Preparation method of zinc-doped sodium-coated electric precursor

Abstract

This invention relates to a method for preparing a zinc-doped sodium-ion battery precursor. The method includes the following steps: a mixed salt solution, a precipitant solution, and a complexing agent solution are introduced concurrently into a base solution; nucleation preparation is performed at pH 11-13; β-Ni(OH)₂ structure preparation is performed at pH 10-11; and hydrotalcite structure preparation is performed at pH 8-10. The mixture is then washed with alkaline solution and water, and dried to obtain the zinc-doped sodium-ion battery precursor. The preparation method provided by this invention utilizes Zn 2+ By exploiting the segregation characteristics during the alkaline washing stage and adjusting the pH value at each reaction stage, the extraction structure of the precursor at each stage can be controlled, resulting in the formation of a hydrotalcite layer on the surface of the β-Ni(OH)2 structure. Finally, alkaline washing is used to enhance the conversion of Zn. 2+ Precipitation to achieve surface Zn 2+ Uniform coating directly yielded Zn-doped sodium-ion battery precursors.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical technology and relates to a method for preparing battery precursor materials, particularly a method for preparing a zinc-doped sodium-coated battery precursor. Background Technology

[0002] Sodium-ion batteries, as an emerging energy storage technology, have received widespread attention in recent years. Compared with traditional lithium-ion batteries, sodium-ion batteries have advantages such as abundant resources, low cost, environmental friendliness, high safety, great performance potential, and wide range of applications.

[0003] Layered oxide sodium cathode materials possess significant advantages and broad development prospects in sodium-ion batteries. Compared to other types of sodium cathode materials such as polyanionic compounds, Prussian blue analogs, and organic materials, they exhibit unique competitiveness in terms of performance, cost, and scalability. However, during the charge-discharge process, layered sodium cathode materials encounter problems such as structural degradation, interfacial side reactions, slow sodium ion diffusion kinetics, transition metal dissolution, and mechanical stress accumulation due to volume changes.

[0004] To alleviate the performance degradation problem of layered sodium-ion battery cathode materials, various improvement strategies have been proposed by those skilled in the art. Among these, Zn doping in the system can stabilize the crystal structure and optimize ion diffusion; while Zn coating on the material surface can suppress interfacial side reactions and improve cycle life. Therefore, Zn doping and coating can greatly solve the problem of poor cycle stability of layered sodium-ion battery cathode materials. Doping and coating of sodium-ion battery cathode materials are often performed at the precursor end.

[0005] During precursor preparation, the resulting precursor structure varies depending on the reaction pH. At higher pH, the precursor crystal structure is β-Ni(OH)₂, while at lower pH, the precursor crystal structure is primarily hydrotalcite. Because of the large number of anions present in the interlayer of the hydrotalcite structure, its formation is generally avoided in precursor preparation processes. Furthermore, alkali washing is typically added during subsequent washing to convert the hydrotalcite structure to the β-Ni(OH)₂ structure. For Zn doping, during precursor preparation, Zn… 2+ This promotes the formation of hydrotalcite structures and increases the pH level at which hydrotalcite is formed. During subsequent alkaline washing, the hydrotalcite structure transforms into a β-Ni(OH)2 structure, and Zn... 2+ It is also very easy to precipitate onto the surface, so the preparation of Zn-doped sodium precursors requires precise control of pH.

[0006] For Zn coating, common coating processes are often carried out separately. They require the preparation of the precursor or the sintering of the cathode to be completed before using methods such as solution impregnation, atomic layer deposition, and chemical vapor deposition. These methods require additional steps and equipment, which is not conducive to large-scale industrial production.

[0007] Therefore, it is necessary to find a method that can achieve Zn doping and coating during the preparation of precursors while solving the problem of Zn segregation. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing a zinc-doped sodium-coated electrical precursor, wherein the preparation method utilizes Zn 2+ By exploiting the segregation characteristics during the alkaline washing stage and adjusting the pH value at each reaction stage, the extraction structure of the precursor at each stage can be controlled, resulting in the coating of a hydrotalcite structure on the surface of the β-Ni(OH)2 structure. Finally, alkaline washing is used to enhance the conversion of Zn. 2+ Precipitation to achieve surface Zn 2+ Uniform coating directly yielded Zn-doped sodium-ion battery precursors.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing a zinc-doped sodium-coated electrical precursor, the method comprising the following steps:

[0011] A mixed salt solution, a precipitant solution, and a complexing agent solution are introduced concurrently into the base solution to sequentially perform nucleation preparation, β-Ni(OH)2 structure preparation, and hydrotalcite structure preparation. Then, the mixture is washed with alkaline solution and water, and dried to obtain the zinc-doped sodium-electric precursor.

[0012] During the nucleation preparation, the pH value is 11-13, and the concentration of the complexing agent is 0.1mol / L-0.7mol / L;

[0013] The β-Ni(OH)2 structure was prepared at a pH of 10-11 and with a complexing agent concentration of 0.1 mol / L-0.7 mol / L.

[0014] The hydrotalcite structure was prepared with a pH of 8-10 and a complexing agent concentration of 0.1 mol / L-0.7 mol / L.

[0015] The preparation method provided by this invention utilizes Zn 2+ By exploiting the segregation characteristics during the alkaline washing stage and adjusting the pH value at each reaction stage, the extraction structure of the precursor at each stage can be controlled, resulting in the coating of a hydrotalcite structure on the surface of the β-Ni(OH)2 structure. Finally, alkaline washing is used to enhance the conversion of Zn. 2+Precipitation to achieve surface Zn 2+ Uniform coating directly yielded Zn-doped sodium-ion battery precursors.

[0016] The pH value during nucleation preparation is 11-13, for example, it can be 11, 11.5, 12, 12.5 or 13, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] The concentration of the complexing agent during nucleation preparation is 0.1 mol / L-0.7 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L or 0.7 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] The pH value for preparing the β-Ni(OH)2 structure is 10-11, for example, it can be 10, 10.5 or 11, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] The concentration of the complexing agent during the preparation of the β-Ni(OH)2 structure is 0.1 mol / L-0.7 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L or 0.7 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] The pH value during the preparation of the hydrotalcite structure is 8-10, for example, it can be 8, 8.5, 9, 9.5 or 10, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] The concentration of the complexing agent during the preparation of the hydrotalcite structure is 0.1 mol / L-0.7 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L or 0.7 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] Preferably, the nucleation preparation time is 4h-20h, for example, it can be 4h, 5h, 8h, 10h, 15h or 20h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] Preferably, the reaction endpoint for preparing the β-Ni(OH)2 structure is a particle size D50 of 4μm-14.8μm, for example, it can be 4μm, 5μm, 8μm, 10μm, 12μm, 14μm or 14.8μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the reaction endpoint for preparing the hydrotalcite structure is that the particle size D50 increases by 0.2 μm-1 μm based on the β-Ni(OH)2 structure preparation. For example, it can be 0.2 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.8 μm or 1 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, the nucleation preparation, β-Ni(OH)2 structure preparation and hydrotalcite structure preparation temperature is 30℃-80℃, for example, it can be 30℃, 40℃, 50℃, 60℃, 70℃ or 80℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0026] Preferably, the nucleation preparation, β-Ni(OH)2 structure preparation, and hydrotalcite structure preparation are carried out in a mixed atmosphere;

[0027] The mixed atmosphere includes air and a protective gas;

[0028] The protective gas includes any one or a combination of at least two of nitrogen, helium, or argon.

[0029] Preferably, the volume percentage of air in the mixed atmosphere is 20%-80%, for example, it can be 20%, 30%, 40%, 50%, 60% or 80%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the alkaline washing is performed using a sodium hydroxide solution with a concentration of 1 mol / L to 10 mol / L, for example, 1 mol / L, 3 mol / L, 5 mol / L, 6 mol / L, 8 mol / L or 10 mol / L, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the washing time with alkaline solution is 0.5h-2h, for example, it can be 0.5h, 0.8h, 1h, 1.2h, 1.5h, 1.8h or 2h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Preferably, the alkaline washing is performed 2 to 5 times, for example, 2, 3, 4 or 5 times.

[0033] Preferably, the washing time is 0.5h-1h, for example, it can be 0.5h, 0.6h, 0.8h, 0.9h or 1h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] Preferably, the number of water washes is 2 to 7 times, for example, 2, 3, 4, 5, 6 or 7 times.

[0035] Preferably, the metal salts in the mixed salt solution include nickel salts, iron salts, manganese salts, and zinc salts, and the concentration of the metal salts in the metal salt solution is 1.5 mol / L to 4 mol / L, for example, it can be 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, or 4 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the molecular formula of the zinc-doped sodium-coated precursor is Ni. a Fe b Mn c Zn d (OH)2, where a+b+c+d=1, 0.1<a<0.5, 0.1<b<0.5, 0.1<c<0.5, 0.02<d<0.1.

[0037] Preferably, the precipitant in the precipitant solution includes any one or a combination of at least two of sodium hydroxide, lithium hydroxide, potassium hydroxide, sodium carbonate, or sodium bicarbonate. Typical but non-limiting combinations include a combination of sodium hydroxide and lithium hydroxide, a combination of potassium hydroxide and sodium carbonate, a combination of sodium carbonate, sodium bicarbonate, and sodium hydroxide, or a combination of sodium hydroxide, lithium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate.

[0038] Preferably, the concentration of the precipitant solution is 1 mol / L to 10 mol / L, for example, it can be 1 mol / L, 3 mol / L, 5 mol / L, 6 mol / L, 8 mol / L or 10 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Preferably, the complexing agent in the complexing agent solution includes any one or a combination of at least two of ammonia, ammonium bicarbonate, ammonium sulfate, oxalic acid, sodium oxalate, citric acid, sodium citrate, EDTA, tartaric acid, sodium tartrate, or sodium hexametaphosphate.

[0040] Preferably, the concentration of the complexing agent solution is 1 mol / L to 10 mol / L, for example, it can be 1 mol / L, 3 mol / L, 5 mol / L, 6 mol / L, 8 mol / L or 10 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] As a preferred embodiment of the preparation method of the present invention, the preparation method includes the following steps:

[0042] (1) Nucleation preparation is carried out in a mixed atmosphere of air and protective gas, with a mixed salt solution, a precipitant solution and a complexing agent solution flowing in parallel into the bottom liquid at a temperature of 30℃-80℃;

[0043] The metal salts in the mixed salt solution include nickel salts, iron salts, manganese salts, and zinc salts, and the concentration of the metal salts in the metal salt solution is 1.5 mol / L-4 mol / L;

[0044] During the nucleation preparation, the pH value is 11-13, the complexing agent concentration is 0.1mol / L-0.7mol / L, and the time is 4h-20h.

[0045] (2) After the nucleation preparation is completed, the β-Ni(OH)2 structure is prepared at a temperature of 30℃-80℃;

[0046] During the preparation of the β-Ni(OH)2 structure, the pH value was 10-11 and the concentration of the complexing agent was 0.1mol / L-0.7mol / L; the reaction endpoint for the preparation of the β-Ni(OH)2 structure was that the particle size D50 reached 4μm-14.8μm.

[0047] (3) After the preparation of the β-Ni(OH)2 structure, the preparation of the hydrotalcite structure was carried out at a temperature of 30℃-80℃.

[0048] During the preparation of the hydrotalcite structure, the pH value is 8-10 and the complexing agent concentration is 0.1mol / L-0.7mol / L; the reaction endpoint for the preparation of the hydrotalcite structure is that the particle size D50 increases by 0.2μm-1μm compared to the preparation of the β-Ni(OH)2 structure.

[0049] (4) After the preparation of the hydrotalcite structure, the sample is washed with alkaline solution and water, and then dried to obtain the zinc-doped sodium-electric precursor Ni. a Fe b Mn c Zn d (OH)2, where a+b+c+d=1, 0.1<a<0.5, 0.1<b<0.5, 0.1<c<0.5, 0.02<d<0.1;

[0050] The alkaline washing is performed using a sodium hydroxide solution with a concentration of 1 mol / L to 10 mol / L for 0.5 h to 2 h, and repeated 2 to 5 times.

[0051] The washing time is 0.5h-1h, and the number of times is 2-7.

[0052] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] The preparation method provided by this invention utilizes Zn 2+ By exploiting the segregation characteristics during the alkaline washing stage and adjusting the pH value at each reaction stage, the extraction structure of the precursor at each stage can be controlled, resulting in the coating of a hydrotalcite structure on the surface of the β-Ni(OH)2 structure. Finally, alkaline washing is used to enhance the conversion of Zn. 2+ Precipitation to achieve surface Zn 2+ Uniform coating directly yielded Zn-doped sodium-ion battery precursors. Attached Figure Description

[0055] Figure 1 This is a SEM image of the zinc-doped sodium-coated precursor obtained in Example 1 of the present invention. Detailed Implementation

[0056] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0057] Example 1

[0058] This embodiment provides a method for preparing a zinc-doped sodium-coated electrode precursor, the method comprising the following steps:

[0059] (1) Nucleation preparation was carried out in a mixed atmosphere of air and protective gas (nitrogen and argon in a volume ratio of 1:1) (air accounted for 40% of the volume), with mixed salt solution, precipitant solution (precipitant concentration of 3 mol / L, sodium hydroxide and potassium hydroxide in a molar ratio of 1:1) and complexing agent solution (comprising water, precipitant solution and complexing agent solution, pH value of 12.3, complexing agent concentration of 0.3 mol / L) flowing in parallel, at a temperature of 50 °C.

[0060] The metal salts in the mixed salt solution include nickel sulfate, ferrous sulfate, manganese sulfate and zinc sulfate, and the concentration of the metal salts in the metal salt solution is 2 mol / L;

[0061] During the nucleation preparation, the pH value was 12.3, the complexing agent concentration was 0.3 mol / L, and the time was 7 h.

[0062] (2) After the nucleation preparation is completed, the β-Ni(OH)2 structure is prepared at a temperature of 50℃;

[0063] The β-Ni(OH)2 structure was prepared at a pH of 10.7 with a complexing agent concentration of 0.3 mol / L. The reaction endpoint for the preparation of the β-Ni(OH)2 structure was a particle size D50 of 7.8 μm.

[0064] (3) After the preparation of the β-Ni(OH)2 structure, the preparation of the hydrotalcite structure was carried out at a temperature of 50℃;

[0065] During the preparation of the hydrotalcite structure, the pH value was 9.2 and the complexing agent concentration was 0.3 mol / L; the reaction endpoint for the preparation of the hydrotalcite structure was an increase of 0.6 μm in particle size D50 compared to the β-Ni(OH)2 structure preparation.

[0066] (4) After the preparation of the hydrotalcite structure, the sample is washed with alkaline solution and water, and then dried to obtain the zinc-doped sodium-electric precursor Ni. 0.3 Fe 0.35 Mn 0.3 Zn 0.05 (OH)2;

[0067] The alkaline washing was performed using a 6 mol / L sodium hydroxide solution for 1.5 hours, repeated 4 times.

[0068] The washing time is 0.7 hours, and the number of washes is 6.

[0069] The SEM image of the zinc-doped sodium-coated electrode precursor obtained in this embodiment is shown below. Figure 1 As shown.

[0070] Example 2

[0071] This embodiment provides a method for preparing a zinc-doped sodium-coated electrode precursor, the method comprising the following steps:

[0072] (1) Nucleation preparation was carried out in a mixed atmosphere of air and protective gas (nitrogen and argon in a volume ratio of 1:1, with air accounting for 20% of the volume) and a mixed salt solution, a precipitant solution (precipitant concentration of 1 mol / L, sodium hydroxide and potassium hydroxide in a molar ratio of 1:1) and a complexing agent solution (comprising water, precipitant solution and complexing agent solution, pH value of 11, complexing agent concentration of 0.1 mol / L) were introduced in parallel at a temperature of 30 °C.

[0073] The metal salts in the mixed salt solution include nickel sulfate, ferrous sulfate, manganese sulfate, and zinc sulfate, and the concentration of the metal salts in the metal salt solution is 1.5 mol / L.

[0074] During the nucleation preparation, the pH value was 11, the complexing agent concentration was 0.1 mol / L, and the time was 20 h.

[0075] (2) After the nucleation preparation is completed, the β-Ni(OH)2 structure is prepared at a temperature of 30℃;

[0076] The β-Ni(OH)2 structure was prepared at a pH of 10 with a complexing agent concentration of 0.1 mol / L; the reaction endpoint for the preparation of the β-Ni(OH)2 structure was when the particle size D50 reached 4 μm.

[0077] (3) After the preparation of the β-Ni(OH)2 structure, the preparation of the hydrotalcite structure was carried out at a temperature of 50℃;

[0078] During the preparation of the hydrotalcite structure, the pH value was 8 and the complexing agent concentration was 0.1 mol / L; the reaction endpoint for the preparation of the hydrotalcite structure was an increase of 0.2 μm in particle size D50 compared to the β-Ni(OH)2 structure preparation.

[0079] (4) After the preparation of the hydrotalcite structure, the sample is washed with alkaline solution and water, and then dried to obtain the zinc-doped sodium-electric precursor Ni. 0.3 Fe 0.35 Mn 0.3 Zn 0.05 (OH)2;

[0080] The alkaline washing was performed using a 1 mol / L sodium hydroxide solution for 2 hours, repeated 5 times.

[0081] The washing time is 0.5 hours, and the number of washes is 7.

[0082] Example 3

[0083] This embodiment provides a method for preparing a zinc-doped sodium-coated electrode precursor, the method comprising the following steps:

[0084] (1) Nucleation preparation was carried out in a mixed atmosphere of air and protective gas (nitrogen and argon in a volume ratio of 1:1, with air accounting for 80% of the volume) and a mixed salt solution, a precipitant solution (precipitant concentration of 10 mol / L, sodium hydroxide and potassium hydroxide in a molar ratio of 1:1) and a complexing agent solution (comprising water, precipitant solution and complexing agent solution, pH value of 13, complexing agent concentration of 0.7 mol / L) were introduced in parallel at a temperature of 80 °C.

[0085] The metal salts in the mixed salt solution include nickel sulfate, ferrous sulfate, manganese sulfate and zinc sulfate, and the concentration of the metal salts in the metal salt solution is 4 mol / L;

[0086] During the nucleation preparation, the pH value was 13, the complexing agent concentration was 0.7 mol / L, and the time was 4 h.

[0087] (2) After the nucleation preparation is completed, the β-Ni(OH)2 structure is prepared at a temperature of 80℃;

[0088] The β-Ni(OH)2 structure was prepared at a pH of 11 with a complexing agent concentration of 0.7 mol / L; the reaction endpoint for the preparation of the β-Ni(OH)2 structure was a particle size D50 of 14.8 μm.

[0089] (3) After the preparation of the β-Ni(OH)2 structure, the preparation of the hydrotalcite structure was carried out at a temperature of 80℃;

[0090] The hydrotalcite structure was prepared at a pH of 10 and with a complexing agent concentration of 0.7 mol / L. The reaction endpoint for preparing the hydrotalcite structure was an increase in particle size D50 of 1 μm compared to the β-Ni(OH)2 structure.

[0091] (4) After the preparation of the hydrotalcite structure, the sample is washed with alkaline solution and water, and then dried to obtain the zinc-doped sodium-electric precursor Ni. 0.3 Fe 0.35 Mn 0.3 Zn 0.05 (OH)2;

[0092] The alkaline washing was performed using a 10 mol / L sodium hydroxide solution for 0.5 hours, repeated twice.

[0093] The water washing time is 1 hour, and the number of times is 2.

[0094] Example 4

[0095] This embodiment provides a method for preparing a zinc-doped sodium-ion battery precursor. Except that the nucleation preparation, β-Ni(OH)2 structure preparation, and hydrotalcite structure preparation are carried out in an air atmosphere, the rest are the same as in Example 1.

[0096] Example 5

[0097] This embodiment provides a method for preparing a zinc-doped sodium-ion battery precursor. Except for the nucleation preparation, β-Ni(OH)2 structure preparation, and hydrotalcite structure preparation, which are carried out in a protective gas atmosphere (nitrogen and argon in a 1:1 volume ratio), the rest are the same as in Example 1.

[0098] Comparative Example 1

[0099] This comparative example provides a method for preparing a zinc-doped sodium-coated precursor, which is the same as in Example 1 except that the pH value during nucleation preparation is 10.

[0100] Comparative Example 2

[0101] This comparative example provides a method for preparing a zinc-doped sodium-coated precursor, which is the same as in Example 1 except that the pH value during nucleation preparation is 14.

[0102] Comparative Example 3

[0103] This comparative example provides a method for preparing a zinc-doped sodium-coated precursor. Except for the pH value of 9 during the preparation of the β-Ni(OH)2 structure, the rest is the same as in Example 1.

[0104] Comparative Example 4

[0105] This comparative example provides a method for preparing a zinc-doped sodium-coated precursor. Except for the pH value of 12 during the preparation of the β-Ni(OH)2 structure, the rest is the same as in Example 1.

[0106] Comparative Example 5

[0107] This comparative example provides a method for preparing a zinc-doped sodium-coated precursor, which is the same as in Example 1 except that the pH value is 7 when preparing the hydrotalcite structure.

[0108] Comparative Example 6

[0109] This comparative example provides a method for preparing a zinc-doped sodium-coated precursor, which is the same as in Example 1 except that the pH value is 11 when preparing the hydrotalcite structure.

[0110] Comparative Example 7

[0111] This comparative example provides a method for preparing a sodium-ionized precursor, which is the same as in Example 1 except that alkaline washing is not performed.

[0112] Performance Characterization

[0113] The precursors provided in the above embodiments and comparative examples were used to prepare cathode materials: the precursors were mixed with sodium carbonate and sintered at 1000°C for 12 hours to obtain cathode materials.

[0114] The positive electrode material, conductive agent, and binder were uniformly mixed in N-methylpyrrolidone at a mass ratio of 90:5:5, and then coated onto an aluminum foil current collector. The mixture was then dried at 120°C under vacuum to obtain a positive electrode sheet, which was subsequently punched into a small circular sheet with a diameter of 2 cm. A coin cell was fabricated using a sodium metal sheet as the counter electrode. The specific capacity, cycle capacity retention, and rate performance were then tested, and the results are shown in Table 1.

[0115] The specific capacity test method is as follows: using the Blue Battery Test System, under 25℃ conditions, the button cell is charged and discharged at 0.1C, and three charge-discharge cycles are performed within the voltage range of 2V to 4.3V, and the specific capacity of the battery is measured.

[0116] The test method for cycle capacity retention rate is as follows: under 25℃ conditions, charge and discharge at 1C, cycle to 100 cycles, and then divide the discharge capacity of the battery at this time by the discharge capacity of the first cycle, which is the battery's 100-cycle capacity retention rate.

[0117] The rate performance test method is as follows: under 25℃ conditions, perform three charge and discharge cycles at 0.1C, 0.2C, 0.5C, and 1C within a voltage range of 2V to 4.3V. Rate performance = discharge capacity at 1C rate / discharge capacity at 0.1C rate.

[0118] Table 1

[0119] Example 1 99.6 93.8 95.1 Example 2 101.6 94.3 96.2 Example 3 102.7 92.9 96.6 Example 4 92.8 89.6 87.6 Example 5 93.7 87.3 88.4 Comparative Example 1 97.2 85.6 86.3 Comparative Example 2 98.3 83.6 84.7 Comparative Example 3 96.4 82.2 84.1 Comparative Example 4 95.6 84.1 85.2 Comparative Example 5 93.8 83.6 82.6 Comparative Example 6 96.8 82.6 81.7 Comparative Example 7 78.6 67.8 62.4

[0120] As shown in Table 1, the cathode material prepared from the zinc-doped sodium-coated precursor provided by the present invention under preferred conditions has a specific capacity of 99.6 mAh / g or higher, a cycle capacity retention of 92.9% or higher, and a rate performance of 95.1% or higher.

[0121] As can be seen from the comparison of Examples 4 and 5 with Example 1, the reaction atmosphere has a certain influence on the electrochemical performance of the zinc-doped sodium-coated precursor obtained in this invention. As a preferred technical solution, the nucleation preparation, β-Ni(OH)2 structure preparation and hydrotalcite structure preparation need to be carried out in a mixed atmosphere of air and protective gas.

[0122] Comparison of Comparative Examples 1 and 2 with Example 1 shows that when the pH value during nucleation preparation is too low or too high, it will cause the precursor to agglomerate and the zinc doping to be uneven, which is not conducive to obtaining zinc-doped sodium-ion precursors with excellent electrochemical performance. As a preferred solution, the pH value during nucleation preparation needs to be controlled at 11-13.

[0123] Comparison of Comparative Examples 3 and 4 with Example 1 shows that if the pH value is too low or too high during the preparation of the β-Ni(OH)2 structure, the subsequent zinc coating will be uneven, which is not conducive to obtaining a zinc-doped sodium-ion precursor with excellent electrochemical performance. As a preferred solution, the pH value during the preparation of the β-Ni(OH)2 structure needs to be controlled at 10-11.

[0124] Comparison of Comparative Examples 5 and 6 with Example 1 shows that when the pH value during the preparation of the hydrotalcite structure is too low, the surface structure changes drastically, and when the pH value is too high, the hydrotalcite structure will not be formed. Both of these conditions affect the uniformity of zinc coating and are not conducive to obtaining zinc-doped sodium-ion precursors with excellent electrochemical performance. As a preferred solution, the pH value during the preparation of the hydrotalcite structure needs to be controlled at 8-10.

[0125] As can be seen from the comparison between Comparative Example 7 and Example 1, alkaline washing is a key step in the preparation of zinc-doped sodium-coated precursors. Without alkaline washing, zinc coating cannot be achieved. At the same time, alkaline washing is also a key step in the precursor preparation process to remove sulfur. If the sulfur content in the precursor is too high, it will also severely degrade the electrochemical performance of the cathode material.

[0126] In summary, the preparation method provided by this invention utilizes Zn 2+ By exploiting the segregation characteristics during the alkaline washing stage and adjusting the pH value at each reaction stage, the extraction structure of the precursor at each stage can be controlled, resulting in the coating of a hydrotalcite structure on the surface of the β-Ni(OH)2 structure. Finally, alkaline washing is used to enhance the conversion of Zn. 2+ Precipitation to achieve surface Zn 2+ Uniform coating directly yielded Zn-doped sodium-ion battery precursors.

[0127] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a zinc-doped sodium-coated electrical precursor, characterized in that, The preparation method includes the following steps: A mixed salt solution, a precipitant solution, and a complexing agent solution are introduced concurrently into the base solution to sequentially perform nucleation preparation, β-Ni(OH)2 structure preparation, and hydrotalcite structure preparation. Then, the mixture is washed with alkaline solution and water, and dried to obtain the zinc-doped sodium-electric precursor. During the nucleation preparation, the pH value is 11-13, and the concentration of the complexing agent is 0.1mol / L-0.7mol / L; The β-Ni(OH)2 structure was prepared at a pH of 10-11 and with a complexing agent concentration of 0.1 mol / L-0.7 mol / L. The hydrotalcite structure was prepared with a pH of 8-10 and a complexing agent concentration of 0.1 mol / L-0.7 mol / L. The metal salts in the mixed salt solution include nickel salts, iron salts, manganese salts, and zinc salts, and the concentration of the metal salts in the metal salt solution is 1.5 mol / L to 4 mol / L.

2. The preparation method according to claim 1, characterized in that, The nucleation preparation time is 4h-20h.

3. The preparation method according to claim 1, characterized in that, The reaction endpoint for preparing the β-Ni(OH)2 structure was a particle size D50 of 4 μm-14.8 μm.

4. The preparation method according to claim 1, characterized in that, The reaction endpoint for the preparation of the hydrotalcite structure is that the particle size D50 increases by 0.2 μm-1 μm compared to the preparation of the β-Ni(OH)2 structure.

5. The preparation method according to claim 1, characterized in that, The nucleation preparation, β-Ni(OH)2 structure preparation, and hydrotalcite structure preparation temperatures are 30℃-80℃.

6. The preparation method according to claim 1, characterized in that, The nucleation preparation, β-Ni(OH)2 structure preparation, and hydrotalcite structure preparation were carried out in a mixed atmosphere; The mixed atmosphere includes air and a protective gas; The protective gas includes any one or a combination of at least two of nitrogen, helium, or argon.

7. The preparation method according to claim 1, characterized in that, Alkaline washing is performed using sodium hydroxide solution with a concentration of 1 mol / L to 10 mol / L.

8. The preparation method according to claim 1, characterized in that, The alkaline washing time is 0.5h-2h.

9. The preparation method according to claim 1, characterized in that, The alkaline solution is used for washing 2 to 5 times.

10. The preparation method according to claim 1, characterized in that, The washing time is 0.5h-1h.

11. The preparation method according to claim 1, characterized in that, The number of times the water is washed is 2 to 7.

12. The preparation method according to claim 1, characterized in that, The molecular formula of the zinc-doped coated sodium pre-charge is Ni a Fe b Mn c Zn d (OH)2, wherein a+b+c+d=1, 0.1 13. The preparation method according to claim 1, characterized in that, The precipitant in the precipitant solution includes any one or a combination of at least two of sodium hydroxide, lithium hydroxide, potassium hydroxide, sodium carbonate, or sodium bicarbonate.

14. The preparation method according to claim 1, characterized in that, The concentration of the precipitant solution is 1 mol / L to 10 mol / L.

15. The preparation method according to claim 1, characterized in that, The complexing agent in the complexing agent solution includes any one or a combination of at least two of the following: ammonia, ammonium bicarbonate, ammonium sulfate, oxalic acid, sodium oxalate, citric acid, sodium citrate, EDTA, tartaric acid, sodium tartrate, or sodium hexametaphosphate.

16. The preparation method according to claim 1, characterized in that, The concentration of the complexing agent solution is 1 mol / L to 10 mol / L.

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