CN115050582A - Porous carbon support composite lithium extraction electrode and preparation method thereof - Google Patents

Abstract

The invention discloses a porous carbon-supported composite lithium extraction electrode and a preparation method thereof. In this method, the active ingredient or its precursor for extracting lithium is mixed with porogen, regulator and organic polymer monomer. Under the action of acid or base catalysis, the polymer monomer undergoes an in-situ polymerization reaction, and the polymer monomer is polymerized in the mold. Cured molding. The formed material is calcined at high temperature for in-situ transformation under oxygen-free conditions, and treated with acid and alkali to remove the porogen to obtain a porous carbon-supported composite lithium extraction electrode. The lithium extraction composite electrode prepared by the invention has the advantages of simple synthesis method and good stability, which not only effectively solves the problem of electrode material falling off in the electrode prepared by the traditional coating method, but also can significantly improve the conductivity, lithium extraction capacity and rate of the electrode, thereby having It is beneficial to promote the large-scale preparation of lithium extraction electrodes and the industrialization and application of electrochemical lithium extraction technology.

Description

A kind of porous carbon-supported composite lithium extraction electrode and preparation method thereof

technical field

The invention belongs to the technical field of lithium extraction, and in particular relates to a porous carbon-supported composite lithium extraction electrode and a preparation method thereof.

Background technique

As the "energy metal of the 21st century", lithium is widely used in lubricants, aerospace, glass, ceramics, lithium batteries and other fields. In recent years, with the rapid development of industries such as portable devices and electric vehicles, the global demand for lithium resources has increased year by year. Although the lithium extraction process from solid ore is mature, there are many problems such as high energy consumption and heavy pollution. The reserves of brine-type liquid lithium ore such as salt lake brine and underground brine have an absolute advantage in various types of lithium ore. Due to the scale and cost advantages of lithium extraction from brine, lithium recovery from liquid lithium ore has become a research hotspot in the global lithium extraction industry.

According to the different compositions and characteristics of different liquid lithium ores, lithium extraction technologies such as precipitation method, solvent extraction method, adsorption method, membrane separation method and electrochemical method have been developed. Compared with several other methods, electrochemical method has attracted extensive attention due to its advantages such as good selectivity and environmental protection. How to efficiently and stably extract lithium from liquid lithium ore has become the focus of electrochemical lithium extraction technology.

The quality of electrode performance is the key to electrochemical lithium extraction technology. When electrochemical lithium extraction is carried out in an aqueous solution, active components (such as LiFePO ₄ , LiMn ₂ O ₄ , etc.) need to be prepared into electrodes of specific shapes first. In order to obtain high-performance enhanced lithium electrodes, relevant research has been carried out. CN113278819A discloses a highly selective and hydrophilic electrode and its preparation method, which improves the hydrophilicity of the adhesive polyvinylidene fluoride (PVDF) and improves the mass transfer of the solution inside the electrode; CN113293285B discloses a The preparation method of fast ion conductor modified lithium extraction electrode effectively improves the selectivity and cycle performance of the electrode; CN113293312B discloses a preparation method of a composite porous electrode for lithium extraction, which improves the hydrophilicity of the electrode by using an aqueous binder instead of PVDF. The strength of the electrode structure is improved by adding a fiber structure reinforcing agent; CN113293291B discloses a method for preparing a high-conductivity lithium-extracting electrode. The electrode with the internal structure of "microcrack" effectively improves the hydrophilicity, conductivity and lithium extraction rate of the electrode.

As disclosed in the related patent technologies or research reports, during electrode preparation, the active material is mainly coated on the current collector with a polymer such as PVDF as a binder. However, due to the high crystallinity and low surface energy of the binder, its lithium ion conductivity is poor, and the lithium extraction capacity of the electrode is reduced due to the use of current collectors and binders. In addition, the electrodes obtained by the coating method have stability problems such as electrode material falling off. In view of this, the development of an electrode with fast lithium extraction rate and high stability and its preparation method is of great significance for the development of brine-type liquid lithium ore resources.

SUMMARY OF THE INVENTION

In order to solve the defects existing in the preparation of lithium extraction electrodes by traditional coating methods, the present invention provides a porous carbon-supported composite lithium extraction electrode with excellent electrochemical lithium extraction performance and high stability and a preparation method thereof.

The innovative point of the present invention is: through the innovative means of resin in-situ polymerization and high-temperature carbonization conversion, a new type of resin-based porous carbon in-situ supported lithium extraction electrode without current collector and binder is developed, which opens up another simple and efficient method. Low-cost preparation method of lithium extraction electrode.

The technical scheme and technological process provided by the present invention are as follows:

method, the steps are as follows:

1) Mix the lithium-extracting active ingredient or its precursor, porogen, regulator, and organic polymer monomer.

2) The polymer monomers in the mixture are polymerized under the action of acid or alkali, and are cured and formed in the mold.

3) The cured and formed material is calcined under anaerobic conditions, the organic polymer is transformed into a carbon support in situ, and the precursor of the active ingredient for lithium extraction is simultaneously transformed into an active ingredient for lithium extraction in situ.

4) After the calcined material is soaked in acid and alkali to remove the porogen, a porous carbon-supported composite lithium extraction electrode is obtained.

Moreover, in step 1), the active ingredient for extracting lithium is one or both of lithium iron phosphate (LiFePO ₄ ), lithium vanadium phosphate (Li ₃ V ₂ (PO ₄ ) ₃ ), and lithium manganate (LiMn ₂ O ₄ ). more than one species.

Moreover, in step 1), the precursor of the active ingredient for extracting lithium includes a lithium source, an iron source, a vanadium source, a manganese source and a phosphorus source. Among them, the lithium source, iron source, vanadium source, and manganese source include one or more of the oxides, hydroxides, chlorides, sulfates, carbonates, and acetates of each metal; phosphorus sources include phosphoric acid One or more of salt, hydrogen phosphate, dihydrogen phosphate and phytic acid.

Moreover, in step 1), the porogen is an inorganic salt, preferably one or more of ammonium salt, carbonate, bicarbonate and hydroxide. Further, the porogen is preferably ammonium carbonate or ammonium bicarbonate.

Moreover, in step 1), the regulator is one or both of polyethylene glycol, cetyltrimethylammonium bromide, hexamethylenetetramine, benzenesulfonic acid, and dodecylbenzenesulfonic acid more than one species. The role of the modifier is to improve the curing rate of the composite material and the dispersion of the lithium-extracting active ingredient in the material.

Moreover, in step 1), the high molecular polymer includes one or more of phenolic resin, urea-formaldehyde resin, melamine-formaldehyde resin, and furfural resin.

Moreover, in step 1), the lithium extraction active ingredients or their precursors, porogens, regulators, and organic polymer monomers account for 10% to 70%, 0% to 10%, and 0% to 0% of the total mass, respectively. 10%, 30% to 80%. Preferably, they account for 40% to 60%, 0% to 6%, 0% to 6%, and 40% to 60% of the total mass, respectively.

Moreover, in step 2), the preferred acid is one or more of sulfuric acid, phosphoric acid, hydrochloric acid, and acetic acid; the preferred alkali is one or two of lithium hydroxide, sodium hydroxide, potassium hydroxide, and aqueous ammonia more than one species.

Moreover, in step 3), the calcination temperature is 400°C to 800°C, and the time is 3h to 8h. Preferably, the calcination temperature is 500°C to 700°C, and the time is 4h to 7h. Temperature lower than 400℃ or time less than 3h may lead to insufficient carbonization of the material.

The advantages and positive effects of the present invention are:

The porous carbon support composite lithium extraction electrode prepared by the invention uses carbon as a support body and a conductive agent, and forms a good conductive network. Compared with the electrodes prepared by the traditional coating method, this method does not use any binder, and the high porosity and specific surface area of the electrode improve the lithium extraction rate and capacity of the electrode, and effectively solve the problem of the electrode prepared by the traditional coating method. The problem of poor stability. In addition, the electrode preparation method disclosed in the present invention has the advantages of simple process, low cost, and the like, and is easy to be mass-produced in an industrialized manner.

Description of drawings

FIG. 1 is a flow chart of electrode preparation in Example 1. FIG.

FIG. 2(A) is the XRD pattern of the electrode prepared in Example 1. FIG.

FIG. 2(B) is a SEM image of the electrode prepared in Example 1. FIG.

FIG. 3 is a graph showing the change of the lithium intercalation capacity with time during the lithium extraction process of the electrode prepared in Example 1. FIG.

FIG. 4 is a graph showing the change of the lithium intercalation capacity with time during the lithium extraction process of the electrode prepared in Example 2. FIG.

FIG. 5 is a graph showing the change of the lithium intercalation capacity with time during the lithium extraction process of the electrode prepared in Example 3. FIG.

FIG. 6 is a graph showing the change of the lithium intercalation capacity with time during the lithium extraction process of the electrode prepared in Example 4. FIG.

FIG. 7(A) is a SEM image of the electrode prepared in Example 5. FIG.

FIG. 7(B) is a graph showing the cyclic lithium extraction stability of the electrode prepared in Example 5. FIG.

FIG. 8(A) is an SEM image of the electrode prepared in Example 6 (the scale is 1 mm).

FIG. 8(B) is an SEM image of the electrode prepared in Example 6 (the scale is 10 μm).

FIG. 9(A) is a SEM image of electrodes prepared by coating method in Comparative Example 1. FIG.

FIG. 9(B) is a graph showing the change of the lithium intercalation capacity with time during the lithium extraction process of the electrode prepared by the coating method in Comparative Example 1. FIG.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are only descriptive, not restrictive, and cannot limit the protection scope of the present invention.

Example 1:

Using phenolic resin as carbon source, (NH ₄ ) ₂ CO ₃ as porogen, and the precursors of LiFePO ₄ LiOH·H ₂ O, FeCl ₃ 6H ₂ O and NH ₄ H ₂ PO ₄ as raw materials, under the action of alkali Synthesis of LiFePO ₄ composite electrodes.

The electrode preparation process is shown in Figure 1. Dissolve 0.02 mol of LiOH·H ₂ O (both as a precursor raw material and as an alkaline catalyst) in an appropriate amount of water, and add 0.01 mol of resorcinol and 3 mL of formaldehyde solution to the above solution. Take 0.02mol NH ₄ H ₂ PO ₄ , 0.02 mol FeCl ₃ ·6H ₂ O and an appropriate amount of (NH ₄ ) ₂ CO ₃ (accounting for 6% of the electrode mass), grind them evenly, pour them into the above solution, and stir until the solution is jelly-like After injection into the electrode silicone mold. Place the silicone mold in an oven to dry and shape, the oven temperature is set to 80°C, and the drying time is 6h. Then, it was calcined in a tube furnace at 700 °C for 8 h under anaerobic conditions. After cooling to room temperature, the electrode was soaked in 1 mol/L HCl and NaOH successively for 4 h each to remove the porogen, and the porous carbon-supported LiFePO ₄ composite electrode was obtained.

The XRD of the obtained electrode is shown in Fig. 2(A), and the SEM image is shown in Fig. 2(B). It can be seen from the figure that LiFePO ₄ was successfully synthesized by the in-situ simultaneous conversion method, and LiFePO ₄ was well dispersed on the carbon support material. 100 mg/L Li ⁺ was extracted, and the change of the intercalation capacity with time during the lithium extraction process is shown in Figure 3. It can be seen from the figure that the equilibrium time of lithium extraction of the electrode is less than 2h, and the equilibrium lithium intercalation capacity is close to 4 mg/cm ³ .

Example 2:

Using phenolic resin as carbon source, polyethylene glycol (PEG6000) as regulator, and the precursors of LiFePO ₄ LiOH·H ₂ O, FeCl ₃ 6H ₂ O and NH ₄ H ₂ PO ₄ as raw materials, the synthesis was carried out under the action of alkali. LiFePO ₄ composite electrode.

The preparation method is similar to that of Example 1, the main difference is that the porogen (NH ₄ ) ₂ CO ₃ in Example 1 is replaced by polyethylene glycol (accounting for 6% of the mass of the electrode) as a regulator. Figure 4 shows the change of the lithium intercalation capacity with time during the lithium extraction process of the obtained electrode. It can be seen from the figure that the lithium extraction balance time of the electrode is less than 1.5h, and the balance lithium insertion capacity is about 5 mg/cm ³ .

Example 3:

Using phenolic resin as carbon source, LiFePO ₄ precursors LiCl, FeCl ₃ ·6H ₂ O and NH ₄ H ₂ PO ₄ as raw materials (without porogen and regulator), LiFePO ₄ composite electrode was synthesized under the action of acid.

According to the molar ratio of 1.05:1.05:1, weigh NH ₄ H ₂ PO ₄ (both as a precursor raw material and as an acidic catalyst), LiCl and FeCl ₃ ·6H ₂ O and dissolve them in an appropriate amount of water to obtain solution A; according to the phenolic ratio of 1 : 0.95 Weigh resorcinol and formaldehyde solution, add appropriate amount of water to obtain solution B. Pour solution B into solution A (the content of LiFePO ₄ in the control electrode is 20%), stir evenly, and pour into a silica gel mold. Subsequent steps are the same as in Example 1. Figure 5 shows the change of the lithium intercalation capacity with time during the lithium extraction process of the obtained electrode. It can be seen from the figure that the adsorption capacity of the obtained electrode is also close to 5 mg/cm ³ by using acid as the catalyst for polymer polymerization.

Example 4:

Using phenolic resin as carbon source, and directly using LiFePO ₄ as the active ingredient for lithium extraction, LiFePO ₄ composite electrode was synthesized under the action of alkali.

The preparation method is similar to that of Example 1, the main difference is that LiOH·H ₂ O, NH ₄ H ₂ PO ₄ and FeCl ₃ ·6H ₂ O are replaced by LiFePO ₄ . In the polymer polymerization process, 0.01mol/L NaOH was used as the catalyst. The change of lithium intercalation capacity with time during the lithium extraction process of the obtained electrode is shown in Figure 6. It can be seen from the figure that directly using LiFePO ₄ as the active ingredient for lithium extraction, its equilibrium lithium intercalation capacity is close to 3.5 mg/cm ³ .

Example 5:

Using melamine-formaldehyde resin as carbon source, LiFePO ₄ precursors LiCl, FeCl ₃ ·6H ₂ O and NH ₄ H ₂ PO ₄ as raw materials, LiFePO ₄ composite electrodes were synthesized under the action of acid.

According to the molar ratio of 1.05:1.05:1, NH ₄ H ₂ PO ₄ , LiCl and FeCl ₃ ·6H ₂ O were weighed and dissolved in an appropriate amount of water to obtain solution A; according to the molar ratio of melamine and resorcinol 1:30, phenolic Weigh melamine, resorcinol and formaldehyde in a ratio of 1:1.4, and add an appropriate amount of water to dissolve to obtain solution B. Pour solution B into solution A (the content of LiFePO ₄ in the control electrode is 30%), stir well, and inject it into a silicone mold. Subsequent steps are the same as in Example 1. The SEM image of the obtained electrode is shown in Fig. 7(A), and the stability of cyclic lithium extraction is shown in Fig. 7(B). It can be seen from the figure that the synthesized LiFePO ₄ is uniformly dispersed inside the carbon support, and the prepared electrode has high cycle stability. After 12 cycles, its lithium intercalation capacity does not decrease significantly.

Example 6:

Using melamine-formaldehyde resin as carbon source and LiMn ₂ O ₄ as active ingredient for lithium extraction, LiMn ₂ O ₄ composite electrode was synthesized under the action of acid.

The preparation method is similar to Example 5, the main difference is that NH ₄ H ₂ PO ₄ , LiCl and FeCl ₃ ·6H ₂ O are replaced by LiMn ₂ O ₄ . In the polymer polymerization process, 0.01mol/L HCl is used as the catalyst. The SEM images of the prepared electrodes are shown in FIG. 8(A) and FIG. 8(B). As can be seen from the figure, _LiMn2O4 was successfully supported _on the carbon support.

Comparative Example 1:

Preparation of LiFePO ₄ Electrodes by Coating Method

NH ₄ H ₂ PO ₄ , LiCl and FeCl ₃ ·6H ₂ O were weighed in a molar ratio of 1.05:1.05:1, and 20% sucrose was weighed, and these substances were mixed and ground uniformly. The obtained material was placed in a tube furnace and calcined at 700° C. for 8 h under oxygen-free conditions to obtain carbon-coated LiFePO ₄ . Acetylene black, PVDF and the prepared carbon-coated LiFePO ₄ were weighed in a mass ratio of 1:1:8, and after grinding uniformly, N-methylpyrrolidone was slowly added, and the obtained slurry was coated with the electrode size of Example 1. The same carbon plate current collector was then dried at 70 °C for 10 h to obtain a coated electrode. The SEM image of the coated electrode is shown in Fig. 9(A), and the change of the lithium intercalation capacity of the electrode with time is shown in Fig. 9(B). It can be seen from the figure that the LiFePO ₄ is agglomerated in the electrode prepared by the coating method, and the lithium extraction capacity of the electrode prepared by the coating method is less than 3 mg/cm ³ .

The embodiments of the present invention are shown and described above, and for those skilled in the art, improvements or changes can be made based on the above descriptions. For example, other organic polymer materials are used as the carbon source of the composite material; or the organic solvent is directly used to dissolve or soften the polymer, and then the lithium extraction active material or its precursor is added for high temperature calcination. All these improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims (8)

1. A preparation method of a porous carbon support composite lithium extraction electrode is characterized by comprising the following steps: the method comprises the following steps:

1) uniformly mixing the lithium extraction active component or a precursor thereof, a pore-forming agent, a regulator and an organic high molecular polymer monomer according to the proportion of 10-70%, 0-10% and 30-80% of the total mass of the mixture respectively; polymerizing the polymer monomers in the mixture under the action of acid or alkali, and curing and molding in a mold;

2) roasting the cured and molded material for 3-8 h at 400-800 ℃ under an oxygen-free condition;

3) soaking the roasted material in acid and alkali to remove the pore-forming agent, and obtaining a porous carbon support composite lithium extraction electrode;

the active component for extracting lithium is LiFePO ₄ 、Li ₃ V ₂ (PO ₄ ) ₃ 、LiMn ₂ O ₄ One or more than two of the above;

the pore-foaming agent is one or more than two of ammonium salt, carbonate, bicarbonate and hydroxide;

the regulator is one or more than two of polyethylene glycol, cetyl trimethyl ammonium bromide, hexamethylene tetramine, benzene sulfonic acid and dodecyl benzene sulfonic acid;

the high molecular polymer is one or more than two of phenolic resin, urea-formaldehyde resin, melamine-formaldehyde resin and furfural resin.

2. The method of claim 1, wherein: in the step 1), precursors of lithium extraction active components comprise a lithium source, an iron source, a vanadium source, a manganese source and a phosphorus source; wherein, the lithium source, the iron source, the vanadium source and the manganese source comprise one or more than two of oxides, hydroxides, chlorides, sulfates, carbonates and acetates of various metals; the phosphorus source comprises one or more of phosphate, hydrogen phosphate, dihydrogen phosphate and phytic acid.

3. The method of claim 1, wherein: the acid in the step 1) is one or more than two of sulfuric acid, phosphoric acid, hydrochloric acid, acetic acid and dihydric phosphate; the alkali is one or more than two of lithium hydroxide, sodium hydroxide, potassium hydroxide and ammonia water.

4. The method of claim 1, wherein: the lithium extraction active component or the precursor thereof, the pore-forming agent, the regulator and the organic high molecular polymer monomer account for 40-60%, 0-6% and 40-60% of the total mass of the mixture.

5. The method of claim 1, wherein: the pore-forming agent is ammonium carbonate or ammonium bicarbonate.

6. The method of claim 1, wherein: the roasting temperature is 500-700 ℃, and the roasting time is 4-7 h.

7. A porous carbon supported composite lithium extraction electrode prepared by the method of any one of claims 1 to 6.

8. Use of the porous carbon-supported composite lithium extraction electrode of claim 7 for electrochemical lithium extraction.

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