Electrochemical lithium extraction electrode, electrochemical lithium extraction device and lithium extraction method

Abstract

Provided in the present disclosure are an electrochemical lithium extraction electrode, an electrochemical lithium extraction device and a lithium extraction method. The electrochemical lithium extraction electrode comprises a cathode flow electrode and an anode flow electrode. The cathode flow electrode comprises a cathode active material, and the anode flow electrode comprises an anode active material, wherein the initial lithium content of each of the cathode active material and the anode active material is 20-80% of a theoretical lithium content of the active material. The present disclosure greatly increases the surface utilization rate of active materials, avoids the problems of detachment of active materials, etc., and is free of the problem of concentration polarization caused by traditional electrodes. Moreover, the electrochemical lithium extraction electrode greatly improves the lithium extraction capacity, eliminates the need to swap the cathode / anode of an electrolytic cell for reverse charging, and only needs replenishment or replacement of electrode materials, thus achieving simplicity and high efficiency; a continuous electrochemical lithium extraction process can be achieved at high voltage and high current density, thereby improving production efficiency.

Description

Electrochemical lithium extraction electrode, electrochemical lithium extraction device and lithium extraction method Technical Field

[0001] The present disclosure belongs to the technical field of lithium extraction, and relates to an electrochemical lithium extraction electrode, an electrochemical lithium extraction device, and a lithium extraction method. Background Art

[0002] Currently, the preparation of lithium-extraction electrodes typically involves coating an electrode active material onto a conductive substrate, assembling the electrode sheet in a diaphragm electrolytic cell, and performing repeated lithium removal and insertion at the anode and cathode. However, this process is complex, requires swapping the anode and cathode of the electrolytic cell for reverse charging, and is only suitable for operation at low voltages and low current densities, resulting in low production efficiency.

[0003] Therefore, it is urgent to develop a new lithium extraction electrode to solve the problems brought about by the above-mentioned traditional electrodes.

[0004] Summary of the Invention

[0005] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0006] In view of the shortcomings of the prior art, the purpose of the present disclosure is to provide an electrochemical lithium extraction electrode, an electrochemical lithium extraction device and a lithium extraction method. The present disclosure adopts a cathode active material and an anode active material containing the same lithium content as the initial active material, wherein the initial cathode active material is reduced by the cathode, and its lithium content is increased by combining / adsorbing with the lithium ions in the lithium-rich raw material, and at the same time, the initial anode active material is anodic oxidized to release lithium ions, thereby increasing the lithium ion concentration in the lithium-rich raw material. It can be seen that the present disclosure greatly increases the surface utilization rate of the active material, while avoiding problems such as the shedding of the active material, and does not need to face the concentration polarization problem brought by the traditional electrode. In addition, the electrochemical lithium extraction electrode greatly increases the lithium extraction capacity, does not need to replace the cathode / anode of the electrolytic cell for reverse charging, only needs to add or replace the electrode material, is simple and efficient, and can realize a continuous electrochemical lithium extraction process at high voltage and high current density, thereby improving production efficiency.

[0007] To achieve this goal, the present disclosure adopts the following technical solutions:

[0008] In a first aspect, the present disclosure provides an electrochemical lithium extraction electrode, wherein the electrochemical lithium extraction electrode comprises a cathode flow electrode and an anode flow electrode;

[0009] The cathode flow electrode comprises a cathode active material, and the anode flow electrode comprises an anode active material. The initial lithium content of the cathode active material and the anode active material is 20-80% of the theoretical lithium content of the active material.

[0010] The present disclosure adopts cathode active materials and anode active materials containing the same lithium content as initial active materials, wherein the initial cathode active material is reduced by the cathode, and its lithium content is increased by combining / adsorbing with lithium ions in the lithium-rich raw material, while the initial anode active material is oxidized by the anode to release lithium ions, thereby increasing the lithium ion concentration in the lithium-rich raw material. It can be seen that the present disclosure greatly increases the surface utilization rate of the active material, while avoiding problems such as the shedding of the active material, and does not need to face the concentration polarization problem brought by the traditional electrode. In addition, the electrochemical lithium extraction electrode greatly increases the lithium extraction capacity, and does not need to replace the cathode / anode of the electrolytic cell for reverse charging. It only needs to add or replace the electrode material. It is simple and efficient, and can realize a continuous electrochemical lithium extraction process at high voltage and high current density, thereby improving production efficiency.

[0011] In the present disclosure, cathode flowing electrodes and anode flowing electrodes are used, so there is no need to coat the active material onto the current collector, and the cathode active material can fully contact / react with the lithium-rich raw material (such as lithium-containing salt lake brine), which greatly increases the surface utilization rate of the active material. At the same time, it can avoid problems such as active material shedding, and there is no need to face the concentration polarization problem brought by traditional electrodes.

[0012] In the present disclosure, when the cathode mobile electrode and the anode mobile electrode are used for electrochemical lithium extraction, the current collector does not participate in the electrochemical reaction and only plays a conductive role, which can basically achieve zero loss and extend the life of the current collector and the equipment; and, only the ion exchange membrane needs to be replaced regularly, and the equipment maintenance cost is low.

[0013] In the present disclosure, the initial lithium content of the cathode active material and the anode active material is 20-80% of the theoretical lithium content of the active material, for example, 20%, 30%, 40%, 50%, 60%, 70% or 80%.

[0014] In the present disclosure, if the lithium content of the (initial) cathode active material and anode active material is too low, i.e., less than 20%, then the amount of lithium ions released when the initial anode active material is anodized is small (the lithium content drops from 20% to 0%). Since the anode / cathode active materials are simultaneously electrolytically oxidized and reduced during electrolysis, and the amount of electrons lost and gained is the same, correspondingly, the amount of lithium ions obtained by the cathode active material from the lithium-containing solution is also small (the lithium content rises from 20% to 40%). In the first cycle, the lithium extraction amount is only 20% of the theoretical lithium extraction amount. In subsequent cycle loops, the lithium content of the active material varies between 0% and 40%, and the material utilization rate is only 40%, resulting in low battery efficiency. If the lithium content of the (initial) cathode active material and anode active material is too high, i.e., greater than 80%, then the increase in the lithium content when the initial cathode active material is cathodically reduced is limited (the lithium content of the cathode active material rises from 80% to 100%, while the lithium content of the anode active material drops from 80% to 60%. In the first cycle, the lithium extraction amount is only 20% of the theoretical lithium extraction amount. In subsequent cycle loops, the lithium content in the active material varies between 60% and 100%, and the utilization rate of the material is only 40%). The battery efficiency is low.

[0015] It should be noted that the theoretical lithium content of the active material refers to the ratio of the atomic weight of lithium to the molecular weight of the active material when 1 mol of the active material contains 1 mol of lithium ions. The same applies hereinafter.

[0016] In one embodiment, the initial lithium contents of the cathode active material and the anode active material are both 50% of the theoretical lithium content of the active material.

[0017] It should be noted that when performing electrochemical lithium extraction using the electrochemical lithium extraction electrode provided by the present disclosure, the lithium content of the cathode active material can rise from 50% to 100%, and the anode active material can drop from 50% to 0. The two reach equilibrium, and the lithium extraction amount is the largest at this time.

[0018] In one embodiment, the cathode active material includes at least one of Li x M 1-z Fe z PO4, Li x Mn2O4, and Li x MO2, where 0 ≤ x < 1, 0 < z ≤ 1, M includes at least one of Ni, Co, Mn, Ti, and Al. The x can be, for example, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, etc., and the z can be, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1, etc.

[0019] In one embodiment, the cathode active material is Li xFePO4 or Li x Mn2O4, where 0 ≤ x < 1.

[0020] In the present disclosure, any one of the above cathode active materials can be selected to achieve electrochemical lithium extraction. Among them, the lithium iron phosphate system or the lithium manganate system is selected, and the raw material sources are more extensive and the cost is lower. For the impurity sodium, the lithium manganate system has a better selective lithium deintercalation effect.

[0021] In one embodiment, the anode active material includes Li y Y 1-m Fe m PO4, Li y Mn2O4 and Li y YO2, where 0 ≤ y < 1, 0 < m ≤ 1, Y includes at least one of Ni, Co, Mn, Ti and Al. The y can be, for example, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.9, etc. The m can be, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, etc.

[0022] In one embodiment, the anode active material is Li y FePO4 or Li y Mn2O4, where 0 ≤ y < 1.

[0023] In the present disclosure, any one of the above anode active materials can be selected to achieve electrochemical lithium extraction. Among them, the lithium iron phosphate system or the lithium manganate system is selected, and the raw material sources are more extensive and the cost is lower. For the impurity sodium, the lithium manganate system has a better selective lithium deintercalation effect.

[0024] In one embodiment, the cathode active material and the anode active material have the same chemical formula.

[0025] In the present disclosure, the cathode active material and the anode active material are the initial active materials for electrochemical lithium extraction. When the cathode active material and the anode active material have the same chemical formula, their constituent elements (such as lithium) and contents are the same, which can simplify the raw material preparation and the raw materials can be formulated according to the same active substance type and content.

[0026] In one embodiment, the cathode flow electrode further includes a lithium-containing salt lake brine and an additive A.

[0027] In the present disclosure, the cathode flow electrode further includes a lithium-containing salt lake brine and an additive A. Among them, the lithium-containing salt lake brine is the raw material for lithium extraction; the introduction of the additive A is to reduce the electrolysis voltage and increase the current density, so as to reduce the energy consumption and improve the production efficiency of the equipment.

[0028] In one embodiment, the lithium ion content of the lithium-containing salt lake brine is greater than 0.1 g / L, for example, it can be 0.15 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.55 g / L, 0.6 g / L, 0.65 g / L, 0.7 g / L, 0.75 g / L, 0.8 g / L, 0.85 g / L or 0.9 g / L. In addition to lithium ions, the lithium-containing salt lake brine also includes chloride ions, sulfate ions, sodium ions, potassium ions, calcium ions, magnesium ions, boron ions and water.

[0029] In one embodiment, the additive A includes a conductive agent and / or a wetting and defoaming agent, and may be a combination of a conductive agent and a wetting and defoaming agent.

[0030] In this disclosure, a combination of a conductive agent and a wetting and defoaming agent is used as Additive A. The conductive agent improves the electronic conductivity of the flowing electrode, ensuring electrode fluidity. The wetting and defoaming agent, while maintaining the conductivity of the flowing electrode, eliminates foam on the slurry surface and improves slurry fluidity. The synergistic combination of the conductive agent and the wetting and defoaming agent effectively reduces the electrolysis voltage, increases the current density, and achieves the effects of reducing energy consumption and improving equipment production efficiency.

[0031] In one embodiment, the conductive agent in the additive A includes conductive carbon black and / or graphite powder, preferably a combination of conductive carbon black and graphite powder.

[0032] In the present disclosure, the conductive agent in additive A is preferably a combination of conductive carbon black and graphite powder. While ensuring the conductivity of the mobile electrode, adding a certain amount of graphite powder can significantly reduce the amount of conductive carbon black used.

[0033] The present disclosure does not specifically limit the type of the wetting and defoaming agent in additive A, as long as it can play a defoaming role. For example, it can be Chemours FS-1.

[0034] In one embodiment, based on the mass of the lithium-containing salt lake brine being 100%, the content of the cathode active material is 1%-7.5%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7% or 7.5%.

[0035] In the present disclosure, when the cathode active material content is preferably within the above range, it can ensure that the active material is excessive relative to the lithium ions, reducing the insertion of sodium ions. In practical applications, the appropriate active material content should be selected based on the lithium ion concentration in the lithium-containing salt lake brine.

[0036] In one embodiment, based on the mass of the lithium-containing salt lake brine being 100%, the content of the conductive carbon black in the additive A is 1%-2.5%, for example, 1%, 1.5%, 2% or 2.5%.

[0037] In the present disclosure, when the content of conductive carbon black in additive A can be selected to be within the above range, it can ensure that the mobile electrode has sufficient electronic conductivity, reduce the working voltage of lithium extraction, and ensure the fluidity of the electrode.

[0038] In one embodiment, based on the mass of the lithium-containing salt lake brine as 100%, the content of graphite powder in additive A is 0-15%, excluding 0, for example, it can be 1%, 2%, 5%, 8%, 10%, 12% or 15%, etc.

[0039] In the present disclosure, when the content of graphite powder in additive A is within the above range, the amount of conductive carbon black can be significantly reduced without affecting the flow electrode.

[0040] In one embodiment, in the additive A, the mass ratio of the conductive agent to the wetting and defoaming agent is 100:(0-5), excluding 0, and the selection range of the wetting and defoaming agent (0-5) can be, for example, 1, 2, 3, 4 or 5.

[0041] In the present disclosure, when the content of the wetting defoaming agent in additive A is within the above-mentioned range, it can eliminate the foam on the surface of the flowing electrode while ensuring the conductivity of the flowing electrode, thereby improving the fluidity of the flowing electrode. At the same time, it cooperates with the conductive agent to effectively reduce the electrolysis voltage and increase the current density, thereby achieving the effect of reducing energy consumption and improving equipment production efficiency.

[0042] In one embodiment, the anode flow electrode further includes a dilute lithium solution and an additive B.

[0043] In the present disclosure, the anode flow electrode also includes a dilute lithium solution and an additive B, wherein the dilute lithium solution can provide liquid for the anode flow electrode to form a flow state; the additive B is introduced to reduce the electrolysis voltage and increase the current density, thereby achieving the effect of reducing energy consumption and improving equipment production efficiency.

[0044] In one embodiment, the lithium ion content of the dilute lithium solution is 0-5 g / L, for example, 0 g / L, 0.5 g / L, 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L or 4.5 g / L, etc., wherein 0 g / L means that the dilute lithium solution does not contain lithium ions (such as water).

[0045] Illustratively, the dilute lithium solution can be water or an aqueous solution containing LiCl. When electrochemical lithium extraction is carried out continuously, it can also be washing water of the anode active material after electrolysis. The use of washing water can achieve water balance and lithium recovery.

[0046] In this disclosure, a dilute lithium solution with a lithium ion content greater than 0 g / L is preferred over water due to its improved conductivity and lower electrolysis voltage. When the lithium ion concentration exceeds 5 g / L, the solution can be used as a product solution and discharged from the system. Therefore, the lithium ion content of the dilute lithium solution does not exceed 5 g / L.

[0047] In the present disclosure, when electrochemical lithium extraction is performed using a cathode flow electrode and an anode flow electrode, the anode active material is oxidized and releases lithium ions, and the released lithium ions increase the lithium ion concentration in the dilute lithium solution.

[0048] In one embodiment, the additive B includes a conductive agent and / or a wetting and defoaming agent, and may be a combination of a conductive agent and a wetting and defoaming agent.

[0049] In this disclosure, a combination of a conductive agent and a wetting and defoaming agent is used as Additive B. The conductive agent improves the electronic conductivity of the flowing electrode, ensuring electrode fluidity. The wetting and defoaming agent, while maintaining the conductivity of the flowing electrode, eliminates foam on the slurry surface and improves slurry fluidity. The synergistic combination of the conductive agent and the wetting and defoaming agent effectively reduces the electrolysis voltage, increases the current density, and achieves the effects of reducing energy consumption and improving equipment production efficiency.

[0050] In one embodiment, the conductive agent in the additive B includes conductive carbon black and / or graphite powder, and can be a combination of conductive carbon black and graphite powder.

[0051] In the present disclosure, the conductive agent in the additive B can be a combination of conductive carbon black and graphite powder. While ensuring the conductivity of the mobile electrode, the addition of graphite powder significantly reduces the amount of conductive carbon black.

[0052] The present disclosure does not specifically limit the type of the wetting and defoaming agent in the additive B, as long as it can play a defoaming role. For example, it can be Heshi HOS425, Chemours FS-1 or Digo 810.

[0053] In one embodiment, the additive A and the additive B are identical.

[0054] In the present disclosure, when Additive A is identical to Additive B, raw material preparation is facilitated, and raw materials can be formulated according to the same substance types and contents, which is beneficial to industrial production. Furthermore, subsequent switching of the cathode / anode slurry cycles will make the additive contents of the cathode / anode tend to be the same, so there is no need to set them differently.

[0055] In one embodiment, the anode flow electrode further comprises a catalyst and / or an electrolyte.

[0056] In the present disclosure, in the anode flow electrode, the catalyst can reduce the proportion of anode oxygen evolution at a high electrolysis voltage, improve current efficiency and protect the anode current collector; the electrolyte can improve the conductivity of the electrode.

[0057] In one embodiment, the catalyst comprises Cl - and / or Mn 2+ For example, it may be manganese chloride or manganese sulfate.

[0058] In the present disclosure, the catalyst can participate in the anode reaction when the additive B is insufficient or absent, and the product then reacts with the anode active material to act as a medium for the anode reaction, thereby improving production efficiency. Moreover, under high electrolysis voltage conditions, the current efficiency can be improved and the amount of oxygen evolution at the anode can be reduced. At the same time, the action of the catalyst can protect the anode current collector (e.g., graphite).

[0059] In one embodiment, the electrolyte includes at least one of a neutral electrolyte, a weak alkaline electrolyte and a weak acidic electrolyte, and can be a weak acidic electrolyte.

[0060] Exemplarily, the neutral electrolyte includes NaCl and / or KCl, the weak alkaline electrolyte includes Na2SO4 and / or K2SO4, and the weak acidic electrolyte includes dilute sulfuric acid and / or dilute hydrochloric acid.

[0061] In the present disclosure, the electrolyte in the anode flow electrode may be selected as a weak acid electrolyte because of its better conductivity and stronger stability of Ca / Mg / B impurity ions in the solution.

[0062] In one embodiment, based on 100% by mass of the dilute lithium solution, the content of the anode active material is 1%-7.5%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7% or 7.5%.

[0063] In the present disclosure, when the content of the anode active material is within the above range, the capacitance of the anode flow electrode is greater, more lithium ions are released from the single electrode, and the fluidity of the slurry is also ensured.

[0064] In one embodiment, based on 100% by mass of the dilute lithium solution, the content of the conductive carbon black in the additive B is 1%-2.5%, for example, 1%, 1.5%, 2%, or 2.5%.

[0065] In the present disclosure, when the content of conductive carbon black in additive B is within the above range, the mobile electrode can be guaranteed to have sufficient electronic conductivity, the operating voltage of lithium extraction can be reduced, and the fluidity of the electrode can be guaranteed.

[0066] In one embodiment, based on the mass of the dilute lithium solution being 100%, the content of graphite powder in additive B is 0-15%, excluding 0, for example, 1%, 2%, 5%, 8%, 10%, 12% or 15%, etc.

[0067] In the present disclosure, when the content of graphite powder in additive B is within the above range, the amount of conductive carbon black can be significantly reduced without affecting the flow electrode.

[0068] In one embodiment, in the additive B, the mass ratio of the conductive agent to the wetting and defoaming agent is 100:(0-5), excluding 0, and the selection range of the wetting and defoaming agent (0-5) can be, for example, 1, 2, 3, 4 or 5.

[0069] In the present disclosure, when the content of the wetting and defoaming agent in additive B is within the above-mentioned range, it can eliminate the foam on the surface of the flowing electrode while ensuring the conductivity of the flowing electrode, thereby improving the fluidity of the flowing electrode. In combination with the conductive agent, it can effectively reduce the electrolysis voltage, increase the current density, and achieve the effect of reducing energy consumption and improving equipment production efficiency.

[0070] In one embodiment, based on the mass of the dilute lithium solution being 100%, the content of the catalyst is 0-1%, excluding 0, for example, 0.2%, 0.4%, 0.6%, 0.8% or 1%.

[0071] In the present disclosure, when the content of the catalyst is within the above range, the proportion of oxygen evolution at the anode can be reduced under high electrolysis voltage, thereby improving current efficiency and protecting the anode current collector.

[0072] In a second aspect, the present disclosure provides an electrochemical lithium extraction device, wherein the electrochemical lithium extraction device adopts the electrochemical lithium extraction electrode described in the first aspect;

[0073] The electrochemical lithium extraction device includes a cathode chamber, an ion exchange membrane and an anode chamber, wherein the cathode chamber and the anode chamber are isolated from each other by the ion exchange membrane; the cathode chamber and the anode chamber respectively contain a cathode flow electrode and an anode flow electrode.

[0074] In one embodiment, the ion exchange membrane comprises an anion exchange membrane.

[0075] In the present disclosure, an anion exchange membrane is used to isolate the cathode / anode solutions (brine / lithium-rich solution), while the anions in the brine move toward the lithium-rich solution in a directional manner, ensuring the normal progress of the electrolysis process.

[0076] In one embodiment, the electrochemical lithium extraction device further includes a cathode current collector and an anode current collector.

[0077] The present disclosure does not impose any specific restrictions on the material of the cathode current collector, as long as it is corrosion-resistant and conductive in brine.

[0078] In one embodiment, the anode current collector comprises at least one of a graphite plate, graphite felt, graphite paper, titanium-manganese alloy, a coated titanium mesh, and a coated titanium plate, and may be a graphite plate.

[0079] In a third aspect, the present disclosure provides a method for extracting lithium using the electrochemical lithium extraction device described in the second aspect, the method comprising: energizing the electrochemical lithium extraction device and performing electrolysis to complete the electrochemical lithium extraction.

[0080] In one embodiment, the electrolysis voltage of the electrochemical lithium extraction device is 0.1-3.5V, for example, it can be 0.1V, 0.15V, 0.2V, 0.25V, 0.3V, 0.35V, 0.4V, 0.45V, 0.5V, 0.7V, 0.9V, 1V, 1.2V, 1.5V, 2V, 2.5V, 3V or 3.5V, etc.

[0081] In the present disclosure, the electrolysis voltage range of the electrochemical lithium extraction device is relatively wide, and it can operate normally under the condition of 0.1-3.5V.

[0082] In one embodiment, the current density of the electrochemical lithium extraction device is 5-60A / m 2 , for example, it can be 5A / m 2 , 10A / m 2 , 20A / m 2 、30A / m 2 , 40A / m 2 , 50A / m 2 or 60A / m 2 wait.

[0083] In the present disclosure, the current density of the electrochemical lithium extraction device is relatively high, which can improve the production efficiency of the equipment. The current density specifically refers to the current density of the projected surface of the working surface of the cathode / anode current collector.

[0084] In one embodiment, the lithium content of the cathode active material after electrolysis in the cathode flow electrode is greater than the lithium content of the cathode active material before electrolysis, and the lithium content of the anode active material after electrolysis in the anode flow electrode is less than the lithium content of the anode active material before electrolysis. The lithium content of the cathode active material after electrolysis is 50-100%, for example, it can be 50%, 60%, 70%, 80%, 90% or 100%, etc., and the lithium content of the anode active material after electrolysis is 0-50%, for example, it can be 0%, 10%, 20%, 30%, 40% or 50%, etc.

[0085] In the present disclosure, the cathode active material after electrolysis can be used as a new anode active material, and the anode active material after electrolysis can be used as a new cathode active material. By repeating the process repeatedly, a continuous electrochemical lithium extraction process can be realized to improve production efficiency.

[0086] In the present disclosure, after the first electrolysis is carried out using an electrochemical lithium extraction device, the cathode product in the cathode chamber is subjected to solid-liquid separation to obtain a mixture containing lithium-rich active materials (i.e., the cathode active materials after one electrolysis) and lithium-poor water. The mixture containing the lithium-rich active materials also contains additives A, etc. The mixture containing the lithium-rich active materials is then washed with water to wash the salt substances attached to the surface into the lithium-poor water. The lithium-poor water can be returned to the salt lake, and the washed mixture containing the lithium-rich active materials can be transported to the anode chamber for further use. At the same time, after the first electrolysis, the mixture in the anode chamber is washed with water. The anode product is subjected to solid-liquid separation to obtain a mixture containing lithium-deficient active material (i.e., the anode active material after one electrolysis) and a lithium-rich solution (i.e., the prepared product). The mixture containing the lithium-deficient active material also contains additive B. The mixture containing the lithium-deficient active material is then washed with water to wash away the lithium ions attached to its surface to obtain washing water. The washing water can be mixed with the mixture containing the lithium-rich active material as a new anode flow electrode. The washed mixture containing the lithium-deficient active material can be mixed with new lithium-containing salt lake brine as a new cathode flow electrode and transported to the cathode chamber. Electrochemical lithium extraction can continue with the use of a new anode flow electrode and a new cathode flow electrode. According to the above scheme, continuous electrochemical lithium extraction can be achieved by only adding or replacing the cathode / anode materials.

[0087] In the above process, if the anode flow electrode contains a catalyst (Cl - and / or Mn 2+ ), then after the first electrolysis and solid-liquid separation, Cl - and / or Mn 2+ into the lithium-rich solution, while the mixture containing the lithium-deficient active material contains Cl - and / or Mn 2+ , after washing, enter the washing water.

[0088] The numerical range described in the present disclosure includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present disclosure no longer exhaustively lists the specific point values ​​included in the range.

[0089] Compared with the prior art, the present invention has the following beneficial effects:

[0090] (1) The present disclosure uses cathode active materials and anode active materials containing the same lithium content as initial active materials, wherein the initial cathode active material is reduced by the cathode, and its lithium content is increased by combining / adsorbing with lithium ions in the lithium-rich raw material, while the initial anode active material is oxidized by the anode to release lithium ions, thereby increasing the lithium ion concentration in the lithium-rich raw material. It can be seen that the present disclosure greatly increases the surface utilization rate of the active material, while avoiding problems such as active material shedding, and does not need to face the concentration polarization problem caused by traditional electrodes. In addition, the electrochemical lithium extraction electrode greatly increases the lithium extraction capacity, and does not require the replacement of the cathode / anode of the electrolytic cell for reverse charging. It only needs to add or replace the electrode material. It is simple and efficient, and can realize a continuous electrochemical lithium extraction process at high voltage and high current density, thereby improving production efficiency.

[0091] (2) In the present disclosure, cathode flow electrodes and anode flow electrodes are used, and there is no need to coat the active material onto the current collector. The cathode active material can fully contact / react with the lithium-rich raw material (such as lithium-containing salt lake brine), which greatly increases the surface utilization rate of the active material. At the same time, it can avoid problems such as active material shedding, and there is no need to face the concentration polarization problem brought by traditional electrodes.

[0092] (3) In the present disclosure, when the cathode mobile electrode and the anode mobile electrode are used for electrochemical lithium extraction, the current collector does not participate in the electrochemical reaction and only plays a conductive role, which can basically achieve zero loss and extend the life of the current collector and the equipment; and, only the ion exchange membrane needs to be replaced regularly, and the equipment maintenance cost is low.

[0093] (4) By using the cathode flow electrode and anode flow electrode disclosed in the present invention, electrochemical lithium extraction can be performed at high voltage (over 1.5V) and high current density. Even if chlorine (oxygen) evolution / hydrogen evolution reaction occurs on the current collector, continuous normal operation can be maintained, which can improve production efficiency.

[0094] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0095] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0096] FIG1 is a schematic structural diagram of a cathode chamber, an anion exchange membrane, and an anode chamber provided in one embodiment of the present disclosure;

[0097] FIG2 is a schematic structural diagram of an electrochemical lithium extraction device provided in one embodiment of the present disclosure;

[0098] Among them, 1-cathode chamber; 2-cathode current collector; 3-anode chamber; 4-anode current collector; 5-anion exchange membrane; 6-first solid-liquid separation equipment; 7-first mixing equipment; 8-first delivery pump; 9-second solid-liquid separation equipment; 10-second mixing equipment; 11-second delivery pump. DETAILED DESCRIPTION

[0099] It should be understood that in the description of the present disclosure, the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation on the present disclosure. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of such features.

[0100] It should be noted that, in the description of this disclosure, unless otherwise expressly specified or limited, the terms "disposed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this disclosure based on specific circumstances.

[0101] The technical solution of the present disclosure is further illustrated below through specific implementation methods.

[0102] In one embodiment, the present disclosure provides an electrochemical lithium extraction device, as shown in Figures 1 and 2, the electrochemical lithium extraction device includes a cathode chamber 1, an anion exchange membrane 5 and an anode chamber 3, and the cathode chamber 1 and the anode chamber 3 are isolated from each other by the anion exchange membrane 5;

[0103] The cathode chamber 1 contains a cathode flow electrode, and a cathode current collector 2 (i.e., a graphite plate) is disposed in the cathode chamber 1. One end of the cathode current collector 2 is exposed from the cathode chamber 1, and the portion of the cathode current collector 2 located in the cathode chamber 1 is immersed in the cathode flow electrode.

[0104] The cathode chamber 1 is externally connected to a circulation pipeline, one end of which is connected to the top of the cathode chamber 1, and the other end is connected to the bottom of the cathode chamber 1. The circulation pipeline is sequentially provided with a first solid-liquid separation device 6, a first mixing device 7 and a first delivery pump 8 along the direction from the top to the bottom of the cathode chamber 1;

[0105] The anode chamber 3 contains an anode flow electrode, and an anode current collector 4 (i.e., a graphite plate) is disposed in the anode chamber 3. One end of the anode current collector 4 is exposed from the anode chamber 3, and the portion of the anode current collector 4 located in the anode chamber 3 is immersed in the anode flow electrode.

[0106] The anode chamber 3 is externally connected to a circulation pipeline, one end of which is connected to the top of the anode chamber 3, and the other end is connected to the bottom of the anode chamber 3. The circulation pipeline is sequentially provided with a second solid-liquid separation device 9, a second mixing device 10 and a second delivery pump 11 along the direction from the top to the bottom of the anode chamber 3.

[0107] In another embodiment, the present disclosure provides a lithium extraction method using the above-mentioned electrochemical lithium extraction device, the lithium extraction method comprising:

[0108] The electrochemical lithium extraction device is powered on to carry out an electrolysis reaction, and the cathode product is outputted at the top of the cathode chamber to the first solid-liquid separation device. After solid-liquid separation, a mixture containing lithium-rich active material (cathode active material after electrolysis) and lithium-poor water are obtained. The mixture containing lithium-rich active material is washed with water, and salt substances attached to its surface are washed into the lithium-poor water, and the lithium-poor water is returned to the salt lake; the anode product is outputted at the top of the anode chamber to the second solid-liquid separation device. After solid-liquid separation, a mixture containing lithium-deficient active material (anode active material after electrolysis) and a lithium-rich solution are obtained. The lithium-rich solution is the obtained product. The mixture containing lithium-deficient active material is washed with water to obtain lithium-deficient active material washing water; the mixture containing lithium-deficient active material and lithium-containing salt lake brine are mixed in the first mixing device and fed into the cathode chamber through the first delivery pump. The mixture containing lithium-rich active material and the lithium-deficient active material washing water are mixed in the second mixing device, and fed into the anode chamber through the second delivery pump to continue the electrolysis reaction.

[0109] Example 1

[0110] This embodiment provides an electrochemical lithium extraction electrode, which includes a cathode flow electrode and an anode flow electrode;

[0111] The cathode flow electrode includes Li 0.5 FePO4, lithium-containing salt lake brine, conductive carbon black, graphite powder and wetting defoaming agent (Chemours FS-1), based on the mass of lithium-containing salt lake brine as 100%, Li 0.5The content of FePO4 is 5%, the content of conductive carbon black is 1.5%, the content of graphite powder is 0.3%, the mass of the wetting and defoaming agent accounts for 3% of the total mass of the conductive carbon black and graphite powder, and the lithium ion content of the lithium salt lake brine is 0.91g / L;

[0112] The anode flow electrode includes Li 0.5 FePO4, water, conductive carbon black, graphite powder and wetting defoamer (Chemours FS-1), based on the mass of water as 100%, Li 0.5 The content of FePO4 is 5%, the content of conductive carbon black is 1.5%, the content of graphite powder is 0.3%, and the mass of the wetting and defoaming agent accounts for 3% of the total mass of the conductive carbon black and graphite powder;

[0113] The initial lithium content of the cathode active material and the anode active material is 50% of the theoretical lithium content of the active material.

[0114] This embodiment also provides a method for preparing the above-mentioned electrochemical lithium extraction electrode, comprising:

[0115] Li 0.5 FePO4, lithium-containing salt lake brine, conductive carbon black, graphite powder and Chemours FS-1 were mixed to obtain a cathode flow electrode;

[0116] Li 0.5 FePO4, water, conductive carbon black, and graphite powder are mixed with Chemours FS-1 to obtain the anode flow electrode.

[0117] This embodiment also provides a method for extracting lithium using the electrochemical lithium extraction electrode. The method is performed in the lithium extraction device of the above embodiment, and the method includes the following steps:

[0118] (1) The cathode flow electrode and the anode flow electrode were continuously injected into the cathode chamber and the anode chamber, respectively. Graphite plates were set as current collectors in both the cathode chamber and the anode chamber. The current collector areas in the two chambers were the same. The electrolysis reaction was carried out at a constant voltage of 0.7 V, with a current of 3.3 Ah / L and a current density of 30 A / m 2 , continuously outputting the cathode product at the top of the cathode chamber to a first solid-liquid separation device, obtaining, after solid-liquid separation, a mixture of lithium-rich active material (lithium content greater than 50% of the theoretical lithium content of the active material), conductive carbon black, graphite powder, a wetting and defoaming agent, and lithium-poor water, washing the mixture with water, and the washing water entering the lithium-poor water, which then returns the lithium-poor water (residual lithium ion concentration <0.15 g / L) to the lithium-containing salt lake brine;

[0119] Continuously outputting the anode product at the top of the anode chamber to a second solid-liquid separation device, obtaining, after solid-liquid separation, a mixture of lithium-deficient active material (lithium content is less than 50% of the theoretical lithium content of the active material), conductive carbon black, graphite powder, and a wetting and defoaming agent, and a lithium-rich solution, and washing the mixture with water to obtain lithium-deficient active material washing water;

[0120] (2) The mixture of the above-mentioned lithium-rich active material, conductive carbon black, graphite powder and wetting defoaming agent is mixed with the water used to wash the lithium-deficient active material and transported to the anode chamber; the mixture of the lithium-deficient active material, conductive carbon black, graphite powder and wetting defoaming agent is mixed with lithium-containing salt lake brine with a lithium ion content of 0.91 g / L and transported to the cathode chamber; the electrolysis reaction is carried out again at a constant voltage of 0.7 V, with a current of 3.3 Ah / L and a current density of 30 A / m 2 After electrolysis, solid-liquid separation can be performed to obtain a secondary lithium-rich active material (lithium content is greater than the lithium content of the lithium-rich active material in step (1)), a mixture of conductive carbon black, graphite powder and a wetting defoaming agent, lithium-deficient water, a secondary lithium-deficient active material (lithium content is less than the lithium content of the lithium-deficient active material in step (1)), a mixture of conductive carbon black, graphite powder and a wetting defoaming agent, and a lithium-rich solution, and the electrolysis reaction is cyclically carried out according to the above method;

[0121] In this embodiment, a total of 6 electrolysis reactions were performed, and the lithium ion concentration of the obtained lithium-rich solution was >4.5 g / L.

[0122] Example 2

[0123] This embodiment provides an electrochemical lithium extraction electrode, which includes a cathode flow electrode and an anode flow electrode;

[0124] The cathode flow electrode includes Li 0.5 Mn2O4, lithium-containing salt lake brine, conductive carbon black, graphite powder and wetting defoaming agent (Chemours FS-1), based on the mass of lithium-containing salt lake brine as 100%, Li 0.5 The content of Mn2O4 is 5%, the content of conductive carbon black is 1.5%, the content of graphite powder is 0.3%, the mass of the wetting and defoaming agent accounts for 3% of the total mass of the conductive carbon black and graphite powder, and the lithium ion content of the lithium salt lake brine is 0.55g / L;

[0125] The anode flow electrode includes Li 0.5 Mn2O4, dilute lithium solution, conductive carbon black, graphite powder, wetting defoamer (Chemours FS-1) and MnCl2 catalyst, based on the mass of dilute lithium solution as 100%, Li 0.5The content of Mn2O4 is 5%, the content of conductive carbon black is 1.5%, the content of graphite powder is 0.3%, the mass of the wetting defoaming agent accounts for 3% of the total mass of the conductive carbon black and graphite powder, and the Mn content in the anode flow electrode is 1.5%. 2+ The concentration of the catalyst is 0.5 g / L, and based on the mass of the dilute lithium solution being 100%, the content of the catalyst is 0.05%; the lithium ion content in the dilute lithium solution is 0.5 g / L;

[0126] The initial lithium content of the cathode active material and the anode active material is 50% of the theoretical lithium content of the active material.

[0127] This embodiment also provides a method for preparing the above-mentioned electrochemical lithium extraction electrode, comprising:

[0128] Li 0.5 Mn2O4, lithium-containing salt lake brine, conductive carbon black, graphite powder and wetting and defoaming agent (Chemours FS-1) were mixed to obtain a cathode flow electrode;

[0129] Li 0.5 Mn2O4, dilute lithium solution, conductive carbon black, graphite powder, wetting and defoaming agent (Chemours FS-1) and MnCl2 catalyst were mixed to obtain the anode flow electrode.

[0130] This embodiment also provides a method for extracting lithium using the electrochemical lithium extraction electrode. The method is performed in the lithium extraction device of the above embodiment, and the method includes the following steps:

[0131] The cathode flow electrode and the anode flow electrode were continuously injected into the cathode chamber and the anode chamber. Graphite plates were set as current collectors in both the cathode chamber and the anode chamber. The current collector areas in the two chambers were the same. The electrolysis reaction was carried out at a constant voltage of 1.5 V, with a current of 2.2 Ah / L and a current density of 60 A / m 2 , continuously outputting the cathode product at the top of the cathode chamber to a first solid-liquid separation device, obtaining, after solid-liquid separation, a mixture of lithium-rich active material (lithium content greater than 50% of the theoretical lithium content of the active material), conductive carbon black, graphite powder, a wetting and defoaming agent, and lithium-poor water, washing the mixture with water, and the washing water entering the lithium-poor water, which then returns the lithium-poor water (residual lithium ion concentration <0.12 g / L) to the lithium-containing salt lake brine;

[0132] The anode product is continuously outputted from the top of the anode chamber to the second solid-liquid separation device, and after solid-liquid separation, a mixture of lithium-deficient active material (lithium content is less than 50% of the theoretical lithium content of the active material), conductive carbon black, graphite powder and wetting defoaming agent, and Mn-containing 2+ and Cl - The lithium-rich solution is washed with water to obtain lithium-deficient active material washing water;

[0133] (2) The mixture of the above-mentioned lithium-rich active material, conductive carbon black, graphite powder and wetting defoaming agent is mixed with the washing water of the lithium-deficient active material and transported to the anode chamber; the mixture of the lithium-deficient active material, conductive carbon black, graphite powder and wetting defoaming agent is mixed with lithium-containing salt lake brine with a lithium ion content of 0.55 g / L and transported to the cathode chamber; the electrolysis reaction is carried out at a constant voltage of 1.5 V, the current is 2.2 Ah / L, and the current density is 60 A / m 2 After electrolysis, solid-liquid separation can be performed to obtain a secondary lithium-rich active material (lithium content is greater than the lithium content of the lithium-rich active material in step (1)), a mixture of conductive carbon black, graphite powder and a wetting and defoaming agent, lithium-deficient water, a secondary lithium-deficient active material (lithium content is less than the lithium content of the lithium-deficient active material in step (1)), a mixture of conductive carbon black, graphite powder and a wetting and defoaming agent, and a lithium-rich solution. The electrolysis reaction is cyclically carried out according to the above method;

[0134] In this embodiment, a total of 10 electrolysis reactions were performed, and the lithium ion concentration of the obtained lithium-rich solution was >4.0 g / L.

[0135] Example 3

[0136] The difference between this embodiment and embodiment 1 is that the Li 0.5 FePO4 is replaced by Li 0.5 Mn2O4, that is, the anode active material in the anode flow electrode and the cathode active material in the cathode flow electrode are different.

[0137] The remaining methods and parameters were the same as those in Example 1. Finally, a lithium-rich solution with a lithium ion concentration of >4.3 g / L was obtained.

[0138] Example 4

[0139] The difference between this embodiment and Example 1 is that neither the cathode flowing electrode nor the anode flowing electrode contains additive A and additive B, that is, the cathode flowing electrode does not contain conductive carbon black, graphite powder and wetting defoaming agent, and the anode flowing electrode does not contain conductive carbon black, graphite powder and wetting defoaming agent.

[0140] The remaining methods and parameters remained the same as in Example 1.

[0141] At 0.7V, the current density is only 2A / m 2 , the equipment operating efficiency is extremely low and electrolysis cannot be carried out.

[0142] Example 5

[0143] The difference between this embodiment and embodiment 1 is that the cathode flowing electrode does not contain graphite powder, and the anode flowing electrode does not contain graphite powder.

[0144] The remaining methods and parameters remained the same as in Example 1.

[0145] In this embodiment, the electrolysis reaction is carried out at a constant voltage of 0.7 V. The conductivity of the cathode / anode slurry is reduced, and the current density output by the lithium extraction device is 22 A / m 2 , the production capacity of the equipment is only 73% of the original.

[0146] Example 6

[0147] The difference between this embodiment and embodiment 1 is that the cathode flow electrode does not contain a wetting and defoaming agent, and the anode flow electrode does not contain a wetting and defoaming agent.

[0148] The remaining methods and parameters remained the same as in Example 1.

[0149] During the circulation of the cathode / anode slurry in this embodiment, a large amount of foam that is difficult to dissipate is generated at the mixing device. As the electrolysis process proceeds, the amount of foam gradually increases and in severe cases even overflows from the mixing device.

[0150] Example 7

[0151] The difference between this embodiment and embodiment 1 is that the cathode flowing electrode does not contain graphite powder and wetting defoaming agent, and the anode flowing electrode does not contain graphite powder and wetting defoaming agent.

[0152] The remaining methods and parameters remained the same as in Example 1.

[0153] In this embodiment, the working current density is the same (30A / m 2 ) under the lithium extraction device, the operating voltage rose to approximately 1.0V, and its electrolysis energy consumption increased by 43%. After three cycles of use, the cathode / anode slurry began to foam from the mixing equipment, and a large number of bubbles were mixed into the slurry, causing the delivery pump to malfunction and production to cease.

[0154] Example 8

[0155] The difference between this embodiment and embodiment 1 is that in both the cathode flow electrode and the anode flow electrode, the mass of the wetting and defoaming agent accounts for 0.1% of the total mass of the conductive carbon black and graphite powder.

[0156] The remaining methods and parameters remained the same as in Example 1.

[0157] During the circulation of the cathode / anode slurry in this embodiment, foam that is difficult to dissipate is generated at the mixing device. As the electrolysis process progresses and the number of times the slurry is used increases, the amount of foam gradually increases.

[0158] Example 9

[0159] The difference between this embodiment and embodiment 1 is that in both the cathode flow electrode and the anode flow electrode, the mass of the wetting and defoaming agent accounts for 5.5% of the total mass of the conductive carbon black and graphite powder.

[0160] The remaining methods and parameters remained the same as in Example 1.

[0161] The cathode / anode slurry in this embodiment has good fluidity and very little foam on the slurry surface. 2 At this current density, the voltage of the lithium extraction device rose to 0.9V, and its electrolysis energy consumption increased by 28.6%. This is because the addition of the wetting and defoaming agent partially covered the surface of the conductive carbon black and graphite powder, increasing the hydrophilicity of the solid particles in the slurry while reducing its conductivity.

[0162] Example 10

[0163] The difference between this embodiment and embodiment 2 is that the amount of MnCl2 catalyst used is 5%.

[0164] The remaining methods and parameters remained the same as in Example 2.

[0165] This embodiment achieves the same technical effect as that of Example 2, but the increased amount of catalyst means that the impurity concentration in the lithium-rich solution is high. When lithium is subsequently precipitated from the lithium-rich solution, the manganese impurity consumes sodium carbonate and causes the product impurity content to be high.

[0166] Example 11

[0167] The difference between this embodiment and embodiment 2 is that no MnCl2 catalyst is added, and the electrolyte used does not contain chloride ions, but a sulfate system electrolyte is used.

[0168] The remaining methods and parameters remained the same as in Example 2.

[0169] In the present embodiment, during the electrolysis process, the anode begins to release oxygen, the graphite plate begins to corrode, and the surface begins to soften.

[0170] Comparative Example 1

[0171] This comparative example provides an electrochemical lithium extraction electrode, including a cathode and an anode, wherein the cathode includes a titanium mesh and a cathode active layer coated on the surface of the titanium mesh, and the cathode active layer contains Li 0.5 FePO4; the anode comprises a titanium mesh and an anode active layer coated on the surface of the titanium mesh, the anode active layer comprising Li 0.5 FePO4.

[0172] This comparative example also provides a method for preparing the above-mentioned electrochemical lithium extraction electrode, comprising:

[0173] The slurry containing cathode active material is coated on the titanium mesh to make a cathode; the slurry containing anode active material is coated on the titanium mesh to make an anode.

[0174] This comparative example also provides a method for electrolytically extracting lithium using the above-mentioned electrochemical lithium extraction electrode, the method comprising the following steps:

[0175] (1) The prepared electrochemical lithium extraction electrode is installed in an electrolytic cell with a diaphragm, and the cathode of the lithium-rich brine area is connected to the negative electrode, and the anode of the lithium-rich liquid area is connected to the positive electrode. Electrolysis is performed at a voltage of 0.35 V under a solution circulation state;

[0176] (2) When the brine current reaches 110% of the theoretical current, replace the brine in the cathode area and discharge the brine in the original electrolysis area, or when the electrode current density is less than 10% of the initial value, release the solution in the cathode / anode area, and rinse the chamber with water. Switch the flow pole area and electrode current direction of the two solutions, continue electrolysis, realize normal lithium removal / insertion of the electrode, and obtain lithium-rich solution from the anode chamber.

[0177] Comparative Example 2

[0178] The difference between this comparative example and Example 1 is that the initial lithium content of the cathode active material and the anode active material is 10% of the theoretical lithium content of the active material.

[0179] The rest of the preparation methods and parameters remained the same as in Example 1.

[0180] Comparative Example 3

[0181] The difference between this comparative example and Example 1 is that the initial lithium content of both the cathode active material and the anode active material is 90% of the theoretical lithium content of the active material.

[0182] The rest of the preparation methods and parameters remained the same as in Example 1.

[0183] analyze:

[0184] It can be seen from the lithium extraction methods of Examples 1-2 and Comparative Example 1 that Comparative Example 1 can also achieve lithium deintercalation and obtain a lithium-rich liquid product, but by comparing the anode and cathode electrodes used, it can be seen that the present disclosure only uses graphite plates as cathode / anode current collectors for electrolysis, and a higher voltage can be used during the electrolysis process without damaging the electrodes. In addition, the cathode / anode used in the present disclosure is a slurry, which fully utilizes the surface area of ​​the active material and improves production efficiency. In the initial state, the active material substances used in the cathode / anode area are the same. During the circulation process, the slurry can be continuously supplemented / discharged / added with active materials, the operation is more stable, and the amount of power flow is simpler to adjust. Lithium-containing salt lake brine can continuously supplement the system and continuously discharge lithium-poor water. Electrochemical lithium extraction can be used to continuously obtain a lithium-rich solution (product). There is no need to clean the cathode / anode chamber.

[0185] It can be seen from Example 1 and Comparative Examples 2-3 that if the initial lithium content of the cathode active material and the anode active material is too small, the actual weight of lithium deintercalated per unit weight of the active material per cycle will be small; if the initial lithium content of the cathode active material and the anode active material is too large, the actual weight of lithium deintercalated per unit weight of the active material per cycle will also be small.

[0186] It can be seen from Examples 1 and 3 that when the anode active material in the anode flow electrode and the cathode active material in the cathode flow electrode are different, lithium transfer from brine to lithium-rich solution can also be achieved by using different electroactive materials.

[0187] From Example 1 and Example 4, it can be seen that when the cathode flow electrode and the anode flow electrode do not contain additive A and additive B, the current density is only 2A / m at a voltage of 0.7V. 2 , the equipment operating efficiency is extremely low and electrolysis cannot be carried out.

[0188] It can be seen from Example 1 and Examples 5-7 that if neither the cathode flowing electrode nor the anode flowing electrode contains graphite powder, the conductivity of the cathode / anode flowing electrodes will be reduced, and the production capacity of the lithium extraction device will be reduced; if neither the cathode flowing electrode nor the anode flowing electrode contains a wetting and defoaming agent, a large amount of foam that is difficult to dissipate will be generated during the electrolysis process, and the lithium extraction device will be difficult to operate normally; if neither the cathode flowing electrode nor the anode flowing electrode contains graphite powder and a wetting and defoaming agent, due to the reduction in conductivity, when the same working current density as in Example 1 is reached, the electrolysis energy consumption of the lithium extraction device increases by 43%, and a large amount of foam will be generated.

[0189] It can be seen from Examples 1 and 8-9 that in the cathode mobile electrode and the anode mobile electrode, if the mass ratio of the wetting and defoaming agent to the sum of the conductive carbon black and graphite powder is too low, foam that is difficult to dissipate will be generated in the mixing equipment; if the mass ratio of the wetting and defoaming agent to the sum of the conductive carbon black and graphite powder is too high, due to the addition of the wetting and defoaming agent, part of the surface of the conductive carbon black and graphite powder is covered, the hydrophilicity of the solid particles in the slurry is increased while the conductivity is reduced, resulting in increased energy consumption of the lithium extraction device.

Claims

1. An electrochemical lithium extraction electrode, comprising a cathode flow electrode and an anode flow electrode; The cathode flow electrode includes a cathode active material, the anode flow electrode includes an anode active material, and the initial lithium content of both the cathode active material and the anode active material is 20 - 80% of the theoretical lithium content of the active material.

2. The electrochemical lithium extraction electrode according to claim 1, wherein, The cathode active material includes Li x M 1-z Fe z PO4, Li x Mn2O4 and Li x MO2, where 0 ≤ x < 1, 0 < z ≤ 1, and M includes at least one of Ni, Co, Mn, Ti, and Al.

3. The electrochemical lithium extraction electrode according to claim 1 or 2, wherein, The anode active material includes Li y Y 1-m Fe m PO4, Li y Mn2O4 and Li y at least one of YO2, where 0 ≤ y < 1, 0 < m ≤ 1, and Y includes at least one of Ni, Co, Mn, Ti, and Al.

4. The electrochemical lithium extraction electrode according to any one of claims 1 - 3, wherein, The chemical formulas of the cathode active material and the anode active material are the same.

5. The electrochemical lithium extraction electrode according to any one of claims 1 - 4, wherein, The cathode flow electrode further includes a lithium-containing salt lake brine and additive A.

6. The electrochemical lithium extraction electrode according to claim 5, wherein, Additive A includes a conductive agent and / or a wetting and defoaming agent, and is further optionally a combination of a conductive agent and a wetting and defoaming agent.

7. The electrochemical lithium extraction electrode according to claim 6, wherein, The conductive agent in additive A includes conductive carbon black and / or graphite powder, and is further optionally a combination of conductive carbon black and graphite powder.

8. The electrochemical lithium extraction electrode according to any one of claims 5 - 7, wherein, Based on the mass of the lithium-containing salt lake brine being 100%, the content of the cathode active material is 1% - 7.5%; Optionally, based on the mass of the lithium-containing salt lake brine being 100%, the content of conductive carbon black in additive A is 1% - 2.5%; Optionally, based on the mass of the lithium-containing salt lake brine being 100%, the content of graphite powder in additive A is 0 - 15%, and does not include 0; Optionally, in additive A, the mass ratio of the conductive agent to the wetting and defoaming agent is 100:(0 - 5), and does not include 0.

9. The electrochemical lithium extraction electrode according to any one of claims 1 - 8, wherein, The anode flow electrode further includes a dilute lithium solution and additive B.

10. The electrochemical lithium extraction electrode according to claim 9, wherein, The lithium ion content of the dilute lithium solution is 0 - 5 g / L.

11. The electrochemical lithium extraction electrode according to claim 9 or 10, wherein, Additive B includes a conductive agent and / or a wetting and defoaming agent, and is further optionally a combination of a conductive agent and a wetting and defoaming agent.

12. The electrochemical lithium extraction electrode according to claim 11, wherein, The conductive agent in additive B includes conductive carbon black and / or graphite powder.

13. The electrochemical lithium extraction electrode according to any one of claims 1 - 12, wherein, The anode flow electrode further includes a catalyst and / or an electrolyte.

14. The electrochemical lithium extraction electrode according to claim 13, wherein, The catalyst includes Cl - and / or Mn 2+ .

15. The electrochemical lithium extraction electrode according to any one of claims 9 - 14, wherein, Based on the mass of the dilute lithium solution being 100%, the content of the anode active material is 1% - 7.5%; Optionally, based on the mass of the dilute lithium solution being 100%, the content of conductive carbon black in additive B is 1% - 2.5%; Optionally, based on the mass of the dilute lithium solution being 100%, the content of graphite powder in additive B is 0 - 15%, and does not include 0; Optionally, in additive B, the mass ratio of the conductive agent to the wetting and defoaming agent is 100:(0 - 5), and does not include 0; Optionally, based on the mass of the dilute lithium solution being 100%, the content of the catalyst is 0 - 1%, and does not include 0.

16. An electrochemical lithium extraction device using the electrochemical lithium extraction electrode according to any one of claims 1-15, comprising a cathode chamber, an ion exchange membrane, and an anode chamber, wherein the cathode chamber and the anode chamber are isolated from each other by the ion exchange membrane; the cathode chamber and the anode chamber are respectively filled with a cathode flow electrode and an anode flow electrode.

17. The electrochemical lithium extraction device according to claim 16, wherein The ion exchange membrane includes an anion exchange membrane.

18. A method for lithium extraction using the electrochemical lithium extraction device according to claim 16 or 17, comprising: The electrochemical lithium extraction device is powered on for electrolysis to complete electrochemical lithium extraction.

19. The method according to claim 18, wherein The electrolysis voltage of the electrochemical lithium extraction device is 0.1 - 3.5 V; Optionally, the current density of the electrochemical lithium extraction device is 5 - 60 A / m 2 ; Optionally, the lithium content of the cathode active material after electrolysis in the cathode flow electrode is greater than the lithium content of the cathode active material before electrolysis, and the lithium content of the anode active material after electrolysis in the anode flow electrode is less than the lithium content of the anode active material before electrolysis; The lithium content of the cathode active material after electrolysis is 50 - 100%; The lithium content of the anode active material after electrolysis is 0 - 50%.

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