Preparation method of zinc-doped coated sodium electric precursor

Abstract

The invention relates to a preparation method of a zinc-doped coated sodium electric precursor, and the preparation method comprises the following steps: a mixed salt solution, a precipitator solution and a complexing agent solution are introduced into a base solution in parallel, and nucleation preparation with the pH value of 11-13, preparation of a beta-Ni (OH) 2 structure with the pH value of 10-11 and preparation of a hydrotalcite structure with the pH value of 8-10 are sequentially carried out, and then washing with alkali liquor, washing with water and drying in sequence to obtain the zinc-doped coated sodium electric precursor. According to the preparation method provided by the invention, the segregation characteristic of Zn < 2 + > in an alkali liquor washing stage is utilized, the pH value of each reaction stage is regulated and controlled, so that the leaching structure of each stage of a precursor is controlled, the surface of a beta-Ni (OH) 2 structure is coated with a layer of hydrotalcite structure, finally, Zn < 2 + > precipitation is enhanced through alkali washing conversion, uniform coating of Zn < 2 + > on the surface is realized, and the surface of the beta-Ni (OH) 2 structure is improved. And the Zn-doped coated sodium electric precursor is directly obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemistry, and relates to a preparation method of a battery precursor material, in particular to a preparation method of a zinc-doped coated sodium battery precursor. Background Art

[0002] As a new energy storage technology, sodium-ion batteries have received extensive attention in recent years. Compared with traditional lithium-ion batteries, sodium-ion batteries have the advantages of rich resources, low cost, environmental friendliness, high safety, great performance potential, and wide application scenarios.

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

[0004] In order to alleviate the performance degradation problem of layered sodium battery cathode materials, those skilled in the art have proposed various improvement strategies. Among them, doping Zn in the system can stabilize the crystal structure and optimize ion diffusion; while coating Zn on the material surface can inhibit interfacial side reactions and improve the cycle life. Therefore, using Zn doping and coating can greatly solve the problem of poor cycle stability of layered sodium battery cathode materials. The doping and coating of sodium battery cathode materials are often carried out at the precursor stage.

[0005] During the preparation process of the precursor, according to the different reaction pH values, the structures of the precursors obtained will be different. When the pH is high, the crystal structure of the precursor is β-Ni(OH)2, while when the pH is low, the crystal structure of the precursor is mainly a hydrotalcite structure. Due to the large amount of anions between the layers in the hydrotalcite structure, the general precursor preparation process will avoid its generation, and at the same time, alkali washing will be added during the subsequent washing process to convert the hydrotalcite structure into a β-Ni(OH)2 structure. For Zn doping, during the preparation process of the precursor, Zn 2+ will promote the formation of the hydrotalcite structure and increase the pH for the formation of hydrotalcite. And during the subsequent alkali washing process, when the hydrotalcite structure is converted into a β-Ni(OH)2 structure, Zn 2+ is very likely to precipitate on the surface. Therefore, the preparation of Zn-doped sodium battery precursors requires precise control of the pH.

[0006] For Zn coating, common coating processes are often carried out separately, requiring the preparation of the precursor or the completion of the positive electrode sintering before using methods such as solution impregnation, atomic layer deposition, and chemical vapor deposition. These methods require additional processes 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 when preparing the precursor, while solving the problem of Zn segregation. Summary of the Invention

[0008] In view of the shortcomings of the prior art, the present invention aims to provide a method for preparing a zinc-doped sodium electrode precursor. 2+ In the alkali washing stage, the segregation characteristics are adjusted to control the pH value of each reaction stage, thereby controlling the extraction structure of each stage of the precursor, and achieving a layer of hydrotalcite structure coated on the surface of the β-Ni(OH)2 structure, and finally strengthening the Zn through alkali washing conversion. 2+ Precipitation, to achieve surface Zn 2+ Uniform coating was achieved, and the Zn-doped and coated sodium electrode precursor was directly obtained.

[0009] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

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

[0011] A mixed salt solution, a precipitant solution and a complexing agent solution are introduced into the base liquid in parallel, and nucleation preparation, β-Ni(OH)2 structure preparation and hydrotalcite structure preparation are sequentially performed, and then the base liquid is washed with alkali solution and water, and dried to obtain the zinc-doped and coated sodium electrode precursor;

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

[0013] When the β-Ni(OH)2 structure is prepared, the pH value is 10-11 and the concentration of the complexing agent is 0.1mol / L-0.7mol / L;

[0014] When the hydrotalcite structure is prepared, the pH value is 8-10 and the concentration of the complexing agent is 0.1 mol / L-0.7 mol / L.

[0015] The preparation method provided by the present invention utilizes Zn 2+ In the alkali washing stage, the segregation characteristics are adjusted to control the pH value of each reaction stage, thereby controlling the extraction structure of each stage of the precursor, and achieving a layer of hydrotalcite structure coated on the surface of the β-Ni(OH)2 structure, and finally strengthening the Zn through alkali washing conversion. 2+Precipitation to achieve surface Zn 2+ Uniform coating, directly obtaining a Zn-doped coated sodium battery precursor.

[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 numerical range are equally applicable.

[0017] The complexing agent concentration 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 numerical range are equally applicable.

[0018] The pH value during the preparation of 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 numerical range are equally applicable.

[0019] The complexing agent concentration 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 numerical range are equally 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 numerical range are equally applicable.

[0021] The complexing agent concentration 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 numerical range are equally applicable.

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

[0023] Preferably, the reaction end point for preparing the β-Ni(OH)2 structure is that the particle size D50 reaches 4 μm - 14.8 μm. For example, it can be 4 μm, 5 μm, 8 μm, 10 μm, 12 μm, 14 μm or 14.8 μm, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0024] Preferably, the reaction end point for preparing the hydrotalcite structure is that the particle size D50 increases by 0.2 μm - 1 μm based on the preparation of the β-Ni(OH)2 structure. 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, and the other unlisted values within the numerical range are equally applicable.

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

[0026] Preferably, the nucleation preparation, the β-Ni(OH)2 structure preparation and the 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, and the other unlisted values within the numerical range are equally applicable.

[0030] Preferably, the alkali solution washing is carried out using a sodium hydroxide solution with a concentration of 1 mol / L - 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, and the other unlisted values within the numerical range are equally applicable.

[0031] Preferably, the time for the alkali solution washing is 0.5 h - 2 h. For example, it can be 0.5 h, 0.8 h, 1 h, 1.2 h, 1.5 h, 1.8 h or 2 h, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0032] Preferably, the number of times of the alkali solution washing is 2 - 5 times. For example, it can be 2 times, 3 times, 4 times or 5 times.

[0033] Preferably, the time for water washing is 0.5 h - 1 h. For example, it can be 0.5 h, 0.6 h, 0.8 h, 0.9 h or 1 h, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0034] Preferably, the number of times of water washing is 2 - 7 times. For example, it can be 2 times, 3 times, 4 times, 5 times, 6 times or 7 times.

[0035] Preferably, the metal salts in the mixed salt solution include nickel salt, iron salt, manganese salt and zinc salt, and the concentration of the metal salts in the metal salt solution is 1.5 mol / L - 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, and the other unlisted values within the numerical range are equally applicable.

[0036] Preferably, the molecular formula of the zinc-doped coated sodium-ion battery 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 the combination of sodium hydroxide and lithium hydroxide, the combination of potassium hydroxide and sodium carbonate, the combination of sodium carbonate, sodium bicarbonate and sodium hydroxide, or the 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 - 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, and the other unlisted values within the numerical range are equally applicable.

[0039] Preferably, the complexing agent in the complexing agent solution includes any one or a combination of at least two of ammonia water, 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 - 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, and the other unlisted values within the numerical range are equally applicable.

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

[0042] (1) In a mixed atmosphere of air and protective gas, a mixed salt solution, a precipitant solution and a complexing agent solution are simultaneously introduced into the bottom liquid, and nucleation preparation is carried out under the condition that the temperature is 30°C - 80°C;

[0043] The metal salts in the mixed salt solution include nickel salt, iron salt, manganese salt and zinc salt, 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 0.1 mol / L - 0.7 mol / L, and the time is 4 h - 20 h;

[0045] (2) After the nucleation preparation is completed, β-Ni(OH)2 structure preparation is carried out under the condition that the temperature is 30°C - 80°C;

[0046] During the β-Ni(OH)2 structure preparation, the pH value is 10 - 11, the complexing agent concentration is 0.1 mol / L - 0.7 mol / L; the reaction end point of the β-Ni(OH)2 structure preparation is that the particle size D50 reaches 4 μm - 14.8 μm;

[0047] (3) After the β-Ni(OH)2 structure preparation is completed, hydrotalcite structure preparation is carried out under the condition that the temperature is 30°C - 80°C;

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

[0049] (4) After the hydrotalcite structure preparation is completed, it is successively washed with alkali solution and water, and then dried to obtain the zinc-doped coated sodium-ion battery 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 caustic solution washing is carried out using a sodium hydroxide solution with a concentration of 1 mol / L - 10 mol / L for 0.5 h - 2 h and for 2 - 5 times;

[0051] The water washing is carried out for 0.5 h - 1 h and for 2 - 7 times.

[0052] The numerical ranges described in the present invention include not only the point values exemplified above, but also any point values between the above numerical ranges not exemplified. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the described ranges.

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

[0054] The preparation method provided by the present invention utilizes the 2+ segregation characteristics during the caustic solution washing stage to regulate the pH value of each reaction stage, thereby controlling the leaching structure of the precursor at each stage, realizing the coating of a hydrotalcite structure on the surface of the β-Ni(OH)2 structure, and finally strengthening the precipitation of Zn through alkali washing 2+ to achieve uniform coating of surface Zn 2+ and directly obtaining a Zn-doped coated sodium-ion battery precursor. Description of the Drawings

[0055] Figure 1 It is the SEM diagram of the Zn-doped coated sodium-ion battery precursor obtained in Example 1 of the present invention. Detailed Embodiments

[0056] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the described embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0057] Example 1

[0058] This example provides a preparation method of a Zn-doped coated sodium-ion battery precursor, and the preparation method includes the following steps:

[0059] (1) In a mixed atmosphere of air and a protective gas (nitrogen and argon with a volume ratio of 1:1, and the air volume accounts for 40%), into the bottom liquid (composed of water, a precipitant solution, and a complexing agent solution, with a pH value of 12.3 and a complexing agent concentration of 0.3 mol / L), a mixed salt solution, a precipitant solution (the precipitant concentration is 3 mol / L, which is sodium hydroxide and potassium hydroxide with a molar ratio of 1:1), and a complexing agent solution (the complexing agent concentration is 5 mol / L, which is citric acid and oxalic acid with a molar ratio of 1:1) are introduced and circulated, and nucleation preparation is carried out under the condition of 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] When the nucleation is prepared, the pH value is 12.3, the concentration of the complexing agent is 0.3 mol / L, and the time is 7 h;

[0062] (2) After the nucleation preparation, the β-Ni(OH)2 structure is prepared under the condition that the temperature is 50 °C;

[0063] When the β-Ni(OH)2 structure is prepared, the pH value is 10.7 and the concentration of the complexing agent is 0.3 mol / L; the reaction end point of the preparation of the β-Ni(OH)2 structure is that the particle size D50 reaches 7.8 μm;

[0064] (3) After the preparation of the β-Ni(OH)2 structure, the hydrotalcite structure is prepared under the condition that the temperature is 50 °C;

[0065] When the hydrotalcite structure is prepared, the pH value is 9.2 and the concentration of the complexing agent is 0.3 mol / L; the reaction end point of the preparation of the hydrotalcite structure is that the particle size D50 increases by 0.6 μm based on the preparation of the β-Ni(OH)2 structure;

[0066] (4) After the preparation of the hydrotalcite structure, it is successively washed with an alkali solution and water, and then dried to obtain the zinc-doped coated sodium-ion battery precursor Ni 0.3 Fe 0.35 Mn 0.3 Zn 0.05 (OH)2;

[0067] The alkali solution washing is carried out with a sodium hydroxide solution with a concentration of 6 mol / L, the time is 1.5 h, and the number of times is 4 times;

[0068] The time for the water washing is 0.7 h and the number of times is 6 times.

[0069] The SEM image of the zinc-doped coated sodium-ion battery precursor obtained in this example is as Figure 1 shown.

[0070] Example 2

[0071] This example provides a preparation method of a zinc-doped coated sodium-ion battery precursor, and the preparation method includes the following steps:

[0072] (1) In a mixed atmosphere of air and a protective gas (nitrogen and argon with a volume ratio of 1:1, and the air volume accounts for 20%), into the bottom liquid (composed of water, a precipitant solution, and a complexing agent solution, with a pH value of 11 and a complexing agent concentration of 0.1 mol / L), a mixed salt solution, a precipitant solution (the precipitant concentration is 1 mol / L, which is sodium hydroxide and potassium hydroxide with a molar ratio of 1:1), and a complexing agent solution (the complexing agent concentration is 1 mol / L, which is citric acid and oxalic acid with a molar ratio of 1:1) are introduced in parallel, and nucleation preparation is carried out under the condition of 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] When carrying out the nucleation preparation, the pH value is 11, the complexing agent concentration is 0.1 mol / L, and the time is 20 h;

[0075] (2) After the nucleation preparation is completed, β-Ni(OH)2 structure preparation is carried out under the condition of a temperature of 30 °C;

[0076] When carrying out the β-Ni(OH)2 structure preparation, the pH value is 10, and the complexing agent concentration is 0.1 mol / L; the reaction end point of the β-Ni(OH)2 structure preparation is that the particle size D50 reaches 4 μm;

[0077] (3) After the β-Ni(OH)2 structure preparation is completed, hydrotalcite structure preparation is carried out under the condition of a temperature of 50 °C;

[0078] When carrying out the hydrotalcite structure preparation, the pH value is 8, and the complexing agent concentration is 0.1 mol / L; the reaction end point of the hydrotalcite structure preparation is that the particle size D50 increases by 0.2 μm based on the β-Ni(OH)2 structure preparation;

[0079] (4) After the hydrotalcite structure preparation is completed, it is successively washed with an alkali solution and water, and then dried to obtain the zinc-doped and coated sodium-ion battery precursor Ni 0.3 Fe 0.35 Mn 0.3 Zn 0.05 (OH)2;

[0080] The alkali solution washing is carried out using a sodium hydroxide solution with a concentration of 1 mol / L, the time is 2 h, and the number of times is 5;

[0081] The time for the water washing is 0.5 h, and the number of times is 7.

[0082] Example 3

[0083] This example provides a preparation method of a zinc-doped and coated sodium-ion battery precursor, and the preparation method includes the following steps:

[0084] (1) In a mixed atmosphere of air and protective gas (nitrogen and argon with a volume ratio of 1:1, and the air volume accounts for 80%), while flowing through a mixed salt solution, a precipitant solution (the precipitant concentration is 10 mol / L, which is sodium hydroxide and potassium hydroxide with a molar ratio of 1:1), and a complexing agent solution (the complexing agent concentration is 10 mol / L, which is citric acid and oxalic acid with a molar ratio of 1:1) into the bottom solution (composed of water, precipitant solution, and complexing agent solution, with a pH value of 13 and a complexing agent concentration of 0.7 mol / L), nucleation preparation is carried out under the condition of 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 is 13, the complexing agent concentration is 0.7 mol / L, and the time is 4 h;

[0087] (2) After the nucleation preparation is completed, β-Ni(OH)2 structure preparation is carried out under the condition of a temperature of 80 °C;

[0088] During the β-Ni(OH)2 structure preparation, the pH value is 11 and the complexing agent concentration is 0.7 mol / L; the reaction end point of the β-Ni(OH)2 structure preparation is that the particle size D50 reaches 14.8 μm;

[0089] (3) After the β-Ni(OH)2 structure preparation is completed, hydrotalcite structure preparation is carried out under the condition of a temperature of 80 °C;

[0090] During the hydrotalcite structure preparation, the pH value is 10 and the complexing agent concentration is 0.7 mol / L; the reaction end point of the hydrotalcite structure preparation is that the particle size D50 increases by 1 μm based on the β-Ni(OH)2 structure preparation;

[0091] (4) After the hydrotalcite structure preparation is completed, it is successively washed with alkali solution and water, and then dried to obtain the zinc-doped and coated sodium-ion battery precursor Ni 0.3 Fe 0.35 Mn 0.3 Zn 0.05 (OH)2;

[0092] The alkali solution washing is carried out using a sodium hydroxide solution with a concentration of 10 mol / L, the time is 0.5 h, and the number of times is 2;

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

[0094] Example 4

[0095] This embodiment provides a method for preparing a zinc-doped coated sodium 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 coated sodium battery precursor. Except that the nucleation preparation, β-Ni(OH)2 structure preparation, and hydrotalcite structure preparation are carried out in a protective gas (nitrogen and argon with a volume ratio of 1:1) atmosphere, 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 coated sodium battery precursor. Except that the pH value during nucleation preparation is 10, the rest are the same as in Example 1.

[0100] Comparative Example 2

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

[0102] Comparative Example 3

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

[0104] Comparative Example 4

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

[0106] Comparative Example 5

[0107] This comparative example provides a method for preparing a zinc-doped coated sodium battery precursor. Except that the pH value during hydrotalcite structure preparation is 7, the rest are the same as in Example 1.

[0108] Comparative Example 6

[0109] This comparative example provides a method for preparing a zinc-doped coated sodium battery precursor. Except that the pH value during hydrotalcite structure preparation is 11, the rest are the same as in Example 1.

[0110] Comparative Example 7

[0111] This comparative example provides a method for preparing a sodium battery precursor. Except that alkali washing is not carried out, the rest are the same as in Example 1.

[0112] Performance characterization

[0113] The above-mentioned examples and the precursors provided in the comparative examples were prepared into cathode materials: the precursors were mixed with sodium carbonate and sintered at 1000 °C for 12 h to obtain the cathode materials.

[0114] The cathode material, conductive agent, and binder were uniformly mixed in a mass ratio of 90:5:5 in N-methylpyrrolidone, then coated on an aluminum foil current collector, dried at 120 °C in a vacuum environment to obtain a cathode sheet, and then punched into small round pieces with a diameter of 2 cm; and a sodium metal sheet was used as the counter electrode to prepare a button cell. Then, its specific capacity, cycle capacity retention rate, and rate performance were tested, and the results are shown in Table 1.

[0115] The test method for specific capacity is as follows: using a Blue Power battery test system, at 25 °C, the button cell was charged and discharged at 0.1C, and three charge and discharge cycles were carried out in the voltage range of 2V to 4.3V to measure the specific capacity of the battery;

[0116] The test method for cycle capacity retention rate is as follows: at 25 °C, charged and discharged at 1C, after cycling to 100 cycles, the discharge capacity of the battery at this time was divided by the discharge capacity of the first cycle, that is, the 100-cycle capacity retention rate of the battery;

[0117] The test method for rate performance is as follows: at 25 °C, at 0.1C, 0.2C, 0.5C, 1C, three charge and discharge cycles were carried out in the voltage range of 2V to 4.3V, and the rate performance = discharge capacity at 1C rate / discharge capacity at 0.1C rate.

[0118] Table 1

[0119] Specific capacity (mAh / g) Cyclic capacity retention rate (%) Rate performance (%) 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 can be seen from Table 1, the cathode material prepared from the zinc-doped and coated sodium-ion battery precursor provided by the present invention under preferred conditions has a specific capacity of more than 99.6 mAh / g, a cycle capacity retention rate of more than 92.9%, and a rate performance of more than 95.1%.

[0121] From the comparison of Example 4, Example 5 and Example 1, it can be seen that the reaction atmosphere has a certain influence on the electrochemical performance of the zinc-doped and coated sodium-ion battery precursor obtained by the present invention. As a preferred technical solution, it is necessary to carry out nucleation preparation, β-Ni(OH)2 structure preparation, and hydrotalcite structure preparation in a mixed atmosphere of air and protective gas.

[0122] It can be seen from the comparison between Comparative Example 1, Comparative Example 2 and Example 1 that if the pH value during nucleation preparation is too low or too high, it will cause agglomeration of the precursor and uneven zinc doping, which is not conducive to obtaining a zinc-doped coated sodium battery precursor with excellent electrochemical performance. As a preferred solution, the pH value during nucleation preparation needs to be controlled at 11-13.

[0123] It can be seen from the comparison between Comparative Example 3, Comparative Example 4 and Example 1 that if the pH value during the preparation of the β-Ni(OH)2 structure is too low or too high, it will cause uneven subsequent zinc coating, which is not conducive to obtaining a zinc-doped coated sodium battery 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] It can be seen from the comparison between Comparative Example 5, Comparative Example 6 and Example 1 that if the pH value during the preparation of the hydrotalcite structure is too low, it will cause a drastic change in the surface structure, and if it is too high, the hydrotalcite structure will not be formed, both of which will affect the uniformity of zinc coating and are not conducive to obtaining a zinc-doped coated sodium battery precursor 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] It can be seen from the comparison between Comparative Example 7 and Example 1 that alkali washing is a key step in the preparation of the zinc-doped coated sodium battery precursor. Without alkali washing, zinc coating cannot be achieved. At the same time, alkali washing is also a key step in removing S during the preparation of the precursor. If the S content in the precursor is too high, it will also extremely deteriorate the electrochemical performance of the cathode material.

[0126] In summary, the preparation method provided by the present invention utilizes the segregation characteristics of Zn 2+ during the alkali solution washing stage to regulate the pH value of each reaction stage, thereby controlling the leaching structure of the precursor at each stage, realizing the coating of a layer of hydrotalcite structure on the surface of the β-Ni(OH)2 structure, and finally strengthening the precipitation of Zn 2+ through alkali washing conversion, realizing uniform coating of surface Zn 2+ and directly obtaining a zinc-doped coated sodium battery precursor.

[0127] The applicant declares that the above description is only a specific implementation manner 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 thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A preparation method of a zinc-doped coated sodium battery precursor, characterized in that The preparation method includes the following steps: Flow a mixed salt solution, a precipitant solution, and a complexing agent solution into the bottom liquid, and successively carry out nucleation preparation, β-Ni(OH)2 structure preparation, and hydrotalcite structure preparation, and then successively wash with an alkali solution and water, and dry to obtain the zinc-doped coated sodium battery precursor; When carrying out the nucleation preparation, the pH value is 11-13, and the concentration of the complexing agent is 0.1 mol / L-0.7 mol / L; When carrying out the β-Ni(OH)2 structure preparation, the pH value is 10-11, and the concentration of the complexing agent is 0.1 mol / L-0.7 mol / L; When carrying out the hydrotalcite structure preparation, the pH value is 8-10, and the concentration of the complexing agent is 0.1 mol / L-0.7 mol / L.

2. The preparation method according to claim 1, wherein The time for the nucleation preparation is 4 h-20 h.

3. The preparation method according to claim 1 or 2, characterized in that, The reaction end point of the β-Ni(OH)2 structure preparation is that the particle size D50 reaches 4 μm-14.8 μm; Preferably, the reaction end point of the hydrotalcite structure preparation is that the particle size D50 increases by 0.2 μm-1 μm based on the β-Ni(OH)2 structure preparation.

4. The preparation method according to any one of claims 1-3, characterized in that, The temperatures for the nucleation preparation, β-Ni(OH)2 structure preparation, and hydrotalcite structure preparation are 30°C-80°C.

5. The preparation method according to any one of claims 1-4, characterized in that, The nucleation preparation, β-Ni(OH)2 structure preparation, and hydrotalcite structure preparation are 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.

6. The preparation method according to any one of claims 1-5, characterized in that, The alkali solution washing is carried out using a sodium hydroxide solution with a concentration of 1 mol / L-10 mol / L; Preferably, the time for the alkali solution washing is 0.5 h-2 h; Preferably, the number of times of the alkali solution washing is 2-5 times.

7. The preparation method according to any one of claims 1-6, characterized in that, The time for the water washing is 0.5 h-1 h; Preferably, the number of times of the water washing is 2-7 times.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The metal salts in the mixed salt solution include nickel salt, iron salt, manganese salt, and zinc salt, and the concentration of the metal salts in the metal salt solution is 1.5 mol / L-4 mol / L; Preferably, the molecular formula of the zinc-doped coated sodium-ion battery 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.

9. The preparation method according to any one of claims 1-8, characterized in that, The precipitants in the precipitant solution include any one or a combination of at least two of sodium hydroxide, lithium hydroxide, potassium hydroxide, sodium carbonate, or sodium bicarbonate; Preferably, the concentration of the precipitant solution is 1 mol / L-10 mol / L.

10. The preparation method according to any one of claims 1-9, characterized in that, The complexing agents in the complexing agent solution include any one or a combination of at least two of ammonia water, ammonium bicarbonate, ammonium sulfate, oxalic acid, sodium oxalate, citric acid, sodium citrate, EDTA, tartaric acid, sodium tartrate, or sodium hexametaphosphate; Preferably, the concentration of the complexing agent solution is 1 mol / L-10 mol / L.

Images