A composite porous carbon electrode and a preparation method and application thereof

Abstract

The application provides a composite porous carbon electrode and a preparation method and application thereof, and the preparation method comprises the following steps: (1) mixing a carbon source and sodium carbonate with a solvent, freeze-drying, and then calcining to obtain three-dimensional porous carbon; (2) mixing the three-dimensional porous carbon with an organic solvent, adding a titanium source, drying, and then annealing to obtain a porous carbon / TiO2 composite material; (3) mixing the porous carbon / TiO2 composite material, a binder and N, N-dimethylacetamide to obtain a paste-like slurry, coating the paste-like slurry on a substrate, and drying and rolling to obtain the composite porous carbon electrode. The porous carbon is compounded with titanium dioxide to obtain a composite porous carbon electrode, and the composite porous carbon electrode can improve the recovery efficiency of lithium extraction from a salt lake.

Description

Technical Field

[0001] This invention belongs to the field of lithium extraction technology from salt lakes, and relates to a composite porous carbon electrode, its preparation method and application. Background Technology

[0002] With the rapid development of electronic products and new energy vehicles, the demand for lithium resources is increasing year by year. The increasingly serious contradiction between lithium resource supply and demand has made its efficient development and extraction a research hotspot. Currently, 59% of the world's proven terrestrial lithium resources are distributed in salt lake brines, which are richer than those from ores. Furthermore, lithium extraction from ores generally suffers from high energy consumption and high pollution, making salt lake brine extraction a primary method for obtaining lithium resources. Currently, the development and utilization of salt lake brine lithium resources mainly utilizes methods such as extraction, nanofiltration, selective electrodialysis, ion exchange and adsorption, and electrochemistry. Among these, electrodialysis, with its advantages of simple operation, good separation performance, and low energy consumption, has become one of the most promising lithium extraction technologies.

[0003] Electrodialysis technology utilizes the selective permeability of ion exchange membranes to anions and cations. Under the action of an applied DC electric field, anions and cations migrate in a directional manner, thereby separating and concentrating electrolytes.

[0004] CN113265538A discloses a method for preparing a highly conductive porous electrode for lithium extraction from salt lakes. The method includes modifying the binder used in the electrode preparation process by blending inorganic nanoparticles and polar hydrophilic organic polymers to improve the hydrophilicity of the binder. During the electrode slurry preparation process, an inorganic salt pore-forming agent is added to create pores of varying sizes on the electrode during drying, thereby improving the mass transfer effect of the solution within the electrode plate.

[0005] CN113293312A discloses a method for preparing a composite porous electrode material for lithium extraction, comprising: using polydopamine to coat and modify the surface of the electrode active material, utilizing the preferential aggregation and transport of lithium ions by polydopamine and its hydrophilicity to improve the affinity of the electrode active material to the solution and the selectivity of lithium; and replacing the traditional PVDF binder with an aqueous binder to further improve the hydrophilicity of the electrode.

[0006] In the process of lithium extraction via electrodialysis, lithium ions migrate directionally through the cation exchange membrane to the cathode chamber under the action of an electric field. Increasing the current efficiency can increase the lithium extraction efficiency, but it will also intensify the hydrolysis reaction in the cathode chamber, resulting in more hydrogen and hydroxide ions. When the concentration of alkali in the cathode chamber is too high, it will intensify the reverse diffusion of lithium ions to the brine raw material chamber, leading to a decrease in the lithium recovery rate. Summary of the Invention

[0007] The purpose of this invention is to provide a composite porous carbon electrode, its preparation method and application. This invention combines porous carbon with titanium dioxide to prepare a composite porous carbon electrode, which can improve the recovery efficiency of lithium extraction from salt lakes.

[0008] To achieve this objective, the present invention employs the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing a composite porous carbon electrode, the method comprising the following steps:

[0010] (1) A three-dimensional porous carbon was obtained by mixing a carbon source and sodium carbonate with a solvent, freeze-drying and then calcining.

[0011] (2) Three-dimensional porous carbon was mixed with an organic solvent, a titanium source was added, and after drying, it was annealed to obtain a porous carbon / TiO2 composite material.

[0012] (3) The porous carbon / TiO2 composite material, binder and N,N-dimethylacetamide are mixed to obtain a paste, the paste is coated on a substrate, and the composite porous carbon electrode is obtained by drying and rolling.

[0013] This invention prepares a composite porous carbon electrode by combining three-dimensional porous carbon and titanium dioxide (TiO2). During lithium extraction, TiO2 increases the content of lithium ions adsorbed in the electrode's double layer, preventing lithium ions from returning to the brine from the cathode chamber. Compared to pure carbon electrodes, this effectively improves lithium recovery. However, due to the low conductivity of TiO2, the current efficiency during lithium extraction is reduced, leading to a decrease in lithium ion mobility and thus affecting the lithium content in the lithium-rich liquid. + At lower concentrations, lithium recovery rates decrease. However, using the composite porous carbon electrode can effectively improve lithium recovery rates compared to using a pure TiO2 electrode.

[0014] Preferably, the carbon source in step (1) includes glucose.

[0015] Preferably, the solvent includes water.

[0016] Preferably, the mass ratio of the carbon source to sodium carbonate is 1:(15-20), for example: 1:15, 1:16, 1:18, 1:19 or 1:20, etc.

[0017] Preferably, the freeze-drying time in step (1) is 20 to 30 hours, for example: 20 hours, 22 hours, 25 hours, 28 hours or 30 hours.

[0018] Preferably, the calcination temperature is 600-800℃, for example: 600℃, 650℃, 700℃, 750℃ or 800℃, etc.

[0019] Preferably, the calcination time is 2 to 3 hours, for example: 2 hours, 2.2 hours, 2.5 hours, 2.8 hours or 3 hours.

[0020] Preferably, the organic solvent in step (2) includes any one or a combination of at least two of methanol, chloroform, or isopropanol.

[0021] Preferably, the solid-liquid ratio of the three-dimensional porous carbon to the organic solvent is 1:1 to 3 g / mL, for example: 1:1 g / mL, 1:1.5 g / mL, 1:2 g / mL, 1:2.5 g / mL or 1:3 g / mL, etc.

[0022] Preferably, the titanium source includes any one or a combination of at least two of tetrabutyl titanate, tetraethyl titanate, or tetrapropyl titanate.

[0023] Preferably, the mass ratio of the titanium source to the three-dimensional porous carbon is 1:(1.5 to 2.5), for example: 1:1.5, 1:1.8, 1:2, 1:2.2 or 1:2.5, etc.

[0024] Preferably, after drying in step (2), an organic solvent is added and the drying process is repeated.

[0025] This invention employs a process of adding organic solvent twice and then drying, which increases the contact density between porous carbon and metal oxide particles, allowing the metal oxide to be fully embedded in the pores of the carbon.

[0026] Preferably, the annealing temperature in step (2) is 400 to 450°C, for example: 400°C, 410°C, 420°C, 440°C or 450°C.

[0027] Preferably, the heating rate of the annealing treatment is 3 to 8°C / min, for example: 3°C / min, 4°C / min, 5°C / min, 6°C / min or 8°C / min, etc.

[0028] Preferably, the annealing time is 2.5 to 3.5 hours, for example: 2.5 hours, 2.8 hours, 3 hours, 3.2 hours or 3.5 hours.

[0029] Preferably, the mass fraction of TiO2 in the porous carbon / TiO2 composite material is 10-20%, for example: 10%, 12%, 15%, 18% or 20%, etc.

[0030] Preferably, the adhesive in step (3) comprises polyvinylidene fluoride.

[0031] Preferably, the mass ratio of the porous carbon / TiO2 composite material to the binder is (2.5 to 3):1, for example: 2.5:1, 2.6:1, 2.8:1, 2.9:1 or 3:1, etc.

[0032] Preferably, the solid-liquid ratio of the porous carbon / TiO2 composite material and N,N-dimethylacetamide is 1:(10-15)g / mL, for example: 1:10g / mL, 1:11g / mL, 1:12g / mL, 1:14g / mL or 1:15g / mL, etc.

[0033] In a second aspect, the present invention provides a composite porous carbon electrode, which is prepared by the method described in the first aspect.

[0034] Thirdly, the present invention provides a lithium extraction device from a salt lake, the salt lake lithium extraction device comprising:

[0035] The system includes a cathode chamber, an anode chamber, and a feed liquid storage chamber disposed between the cathode chamber and the anode chamber. The anode chamber and the cathode chamber are respectively provided with composite porous carbon electrodes as described in the second aspect. A monovalent cation exchange membrane is disposed between the cathode chamber and the feed liquid storage chamber, and an anion exchange membrane is disposed between the anode chamber and the feed liquid storage chamber. A lithium-ion selective cation exchange membrane is disposed between the composite porous carbon electrode of the cathode chamber and the monovalent cation exchange membrane.

[0036] This invention uses two types of cation exchange membranes in the cathode chamber. During the movement of cations to the cathode, the use of a monovalent cation exchange membrane can preferentially remove divalent cations in the brine, avoiding the reduction in lithium ion flux caused by excessive cation blockage during the use of a lithium-ion selective cation exchange membrane alone.

[0037] Fourthly, the present invention provides a method for lithium extraction from salt lakes, the method comprising the following steps:

[0038] Water is injected into the cathode chamber and anode chamber of the lithium extraction device from the salt lake as described in the third aspect, brine is injected into the raw material liquid chamber, and voltage is applied to carry out the lithium extraction reaction.

[0039] After the lithium extraction reaction is completed, the solutions in the feed liquid chamber and the anode chamber are replaced with deionized water, and the positive and negative electrodes are short-circuited to obtain a lithium-rich solution.

[0040] The positive and negative electrode short-circuiting described in this invention involves short-circuiting the composite porous carbon electrode in the cathode chamber with the composite porous carbon electrode in the anode chamber.

[0041] In the lithium extraction method from salt lakes described in this invention, after applying voltage, Li in the brine is extracted under the action of an electric field. + It passes through the monovalent cation exchange membrane to reach the cathode chamber, where it reacts with OH- produced by the electrolysis of water in the cathode chamber. - Pairing forms a lithium hydroxide solution, while some lithium ions are adsorbed onto the electrode surface through the double layer. The anions X in the brine... - (Cl- SO4 2- CO3 2- It passes through the anion exchange membrane to reach the anode chamber, where it reacts with H+ generated by the electrolysis of water in the anode chamber. + The lithium ions pair up to form an HX solution. After the reaction is complete, the power supply is removed and the positive and negative electrodes are short-circuited. Due to the disappearance of the DC electric field, the lithium ions stored in the double layer return to the solution, resulting in a lithium-rich liquid.

[0042] Preferably, the voltage is 4 to 10V, for example: 4V, 5V, 8V, 9V or 10V, etc.

[0043] Preferably, the voltage is applied for 2 to 4 hours, for example: 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours.

[0044] Preferably, the short-circuit reaction time of the positive and negative electrodes is 10 to 20 minutes, for example: 10 minutes, 12 minutes, 15 minutes, 18 minutes or 20 minutes.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] (1) This invention combines electrodialysis and electroadsorption. By using a composite porous carbon electrode as the cathode, when lithium ions migrate into the cathode chamber, they react with OH- generated by the electrolysis of water in the cathode chamber. - The electrodes pair to form a lithium hydroxide solution. Simultaneously, an electrostatic field is created between the anode and cathode after an external voltage is applied. Lithium ions, under electrostatic force, move towards the electrode with the opposite charge, forming an electric double layer on the electrode surface. The lithium ions are adsorbed and temporarily stored in the double layer. As the reaction proceeds, the pH value in the cathode chamber continuously increases, making it easier for the TiO2 particles in the cathode to lose protons (H+). + [Ti-O] formation - The increased negative charge on the surface of TiO2 particles allows the cathode to adsorb more lithium ions. The increased thickness of the double layer formed on the cathode surface prevents the reverse diffusion of lithium ions into the feed chamber, thus improving the lithium recovery rate.

[0047] (2) The composite porous carbon electrode prepared by the method of the present invention is used in the lithium extraction method of the salt lake of the present invention to obtain Li in lithium-rich liquid. + The concentration can reach over 3.95 g / L, and the lithium recovery rate can reach over 86%. Attached Figure Description

[0048] Figure 1 This is the XRD pattern of the porous carbon / TiO2 composite material prepared in Example 1 of the present invention.

[0049] Figure 2 This is a schematic diagram of the structure of a lithium extraction device from a salt lake, which is an application example of the present invention. Detailed Implementation

[0050] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0051] Example 1

[0052] This embodiment provides a composite porous carbon electrode, which is prepared by the following method:

[0053] (1) Weigh a certain amount of glucose and sodium carbonate in a mass ratio of 1:17, dissolve them in water, mix them well, and freeze-dry for 25 hours; calcine the dried product at 700℃ for 2.5 hours, and then wash and dry it to obtain three-dimensional porous carbon.

[0054] (2) Three-dimensional porous carbon was added to methanol solution at a solid-liquid ratio of 1g:2mL to ensure thorough dispersion. Then, tetrabutyl titanate was added at a mass ratio of porous carbon to titanium salt of 2:1 and mixed thoroughly. The methanol was then dried at 100℃. Methanol solution was added to the resulting mixture again and dried. The dried mixture was then placed in a tube furnace and annealed at 420℃ for 3 hours at a rate of 5℃ / min to obtain a porous carbon / TiO2 composite material. The metal oxide was supported in the three-dimensional network structure formed by the porous carbon, and the TiO2 loading percentage in the composite material was 15wt%. The XRD pattern of the prepared porous carbon / TiO2 composite material is shown below. Figure 1 As shown, by Figure 1 It can be seen that the peak values ​​of the composite material are in good agreement with those of the TiO2 standard card, indicating that the crystal form of TiO2 loaded on porous carbon has not changed, and a strong peak appears at 23℃, which is the diffraction peak of carbon.

[0055] (3) The porous carbon / TiO2 composite material and polyvinylidene fluoride are mixed at a mass ratio of 2.7:1. Then, N,N-dimethylacetamide is added to form a paste according to the solid-liquid ratio of porous carbon / TiO2 composite material and N,N-dimethylacetamide of 1g:12mL. The paste is coated on a graphite plate, placed in a vacuum drying oven and dried at 70℃. Then, it is pressed into a 500μm thin sheet using a roller press to obtain the composite porous carbon electrode.

[0056] Example 2

[0057] This embodiment provides a composite porous carbon electrode, which is prepared by the following method:

[0058] (1) Weigh a certain amount of glucose and sodium carbonate at a mass ratio of 1:15, dissolve them in water, mix them well, and freeze dry for 20 hours; calcine the dried product at 600℃ for 3 hours, and clean and dry it after calcine to obtain three-dimensional porous carbon.

[0059] (2) Three-dimensional porous carbon was added to methanol solution at a solid-liquid ratio of 1g:1mL to disperse it fully. Then, tetrabutyl titanate was added at a mass ratio of porous carbon to titanium salt of 2.5:1 and mixed evenly. Then, methanol was dried at 100℃. Then, methanol solution was added to the mixture and dried again. Then, the dried mixture was placed in a tube furnace and heated to 450℃ at a rate of 5℃ / min for annealing for 2.5h to obtain a composite material of porous carbon / TiO2, wherein the metal oxide is loaded in the three-dimensional network structure formed by the porous carbon and the loading percentage of TiO2 in the composite material is 10wt%.

[0060] (3) The porous carbon / TiO2 composite material and polyvinylidene fluoride are mixed at a mass ratio of 2.5:1. Then, N,N-dimethylacetamide is added to form a paste according to the solid-liquid ratio of porous carbon / TiO2 composite material and N,N-dimethylacetamide of 1g:10mL. The paste is coated on a graphite plate, placed in a vacuum drying oven and dried at 70℃. Then, it is pressed into a 500μm thin sheet using a roller press to obtain the composite porous carbon electrode.

[0061] Example 3

[0062] This embodiment provides a composite porous carbon electrode, which is prepared by the following method:

[0063] (1) Weigh a certain amount of glucose and sodium carbonate at a mass ratio of 1:20, dissolve them in water, mix them well, and freeze dry for 30 hours; calcine the dried product at 800℃ for 2 hours, and then wash and dry it to obtain three-dimensional porous carbon.

[0064] (2) Three-dimensional porous carbon was added to methanol solution at a solid-liquid ratio of 1g:1mL to disperse it fully. Then, tetrabutyl titanate was added at a mass ratio of porous carbon to titanium salt of 1.5:1 and mixed evenly. Then, methanol was dried at 100℃. Then, methanol solution was added to the mixture and dried again. Then, the dried mixture was placed in a tube furnace and heated to 400℃ at a rate of 5℃ / min for annealing for 3.5h to obtain a composite material of porous carbon / TiO2, wherein the metal oxide is loaded in the three-dimensional network structure formed by the porous carbon and the loading percentage of TiO2 in the composite material is 20wt%.

[0065] (3) The porous carbon / TiO2 composite material and polyvinylidene fluoride are mixed at a mass ratio of 3:1. Then, N,N-dimethylacetamide is added to form a paste according to the solid-liquid ratio of porous carbon / TiO2 composite material and N,N-dimethylacetamide of 1g:5mL. The paste is coated on a graphite plate, placed in a vacuum drying oven and dried at 70℃. After drying, it is pressed into a 500μm sheet using a roller press to obtain the composite porous carbon electrode.

[0066] Example 4

[0067] The only difference between this embodiment and Embodiment 1 is that the mass ratio of porous carbon to titanium salt is 3:1, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0068] Example 5

[0069] The only difference between this embodiment and Embodiment 1 is that the mass ratio of porous carbon to titanium salt is 1:1, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0070] Example 6

[0071] The only difference between this embodiment and embodiment 1 is that step (2) is dried only once, without adding organic solvent and drying again. Other conditions and parameters are exactly the same as in embodiment 1.

[0072] Schematic diagrams of the application examples and comparative application examples of the present invention using a lithium extraction device from a salt lake are shown below. Figure 2 As shown: The lithium extraction device from the salt lake includes:

[0073] The system includes a cathode chamber, an anode chamber, and a feed liquid storage chamber disposed between the cathode chamber and the anode chamber. Electrodes are disposed in the anode chamber and the cathode chamber respectively. A monovalent cation exchange membrane is disposed between the cathode chamber and the feed liquid storage chamber, and an anion exchange membrane is disposed between the anode chamber and the feed liquid storage chamber. A lithium-ion selective cation exchange membrane is disposed between the composite porous carbon electrode of the cathode chamber and the monovalent cation exchange membrane.

[0074] Application Example 1

[0075] This application example provides a method for lithium extraction from salt lakes, and a schematic diagram of the apparatus used in the method is shown below. Figure 2 As shown, the electrode used in the device is the composite porous carbon electrode prepared in Example 1, and the lithium extraction method from the salt lake includes the following steps:

[0076] In such Figure 2Water is injected into the cathode and anode chambers of the lithium extraction device shown in the diagram, and brine is injected into the feed liquid chamber. A constant voltage of 7V is applied for 3 hours. After the reaction is completed, the power supply is removed, and the brine in the feed liquid chamber and the impurity solution containing divalent cations in the anode chamber are replaced with deionized water. The positive and negative electrodes are short-circuited for 20 minutes to obtain a lithium-rich solution.

[0077] Application Example 2

[0078] This application example provides a method for lithium extraction from salt lakes, and a schematic diagram of the apparatus used in the method is shown below. Figure 2 As shown, the electrode used in the device is the composite porous carbon electrode prepared in Example 2, and the lithium extraction method from the salt lake includes the following steps:

[0079] In such Figure 2 Water is injected into the cathode and anode chambers of the lithium extraction device shown in the diagram, and brine is injected into the feed liquid chamber. A constant voltage of 4V is applied for 4 hours. After the reaction is completed, the power supply is removed, and the brine in the feed liquid chamber and the impurity solution containing divalent cations in the anode chamber are replaced with deionized water. The positive and negative electrodes are short-circuited for 10 minutes to obtain a lithium-rich solution.

[0080] Application Example 3

[0081] This application example provides a method for lithium extraction from salt lakes, and a schematic diagram of the apparatus used in the method is shown below. Figure 2 As shown, the electrode used in the device is the composite porous carbon electrode prepared in Example 3, and the lithium extraction method from the salt lake includes the following steps:

[0082] In such Figure 2 Water is injected into the cathode and anode chambers of the lithium extraction device shown in the diagram, and brine is injected into the feed liquid chamber. A constant voltage of 10V is applied for 2 hours. After the reaction is completed, the power supply is removed, and the brine in the feed liquid chamber and the impurity solution containing divalent cations in the anode chamber are replaced with deionized water. The positive and negative electrodes are short-circuited for 10 minutes to obtain a lithium-rich solution.

[0083] Application Example 4

[0084] The only difference between this application example and application example 1 is that the composite porous carbon electrode prepared in example 1 is replaced with the composite porous carbon electrode prepared in example 4, while the other conditions and parameters are exactly the same as in application example 1.

[0085] Application Example 5

[0086] The only difference between this application example and application example 1 is that the composite porous carbon electrode prepared in example 1 is replaced with the composite porous carbon electrode prepared in example 5, while the other conditions and parameters are exactly the same as in application example 1.

[0087] Application Example 6

[0088] The only difference between this application example and application example 1 is that the composite porous carbon electrode prepared in example 1 is replaced with the composite porous carbon electrode prepared in example 6, while the other conditions and parameters are exactly the same as in application example 1.

[0089] Comparative Application Example 1

[0090] The only difference between this comparative application example and application example 1 is that the composite porous carbon electrode prepared in example 1 is replaced with a pure carbon electrode, while the other conditions and parameters are exactly the same as in application example 1.

[0091] Comparative Application Example 2

[0092] The only difference between this comparative application example and application example 1 is that the composite porous carbon electrode prepared in example 1 is replaced with a TiO2 electrode, while the other conditions and parameters are exactly the same as in application example 1.

[0093] Performance testing:

[0094] Lithium extraction experiments were conducted in brine with a lithium ion concentration of 0.8 g / L for both the application example and the comparative application example. Inductively coupled plasma atomic emission spectrometry (ICP) was used to determine the Li content in the lithium-rich solutions after lithium extraction in both examples. + The concentration was calculated using the formula (extracted lithium content / original brine lithium content) × 100%. The lithium recovery rate test results are shown in Table 1.

[0095] Table 1

[0096]

[0097]

[0098] As can be seen from Table 1, based on Application Examples 1-3, the composite porous carbon electrode prepared by the method of the present invention can be used in the lithium extraction method from salt lakes of the present invention to obtain Li from lithium-rich liquids. + The concentration can reach over 3.95 g / L, and the lithium recovery rate can reach over 86%.

[0099] A comparison of Application Examples 1 and 4-5 shows that the mass ratio of porous carbon to titanium salt affects the performance of the composite porous carbon electrode during its preparation, thus impacting the lithium extraction efficiency from salt lakes. Controlling the mass ratio of porous carbon to titanium salt to 1.5–2.5:1 yields a composite porous carbon electrode with better performance. If the amount of titanium salt added is too large, the titanium oxide content in the prepared composite electrode will be too high, affecting the conductivity of the electrode material and consequently reducing the lithium ion migration rate and lithium recovery rate. Conversely, if the amount of titanium salt added is too small, the titanium oxide content in the prepared composite electrode will be too low, resulting in a thinner double layer formed on the cathode surface during lithium extraction. This makes it easier for lithium ions to diffuse backwards into the raw material chamber, reducing the lithium recovery rate.

[0100] Comparing Application Example 1 and Application Example 6, it can be seen that the present invention improves the contact density between porous carbon and metal oxide particles by repeatedly adding organic solvent and drying, so that the metal oxide is fully embedded in the pores of carbon, thereby improving the lithium extraction performance of the composite porous carbon electrode in salt lakes.

[0101] As can be seen from the comparison between Application Example 1 and Comparative Application Example 1, TiO2 can increase the content of lithium ions adsorbed by the electrode double layer during the lithium extraction process, and prevent lithium ions from returning to the brine from the cathode chamber. Therefore, the lithium recovery rate can be effectively improved by using the composite porous carbon electrode described in this invention compared with the lithium extraction using a pure carbon electrode.

[0102] A comparison of Application Example 1 and Comparative Application Example 2 shows that TiO2 itself has low conductivity, which reduces the current efficiency of the lithium extraction process, leading to a decrease in lithium ion mobility and reduced Li ion concentration in the lithium-rich liquid. + At lower concentrations, lithium recovery rates decrease. Therefore, using the composite porous carbon electrode described in this invention can effectively improve lithium recovery rates compared to using a pure TiO2 electrode.

[0103] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a composite porous carbon electrode, characterized by, The preparation method includes the following steps: (1) A three-dimensional porous carbon was obtained by mixing a carbon source and sodium carbonate with a solvent, freeze-drying and then calcining. (2) Three-dimensional porous carbon is mixed with organic solvent, titanium source is added, and after drying, porous carbon / TiO2 composite material is obtained by annealing. (3) The porous carbon / TiO2 composite material, binder and N,N-dimethylacetamide are mixed to obtain a paste slurry, the paste slurry is coated on the substrate, and the composite porous carbon electrode is obtained by drying and rolling. The mass ratio of the titanium source and the three-dimensional porous carbon in step (2) is 1:(1.5~2.5); After drying as described in step (2), an organic solvent is added and the drying process is repeated. The mass fraction of TiO2 in the porous carbon / TiO2 composite material is 10~20%; The mass ratio of the carbon source to sodium carbonate is 1:(15~20); Organic solvents include any one or a combination of at least two of methanol, chloroform, or isopropanol; The solid-liquid ratio of the three-dimensional porous carbon to the organic solvent is 1:1~3 g / mL; The titanium source includes any one or a combination of at least two of tetrabutyl titanate, tetraethyl titanate, or tetrapropyl titanate.

2. The production method according to claim 1, wherein The carbon source in step (1) includes glucose.

3. The production method according to claim 1, wherein The solvent in step (1) includes water.

4. The production method according to claim 1, wherein The freeze-drying time in step (1) is 20~30h.

5. The preparation method according to claim 1, characterized in that, The calcination temperature in step (1) is 600~800℃.

6. The production method according to claim 1, wherein The calcination time in step (1) is 2-3 hours.

7. The production method according to claim 1, wherein The annealing temperature in step (2) is 400~450℃.

8. The production method according to claim 1, wherein The heating rate of the annealing process in step (2) is 3~8℃ / min.

9. The production method according to claim 1, wherein The annealing process in step (2) takes 2.5 to 3.5 hours.

10. The production method according to claim 1, wherein The adhesive in step (3) includes polyvinylidene fluoride.

11. The production method according to claim 1, wherein The mass ratio of the porous carbon / TiO2 composite material to the binder is (2.5~3):

1.

12. The production method according to claim 1, wherein The solid-liquid ratio of the porous carbon / TiO2 composite material and N,N-dimethylacetamide is 1:(10~15)g / mL.

13. A composite porous carbon electrode, characterized by, The composite porous carbon electrode is prepared by the preparation method according to any one of claims 1-12.

14. A lithium extraction plant from salt lakes, characterized in that, The lithium extraction device from the salt lake includes: The system includes a cathode chamber, an anode chamber, and a feed liquid storage chamber disposed between the cathode chamber and the anode chamber. The anode chamber and the cathode chamber are respectively provided with the composite porous carbon electrode as described in claim 13. A monovalent cation exchange membrane is disposed between the cathode chamber and the feed liquid storage chamber, and an anion exchange membrane is disposed between the anode chamber and the feed liquid storage chamber. A lithium-ion selective cation exchange membrane is disposed between the composite porous carbon electrode of the cathode chamber and the monovalent cation exchange membrane.

15. A method for lithium extraction from salt lakes, characterized in that, The lithium extraction method from the salt lake includes the following steps: Water is injected into the cathode chamber and anode chamber of the lithium extraction device from the salt lake as described in claim 14, brine is injected into the raw material liquid chamber, and a voltage is applied to carry out the lithium extraction reaction. After the lithium extraction reaction is completed, the solutions in the feed liquid chamber and the anode chamber are replaced with deionized water, and the positive and negative electrodes are short-circuited to obtain a lithium-rich solution.

16. The method of claim 15, wherein the brine is a salt lake brine. The voltage is 4~10V.

17. The method of claim 15, wherein the brine is a salt lake brine. The voltage is applied for 2 to 4 hours.

18. The method of claim 15, wherein the brine is a salt lake brine. The reaction time for the positive and negative electrodes to be shorted is 10-20 minutes.

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