An electrochemical lithium extraction device and method based on interfacial evaporation

Abstract

The present application relates to the technical field of lithium ion extraction, and particularly relates to an electrochemical lithium extraction device and method based on interfacial evaporation. The device comprises an upper end plate provided with a light transmission hole, a middle chamber and a lower end plate; the middle chamber takes a composite lithium extraction electrode as a top cover, and the bottom of the middle chamber is provided with an auxiliary electrode; the composite lithium extraction electrode comprises, from top to bottom, a photothermal material layer, a current collector layer and an electrode material layer; the electrode material layer is loaded with lithium ion selective electrode active material; the sidewall of the middle chamber is provided with a water inlet hole and a drainage hole, the water inlet hole and the drainage hole are connected with a water pump through a pipeline to form a solution circulation loop; the auxiliary electrode is connected with a power supply and the current collector layer through a wire in sequence to form a power supply circuit. Through the organic integration of photothermal interfacial evaporation and electrochemical ion pump, the present application effectively solves the problems of concentration polarization and reaction kinetics limitation in the process of low lithium source lithium extraction, and significantly improves the extraction efficiency of lithium ions and the system performance.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion extraction technology, and in particular to an electrochemical lithium extraction device and method based on interfacial evaporation. Background Technology

[0002] With the widespread application of lithium-ion batteries in portable electronic devices, electric vehicles, and large-scale energy storage systems, global demand for lithium resources continues to grow rapidly. Lithium resources are mainly found in media such as ores, brine from salt lakes, and seawater; the total amount of resources is large, but their distribution is uneven.

[0003] Currently, lithium mining and processing from ores mainly relies on energy-intensive, water-intensive, and environmentally damaging mechanical and chemical processes. The development of new mines and the construction of processing facilities are time-consuming and costly, resulting in significant bottlenecks in capacity expansion. While salt lake brines are rich in lithium reserves, existing lithium extraction technologies generally employ open-air evaporation and concentration methods, which are slow, cause significant water resource loss, and require high brine quality; low-grade brines with lithium ion concentrations below 100 mg / L are difficult to utilize effectively. Seawater contains approximately 205 billion tons of lithium, but its concentration is extremely low (only 0.17 mg / L), making traditional extraction methods almost unusable.

[0004] Electrochemical ion pumping (EIP) technology is considered a promising alternative to traditional lithium extraction methods due to its environmental friendliness, high selectivity, and low cost. However, EIP technology faces significant challenges when applied in low-lithium sources (such as low-grade brine and seawater): on the one hand, the extremely low lithium-ion concentration leads to severe concentration polarization at the electrode / electrolyte interface, significantly increasing energy consumption and reducing the lithium-ion extraction rate; on the other hand, high concentrations of impurity ions (such as sodium and magnesium) compete with lithium ions for electrode insertion, further interfering with extraction efficiency. Summary of the Invention

[0005] The purpose of this invention is to address the problem of poor lithium extraction efficiency in existing electrochemical lithium extraction technologies when dealing with low lithium sources. This invention provides an electrochemical lithium extraction device and method based on interfacial evaporation. By organically integrating photothermal interfacial evaporation with an electrochemical ion pump, the invention effectively solves the problems of concentration polarization and reaction kinetics limitations in the low lithium source lithium extraction process, and significantly improves the lithium ion extraction efficiency and system performance.

[0006] To achieve the above objectives, the present invention provides an electrochemical lithium extraction device based on interfacial evaporation, comprising an upper end plate, an intermediate chamber, and a lower end plate; The upper plate is provided with a light-transmitting hole; the middle chamber is covered by a composite lithium extraction electrode, and an auxiliary electrode is provided at the bottom of the middle chamber; the composite lithium extraction electrode includes a photothermal material layer, a current collector layer and an electrode material layer arranged sequentially from top to bottom; the electrode material layer is loaded with lithium-ion selective electrode active material; The side wall of the intermediate chamber is provided with a water inlet and a drain outlet, which are connected to the water pump through pipes to form a solution flow circuit; the auxiliary electrode is connected to the power supply and the current collector layer in sequence through wires to form a power supply circuit.

[0007] Preferably, the device is used to treat salt lake brine or seawater with a lithium ion concentration of less than 100 mg / L.

[0008] Preferably, the photothermal material layer includes a photothermal material and a hydrophobic binder, and the photothermal material layer is disposed on one side of the current collector layer; the electrode material layer includes a lithium-ion selective electrode active material, a conductive agent and a binder, and the electrode material layer is disposed on the other side of the current collector layer opposite to the photothermal material layer.

[0009] Preferably, the photothermal material includes one or more of the following: nano-alumina, nano-gold, nano-titanium dioxide, activated carbon, carbon black, graphene, and carbon nanotubes.

[0010] Preferably, the current collector layer is made of carbon cloth or carbon paper.

[0011] Preferably, the active material for the lithium-ion selective electrode includes lithium iron phosphate, lithium manganese oxide, or lithium nickel cobalt manganese oxide.

[0012] Preferably, the auxiliary electrode is a silver electrode, an activated carbon electrode, a nickel hexacyanoferrate electrode, or a chlorine-doped polyaniline electrode.

[0013] Preferably, the composite lithium extraction electrode is fixed to the inner wall of the intermediate chamber by a support member.

[0014] This invention also provides an electrochemical lithium extraction method based on interfacial evaporation, using the aforementioned apparatus, comprising the following steps: Under illumination, lithium-containing raw material liquid is introduced into the intermediate chamber through the solution flow circuit, and the power supply circuit is activated to enter the discharge mode, so that lithium ions are embedded in the electrode material layer. Under conditions of no light, the receiving liquid is introduced into the intermediate chamber through the solution flow circuit, and the power supply circuit is activated to enter the charging mode, so that lithium ions are extracted from the electrode material layer and enriched in the receiving liquid.

[0015] Preferably, before introducing the receiving liquid into the intermediate chamber, the process further includes a step of rinsing the intermediate chamber by introducing water into it.

[0016] The beneficial effects of this invention are as follows: 1. This invention provides an electrochemical lithium extraction device based on interfacial evaporation, comprising an upper end plate, a middle chamber, and a lower end plate; the upper end plate has a light-transmitting hole; the middle chamber has a composite lithium extraction electrode as its top cover, and an auxiliary electrode is located at the bottom of the middle chamber; the composite lithium extraction electrode comprises a photothermal material layer, a current collector layer, and an electrode material layer arranged sequentially from top to bottom; the electrode material layer is loaded with a lithium-ion selective electrode active material; the side wall of the middle chamber has a water inlet hole and a water outlet hole, which are connected to a water pump through pipes to form a solution flow loop; the auxiliary electrode is connected to a power source and the current collector layer sequentially through wires to form a power supply loop. This invention creatively combines photothermal interfacial evaporation (SE) with electrochemical ion pump (EIP) technology to construct a composite lithium extraction electrode with a solid-liquid-gas three-phase interface. Under illumination, the photothermal material layer absorbs light energy and generates local heating, driving the rapid evaporation of water molecules at the interface. This not only effectively increases the lithium ion concentration at the electrode / solution interface and alleviates the concentration polarization problem caused by low lithium concentration, but also further improves the kinetics of the electrochemical reaction by local heating, significantly increasing the lithium ion insertion rate and extraction capacity.

[0017] 2. The composite lithium extraction electrode adopts a multi-layer structure design, with the photothermal material layer located on the hydrophobic side and the current collector layer and electrode material layer located on the hydrophilic side, realizing the separation of the liquid phase and gas phase and avoiding liquid water leakage. By tilting the device to form a certain angle between one side of the composite lithium extraction electrode and the horizontal plane, it is ensured that it is in continuous and stable contact with the liquid surface, effectively preventing the water level from dropping due to evaporation or the impact of residual bubbles on the reaction interface, thus ensuring the stability and reliability of the device during continuous operation.

[0018] 3. The device of the present invention is particularly suitable for low-grade salt lake brine or seawater with lithium ion concentration below 100 mg / L. It achieves local concentration through photothermal evaporation, which enhances the selective capture capability of lithium ions in low-lithium and high-impurity ion environments, and provides a feasible extraction solution for low-concentration lithium resources that are difficult to utilize effectively by traditional technologies.

[0019] 4. This invention fully utilizes solar energy as the driving energy source to achieve simultaneous photothermal evaporation and electrochemical lithium extraction, reducing external energy consumption; at the same time, the entire extraction process does not require the addition of chemical reagents, avoiding secondary pollution, and conforming to the green and sustainable energy development strategy.

[0020] In summary, this invention effectively solves the problems of concentration polarization and reaction kinetics limitations in the lithium extraction process from low-lithium sources by organically integrating photothermal interfacial evaporation and electrochemical ion pumps, significantly improving the extraction efficiency and system performance of lithium ions, and providing a new technical approach for the large-scale development and utilization of low-grade lithium resources. Attached Figure Description

[0021] Figure 1This is a schematic diagram of the electrochemical lithium extraction device based on interfacial evaporation in this invention; Figure 1 In the diagram, 1 is a pipe, 2 is an auxiliary electrode, 3 is a wire, 4 is a power source, 5 is a drain hole, 6 is sunlight, 7 is water vapor, 8 is a photothermal material layer, 9 is a current collector layer, 10 is an electrode material layer, 11 is lithium ions, 12 is a lithium salt solution, 13 is a water inlet, and 14 is a water pump. Figure 2 These are constant current discharge curves corresponding to Embodiment 1 and Comparative Example 1 of the present invention; Figure 3 This is a cyclic voltammetry curve of the electrochemical lithium extraction device in Example 1 of the present invention under the condition of lithium chloride concentration of 0.25 mmol / L; Figure 4 This is a cyclic voltammetry curve of the electrochemical lithium extraction device in Example 1 of the present invention under the condition of lithium chloride concentration of 10 mmol / L; Figure 5 This is a graph showing the open-circuit potential change of the electrochemical lithium extraction device in Embodiment 1 of the present invention under alternating conditions of "no light - applied light - no light". Detailed Implementation

[0022] This invention provides an electrochemical lithium extraction device based on interfacial evaporation, comprising an upper end plate, a middle chamber, and a lower end plate; The upper plate is provided with a light-transmitting hole; the middle chamber is covered by a composite lithium extraction electrode, and an auxiliary electrode is provided at the bottom of the middle chamber; the composite lithium extraction electrode includes a photothermal material layer, a current collector layer and an electrode material layer arranged sequentially from top to bottom; the electrode material layer is loaded with lithium-ion selective electrode active material; The side wall of the intermediate chamber is provided with a water inlet and a drain outlet, which are connected to the water pump through pipes to form a solution flow circuit; the auxiliary electrode is connected to the power supply and the current collector layer in sequence through wires to form a power supply circuit.

[0023] In this invention, the device is used to treat salt lake brine or seawater with a lithium ion concentration of less than 100 mg / L.

[0024] In this invention, the photothermal material layer includes a photothermal material and a hydrophobic binder, and the photothermal material layer is disposed on one side of the current collector layer; the electrode material layer includes a lithium-ion selective electrode active material, a conductive agent and a binder, and the electrode material layer is disposed on the other side of the current collector layer opposite to the photothermal material layer.

[0025] In this invention, the photothermal material layer includes one or more of the following: nano-alumina, nano-gold, nano-titanium dioxide, activated carbon, carbon black, graphene, and carbon nanotubes; the nano-alumina has a particle size of 10-100 nm, the nano-gold has a particle size of 10-60 nm, and the nano-titanium dioxide has a particle size of 10-30 nm.

[0026] In this invention, the hydrophobic binder in the photothermal material layer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, and polydimethylsiloxane.

[0027] In this invention, a photothermal material layer is formed by dispersing a photothermal material and a hydrophobic binder in a solvent and then loading them onto one side of a current collector layer; the solvent includes water, ethanol, or N-methylpyrrolidone.

[0028] In this invention, the current collector layer is made of carbon cloth or carbon paper. With its hydrophilicity and breathability, it ensures that the electrode is fully wetted on the one hand, and that the water vapor generated by the reaction can be smoothly discharged on the other hand.

[0029] In this invention, lithium-ion selective electrode active material refers to a material that can specifically and selectively undergo insertion and extraction reactions with lithium ions during the electrochemical lithium extraction process.

[0030] In this invention, the lithium-ion selective electrode active material in the electrode material layer includes lithium iron phosphate, lithium manganese oxide, or lithium nickel cobalt manganese oxide; the conductive agent includes one or more of acetylene black, Ketjen black, Super P carbon black, carbon nanotubes, and graphene; and the binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, polyaniline, and polypyrrole.

[0031] In this invention, an electrode material layer is formed by dispersing lithium-ion selective electrode active material, conductive agent and binder in a solvent, and then loading them onto the opposite side of the current collector layer opposite to the photothermal material layer; the solvent includes water or N-methylpyrrolidone.

[0032] In this invention, the auxiliary electrode is a silver electrode, an activated carbon electrode, a nickel hexacyanoferrite electrode, or a chlorine-doped polyaniline electrode.

[0033] In this invention, the composite lithium extraction electrode is fixed to the inner wall of the intermediate chamber by a support member. The electrode forms a solid-liquid-gas three-phase interface: its outer side (in contact with the atmosphere) is the gas phase side composed of a hydrophobic photothermal material layer; and its inner side (in contact with the solution) is the liquid phase side composed of a hydrophilic current collector layer and an electrode material layer.

[0034] This structure utilizes the barrier effect of the hydrophobic side to achieve separation of the liquid and gas phases, allowing only water molecules to escape in gaseous form under photothermal action, while preventing liquid water leakage. Simultaneously, by tilting the device to create an angle between one side of the composite lithium extraction electrode and the horizontal plane, it ensures stable and sufficient contact with the liquid surface, effectively preventing water level drops due to evaporation or residual bubbles during the reaction, thereby maintaining the stability of the electrode interface and ensuring the continuous progress of the reaction.

[0035] A schematic diagram of the electrochemical lithium extraction device based on interfacial evaporation in this invention is shown below. Figure 1 As shown; Figure 1 In the diagram, 1 is a pipe, 2 is an auxiliary electrode, 3 is a wire, 4 is a power source, 5 is a drain hole, 6 is sunlight, 7 is water vapor, 8 is a photothermal material layer, 9 is a current collector layer, 10 is an electrode material layer, 11 is lithium ions, 12 is a lithium salt solution, 13 is a water inlet, and 14 is a water pump.

[0036] This invention also provides an electrochemical lithium extraction method based on interfacial evaporation, using the aforementioned apparatus, comprising the following steps: Under illumination, lithium-containing raw material liquid is introduced into the intermediate chamber through the solution flow circuit, and the power supply circuit is activated to enter the discharge mode, so that lithium ions are embedded in the electrode material layer. Under conditions of no light, the receiving liquid is introduced into the intermediate chamber through the solution flow circuit, and the power supply circuit is activated to enter the charging mode, so that lithium ions are extracted from the electrode material layer and enriched in the receiving liquid.

[0037] In this invention, the device is placed under sunlight, and a lithium-containing raw material solution (lithium salt solution) is pumped into the intermediate chamber. Under illumination, the power supply circuit is activated to enter discharge mode, and lithium ions begin to embed into the electrode material layer. The core of this process lies in the interfacial evaporation (SE) effect generated by the photothermal material layer on the surface of the composite lithium extraction electrode under solar energy, which rapidly vaporizes the water adsorbed in the current collector layer. This effect increases the lithium ion concentration at the electrode interface, enhancing ion diffusion performance and thus reducing concentration polarization. Furthermore, the photothermal effect raises the local temperature of the electrode, improving electrochemical performance at low temperatures. Simultaneously, in the lower electrode material layer, the electrochemical ion pump (EIP) effect works synergistically to achieve highly efficient and specific capture of lithium ions.

[0038] In this invention, before introducing the receiving liquid into the intermediate chamber, a step of rinsing the intermediate chamber by introducing water (deionized water) is also included.

[0039] In this invention, lithium desorption and enrichment are performed under light-free conditions (such as night): First, water (deionized water) is introduced into the intermediate chamber to clean the electrodes and the chamber, removing residual lithium-containing salt solution. Then, a specific lithium-ion recovery solution (i.e., the receiving liquid) is introduced, and the power supply circuit is activated to enter charging mode. Under these conditions, the electrode active material is charged, and the previously embedded lithium ions are desorbed through an electrochemical ion pump (EIP) mechanism and released into the recovery solution, thereby achieving lithium enrichment. The following day, the device is placed under sunlight again, and a new lithium-containing feedstock solution (lithium-containing salt solution) is introduced into the intermediate chamber, starting a new lithium extraction cycle. By repeating this cycle of "adsorption under light - desorption under darkness," lithium ions in the lithium-containing salt solution can be continuously transferred and concentrated into the recovery solution.

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0041] In the following embodiments and comparative examples of the present invention, the upper end plate and the lower end plate are FR-4 insulation boards produced by Hangzhou Liansheng Insulation Materials Co., Ltd.; the carbon cloth is W0S1011 carbon cloth produced by Taiwan Carbon Energy Technology Co., Ltd.; and the carbon paper is Toray TGP-H-060 carbon paper produced by Toray Industries, Inc. of Japan.

[0042] Example 1 This embodiment provides an electrochemical lithium extraction device based on interfacial evaporation, including an upper end plate with a light-transmitting hole, an intermediate chamber, and a lower end plate; the intermediate chamber has a composite lithium extraction electrode as its top cover, and an auxiliary electrode (with a mass of 50 mg and a surface area of ​​9 cm²) is provided at the bottom of the intermediate chamber. 2 (Silver electrode). The side wall of the intermediate chamber is provided with a water inlet and a water outlet, which are connected to the water pump through pipes to form a solution flow circuit; the auxiliary electrode is connected to the power supply and the current collector layer in sequence through wires to form a power supply circuit.

[0043] The composite lithium extraction electrode comprises, from top to bottom, a photothermal material layer, a current collector layer, and an electrode material layer: 45 mg of carbon black, 0.45 mL of a 60% (w / w) polytetrafluoroethylene aqueous solution, and 0.15 mL of water are mixed and coated entirely to a surface area of ​​9 cm². 2 Current collector layer (carbon cloth, 0.36 mm thick, with an areal density of 130 g / m³) 2 On the surface of the carbon cloth, a photothermal material layer is formed; then, 90 mg of lithium manganese oxide, 11.25 mg of Super P carbon black, 11.25 mg of polyvinylidene fluoride and 0.45 mL of N-methylpyrrolidone are mixed and applied to the other side of the carbon cloth to form an electrode material layer.

[0044] The composite lithium extraction electrode is fixed to the inner wall of the intermediate chamber by a support member, and its side facing the solution forms a 90° angle with the horizontal plane.

[0045] This embodiment also provides an electrochemical lithium extraction method based on interfacial evaporation, using the above-mentioned apparatus, including the following steps: The device was placed under a xenon lamp light source with an illumination intensity of 3000 W / m². 2Under these conditions, a lithium-containing raw material solution (lithium salt solution) is pumped into the intermediate chamber at a flow rate of 9 mL / min through a solution flow circuit. The lithium salt solution contains 0.15 mmol / L of lithium chloride and 3000 mmol / L of sodium chloride. Subsequently, the power supply circuit is activated to enter the discharge mode and discharges at a constant current of 1.25 mA / g. The cutoff potential is set to 0.4 V vs. Ag / AgCl, which allows lithium ions to be embedded in the electrode material layer.

[0046] After stopping the illumination, deionized water was introduced into the intermediate chamber for rinsing to remove residual lithium salt solution. Subsequently, a 30 mmol / L LiCl aqueous solution was introduced as the receiving solution at a flow rate of 9 mL / min, and the power supply circuit was activated to apply a 1 mA reverse current for constant current charging. Under these conditions, lithium ions were desorbed and released into the receiving solution, achieving lithium enrichment.

[0047] Example 2 This embodiment provides an electrochemical lithium extraction device based on interfacial evaporation, which differs from Embodiment 1 in that carbon black is replaced with nano-titanium dioxide and lithium manganese oxide is replaced with lithium iron phosphate.

[0048] This embodiment also provides an electrochemical lithium extraction method based on interfacial evaporation, which is the same as in Example 1.

[0049] Example 3 This embodiment provides an electrochemical lithium extraction device based on interfacial evaporation, which differs from Embodiment 1 in that: activated carbon is replaced with carbon black, and carbon cloth is replaced with a material with a surface area of ​​9 cm². 2 The carbon paper (0.19 mm thick, 0.44 g / cm³) 3 ).

[0050] This embodiment also provides an electrochemical lithium extraction method based on interfacial evaporation, which is the same as in Example 1.

[0051] Example 4 This embodiment provides an electrochemical lithium extraction device based on interfacial evaporation, which differs from Embodiment 1 in that carbon black is replaced with graphene and the auxiliary electrode is replaced with a nickel hexacyanoferrite electrode.

[0052] The preparation method of the nickel hexacyanoferrite electrode includes the following steps: 5 mmol of potassium ferricyanide was dissolved in 50 mL of deionized water to obtain solution A; 5 mmol of nickel nitrate and 5 mmol of citric acid were dissolved in 50 mL of deionized water to obtain solution B; then solutions A and B were simultaneously and slowly added dropwise to 50 mL of deionized water at a flow rate of 1 mL / min, and allowed to stand for 24 h to allow precipitation to complete; finally, the precipitate was centrifuged, washed, and dried under vacuum at 60 °C to obtain potassium nickel hexacyanoferrate.

[0053] 108 mg of potassium nickel hexacyanoferrate, 13.5 mg of Super P carbon black, 13.5 mg of polyvinylidene fluoride, and 0.54 mL of N-methylpyrrolidone were mixed and applied to a surface with a 9 cm² area. 2 Potassium nickel hexacyanoferrite electrode is fabricated by drying the carbon cloth under vacuum at 60°C.

[0054] This embodiment also provides an electrochemical lithium extraction method based on interfacial evaporation, which is the same as in Example 1.

[0055] Comparative Example 1 This comparative example provides an electrochemical lithium extraction device based on interfacial evaporation, which is the same as that in Example 1.

[0056] This comparative example also provides an electrochemical lithium extraction method based on interfacial evaporation, which differs from Example 1 in that the illumination conditions are adjusted to be without light.

[0057] Experimental Example 1 The constant current discharge curves corresponding to Example 1 and Comparative Example 1 are as follows: Figure 2 As shown in the figure, the discharge capacity reached 5.24 mAh / g under illumination, significantly higher than 1.44 mAh / g under no-illumination conditions, representing an increase of 263.89%. This result indicates that the photothermal interface evaporation effect significantly enhances the lithium-ion intercalation capability, effectively improving the electrochemical lithium extraction performance.

[0058] Experiment Example 2 To investigate the effect of photothermal effect on the electrochemical lithium intercalation reaction of the electrode, cyclic voltammetry was performed on the electrochemical lithium extraction device in Example 1. The specific steps are as follows: The device was placed under a xenon lamp light source with an illumination intensity of 1000 W / m². 2Under the specified conditions, a lithium-containing feed solution (lithium salt solution) was pumped into the intermediate chamber at a flow rate of 9 mL / min through a solution flow loop. The lithium salt solution contained 0.25 mmol / L lithium chloride and 100 mmol / L potassium chloride, with a silver / silver chloride electrode as a reference. Subsequently, a Chenhua CHI660D electrochemical workstation was connected, and cyclic voltammetry was initiated within the range of 0.3–1.1 V (vs. Ag / AgCl) at a scan rate of 0.1 mV / s. The test first performed a cathode scan, scanning from 1.1 V (vs. Ag / AgCl) to 0.3 V (vs. Ag / AgCl) at a scan rate of 0.1 mV / s. During this stage, the electrode was in the reduction phase, with lithium ions intercalating into the electrode material layer. When the potential scan reached 0.3 V (vs. Ag / AgCl), illumination was stopped, and an anodic scan began, scanning from 0.3 V to 1.1 V (scan rate of 0.1 mV / s). At this point, the electrode is in the oxidation stage, and lithium ions are released from the electrode material.

[0059] Under the same conditions, the above tests were repeated, but without any light exposure, to compare the effect of light exposure on the electrode reaction. This yielded the cyclic voltammetry curves of the electrochemical lithium extraction device in Example 1 at a lithium chloride concentration of 0.25 mmol / L, as shown below. Figure 3 As shown. Figure 3 The two upper lines correspond to the oxidation stage, and the two lower lines correspond to the reduction stage. From Figure 3 As can be seen, the peak current of the oxidation peak under illumination was 13.83 mA / g, which was 136.41% higher than that under no illumination (5.85 mA / g). Although the reduction peak was not significant due to the low ion concentration, the significant enhancement of the oxidation peak fully demonstrates that the photothermal effect promoted the electrode reaction kinetics and improved the lithium ion capture and release efficiency.

[0060] The concentration of lithium chloride in the lithium salt solution was further adjusted to 10 mmol / L, and the above test was repeated to obtain the cyclic voltammetry curve of the electrochemical lithium extraction device in Example 1 under the condition of a lithium chloride concentration of 10 mmol / L, as shown below. Figure 4 As shown. Figure 4The two upper lines correspond to the oxidation stage, and the two lower lines correspond to the reduction stage. Two oxidation peaks (oxidation peak 1 and oxidation peak 2) can be identified from left to right. Under no-light conditions, the peak currents of reduction peak 1 and reduction peak 2 are 29.41 mA / g and 28.21 mA / g, respectively, while the peak currents of oxidation peak 1 and oxidation peak 2 are 37.43 mA / g and 112.11 mA / g, respectively. Under light conditions, the peak currents of reduction peak 1 and reduction peak 2 increase to 46.78 mA / g and 45.54 mA / g, respectively, while the peak currents of oxidation peak 1 and oxidation peak 2 increase to 56.86 mA / g and 119.19 mA / g, respectively. The general enhancement of peak currents under light further confirms the promoting effect of the photothermal effect on the electrode reaction kinetics.

[0061] Experimental Example 3 To investigate the effect of photothermal effect on the local lithium-ion concentration at the electrode interface, this experimental example monitored the open-circuit potential of the electrochemical lithium extraction device in Example 1. In the experiment, the lithium salt solution was replaced with a single-component LiCl aqueous solution at a concentration of 0.25 mmol / L, with a silver / silver chloride electrode used as a reference. Before the experiment, the electrode was charged and discharged to 50% SOC to ensure it was in ideal initial conditions of thermodynamic stability, minimal polarization, and no phase transition. Subsequently, under continuous flow of LiCl aqueous solution, open-circuit potential tests were performed in three alternating stages: Stage 1 (darkness): Without illumination, the open-circuit potential of the working electrode was continuously monitored for 8 hours in darkness to obtain a stable potential baseline before illumination; Stage 2 (illumination): A xenon lamp source was turned on, with an intensity of 1000 W / m². 2 Under illumination conditions, monitoring continued for 24 hours, recording the potential changes caused by illumination. In the third stage (returning to darkness), the light source was turned off, returning to darkness conditions, and monitoring continued for 40 hours to examine the potential recovery behavior after illumination was stopped. Throughout the process, an infrared thermal imager was used to measure the electrode surface temperature in real time, and the Nernst equation was used to quantitatively analyze the interfacial lithium ion concentration. The open-circuit potential change curves of the electrochemical lithium extraction device in Example 1 under alternating "no illumination - illumination applied - no illumination" conditions are shown below. Figure 5 As shown. The results show that after illumination, the open-circuit potential increased by 22.5 mV, according to the Nernst equation. Based on the measured potential and temperature data (dark conditions: 29.2℃, potential 0.5925V; illuminated conditions: 38℃, potential 0.615V), the lithium-ion concentration at the electrode interface was calculated to have increased from 0.25 mmol / L in the dark to 0.73 mmol / L, an increase of 192.0%. This result directly confirms that photothermal evaporation can effectively increase the local lithium-ion concentration near the electrode interface, significantly alleviate concentration polarization, and thus create a more favorable reaction environment for the electrochemical lithium extraction process.

[0062] Based on the above experimental results, it can be seen that the present invention significantly improves the extraction efficiency and reaction rate of lithium ions from low lithium sources through the synergistic effect of photothermal interface evaporation and electrochemical ion pump, and has good application prospects.

[0063] Therefore, the present invention employs the above-mentioned electrochemical lithium extraction device and method based on interfacial evaporation. By organically integrating photothermal interfacial evaporation with an electrochemical ion pump, it effectively solves the problems of concentration polarization and reaction kinetics limitation in the lithium extraction process from low lithium sources, significantly improves the lithium ion extraction efficiency and system performance, and provides a new technical approach for the large-scale development and utilization of low-grade lithium resources.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An electrochemical lithium extraction device based on interfacial evaporation, characterized in that, Includes an upper end plate, a middle chamber, and a lower end plate; The upper plate is provided with a light-transmitting hole; the middle chamber is covered by a composite lithium extraction electrode, and an auxiliary electrode is provided at the bottom of the middle chamber; the composite lithium extraction electrode includes a photothermal material layer, a current collector layer and an electrode material layer arranged sequentially from top to bottom, forming a solid-liquid-gas three-phase interface; the electrode material layer is loaded with lithium-ion selective electrode active material; the composite lithium extraction electrode achieves local concentration through photothermal evaporation; The side wall of the intermediate chamber is provided with a water inlet and a water outlet. The water inlet and the water outlet are connected to the water pump through pipes to form a solution flow circuit. The auxiliary electrode is connected to the power supply and the current collector layer in sequence through wires to form a power supply circuit. The photothermal material layer includes a photothermal material and a hydrophobic binder, and the photothermal material layer is disposed on one side of the current collector layer; the electrode material layer includes a lithium-ion selective electrode active material, a conductive agent and a binder, and the electrode material layer is disposed on the other side of the current collector layer opposite to the photothermal material layer. Photothermal materials include one or more of the following: nano-alumina, nano-gold, nano-titanium dioxide, activated carbon, carbon black, graphene, and carbon nanotubes. The current collector layer is made of carbon cloth or carbon paper.

2. The electrochemical lithium extraction device based on interfacial evaporation according to claim 1, characterized in that, The device is used to treat salt lake brine or seawater with a lithium ion concentration of less than 100 mg / L.

3. The electrochemical lithium extraction device based on interfacial evaporation according to claim 1, characterized in that, Lithium-ion selective electrode active materials include lithium iron phosphate, lithium manganese oxide, or lithium nickel cobalt manganese oxide.

4. The electrochemical lithium extraction device based on interfacial evaporation according to claim 1, characterized in that, The auxiliary electrode is a silver electrode, an activated carbon electrode, a nickel hexacyanoferrate electrode, or a chlorine-doped polyaniline electrode.

5. The electrochemical lithium extraction device based on interfacial evaporation according to claim 1, characterized in that, The composite lithium extraction electrode is fixed to the inner wall of the intermediate chamber by a support member.

6. An electrochemical lithium extraction method based on interfacial evaporation, characterized in that, The apparatus according to any one of claims 1-5 comprises the following steps: Under illumination, lithium-containing raw material liquid is introduced into the intermediate chamber through the solution flow circuit, and the power supply circuit is activated to enter the discharge mode, so that lithium ions are embedded in the electrode material layer. Under conditions of no light, the receiving liquid is introduced into the intermediate chamber through the solution flow circuit, and the power supply circuit is activated to enter the charging mode, so that lithium ions are extracted from the electrode material layer and enriched in the receiving liquid.

7. The electrochemical lithium extraction method based on interfacial evaporation according to claim 6, characterized in that, Before introducing the receiving liquid into the intermediate chamber, a step of rinsing the intermediate chamber by introducing water is also included.

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