at least one of NaF and NH4F.

[0009] Furthermore, in the above preparation method: the total concentration of each salt in solution A is 80~100g / L, the concentration of the chelating agent in solution B is 0.6~0.8mol / L, and the molar ratio of the total amount of each salt to the chelating agent during mixing is 1:0.8~1.5.

[0010] Furthermore, in step (3) of the above preparation method: the mixing treatment involves mixing solution A and solution B, and then stirring at 60℃~100℃ for 3~5 hours. The drying temperature is 80℃~140℃, and the drying time is 8~14 hours.

[0011] Furthermore, in step (4) of the above preparation method, the heating rate of the first sintering stage is 5~8℃ / min, and the heating rate of the second sintering stage is 3~5℃ / min.

[0012] Compared with existing technologies, the beneficial effects of this invention are reflected in: This invention, through Zn / Cu / F doping and material structure modulation, suppresses phase transitions and synergistically promotes solid solution reactions, exhibiting excellent Na... + The diffusion kinetics exhibit excellent rate performance and cycle performance within the high-voltage window. The multi-component doping method of this invention is simple, controllable, has a short process, and low cost, making it suitable for large-scale production of sodium-ion battery cathode materials. Attached Figure Description

[0013] Figure 1 This is a scanning electron microscope image of the cathode material obtained in Example 1.

[0014] Figure 2 This is a transmission electron microscope image of the cathode material obtained in Example 1.

[0015] Figure 3 This is a scanning electron microscope image of the cathode material obtained in Comparative Example 1.

[0016] Figure 4 The images show the XRD characterization patterns of the cathode materials obtained in Comparative Examples 1-4 and Example 1.

[0017] Figure 5 The graph shows the cycle performance of button batteries assembled with the cathode materials obtained in Comparative Example 1 and Example 1 at a 2C rate.

[0018] Figure 6 The rate performance diagram shows the coin cell assembled with the cathode materials obtained in Comparative Example 1 and Example 1. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The following examples are intended to illustrate the present invention and not to further limit the present invention.

[0020] Example 1 This embodiment provides a layered oxide cathode material for sodium-ion batteries, and the preparation method is as follows: (1) Nickel acetate, manganese acetate, zinc acetate, copper acetate, ammonium fluoride, and sodium acetate (5% excess) were dissolved in deionized water in a stoichiometric ratio (Na:Ni:Mn:Zn:Cu:F=0.67:0.21:0.67:0.09:0.03:0.04) to obtain solution A with a total salt concentration of 90 g / L.

[0021] (2) Dissolve the chelating agent citric acid in deionized water to obtain solution B with a chelating agent concentration of 0.6 mol / L.

[0022] (3) According to the molar ratio of chelating agent to total amount of each salt being 1:1, solution A and solution B were mixed and heated and stirred in an oil bath at 80°C for 4 hours to obtain a mixed system (gel-like liquid). The mixed system was placed in a forced-air drying oven and dried at 120°C for 12 hours to obtain a light green solid mixture, which was then ground to obtain precursor powder.

[0023] (4) The precursor was sintered in air at 450°C (heating rate of 5°C / min) for 5 hours, and then sintered in air at 900°C (heating rate of 5°C / min) for 12 hours to obtain a layered oxide cathode material for sodium-ion batteries with the chemical formula Na. 0.67 Ni 0.21 Mn 0.67 Zn 0.09 Cu 0.03 O 1.96 F 0.04 .

[0024] The scanning electron microscope image of the cathode material prepared in this embodiment is shown below. Figure 1 As shown, the material size is between 1 and 4 μm.

[0025] The transmission electron microscope image of the cathode material prepared in this embodiment is as follows: Figure 2 As shown, the material has a multi-layered, stacked hexagonal morphology.

[0026] Example 2 This embodiment provides a layered oxide cathode material for sodium-ion batteries. The preparation method is basically the same as in Example 1, except that the stoichiometric ratio of Na:Ni:Mn:Zn:Cu:F is adjusted to 0.67:0.24:0.67:0.07:0.02:0.04, resulting in a material with the chemical formula Na. 0.67 Ni 0.24 Mn 0.67 Zn 0.07 Cu 0.02 O 1.96 F 0.04 The positive electrode material.

[0027] Example 3 This embodiment provides a layered oxide cathode material for sodium-ion batteries. The preparation method is basically the same as in Example 1, except that the stoichiometric ratio of Na:Ni:Mn:Zn:Cu:F is adjusted to 0.67:0.24:0.67:0.045:0.045:0.04, resulting in a material with the chemical formula Na. 0.67 Ni 0.24 Mn 0.67 Zn 0.045 Cu 0.045 O 1.96 F 0.04 The positive electrode material.

[0028] Example 4 This embodiment provides a layered oxide cathode material for sodium-ion batteries. The preparation method is basically the same as in Example 1, except that the stoichiometric ratio of Na:Ni:Mn:Zn:Cu:F is adjusted to 0.67:0.24:0.67:0.02:0.07:0.04, resulting in a material with the chemical formula Na. 0.67 Ni 0.24 Mn 0.67 Zn 0.02 Cu 0.07 O 1.96 F 0.04 The positive electrode material.

[0029] Example 5 This embodiment provides a layered oxide cathode material for sodium-ion batteries. The preparation method is basically the same as in Example 1, except that the stoichiometric ratio of Na:Ni:Mn:Zn:Cu:F is adjusted to 0.67:0.21:0.67:0.06:0.06:0.04, resulting in a material with the chemical formula Na. 0.67 Ni 0.21 Mn 0.67 Zn 0.06 Cu 0.06 O 1.96 F 0.04 The positive electrode material.

[0030] Example 6 This embodiment provides a layered oxide cathode material for sodium-ion batteries. Its preparation method is basically the same as in Example 1, except that the stoichiometric ratio of Na:Ni:Mn:Zn:Cu:F is adjusted to 0.67:0.21:0.67:0.03:0.09:0.04, resulting in a material with the chemical formula Na. 0.67 Ni 0.21 Mn 0.67 Zn 0.03 Cu 0.09 O 1.96 F 0.04The positive electrode material.

[0031] Comparative Example 1 This comparative example provides a sodium-ion battery cathode material, the preparation method of which is basically the same as that in Example 1, except that: no Zn / Cu / F elements are doped, and each metal salt (sodium acetate in excess of 5%) is weighed according to the Na:Ni:Mn elemental stoichiometry ratio of 0.67:0.33:0.67 to prepare the material with the chemical formula Na 0.67 Ni 0.33 Mn 0.67 O2 cathode material.

[0032] The microstructure of the sodium ion cathode material obtained in this comparative example is shown in the figure below. Figure 3 As shown.

[0033] Comparative Example 2 This comparative example provides a sodium-ion battery cathode material, the preparation method of which is basically the same as that of Example 1, except that: no Zn / Cu elements are doped, and each metal salt (sodium acetate in excess of 5%) is weighed according to the Na:Ni:Mn:F elemental stoichiometry ratio of 0.67:0.33:0.67:0.04 to prepare the material with the chemical formula Na 0.67 Ni 0.33 Mn 0.67 O 1.96 F 0.04 The positive electrode material.

[0034] Comparative Example 3 This comparative example provides a sodium-ion battery cathode material, the preparation method of which is basically the same as that of Example 1, except that: no Zn element is doped, and each metal salt (sodium acetate in excess of 5%) is weighed according to the elemental stoichiometry of Na:Ni:Mn:Cu:F of 0.67:0.30:0.67:0.03:0.04 to prepare the material with the chemical formula Na 0.67 Ni 0.30 Mn 0.67 Cu 0.03 O 1.96 F 0.04 The positive electrode material.

[0035] Comparative Example 4 This comparative example provides a sodium-ion battery cathode material, the preparation method of which is basically the same as that of Example 1, except that: Cu element is not doped, and each metal salt (sodium acetate in excess of 5%) is weighed according to the elemental ratio of Na:Ni:Mn:Zn:F of 0.67:0.24:0.67:0.09:0.04 to prepare the material with the chemical formula Na 0.67 Ni 0.24 Mn 0.67 Zn 0.09 O 1.96 F 0.04The positive electrode material.

[0036] The XRD characterization patterns of the cathode materials obtained in Comparative Examples 1-4 and Example 1 are shown below. Figure 4 As shown, it is related to Na 0.67 Ni 0.33 Mn 0.67 Corresponds to the O2 standard card (JCPDS No. 054-0894).

[0037] The performance of the samples obtained in each embodiment and comparative example was tested using the following method. The specific test process and related parameters are as follows: (1) Test method: The positive electrode material in the above embodiments and comparative examples was mixed with polyvinylidene fluoride (PVDF) and conductive carbon black (SP) in a ratio of 8:1: Mix the components at a mass ratio of 1, add N-methylpyrrolidone (NMP) solvent, grind thoroughly until uniformly mixed, coat the mixture onto the surface of carbon-coated aluminum foil, and dry to obtain a positive electrode sheet; press the dried positive electrode sheet into a round sheet with a diameter of 12 mm for later use.

[0038] Electrochemical testing employed a half-cell system with the following assembly parameters: the electrolyte was a 1 M NaClO4 solution (solvent ratio EC:PC = 1:1, volume ratio, with 5% FEC added as an additive); the battery casing was a KELU CR2032 button cell casing; the separator was a Whatman GF / D glass fiber membrane; a sodium sheet was used as the negative electrode, assembled with the prepared positive electrode disc, separator, and electrolyte to form a half-cell. The voltage range for electrochemical testing was set to 2–4.2 V.

[0039] (2) Test results: Table 1 Combining the data in Table 1 with Figure 5 Comparison of cycle performance curves shows that, compared to the unmodified and binary-doped samples, the cathode material modified with ternary co-doping of Zn, Cu, and F exhibits both higher initial discharge specific capacity and better long-cycle capacity retention at a 2C rate (1C=150 mA / g). Specifically, in Comparative Example 1, Na... 0.67 Ni 0.33 Mn 0.67 The O2 material exhibits an initial discharge specific capacity of only 77.46 mAh / g at a 2C rate, with a capacity retention rate as low as 61.71% after 300 cycles. In contrast, the optimally proportioned ternary doped sample can increase the initial discharge specific capacity to 91.43 mAh / g, and the capacity retention rate can still reach 95.36% after 300 cycles, demonstrating a significant improvement in cycle stability.

[0040] Comparing the test results of Examples 1 to 6, it can be found that the doping ratio of Zn to Cu directly affects the electrochemical performance of the material, and an imbalance in the doping ratio will cause a decline in the overall performance of the electrode. When the proportion of Zn doping decreases and the relative content of Cu increases, the Ginger-Taylor distortion effect inside the material intensifies, causing the sodium ion diffusion channel to shrink and narrow, ultimately resulting in a significant decrease in the initial reversible sodium storage capacity of the material.

[0041] Comparison of Example 1 with Comparative Examples 1, 2, 3, and 4 confirms that single-element doping and any two-element composite doping schemes cannot simultaneously achieve high discharge specific capacity and high cycle stability. The overall modification effect is weaker than that of the Zn-Cu-F ternary synergistic doping system. F element effectively stabilizes the electrode-electrolyte interface, Zn element suppresses irreversible crystal phase transitions during charge and discharge, and Cu element buffers lattice stress and improves the local conductivity of the material. These three elements form a synergistic modification effect, achieving a bidirectional balance between rapid ion charge transport and flexible lattice structure control while ensuring the integrity and stability of the material's crystal framework structure.

[0042] Depend on Figure 6 The rate performance test results show that the pure phase substrate material has poor rate adaptability. The discharge specific capacity of the sample in Comparative Example 1 at different rates of 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, and 10C is 134.44 mAh / g, 96.59 mAh / g, 79.37 mAh / g, 75.70 mAh / g, 71.17 mAh / g, 65.34 mAh / g, and 59.92 mAh / g, respectively. After high-rate charge and discharge, when it recovers to 0.1C, the discharge specific capacity is only 111.10 mAh / g, indicating a significant capacity decay problem under high-rate conditions. Example 1 shows that the ternary doped cathode material exhibits superior rate performance. Its discharge specific capacity at the aforementioned gradient rates is 120.40 mAh / g, 113.36 mAh / g, 105.27 mAh / g, 100.84 mAh / g, 95.98 mAh / g, 87.23 mAh / g, and 74.58 mAh / g, respectively. After completing the full gradient rate test and returning to 0.1C, the discharge specific capacity still reaches 118.78 mAh / g, demonstrating superior rate adaptability and capacity recovery performance.

[0043] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A multi-element doped P2 phase sodium-ion battery layered oxide cathode material, characterized in that, The chemical formula of the sodium-ion battery layered oxide cathode material is: Na 0.67 Ni 0.33-x-y Mn 0.67 Zn x Cu y O 2-z F z , where 0 < x ≤ 0.09, 0 < y ≤ 0.09, and 0 < z ≤ 0.06; The sodium-ion battery layered oxide cathode material has a multi-layered stacked hexagonal morphology; In the sodium-ion battery layered oxide cathode material, some Ni sites are replaced by Zn and Cu elements, and some O sites are replaced by F elements.

2. A method for preparing the multi-element doped P2 phase sodium-ion battery layered oxide cathode material according to claim 1, characterized in that, Includes the following steps: (1) Dissolve soluble sodium source, soluble nickel salt, soluble manganese salt, soluble zinc salt, soluble copper salt and soluble fluoride source in deionized water according to stoichiometric ratio to obtain solution A; (2) Dissolve the chelating agent in deionized water to obtain solution B; (3) Mix solution A and solution B; after the treatment, dry the mixture, collect the solid product and grind it to obtain precursor powder; (4) The precursor is sintered at 450~550℃ for 4~6h in the first stage and then sintered at 850~950℃ for 12~16h in the second stage to obtain a multi-element doped P2 phase sodium-ion battery layered oxide cathode material.

3. The preparation method according to claim 2, characterized in that, The chelating agent is selected from at least one of citric acid, oxalic acid, and ammonia.

4. The preparation method according to claim 2, characterized in that: The soluble nickel salt is selected from at least one of nickel carbonate, nickel acetate, and nickel nitrate; the soluble manganese salt is selected from at least one of manganese carbonate, manganese acetate, and manganese nitrate; the soluble zinc salt is selected from at least one of zinc carbonate, zinc acetate, and zinc nitrate; the soluble copper salt is selected from at least one of copper carbonate, copper acetate, and copper nitrate; the soluble sodium source is selected from at least one of sodium carbonate, sodium bicarbonate, sodium nitrate, sodium acetate, and trisodium citrate; and the soluble fluorine source is selected from at least one of NaF and NH4F.

5. The preparation method according to claim 2, characterized in that, The total concentration of each salt in solution A is 80~100g / L, and the concentration of the chelating agent in solution B is 0.6~0.8mol / L. When mixed, the molar ratio of the total amount of each salt to the chelating agent is 1:0.8~1.

5.

6. The preparation method according to claim 2, characterized in that, In step (3), the mixing process involves mixing solution A and solution B and then stirring at a heating temperature of 60°C to 100°C for 3 to 5 hours.

7. The preparation method according to claim 2, characterized in that, In step (3), the drying temperature is 80℃~140℃ and the drying time is 8~14 hours.

8. The preparation method according to claim 2, characterized in that, In step (4), the heating rate of the first sintering stage is 5~8℃ / min, and the heating rate of the second sintering stage is 3~5℃ / min.

9. A sodium-ion battery, characterized in that: The multi-element doped P2 phase sodium-ion battery layered oxide cathode material described in claim 1 is used.

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