阅读说明：本技术 用于盐湖提锂的多孔圆片状锰酸锂电极、及其制备方法 (Porous disc-shaped lithium manganate electrode for extracting lithium from salt lake and preparation method thereof ) 是由 朱文帅 周国狼 陈琳琳 巢艳红 李小为 罗贵玲 于 2021-09-09 设计创作，主要内容包括：本发明提供了一种用于盐湖提锂的多孔圆片状锰酸锂电极、及其制备方法,该方法包括以下步骤：在锰盐水溶液中加入乙酰丙酮,然后再加入聚乙烯吡咯烷酮,形成透明溶液；在搅拌条件下加入水合肼形成黄色沉淀,沉淀经过离心分离烘干得到黄色前驱体；将所得的前驱体在空气中煅烧得到Mn-(5)O-(8),随后将Mn-(5)O-(8)与锂盐混合用控温马弗炉进行高温煅烧,自然冷却后得到多孔圆片状锰酸锂。本发明的多孔圆片状锰酸锂电极对锂离子选择性高,吸附容量大,可以用于电化学盐湖提锂。(The invention provides a porous disc-shaped lithium manganate electrode for extracting lithium from a salt lake and a preparation method thereof, wherein the method comprises the following steps: adding acetylacetone into a manganese salt aqueous solution, and then adding polyvinylpyrrolidone to form a transparent solution; adding hydrazine hydrate under the stirring condition to form yellow precipitate, and centrifugally separating and drying the precipitate to obtain a yellow precursor; calcining the obtained precursor in air to obtain Mn 5 O 8 Subsequently adding Mn 5 O 8 Mixing with lithium salt, calcining at high temperature in a temperature-controlled muffle furnace, and naturally cooling to obtain porous disk-shaped lithium manganate. The porous disk-shaped lithium manganate electrode has high lithium ion selectivity and large adsorption capacity, and can be used for extracting lithium in an electrochemical salt lake.)

1. A preparation method of a porous disk-shaped lithium manganate electrode for extracting lithium from a salt lake is characterized by comprising the following steps:

step 1, dissolving manganese salt in water to prepare a manganese salt solution;

step 2, adding acetylacetone and polyvinylpyrrolidone under the condition of stirring to form a transparent solution;

step 3, adding hydrazine hydrate into the transparent solution obtained in the step 2, and then placing in the air for aging; washing the precipitate with centrifugal separation deionized water for three times, washing with absolute ethyl alcohol for three times, and drying to obtain a yellow precursor;

step 4, calcining the yellow precursor prepared in the step 3 in air to obtain Mn₅O₈；

Step 5, Mn prepared in the step 4₅O₈Mixing the lithium manganate with a lithium compound, placing the mixture in a crucible, calcining the mixture at a high temperature by using a temperature-controlled muffle furnace, and naturally cooling the calcined mixture to obtain the porous disk-shaped lithium manganate.

2. The method according to claim 1, wherein the manganese salt solution prepared in step 1 has a concentration of 0.02 to 0.6 mol/L.

3. The method of claim 1, wherein the manganese salt solution in step 1 is one of an aqueous manganese nitrate solution, an aqueous manganese chloride solution, an aqueous manganese sulfate solution and an aqueous manganese acetate solution.

4. The method as claimed in claim 1, wherein the temperature in the stirring condition in step 2 is 20-35 ℃ and the rotation speed is 180-220 r/min.

5. The method according to claim 1, wherein the molar ratio of the manganese salt to the acetylacetone in step 2 is 1:5 to 1: 10; the mass ratio of the manganese salt to the polyvinylpyrrolidone is 2:1-15: 1.

6. The preparation method according to claim 1, wherein the mass concentration of hydrazine hydrate in the step 3 is 50% -90%, and the molar ratio of the manganese salt to the hydrazine hydrate is 1:5-6: 1.

7. The method according to claim 1, wherein the reaction temperature in the step 1-3 is 15-30 ℃ and the drying temperature is 40-80 ℃.

8. The method as claimed in claim 1, wherein the calcination temperature in step 4 is 300-600 ℃, the calcination time is 1-6 hours, and the temperature rise rate is 1-5 ℃/min; the calcination temperature in the step 5 is 600-900 ℃, the calcination time is 6-15 hours, and the heating rate is 1-5 ℃/min.

9. The method of claim 1, wherein the lithium compound in step 5 is one of lithium chloride, lithium nitrate, lithium sulfate, lithium carbonate and lithium hydroxide.

10. The porous disc-shaped lithium manganate electrode prepared by the preparation method according to any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of lithium extraction in salt lakes, and particularly relates to a preparation method of a porous disc-shaped lithium manganate electrode for lithium extraction in salt lakes.

Background

Lithium is called an energy metal of the 21 st century, and is a resource having strategic significance in national economy and national defense construction. With the increasing prominence of resource and environmental issues, lithium batteries are becoming one of the most important electric energy storage devices in daily life, resulting in a rapid increase in demand for lithium. The global lithium resource mainly comprises a liquid-phase lithium resource and a solid-phase lithium resource, the solid-phase lithium resource mainly exists in the form of lithium ore, solid-phase lithium is gradually exhausted along with continuous exploitation for many years, however, the liquid-phase lithium resource occupying 80% of the global lithium resource is not effectively utilized all the time due to technical limitation, so that the research on extracting lithium from salt lake brine and seawater is of great significance in order to prevent the problem of lithium resource supply caused by lithium ore resource exhaustion.

The method for extracting lithium from lithium-containing brine mainly comprises a precipitation method, a solvent extraction method, an ion exchange method, a calcination leaching method and the like. Among them, the technology of extracting lithium salt by ion exchange method based on inorganic ion sieve is receiving attention due to high extraction efficiency. However, the ion exchange method of the inorganic ion sieve must use a large amount of strong acid for washing during desorption, which causes serious corrosion and pollution to equipment and environment.

On this basis, researchers have proposed using electrochemical methods to adsorb and desorb lithium ions, which can avoid the use of strong acids. In the Chinese invention patent CN105600807B, Yanwensheng et al used lithium manganate as electrode material to obtain Li with about 4mmol of Li-insertion and lithium-removal capacity⁺The extraction efficiency is low, but the single electrochemical adsorption time is 4-7 hours. Chinese invention patent CN103498172B, zhao zhong wei et al, proposed an electrochemical lithium extraction method based on lithium iron phosphate and vanadium oxide, and obtained a higher adsorption capacity.

In consideration of biosafety and lithium extraction efficiency of electrode materials, lithium manganate is one of the most promising electrode materials in the field of electrochemical lithium extraction. Therefore, the design and synthesis of the lithium manganate electrode material with abundant electroactive sites and capability of shortening the lithium ion transmission path have important significance for promoting the electrochemical lithium extraction industrialization.

Disclosure of Invention

Based on the technical background, the invention provides a preparation method of a porous disc-shaped lithium manganate electrode for extracting lithium from a salt lake. The method has the advantages of mild reaction conditions, simple process, low energy consumption and short time consumption; the porous lithium manganate wafer prepared by the method has high selectivity and adsorption capacity on lithium ions, and can be used for lithium extraction in an electrochemical salt lake.

In order to solve the technical problem, the application discloses a preparation method of a porous disk-shaped lithium manganate electrode for extracting lithium from a salt lake, which comprises the following steps:

step 1, dissolving manganese salt in water to prepare a manganese salt solution;

step 2, adding acetylacetone and polyvinylpyrrolidone under the condition of stirring to form a transparent solution;

step 3, adding hydrazine hydrate into the transparent solution obtained in the step 2, and then placing in the air for aging; washing the precipitate with centrifugal separation deionized water for three times, washing with absolute ethyl alcohol for three times, and drying to obtain a yellow precursor;

step 4, calcining the yellow precursor prepared in the step 3 in air to obtain Mn₅O₈。

Step 5, Mn prepared in the step 4₅O₈Mixing the lithium manganate with a lithium compound, placing the mixture in a crucible, calcining the mixture at a high temperature by using a temperature-controlled muffle furnace, and naturally cooling the calcined mixture to obtain the porous disk-shaped lithium manganate.

Further, the concentration of the manganese salt solution in the step 1 is 0.02-0.6 mol/L.

Further, the manganese salt solution in step 1 is one of a manganese nitrate aqueous solution, a manganese chloride aqueous solution, a manganese sulfate aqueous solution or a manganese acetate aqueous solution.

Further, the temperature in the stirring condition in the step 2 is 20-35 ℃, and the rotating speed is 180-220 r/min.

Further, the molar ratio of the manganese salt to the acetylacetone in the step 2 is 1:5-1: 10; the mass ratio of the manganese salt to the polyvinylpyrrolidone is 2:1-15: 1.

Further, in the step 3, the concentration of hydrazine hydrate is 50% -90%, and the molar ratio of the manganese salt to the hydrazine hydrate is 1:5-6: 1.

Further, the reaction temperature in the step 1-3 is 15-30 ℃, and the drying temperature is 40-80 ℃.

Furthermore, the calcination temperature in step 4 is 300-600 ℃, the calcination time is 1-6 hours, and the temperature rise rate is 1-5 ℃/min.

Furthermore, the calcination temperature in step 5 is 600-900 ℃, the calcination time is 6-15 hours, and the heating rate is 1-5 ℃/min.

Further, the lithium compound in step 5 is one of lithium chloride, lithium nitrate, lithium sulfate, lithium carbonate and lithium hydroxide.

The invention also discloses a porous disc-shaped lithium manganate electrode for extracting lithium from a salt lake, which is prepared by the preparation method.

The method comprises the steps of obtaining a manganese precursor by taking manganese salt as a manganese source, acetylacetone as a coordination agent, polyvinylpyrrolidone as a template agent and hydrazine hydrate as a precipitating agent at room temperature, and sintering at high temperature to obtain the wafer-shaped Mn₅O₈And (3) precursor. Subsequently adding Mn₅O₈And mixing and calcining the precursor and lithium salt to obtain a porous lithium manganate wafer. Compared with the prior art, the invention can obtain the following technical effects:

(1) the preparation method is simple in preparation process and high in production efficiency, and the manganese precursor is obtained by a one-step method at room temperature and then is sintered at high temperature twice to obtain the product.

(2) The conversion rate of the raw materials of the invention can reach more than 90 percent in terms of manganese.

(3) The porous disc-shaped lithium manganate electrode prepared by the method has high selectivity on lithium ions, has excellent electrochemical lithium extraction performance in a salt lake, has the extraction amount of 4.85-5.32 mg/g on the lithium ions after discharging for 1 hour under the current density of 50mA/g, and can realize the rapid extraction of the lithium ions.

(4) The regular two-dimensional disk-shaped lithium manganate can greatly shorten the transmission path of lithium ions, improve the extraction efficiency of the lithium ions, increase the specific surface area of an electrode material due to the existence of a porous structure, promote the sufficient contact between the lithium ions in the electrolyte and the electrode material, and further promote the transmission of the lithium ions.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is an SEM picture of porous disk-shaped lithium manganate prepared in example 1 of the present invention;

FIG. 2 is an XRD picture of porous disk-shaped lithium manganate prepared in example 1 of the present invention;

FIG. 3 is a graph showing the variation of various ion concentrations in the electrolyte during the extraction of lithium ions in example 1 of the present invention.

Detailed Description

The present invention will be further described with reference to the accompanying drawings and specific embodiments, so that the implementation process of how to apply the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented, but the scope of the present invention is not limited thereto.

The preparation method of the porous disk-shaped lithium manganate electrode for extracting lithium from salt lake, provided by the invention, comprises the steps of taking manganese salt as a manganese source, acetylacetone as a coordination agent, polyvinylpyrrolidone as a template agent and hydrazine hydrate as a precipitating agent to obtain a manganese precursor, and sintering at high temperature to obtain disk-shaped Mn₅O₈And (3) precursor. Subsequently adding Mn₅O₈And mixing and calcining the precursor and lithium salt to obtain a porous lithium manganate wafer. The method specifically comprises the following steps:

step 1, dissolving manganese salt in water to prepare a manganese salt solution with the concentration of 0.02-0.6 mol/L; the manganese salt solution is one or more of manganese nitrate aqueous solution, manganese chloride aqueous solution, manganese sulfate aqueous solution or manganese acetate aqueous solution.

Step 2, adding acetylacetone and then adding polyvinylpyrrolidone into the mixture at the temperature of 20-35 ℃ and the stirring speed of 180-220r/min to form transparent solution, wherein the molar ratio of the manganese salt to the acetylacetone is 1:5-1: 10; the mass ratio of the manganese salt to the polyvinylpyrrolidone is 2:1-15: 1.

Step 3, adding 50-90% hydrazine hydrate solution into the transparent solution prepared in the step 2, and then placing in the air for aging; washing the precipitate with deionized water for three times, washing with anhydrous ethanol for three times, and oven drying

Obtaining a light yellow precursor, wherein the molar ratio of the manganese salt to the hydrazine hydrate is 1:5-6:1, the reaction temperature is 15-30 ℃, and the drying temperature is 40-80 ℃.

Step 4, placing the light yellow precursor prepared in the step 3 into a crucible, calcining for 1-6 hours at the temperature rise rate of 1-5 ℃/min by using a temperature control muffle furnace at the temperature of 300-600 ℃, and naturally cooling to obtain Mn₅O₈。

Step 5, Mn in the step 4₅O₈Mixing with lithium salt or lithium hydroxide, calcining for 6-15 hours at the temperature rise rate of 1-5 ℃/min in a temperature-controlled muffle furnace at the temperature of 600-900 ℃, and naturally cooling to obtain the porous disk-shaped lithium manganate.

In the present preparation method:

1. the acetylacetone has larger molecules and is a polydentate ligand, has tautomerism of enol and ketone, namely a dicarbonyl structure, and can be used as a bidentate ligand to coordinate with manganese ions to form a stable manganese acetylacetonate complex.

2. The polyvinylpyrrolidone has both hydrophilic groups and hydrophobic groups in molecules, and can be dissolved in water and most organic solvents, so that the hydrophilic groups are close to water molecules, the hydrophobic groups are close to manganese acetylacetonate, and the special acting force plays a role in structure guiding on the appearance of the wafer-shaped precursor.

3. Two nitrogen atoms in the hydrazine hydrate structure have lone electron pairs, so that the hydrazine hydrate structure has strong alkalinity and coordination capacity, can form a stable complex with manganese ions, and the hydrazine hydrate plays a dual role of a second ligand and a precipitator in the synthesis process.

4. During the first high temperature calcination, the ligand decomposes to form Mn₅O₈. During the second sintering process with lithium salt or lithium hydroxide, the flaky Mn is formed by the etching of lithium hydroxide and lithium salt₅O₈The structure gradually changes into a porous structure, and lithium salt or lithium hydroxide acts as both a lithium source and an etchant in the reaction.

5. The regular two-dimensional disk-shaped lithium manganate can greatly shorten the transmission path of lithium ions, improve the extraction efficiency of the lithium ions, increase the specific surface area of an electrode material due to the existence of a porous structure, promote the sufficient contact between the lithium ions in the electrolyte and the electrode material, and further promote the transmission of the lithium ions.

Example 1

Dissolving 1mmol of manganese chloride in 20mL of deionized water to obtain 0.05mol/L manganese chloride solution, adding 0.5mL of acetylacetone and 30mg of polyvinylpyrrolidone under the stirring condition of the rotation speed of 200r/min and the temperature of 25 ℃, and adding 4mL of 50% hydrazine hydrate solution after complete dissolution. And carrying out centrifugal separation, washing with deionized water for three times, washing with absolute ethyl alcohol for three times, and drying at 60 ℃ to obtain a light yellow precursor. Transferring the dried precursor sample into a crucible, sintering at high temperature by using a temperature-controlled muffle furnace, heating at the rate of 5 ℃/min, and preserving heat for 3 hours at the temperature of 450 ℃ to obtain Mn₅O₈. Adding Mn₅O₈And adding lithium hydroxide into a mortar according to the molar ratio of lithium to manganese of 1:2 for full grinding, then calcining in a muffle furnace at the temperature rise rate of 5 ℃/min, and preserving heat for 10 hours at 700 ℃ to obtain the porous disk-shaped lithium manganate.

The scanning electron micrograph of the obtained product is shown in figure 1, and the XRD pattern is shown in figure 2. The scanning electron microscope image shows that the product is a porous disc-shaped structure with uniform appearance, the two-dimensional sheet-shaped structure shortens a transmission channel of lithium ions, and the porous structure can further promote the transmission of the lithium ions, so that the extraction efficiency of the lithium ions is improved. As can be seen from the XRD pattern, the diffraction peak intensity of the product is high and is consistent with the peak position of a standard card (PDF #35-0782) of lithium manganate, and the product is high-crystallinity and high-purity lithium manganate.

The prepared porous disk-shaped lithium manganate is used as an electrode, a mixed solution with the same concentrations of lithium ions, sodium ions, potassium ions, magnesium ions and calcium ions is subjected to ion extraction, the concentration change of various ions in the extraction process is shown in figure 3, after 5 times of cyclic extraction process, the concentration of the lithium ions in the electrolyte is reduced by 1.12mmol/L, the concentrations of other coexisting ions are almost unchanged, the extraction amount of the lithium ions after discharging for 1 hour is 4.85mg/g under the current density of 50mA/g, and the other coexisting ions are almost not extracted. The porous disk-shaped lithium manganate electrode has high selectivity and adsorption capacity for lithium ions.

Example 2

Dissolving 1mmol of manganese chloride in 20mL of deionized water to obtain 0.05mol/L manganese chloride solution, adding 0.5mL of acetylacetone and 40mg of polyvinylpyrrolidone under the stirring condition of the rotation speed of 200r/min and the temperature of 25 ℃, and adding 4mL of 50% hydrazine hydrate solution after complete dissolution. And carrying out centrifugal separation, washing with deionized water for three times, washing with absolute ethyl alcohol for three times, and drying at 60 ℃ to obtain a light yellow precursor. Transferring the dried precursor sample into a crucible, sintering at high temperature by using a temperature-controlled muffle furnace, heating at the rate of 2 ℃/min, and preserving heat for 3 hours at the temperature of 450 ℃ to obtain Mn₅O₈. Adding Mn₅O₈And adding lithium hydroxide into a mortar according to the molar ratio of lithium to manganese of 1:2 for full grinding, then calcining in a muffle furnace at the temperature rise rate of 5 ℃/min, and preserving heat for 10 hours at 700 ℃ to obtain the porous disk-shaped lithium manganate.

The prepared porous disk-shaped lithium manganate is used as an electrode, after 5 times of cyclic extraction processes, the concentration of lithium ions in the electrolyte is reduced by 1.23mmol/L, the concentrations of other coexisting ions are almost unchanged, the extraction amount of the lithium ions after discharging for 1 hour is 5.32mg/g under the current density of 50mA/g, and the other coexisting ions are almost not extracted. The porous disk-shaped lithium manganate electrode has high selectivity and adsorption capacity for lithium ions.

Example 3

Dissolving 1mmol of manganese chloride in 20mL of deionized water to obtain 0.05mol/L manganese chloride solution, adding 0.5mL of acetylacetone and 50mg of polyvinylpyrrolidone under the stirring condition of the rotation speed of 300r/min and the temperature of 25 ℃, and adding 4mL of 50% hydrazine hydrate solution after complete dissolution. And carrying out centrifugal separation, washing with deionized water for three times, washing with absolute ethyl alcohol for three times, and drying at 80 ℃ to obtain a light yellow precursor. Transferring the dried precursor sample into a crucible, sintering at high temperature by using a temperature-controlled muffle furnace, heating at the rate of 5 ℃/min, and preserving heat for 3 hours at the temperature of 450 ℃ to obtain Mn₅O₈. Adding Mn₅O₈And adding lithium hydroxide into a mortar according to the molar ratio of lithium to manganese of 1:2 for full grinding, then calcining in a muffle furnace at the temperature rise rate of 5 ℃/min, and preserving heat for 12 hours at 700 ℃ to obtain the porous disk-shaped lithium manganate.

While the foregoing description shows and describes several preferred embodiments of the invention, it is to be understood, as noted above, that the invention is not limited to the forms disclosed herein, but is not to be construed as excluding other embodiments and is capable of use in various other combinations, modifications, and environments and is capable of changes within the scope of the inventive concept as expressed herein, commensurate with the above teachings, or the skill or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.