A precursor of a zinc-containing sodium-ion battery cathode material and a preparation method thereof

Abstract

The present invention discloses a zinc-containing sodium-ion cathode material precursor and a preparation method thereof. Instead of preparing a zinc salt solution with a certain concentration in the past, zinc salt is added to excessive alkali solution to form zincate to participate in the co-deposition reaction. The primary particles of the precursor prepared by this method are uniform and have a relatively high tap density. Moreover, the addition of zinc element in the cathode material is beneficial to improving its crystallization degree. Since zinc is a fixed-valence element, it can stabilize the crystal structure of the active material during charge and discharge, preventing the crystal structure from collapsing due to instability during the charge and discharge process, thereby greatly improving the cycle reversibility and discharge specific capacity of the sodium-ion battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of positive electrode materials for sodium-ion batteries, and particularly relates to a zinc-containing sodium-ion positive electrode material precursor and a preparation method thereof. Background Art

[0002] At present, the new energy battery industry is divided into lead-acid batteries, lithium iron phosphate batteries, lithium-ion batteries and sodium-ion batteries. Among them, lead-acid batteries have relatively poor environmental protection, lithium iron phosphate batteries have good environmental protection but poor low-temperature performance, lithium-ion batteries have advantages in environmental protection compared with lithium iron phosphate batteries but poor high and low-temperature performance, while sodium-ion batteries have relative advantages in both environmental protection and high and low-temperature performance. For current sodium-ion batteries, due to the large radius of Na ions and slow transmission process, their capacitance is relatively low. If the nickel content is increased to improve the capacity, the cost will increase.

[0003] The patent application with publication number CN 117401726A discloses a zinc-doped sodium-ion battery positive electrode material precursor and a preparation method thereof. By doping zinc elements to modify the material, a zinc-doped sodium-ion battery positive electrode material precursor is prepared by a coprecipitation method. The specific preparation steps are as follows: Step 1, prepare metal salt solutions of Zn, Fe, Mn, and Ni according to the stoichiometric ratio; Step 2, prepare a mother liquor solution with a pH value of 10.5 - 10.8 and an ammonia concentration of 10 ± 1 g / L in a container; Step 3, simultaneously add the metal salt solution, sodium hydroxide solution and ammonia water solution to the container at different flow rates to carry out a coprecipitation reaction to obtain a coprecipitation product; Step 4, filter, wash and dry the coprecipitation product to obtain a zinc-doped sodium-ion battery positive electrode material precursor. This precursor can increase the contact area with the electrolyte and improve the sodium-ion transmission efficiency, thereby improving the electrochemical performance. However, in this method, the metal salt solutions of Zn, Fe, Mn, and Ni are used to carry out a coprecipitation reaction with the sodium hydroxide solution and the ammonia water solution, and the tap density of the prepared precursor is 0.85 - 0.98 g / cm 3 , and its tap density still needs to be further improved to better meet the requirements of high electrochemical performance of sodium-ion batteries. Summary of the Invention

[0004] The technical problem solved by the present invention is to provide a zinc-containing sodium-ion cathode material precursor and a preparation method thereof. During the preparation process of the precursor, zinc element is doped by co-deposition, which can make the zinc element evenly distributed. The difference between the present invention and the previous co-deposition is that during the co-deposition reaction process, the previous preparation of a zinc salt solution with a certain concentration is replaced by adding zinc salt to an excessive amount of alkali solution to form zinc meta-aluminate to participate in the co-deposition reaction. The primary particles of the precursor prepared by this method are uniform and the tap density is relatively high. Moreover, the addition of zinc element in the cathode material is beneficial to improving its crystallization degree. Since zinc is a fixed-valence element, it can stabilize the crystal structure of the active material during charge and discharge, preventing the crystal structure from collapsing due to instability during charge and discharge, thereby greatly improving the cycle reversibility and discharge specific capacity of the sodium-ion battery.

[0005] The present invention adopts the following technical solution to solve the above technical problem. A preparation method of a zinc-containing sodium-ion cathode material precursor, characterized in that the specific steps are as follows:

[0006] Step S1, prepare a nickel-manganese-iron mixed salt solution. The nickel salt in the nickel-manganese-iron mixed salt solution is one or more of nickel sulfate, nickel nitrate or nickel chloride; the manganese salt is one or more of manganese sulfate, manganese nitrate or manganese chloride; the ferrous salt is one or more of ferrous sulfate, ferrous nitrate or ferrous chloride. Dissolve the zinc salt in an excessive amount of alkali solution to prepare a zinc meta-aluminate and alkali mixed solution, that is, a zinc salt solution, wherein the zinc salt is one or more of zinc sulfate, zinc chloride or zinc nitrate, and the alkali solution is sodium hydroxide solution or potassium hydroxide solution. Prepare a precipitant solution, and the precipitant in the precipitant solution is one or more of sodium hydroxide, potassium hydroxide or lithium hydroxide. Prepare a complexing agent solution, and the complexing agent in the complexing agent solution is one or more of ammonia water or ammonium bicarbonate.

[0007] Step S2, add a mixed solution of the precipitant solution, the complexing agent solution and pure water to the reaction kettle and continuously introduce a protective gas. Then, respectively pump the nickel-manganese-iron mixed salt solution, the zinc salt solution, the precipitant solution and the complexing agent solution into the reaction kettle through a precision metering pump for co-deposition reaction. When the particle size of the precipitate grows to 3 - 15 μm, stop the reaction. During the whole reaction process, the temperature of the reaction kettle is 30 - 80 °C, the pH value is 9 - 13, the content of the complexing agent is 1 - 20 g / L, and the stirring speed is 200 - 1000 rpm. Carry out solid-liquid separation on the reaction slurry obtained by the reaction to obtain the dehydrated precursor material, and then dry the precursor material at 80 - 150 °C to obtain the Ni X Fe Y Mn 1-X-Y-Z Zn Z (OH)2 precursor.

[0008] Further limited, in step S1, the concentration of the nickel-manganese-iron mixed salt solution is 1.0-2.5 mol / L; the concentration of metazincate in the zinc salt solution is 0.1-0.5 mol / L; the concentration of the precipitant solution is 1-8 mol / L; the concentration of the complexing agent solution is 1-10 mol / L.

[0009] The zinc-containing sodium-ion cathode material precursor of the present invention has the molecular formula Ni X Fe Y Mn 1-X-Y-Z Zn Z (OH)2, where 0 < X < 0.5, 0 < Y < 0.5, 0.01 ≤ Z < 0.2.

[0010] Compared with the prior art, the present invention has the following obvious beneficial effects:

[0011] (1) The present invention uses a co-deposition method to add zinc elements, making the doping of zinc elements more uniform. The zinc salt is added to an excessive sodium hydroxide solution for mixing to form metazincate to participate in the co-deposition reaction. The primary particles of the precursor prepared by this method are evenly distributed and have a higher tap density.

[0012] (2) The Ni X Fe Y Mn 1-X-Y-Z Zn Z (OH)2 precursor prepared by the present invention has high crystallinity and a stable crystal structure. The sodium-ion cathode material prepared by sintering is not easily collapsed during the charge and discharge process of the battery, and the prepared sodium-ion battery has a high capacity and good cycle stability. Description of the Drawings

[0013] Figure 1 SEM image of the precursor prepared in Example 1;

[0014] Figure 2 SEM image of the precursor prepared in Example 2;

[0015] Figure 3 SEM image of the precursor prepared in Example 3;

[0016] Figure 4 Discharge capacity comparison curves of sodium-ion batteries assembled with the cathode materials prepared by sintering the precursors prepared in Example 1 and Comparative Examples 1-2. Detailed Description of the Invention

[0017] The following further elaborates on the above content of the present invention through examples, but it should not be understood that the scope of the above subject matter of the present invention is limited to the following examples. All technologies implemented based on the above content of the present invention belong to the scope of the present invention. Example 1

[0018] Step S1: Prepare a nickel-manganese-iron mixed salt solution with a total metal concentration of 2.0 mol / L using nickel sulfate, manganese sulfate, and ferrous sulfate, where the molar ratio of nickel, manganese, and iron is 38.9:38.9:22.2; add zinc sulfate to the prepared 6 mol / L sodium hydroxide solution to form a mixed solution of sodium zincate and sodium hydroxide. The specific preparation process is to add 120 g of zinc sulfate to 1 L of 6 mol / L sodium hydroxide solution; prepare a 4 mol / L ammonia water solution as a complexing agent solution and a 6 mol / L sodium hydroxide solution as a precipitating agent solution.

[0019] Step S2: Add 79 L of pure water, 0.635 L of complexing agent solution, and 0.365 L of precipitating agent solution to the reaction kettle to prepare a bottom liquid with a total volume of 80 L, adjust its pH value to 12.5 - 12.6, ammonia content to 1 - 1.5 g / L, and temperature to 50 °C. Turn on the stirring device with a stirring speed of 950 r / min, and continuously introduce nitrogen into the reaction kettle at a rate of 10 L / min below the liquid surface. Add the above-prepared nickel-manganese-iron mixed salt solution, mixed solution of sodium zincate and sodium hydroxide, complexing agent solution, and precipitating agent solution into the reaction kettle through 4 precision metering pumps for co-precipitation reaction. During the entire reaction process, the reaction temperature is 50 °C, the pH value is controlled at 11.5 - 11.6, the flow rate of the nickel-manganese-iron mixed salt solution is 80 mL / min, the ammonia content is 5 - 6 g / L, and the reaction stops when the particle size of the precipitate grows to 4.5 μm. The slurry obtained from the reaction is centrifuged for solid-liquid separation, and after separation, it is washed with water and dried to obtain the Ni 0.35 Fe 0.20 Mn 0.35 Zn 0.10 (OH)₂ precursor.

[0020] Test: Conduct a scanning electron microscope test on the above-obtained Ni 0.35 Fe 0.20 Mn 0.35 Zn 0.10 (OH)₂ precursor. Figure 1 For the scanning electron microscope image of the precursor prepared in this example, as can be seen from the figure, the prepared Ni 35 Fe 20 Mn 35 Zn 10 (OH)₂ precursor has good sphericity and uniform primary particles; the precursor prepared in this example is measured by a Malvern particle size analyzer to have a D 50 of 4.486 μm, a specific surface area of 12.20 m 2 / g, and a tapped density of 1.88 g / cm 3 .

[0021] Comparative Example 1

[0022] Step S1: Prepare a nickel-manganese-iron mixed salt solution with a total metal concentration of 2.0 mol / L using nickel sulfate, manganese sulfate, and ferrous sulfate, where the molar ratio of nickel, manganese, and iron is 38.9:38.9:22.2; prepare a 0.35 mol / L zinc sulfate solution, and then mix the zinc sulfate solution with 9 mol / L ammonia water at a volume ratio of 1:0.27 to form a zinc-ammonia complex solution, and prepare a 4 mol / L ammonia water solution as a complexing agent solution; prepare a 6 mol / L sodium hydroxide solution as a precipitating agent solution.

[0023] Step S2: Add 79 L of pure water, 0.635 L of complexing agent solution, and 0.365 L of precipitating agent solution to the reaction kettle to prepare a bottom liquid with a total volume of 80 L, adjust its pH value to 12.5 - 12.6, ammonia content to 1 - 1.5 g / L, and temperature to 50 °C. Turn on the stirring device with a stirring speed of 950 r / min, and continuously introduce nitrogen into the liquid surface of the reaction kettle at a rate of 10 L / min. Add the above-prepared nickel-manganese-iron mixed salt solution, zinc-ammonia complex solution, precipitating agent solution, and complexing agent solution into the reaction kettle through 4 precision metering pumps for co-precipitation reaction. During the entire reaction process, the reaction temperature is 50 °C, the pH value is controlled at 11.5 - 11.6, the flow rate of the nickel-manganese-iron mixed salt solution is 80 mL / min, the ammonia content is 5 - 6 g / L, and the reaction stops when the particle size of the precipitate grows to 4.5 μm. The slurry obtained from the reaction is centrifuged for solid-liquid separation, and the separated solid is washed and dried to obtain a Ni 0.35 Fe 0.20 Mn 0.35 Zn 0.10 (OH)₂ precursor.

[0024] Test: Conduct a scanning electron microscope test on the above-obtained Ni 0.35 Fe 0.20 Mn 0.35 Zn 0.10 (OH)₂ precursor, Figure 2 which is the scanning electron microscope image of the precursor prepared for this comparative example; use a Malvern particle size analyzer to measure that the precursor D 50 prepared in this example is 4.636 μm, its specific surface area is 17.22 m 2 / g, and its tapped density is measured to be 1.58 g / cm 3 .

[0025] Comparative Example 2

[0026] Step S1: Prepare a nickel-manganese-iron-zinc mixed salt solution with a total metal concentration of 2.0 mol / L using nickel sulfate, manganese sulfate, ferrous sulfate, and zinc sulfate, where the molar ratio of nickel, manganese, iron, and zinc is 35 / 35 / 20 / 10; prepare a 4 mol / L ammonia water solution as a complexing agent solution; prepare a 6 mol / L sodium hydroxide solution as a precipitating agent solution.

[0027] Step S2: Add 79 L of pure water, 0.635 L of the complexing agent solution, and 0.365 L of the precipitating agent solution to the reaction kettle to prepare a bottom liquid with a total volume of 80 L. Adjust its pH value to 12.5 - 12.6, ammonia content to 1 - 1.5 g / L, and temperature to 50 °C. Turn on the stirring device with a stirring speed of 950 r / min, and continuously introduce nitrogen into the reaction kettle at a rate of 10 L / min below the liquid surface. Add the above-prepared nickel-manganese-iron-zinc mixed salt solution, precipitating agent solution, and complexing agent solution to the reaction kettle through three precision metering pumps for coprecipitation reaction. During the entire reaction process, the reaction temperature is 50 °C, the pH value is controlled at 11.5 - 11.6, the mixed liquid flow rate is 80 mL / min, the ammonia content is 5 - 6 g / L, and the reaction stops when the particle size of the precipitate grows to 4.5 μm. The slurry obtained from the reaction is centrifuged for solid-liquid separation, and after separation, it is washed with water and dried to obtain Ni0. 35 Fe 0.20 Mn 0.35 Zn 0.10 (OH)2 precursor.

[0028] Test: Conduct a scanning electron microscope test on the above-obtained Ni 0.35 Fe 0.20 Mn 0.35 Zn 0.10 (OH)2 precursor, Figure 3 which is the scanning electron microscope image of the precursor prepared for this comparative example; use a Malvern particle size analyzer to measure that the precursor D prepared in this example 50 is 4.536 μm, its specific surface area is 20.42 m 2 / g, and its tapped density is measured to be 1.38 g / cm 3 .

[0029] Figure 4 This is the discharge capacity comparison curve of sodium-ion batteries assembled with the cathode materials prepared by sintering the precursors obtained in Example 1 and Comparative Examples 1 - 2. As can be seen from the figure, compared with the zinc-doping processes in Comparative Examples 1 - 2, the cycling reversibility and discharge specific capacity of the sodium-ion batteries assembled with the cathode materials prepared by sintering the precursors finally prepared in the present invention have been greatly improved.

[0030] The above embodiments have described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the scope of the principles of the present invention, the present invention will have various changes and improvements, and all these changes and improvements fall within the scope of protection of the present invention.

Claims

1. A method for preparing a zinc-containing sodium-ion cathode material precursor, characterized in that The specific steps are as follows: Step S1: Prepare a nickel-manganese-iron mixed salt solution. The nickel salt in the nickel-manganese-iron mixed salt solution is one or more of nickel sulfate, nickel nitrate, or nickel chloride; the manganese salt is one or more of manganese sulfate, manganese nitrate, or manganese chloride; the ferrous salt is one or more of ferrous sulfate, ferrous nitrate, or ferrous chloride. Dissolve the zinc salt in an excessive amount of alkali solution to prepare a mixed solution of zincate and alkali, i.e., a zinc salt solution, where the zinc salt is one or more of zinc sulfate, zinc chloride, or zinc nitrate, and the alkali solution is sodium hydroxide solution or potassium hydroxide solution. Prepare a precipitant solution, where the precipitant in the precipitant solution is one or more of sodium hydroxide, potassium hydroxide, or lithium hydroxide. Prepare a complexing agent solution, where the complexing agent in the complexing agent solution is one or more of ammonia water or ammonium bicarbonate. Step S2, add a mixed solution of a precipitant solution, a complexing agent solution and pure water into the reaction kettle and continuously introduce a protective gas. Then, respectively pump the nickel-manganese-iron mixed salt solution, the zinc salt solution, the precipitant solution and the complexing agent solution into the reaction kettle through precision metering pumps for co-deposition reaction. When the particle size of the precipitate grows to 3-15 μm, stop the reaction. During the whole reaction process, the temperature of the reaction kettle is 30-80 °C, the pH value is 9-13, the content of the complexing agent is 1-20 g / L, the stirring speed is 200-1000 rpm. After solid-liquid separation of the reaction slurry obtained by the reaction, the dehydrated precursor material is obtained. Then, the precursor material is dried at 80-150 °C to obtain the Ni X Fe Y Mn 1-X-Y-Z Zn Z (OH)2 precursor, where 0 < X < 0.5, 0 < Y < 0.5, 0.01 ≤ Z < 0.

2.

2. The preparation method of the zinc-containing sodium ion cathode material precursor according to claim 1, characterized in that: In step S1, the concentration of the nickel-manganese-iron mixed salt solution is 1.0 - 2.5 mol / L; the concentration of zincate in the zinc salt solution is 0.1 - 0.5 mol / L; the concentration of the precipitant solution is 1 - 8 mol / L; the concentration of the complexing agent solution is 1 - 10 mol / L.

Images