A method and apparatus for extracting lithium from solution using a membraneless bipolar electrode

Abstract

The application belongs to the field of lithium extraction metallurgy, and particularly relates to a device for extracting lithium from a solution by a membrane-free bipolar electrode, comprising an electrolytic cell, end electrodes and one or more conductive separators; the end electrodes comprise a first end electrode and a second end electrode arranged at two ends of the electrolytic cell respectively; the conductive separators are arranged inside the electrolytic cell and between the two end electrodes; only the two end electrodes are connected with a power supply, so that an induced electric field is generated to drive the bipolar electrodes in the whole electrolytic cell to work in a series mode, thereby realizing synchronous and same-pace reaction of electrically active materials in the electrolytic cell, improving stability and circulation of electrode materials in the electrolytic cell, keeping current consistent and small, reducing control precision and manufacturing requirements of the power supply, reducing reactive power consumption and cost, eliminating the anticorrosion problem of copper bars, reducing the energy consumption of resistance heating of wires, not using conductive separators, simplifying the structure of the device, reducing cost, and reducing the water quality requirement of the solution to be extracted.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of lithium extraction metallurgy, and particularly relates to an electrochemical lithium extraction method and device using a bipolar electrode. BACKGROUND

[0002] Salt lake brine stores a large amount of lithium resources, accounting for about 78.3% of the total lithium reserves. At present, about 80% of lithium salt products are produced by using salt lake brine as raw material. However, the brine with low magnesium-lithium ratio is used in large-scale industrial production at present, while the magnesium-lithium ratio of most salt lakes in China is high, such as the magnesium-lithium ratio of Xitaijinaier salt lake brine is as high as 40 or more, and a small amount of Li + coexists with a large amount of Mg 2+ . Since the chemical properties of Li + and Mg 2+ are similar, it is very difficult to extract lithium.

[0003] Chinese patent CN 102382984 A discloses a method and device for separating and enriching lithium from salt lake brine. The method uses an anion exchange membrane to separate the electrodialysis device into a lithium salt chamber and a brine chamber. The brine chamber is filled with salt lake brine, and the lithium salt chamber is filled with a supporting electrolyte solution without Mg 2+ . A conductive substrate coated with an ion sieve is placed in the brine chamber as a cathode; a conductive substrate coated with a lithium-intercalated ion sieve is placed in the lithium salt chamber as an anode; under the driving of an external potential, Li + in the brine is intercalated into the ion sieve to form a lithium-intercalated ion sieve, and the lithium-intercalated ion sieve in the lithium salt chamber releases Li+ into the electrolyte to restore to the ion sieve. The method has the advantages of short process and high lithium selectivity.

[0004] However, the method needs to set an anion membrane between the cathode and the anode to separate the brine and the lithium-rich solution. However, on the one hand, the ion membrane is high in cost and easy to be contaminated, affecting the service life; on the other hand, the ion membrane is easy to be physically damaged during equipment assembly and use, causing the mixing of the brine and the lithium-rich solution and thus unable to extract lithium. Especially, the damage of the membrane during long-term continuous operation of the device is difficult to judge, and the only way is to disassemble the equipment for repair, which is complicated and not conducive to industrial production.

[0005] To eliminate the influence of the diaphragm, Chinese patent CN 110643831 A discloses a diaphragm-free electrochemical lithium extraction system and method, which uses a device composed of an electrolytic cell, a washing tank, a power supply, a series of lithium absorption and desorption electrodes, and an electronic balancing electrode. The electrolytic cell is divided into a series of raw material pools and recovery pools by a series of partitions, and is connected in series by connecting pipes between different raw material pools and recovery pools. The raw material to be extracted and the recovery liquid are introduced into the raw material pool and the recovery pool, respectively. By switching the electrodes between the raw material pool and the recovery pool, lithium is separated from the raw material pool and enriched in the recovery liquid.

[0006] In addition, Chinese patents 201810262464.8 and 201811210840.5 respectively disclose a continuous flow control asymmetric lithium ion capacitor lithium extraction device and method and a flow type electrochemical lithium extraction system. These methods do not require an ion membrane and do not require the use of a partition to physically separate the cathode region and the anode region.

[0007] These methods omit the diaphragm and can reduce costs. SUMMARY

[0008] The inventors have found that although the diaphragm-free electrochemical lithium extraction system and method omit the diaphragm, they still have the following problems:

[0009] First, each electrode in the above method needs to be connected to the power supply through a wire, and the use of a large number of wires also makes the device structure complex, increases the failure rate, and increases the safety hazard and production cost. Moreover, a large number of wires need to occupy a large amount of space, so the device layout requirements are quite harsh.

[0010] Second, the electrodes need to be moved between the raw material pool, the washing pool, and the recovery pool constantly, which requires repeated switching of the power supply, which undoubtedly increases energy consumption and operation difficulty, making the production discontinuous and difficult to be applied on a large scale.

[0011] Third, each electrode needs to be connected to the positive or negative electrode of the electrode, and the lithium extraction device has a large current and a low voltage. In the working process, the voltage between adjacent electrodes needs to be accurately controlled. In the large current working mode, the voltage drop of the wire is large. Taking the FePO4 / KNiFe(CN)6 electrode described in Chinese patent 201910930569.0 as an example, the working area of an electrode plate required in industrial production is usually 1 m 2 . Assuming that a pair of positive and negative electrodes generates a current of 10 amperes when working, placing 100 pairs of electrodes in an electrolytic cell will generate a current of 1000 amperes. If the cross-sectional area of the wire is 200 mm 2 (thickness x width: 5 x 40 mm 2A 1-meter-long copper busbar was used as the conductor (copper resistivity is 0.072 Ω·mm). 2 The voltage difference across the copper busbar reaches an astonishing 0.36 volts (1000 × 0.072 / 200V = 0.36 volts). However, the actual operating cell voltage across the electrodes is often only 0.3–0.5V, and the current changes continuously as the reaction progresses, causing the voltage drop to also change continuously, further deteriorating the precise control of the voltage between adjacent electrodes. This results in differences in cell voltage for each pair of electrodes during the extraction process, leading to inconsistent reaction progress for each electrode. Too low a cell voltage results in a slow reaction rate, reducing lithium extraction efficiency; too high a cell voltage easily leads to overcharging of the electrode plate material, severely affecting the material's cycle performance.

[0012] Fourth, high-current-low-voltage power supply systems are complex, expensive to customize, and have high reactive power consumption, which is not conducive to the automated control of the process.

[0013] This invention addresses the problems of existing electrochemical methods for lithium extraction from brine, such as complex device connections, difficulties in fabricating high-current-low-voltage power supply systems, inconsistent electrode reaction progress, and challenges in automatic control.

[0014] The present invention provides an apparatus for extracting lithium from solution using a membrane-free bipolar electrode, comprising an electrolytic cell, an end electrode, and one or more conductive separators;

[0015] The end electrodes include a first end electrode and a second end electrode respectively disposed at both ends of the electrolytic cell; the conductive partition is disposed inside the electrolytic cell and located between the two end electrodes; the first end electrode and the second end electrode are respectively used to connect to the positive and negative terminals of the power supply;

[0016] The conductive separator is coated with a lithium extraction layer on the surface facing the first end electrode; the lithium extraction layer is made of a lithium-ion battery active material that can be de-intercalated and de-intercalated but is in a lithium-deficient state; the conductive separator is coated with an ion balance layer material on the surface facing the second end electrode, and the ion balance layer maintains the ion neutrality balance in the lithium-containing solution through a chemical reaction; after the conductive separator is coated with a lithium-ion battery active material that can be de-intercalated and de-intercalated but is in a lithium-deficient state and an ion balance layer material on both sides, a bipolar electrode is formed.

[0017] The material with selective deintercalation of lithium ions and non-lithium ions is coated on both sides of the separator material with electronic conduction and ion non-conduction to form a bipolar electrode; the above several coated bipolar electrodes are inserted into the electrolytic cell, and the specially designed first end electrode and second end electrode are respectively placed at both ends of the electrolytic cell and connected with the positive and negative electrodes of the power supply, and the lithium ion-containing solution to be extracted is injected. After the power supply is turned on, the two end electrodes generate an electric field, and the surface of the intermediate bipolar electrode generates an induced electric field and induced charge; under the action of the electric field, the lithium ions in the solution to be extracted are adsorbed onto the lithium extraction layer adsorption material, and the positive and negative ions in the solution to be extracted are balanced through the action of the ion balance layer. Since only the electrodes at both ends of the electrolytic cell are connected with the positive and negative electrodes of the power supply, the current passing through each electrode in the electrolytic cell is consistent, and the reaction progress and degree of each electrode are synchronized, and the process is easy to control.

[0018] The essence of the technical solution is to use the electrodes at both ends of the electrolytic cell to create a uniform and stable electric field environment, and the operating environment of the surface of each bipolar electrode is the same, so that the working mode of the electrolytic cell is conventional voltage-low current, the power supply system is simple, and the amount of conductive busbar is significantly reduced; in addition, no membrane is arranged, thereby reducing the overall cost of the device and the requirement for the water quality of the solution to be extracted.

[0019] Further, the ion balance layer is a cation balance layer, and the cation balance layer material comprises an electroactive material for adsorbing or desorbing cations other than lithium ions.

[0020] Further, the cation balance layer material comprises at least one material with a chemical formula of (M1) x Fe y (M2) z (CN)6, wherein 0≤x≤2, 0

[0021] Further, the ion balance layer is an anion balance layer, and the anion balance layer material comprises an electroactive material for adsorbing or desorbing anions.

[0022] Further, the anion balance layer material comprises at least one of polyferrocene, polypyrrole, polyaniline, polythiophene, porous carbon material, antimony, silver, bismuth.

[0023] Further, the surface of the first end electrode facing the conductive separator is coated with the ion balance layer material, and the surface of the second end electrode facing the conductive separator is coated with the lithium extraction layer material.

[0024] Preferably, the first end electrode, the second end electrode and the conductive separator are arranged in parallel.

[0025] Preferably, the plurality of bipolar electrodes have the same spacing. Further, the lithium active material in the lithium extraction layer is a material capable of realizing reversible adsorption / desorption of lithium ions through valence change.

[0026] Preferably, the lithium extraction layer can be a mixture of one or more of LiFePO4, LiMn2O4, LiMeO2 and doped derivatives thereof (Me is one or more of Ni, Co, Mn), prepared by removing part or all of lithium after chemical oxidation or electrochemical oxidation.

[0027] In order to avoid two-pole short circuit, there must be a gap between the two conductive separators.

[0028] Preferably, one more insulating water distribution net than the number of conductive separators is further included, and the water distribution net can be a nylon net, a PP net, a PVC net, a sponge or other porous materials, which are arranged in the electrolytic cell and distributed on both sides of the conductive separator. The arrangement of the water distribution net can make the distribution of the to-be-extracted liquid on the electrode surface more uniform, and can also separate the two conductive separators to prevent short circuit.

[0029] Since the two sides of the conductive separator present different polarities during lithium extraction, the matrix material of the conductive separator needs to not only conduct electricity, but also resist electro-oxidation and electrochemical reduction corrosion. Further, the matrix material of the conductive separator is an inert conductive material.

[0030] Preferably, the matrix material of the conductive separator adopts dense carbon paper, dense carbon fiber sintered cloth, graphite, corrosion-resistant intermetallic compound, ruthenium-titanium coated, gold, platinum group metal and / or alloy thereof, or titanium, zirconium, hafnium, tantalum, niobium and / or alloy thereof. The shape can be a flat plate, a corrugated plate or other special-shaped structures, and the surface can also be subjected to physical and chemical treatments such as smoothing and roughening.

[0031] The application also discloses a method for extracting lithium from solution by using the membrane-free bipolar electrode.

[0032] Step 1, lithium extraction;

[0033] Taking the device for extracting lithium from solution by using the membrane-free bipolar electrode, the first end electrode is connected to the positive pole of the power supply, the second end electrode is connected to the negative pole of the power supply, and the to-be-extracted liquid containing lithium elements is injected into the electrolytic cell; the power supply is turned on, the current flows from the first end electrode and flows out from the second end electrode, and the following changes occur at the same time:

[0034] The lithium ions in the solution to be extracted enter the lithium extraction layer and are extracted by being embedded into the lithium-deficient lithium electroactive material; the electroactive material in the ion balance layer maintains the ion charge balance in the solution to be extracted by adsorbing anions or releasing cations other than lithium ions;

[0035] Step 2, lithium-depleted solution discharge;

[0036] After the reaction in Step 1, the solution to be extracted is converted into a lithium-depleted solution, the power supply is turned off, the lithium-depleted solution is discharged, and the electrolytic cell is cleaned;

[0037] Step 3, lithium enrichment;

[0038] The electrolyte supporting solution is injected into the electrolytic cell in Step 3; the positive and negative poles of the power supply are exchanged and the power supply is turned on, and the current flows in from the second end electrode and out from the first end electrode, while the following changes occur:

[0039] The lithium electroactive material in the lithium extraction layer is oxidized, thereby releasing the adsorbed lithium ions and releasing them into the electrolyte supporting solution; the electroactive material in the ion balance layer maintains the ion charge balance in the electrolyte supporting solution by releasing anions or adsorbing cations other than lithium ions;

[0040] Step 4, lithium-rich solution discharge;

[0041] After the reaction in Step 3, the electrolyte supporting solution is converted into a lithium-rich solution, the power supply is turned off, and the lithium-rich solution is discharged and collected; the device for extracting lithium from solution using the aforementioned membrane-free bipolar electrode returns to the state before Step 1, and is ready for reuse.

[0042] In one embodiment, when the ion balance layer is a cation balance layer,

[0043] Step 1, lithium extraction;

[0044] Take the device for extracting lithium from solution using the aforementioned membrane-free bipolar electrode, connect the first end electrode to the positive pole of the power supply and the second end electrode to the negative pole of the power supply, and inject a solution to be extracted containing lithium elements into the electrolytic cell; turn on the power supply, and the current flows in from the first end electrode and out from the second end electrode, while the following changes occur:

[0045] The lithium ions in the solution to be extracted enter the lithium extraction layer and are extracted by being embedded into the lithium-deficient lithium electroactive material; the electroactive material in the ion balance layer maintains the ion charge balance in the solution to be extracted by adsorbing anions or releasing cations other than lithium ions;

[0046] Step 2, lithium-depleted solution discharge;

[0047] After the reaction of step 1, the to-be-extracted solution is converted into a lithium-depleted solution, the power supply is turned off, the lithium-depleted solution is discharged, and the electrolytic cell is cleaned;

[0048] Step 3, lithium enrichment;

[0049] The electrolytic cell of step 3 is injected with a supporting electrolyte; the positive and negative poles of the power supply are exchanged, and the power supply is turned on, with the current flowing in from the second end electrode and out from the first end electrode, while the following changes occur:

[0050] The lithium electroactive material in the lithium extraction layer is oxidized, thereby releasing the adsorbed lithium ions into the supporting electrolyte; the electroactive material in the cation balance layer is reduced, and other cations in the supporting electrolyte are intercalated into the electroactive material.

[0051] Step 4, discharge of the lithium-rich solution;

[0052] After the reaction of step 3, the supporting electrolyte is converted into a lithium-rich solution, the power supply is turned off, and the lithium-rich solution is discharged and collected; the bipolar electrode device for extracting lithium from solution returns to the state before step 1, ready for reuse.

[0053] In another embodiment, when the ion balance layer is an anion balance layer,

[0054] Step 1, lithium extraction;

[0055] Take the aforementioned bipolar electrode device for extracting lithium from solution, connect the first end electrode to the positive pole of the power supply and the second end electrode to the negative pole of the power supply, and inject a to-be-extracted solution containing lithium elements into the electrolytic cell; turn on the power supply, with the current flowing in from the second end electrode and out from the first end electrode, while the following changes occur:

[0056] The lithium ions in the to-be-extracted solution enter the lithium extraction layer and are intercalated into the lithium electroactive material in the lithium-depleted state, thereby being extracted; the anions in the to-be-extracted solution enter the anion balance layer and are solidified;

[0057] Step 2, discharge of the lithium-depleted solution;

[0058] After the reaction of step 1, the to-be-extracted solution is converted into a lithium-depleted solution, the power supply is turned off, the lithium-depleted solution is discharged, and the electrolytic cell is cleaned;

[0059] Step 3, lithium enrichment;

[0060] The electrolytic cell of step 3 is injected with a supporting electrolyte; the positive and negative poles of the power supply are exchanged, and the power supply is turned on, with the current flowing in from the second end electrode and out from the first end electrode, while the following changes occur:

[0061] The lithium electroactive material in the lithium extraction layer is oxidized, and then releases the adsorbed lithium ions into the supporting electrolyte; the adsorbed anions in the anion balance layer are desorbed and released into the supporting electrolyte.

[0062] Step 4, draining the lithium-rich solution;

[0063] After the reaction in step 3, the supporting electrolyte is converted into a lithium-rich solution, the power is turned off, and the lithium-rich solution is drained and collected; the device for extracting lithium from the solution by the bipolar electrode returns to the state before step 1, and is ready for reuse.

[0064] Further, the lithium-rich solution from the previous cycle can be used as the supporting electrolyte in the next cycle to continue extracting lithium to increase the lithium concentration in the solution; the lithium-poor solution from the previous cycle can continue to be used as the lithium extraction solution in the next cycle to increase the lithium recovery rate.

[0065] Further, the lithium extraction solution is any one or a mixture of several of the following: salt lake raw brine, brine obtained by processing raw brine at any stage, old brine, underground brine, oil field brine, ore decomposition, and lithium-containing solution obtained by recycling secondary resources.

[0066] Further, to balance the extraction of lithium and the intercalation of other cations, the total number of moles of cations adsorbed by the cation balance layer material in the supporting electrolyte is greater than the number of moles of lithium removed from the lithium electroactive material.

[0067] The higher the lithium concentration in the extraction solution, the faster the electrochemical lithium extraction rate. Therefore, to maintain a reasonable lithium extraction rate, there are certain requirements for the lithium concentration in the solution.

[0068] Preferably, the lithium concentration in the extraction solution is preferably not less than 0.05 g / L.

[0069] Due to the difference in the lithium deintercalation / intercalation potential of the lithium extraction layer material used (wherein LiFePO4 is 0.4-0.6 V vs. SHE, LiMn2O4 is 0.7-1.0 vs. SHE, ternary material LiMeO2 is 0.7-1.0 vs. SHE, (M1) x Fe y (M2) z (CN)6 is about 0.4-0.6 V vs. SHE), the voltage required during the lithium extraction process is different when the materials coated on the two sides of the bipolar electrode are different. And according to the different lithium concentrations in the lithium-containing solution, the required voltage can also be adjusted within a certain range.

[0070] Preferably, the power supply voltage is (0.05-0.8) x (n+1) volts, where n is the number of conductive separators.

[0071] The present application has the advantages of:

[0072] 1. The induced electric field generated by the connection of the end electrode and the power source drives the entire electrolytic cell inside the bipolar electrode to work, realizing the synchronous and same progress reaction of the electroactive material inside the electrolytic cell, and improving the stability and cycle of the electrolytic cell electrode material;

[0073] 2. The current passing through each electrode is consistent, and the current is small, the control accuracy and manufacturing requirements of the power source are low, the reactive power consumption is low, and the cost is low;

[0074] 3. The use of a large number of busbars in the traditional electrochemical lithium extraction method is greatly reduced, and there is no problem of corrosion and voltage drop of the copper bar;

[0075] 4. The traditional anion membrane is not used, the device structure is simple, the cost is low, and the equipment is easy to be large and easy to be maintained;

[0076] 5. The environmental protection benefit of the lithium extraction process is remarkable, and high multiple enrichment of lithium can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0077] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and should not be considered as a limitation to the scope. For those skilled in the art, other drawings can also be obtained without creative labor.

[0078] Figure 1 is a simplified schematic diagram of the device for extracting lithium from solution provided by the present application using bipolar electrodes;

[0079] Figure 2 is a simplified structure schematic diagram of the device for Figure 1 series integration of the device in

[0080] Figure 3 The lithium concentration of brine and the lithium concentration of lithium-rich liquid of examples 1-7 change with time;

[0081] Figure 4 The adsorption capacity of the electrode material of examples 1-7 changes with time;

[0082] Figure 5 The relationship between the lithium concentration of lithium-rich liquid and the cycle number in the 6-cycle lithium extraction process in example 7 is shown in the figure;

[0083] Figure 6 The lithium concentration of brine in the lithium extraction process of example 8, and the lithium concentration change of lithium-rich liquid in the lithium extraction process;

[0084] Figure 7 Example 8: Changes in cell voltage over time during lithium extraction;

[0085] Figure 8 Example 8: Changes in the adsorption capacity of materials during cyclic lithium extraction;

[0086] Figure 9 Example 9: Changes in lithium concentration in brine during lithium extraction and lithium concentration in lithium-rich solution during delithiation;

[0087] Figure 10 Example 9: Changes in adsorption capacity during the cycling process.

[0088] Icons: 1-Electrolytic cell, 2-First end electrode, 3-Second end electrode, 4-Water distribution network, 5-Ion balance layer, 6-Lithium extraction layer, 7-Conductive separator, 8-Power supply. Detailed Implementation

[0089] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0090] Figure 1 This is a simplified schematic diagram of the apparatus for extracting lithium from solution using bipolar electrodes provided by the present invention; Figure 2 It is Figure 1 A simplified structural diagram of a device that integrates multiple devices in series. Please refer to [link / reference]. Figure 1 , Figure 2 The device includes an electrolytic cell 1, a first end electrode 2 and a second end electrode 3, and a conductive partition 7.

[0091] The first end electrode 2 and the second end electrode 3 are respectively disposed at both ends of the electrolytic cell 1 and are located inside the electrolytic cell 1; the conductive partition 7 is disposed inside the electrolytic cell 1 and is located between the first end electrode 2 and the second end electrode 3; the first end electrode 2 and the second end electrode 3 are respectively used to connect the positive and negative terminals of the power supply.

[0092] The conductive separator 7 has a lithium extraction layer 6 coated on the surface facing the first end electrode 2. The lithium extraction layer 6 is made of a lithium-ion battery active material that can be de-intercalated and de-lithiated but is in a lithium-deficient state. The conductive separator 7 has an ion balance layer 5 coated on the surface facing the second end electrode 3. The ion balance layer 5 is used to balance the ion charges in the lithium-containing solution. The ion balance layer 5, the lithium extraction layer 6, and the conductive separator 7 together form a bipolar electrode.

[0093] The water distribution nets 4 are all installed inside the electrolytic cell 1 and distributed on both sides of the conductive partition 7. The water distribution nets 4 are installed between the electrodes to prevent short circuits and to ensure uniform distribution of the solution on the electrode surfaces. Figure 1 As shown, the material of the conductive separator 7 can be the same as or different from the material of the first end electrode 2 and the second end electrode 3. This application does not limit this. Figure 1 The number of bipolar electrodes is not limited to the number shown in the figure and can be set according to specific lithium extraction requirements. In addition, the electrodes can be arranged vertically in parallel, horizontally stacked, or arranged in multiple vertical layers or alternating vertical / horizontal layers in the electrolyzer 1 as needed.

[0094] Figure 2 It is Figure 1 The simplified structural diagram of the device for series integration shows that when the number of bipolar electrodes in a single electrolytic cell is too large, it can be controlled in modules according to the power output; alternatively, multiple electrolytic cells can be connected in series and parallel externally via a power supply system. Furthermore, when multiple electrolytic cells are operating in series and parallel externally, the solution transport within the electrolytic cells can be configured with independent water paths connected in series and parallel as needed.

[0095] The present invention will be further described in detail below with reference to the embodiments.

[0096] Example 1

[0097] Fabrication of a membrane-free bipolar electrode and its lithium extraction device (using a cation balance layer):

[0098] (1) 1600g of lithium iron phosphate powder, acetylene black and polyvinylidene fluoride were dry mixed at a ratio of 8:1:1, and then 2500g of N-methylpyrrolidone was added. The mixture was stirred using a double planetary mixer at a speed of 80r / min and a dispersion speed of 1000r / min. After stirring evenly for 10 hours, a homogeneous slurry was obtained.

[0099] (2) 1600g of K2MnFe(CN)6 powder was dry-mixed with acetylene black and polyvinylidene fluoride at a ratio of 8:1:1. Then 2500g of N-methylpyrrolidone was added and stirred using a double planetary mixer at a speed of 80r / min and a dispersion speed of 1000r / min. After stirring evenly for 10 hours, a mixed slurry was obtained.

[0100] (3) Take two sheets, each 10×10cm in size. 2 Titanium sheets, designated as the first and second end electrodes, are coated with a lithium iron phosphate slurry on one side of the first end electrode and a K2MnFe(CN)6 slurry on the other side of the second end electrode. The coating density of both slurries is 80 mg / cm³. 2The coated electrode is then vacuum dried at 90°C for 12 hours.

[0101] (4) Another 4 pieces of titanium sheet with size of 10 x 10 cm 2 are prepared. Lithium iron phosphate is uniformly coated on one side of the titanium sheet (marked as side A). The coated electrode is then vacuum dried at 90°C for 12 hours.

[0102] (5) The electrolytic cell is divided into anode and cathode compartments by an anion exchange membrane. The electrode coated with lithium iron phosphate in step (3) is used as the anode, and foamed nickel is used as the cathode. Both the anode and the cathode are added with 1L of 10g / L NaCl as the supporting electrolyte, and the pH of the cathode is adjusted to 2-3 with sulfuric acid. Constant voltage electrolysis is carried out at a voltage of 1.0V until the current decreases to 20% of the initial current, ending the lithium extraction pretreatment process of the electrode plate. The lithium extraction pretreated electrode is washed with water, dried, and ready for use.

[0103] (6) After drying the lithium extraction electrode, K2MnFe(CN)6 is uniformly coated on the other side of the titanium sheet (marked as side B). The uniform coating density is maintained at 80mg / cm 2 . The coated electrode is then vacuum dried at 90°C for 12 hours, which is a bipolar electrode.

[0104] (7) Four bipolar electrodes, a first end electrode, and a second end electrode are assembled together to form a lithium extraction electrolytic cell. The first end electrode and the second end electrode are end plates, respectively. The A side of the bipolar plate is opposite to the second end electrode plate, and similarly, the B side of the bipolar plate is opposite to the first end electrode plate.

[0105] Method for extracting lithium from solution by membraneless bipolar electrode (using cation balance layer):

[0106] (1) 1L of salt lake brine (brine composition is shown in Table 1) is injected into the chamber of the electrolytic cell, and constant voltage electrolysis is carried out at an applied voltage of 1.5V for lithium extraction. The first end electrode is connected to the negative electrode of the power supply, and the second end electrode is connected to the positive electrode of the power supply. When the current during lithium extraction decreases to 10% of the initial current, the lithium extraction process is ended, and then the lithium-depleted liquid is discharged and 1L of clean water is injected to clean the chamber for 3 times.

[0107] (2) 1L of 10g / L KCl solution is injected into the chamber of the electrolytic cell as the supporting electrolyte. The first end electrode is connected to the positive electrode of the power supply, and the second end electrode is connected to the negative electrode of the power supply. Constant voltage electrolysis is carried out at an applied voltage of 1.5V for lithium extraction. When the current during lithium extraction decreases to 10% of the initial current, the lithium extraction process is ended, and then the lithium-rich liquid is discharged and 1L of clean water is injected to clean the chamber.

[0108] Table 1 Main ionic composition of brine

[0109]

[0110] Examples 2-6

[0111] Examples 2-6 are similar to the operation of Example 1, only the specific parameters are changed, the specific changes are as follows in Table 2-3:

[0112] Table 2 Preparation of the device for extracting lithium in Examples 1-6

[0113]

[0114] Table 3 Main operating parameters and extraction performance of the lithium extraction process in Examples 1-6

[0115]

[0116] In order to further illustrate the beneficial effects of the present application, the composition of the lithium-rich liquid obtained in Examples 1-6 is tested, and the data are as follows in Table 4:

[0117] Table 4 Composition of the lithium-rich liquid obtained in Examples 1-6

[0118]

[0119] Note: * 10 g / L of KCl is added as a supporting electrolyte, and # 10 g / L of NaCl is added as a supporting electrolyte.

[0120] From the results in Figure 3 , Figure 4 and Table 4, it can be seen that the specific capacity of the electrode in Examples 1-3 is slightly greater than that in Examples 4-6. Therefore, the lithium concentration in the brine can be reduced more in one cycle in Examples 1-3. In addition, the impurity ions in the obtained lithium-rich liquid are less, and the retention rate of impurity ions in the lithium-rich liquid can reach more than 98%.

[0121] Example 7

[0122] The operating parameters of this example are the same as those of Example 1, the difference is that this example is repeated step (5) and step (6) of Example 1 for 6 cycles of lithium extraction experiment, the brine used for each lithium extraction is fresh brine, the lithium-rich liquid used is the lithium-rich liquid obtained in the last cycle, and a certain amount of KCl is added to the lithium-rich liquid to control the KCl concentration at 10 g / L.

[0123] The change of lithium concentration in the lithium-rich liquid during the 6 cycles is shown in Figure 5 From the figure, it can be seen that through the cyclic lithium extraction, the lithium can be continuously enriched.

[0124] Comparative Example 1

[0125] The difference between the present embodiment and embodiment 1 is that both sides of each titanium sheet are coated with the same material, wherein 3 titanium sheets are coated with lithium iron phosphate slurry, and the lithium is removed from the electrode coated with lithium iron phosphate to prepare iron phosphate by the method of embodiment 1; the other 3 electrode sheets are coated with K2MnFe(CN)6, and the coating density of the two electrode materials is 80 mg / cm 2 (both sides), and the electrode sheets coated with the two electrode materials are arranged alternately. In the lithium extraction process, 3 iron phosphate electrodes are used as cathodes, and each cathode electrode is connected to the negative electrode of the power supply; 3 K2MnFe(CN)6 electrodes are used as anodes, and each anode electrode is connected to the positive electrode of the power supply. In the lithium extraction process, the cell voltage is controlled to be 0.3 V, the current control at the end of the electrolysis process is 10% of the initial current of the reaction, and the average current during the process is 1.83 A; in the lithium removal process, the cell voltage is controlled to be 0.3 V, and the average current during the process is 1.92 A.

[0126] According to the experimental results of comparative example 1 and comparative example 1, the lithium extraction effects of the two methods are not much different, but the current value of the bipolar electrode lithium extraction method of embodiment 1 is 1 / 5 of that of comparative example 1, and the voltage is 5 times that of comparative example 1.

[0127] In the process of industrial production, the electrode area of a single electrode generally needs to reach 1 m 2 According to the area of a single electrode in embodiment 1, which is 0.01 m 2 It can be roughly calculated that the average current of a single electrode in the industrial lithium extraction process will reach 36 A, and if 100 bipolar electrodes are equipped, the cell voltage is about 35 V, and the two are well matched, and a conventional power supply can meet the power supply. However, according to the lithium extraction method of comparative example 1, the current will reach 3500 A, and the voltage at this time is only 0.35 V, and the current-voltage matching degree is poor, and the power supply system needs to be specially customized and processed.

[0128] Embodiment 8

[0129] Preparation of a membrane-free bipolar electrode and its lithium extraction device (using an anion balance layer):

[0130] (1) Add lithium iron phosphate material to 0.1 mol / L sodium persulfate solution, control the molar ratio of lithium iron phosphate to sodium persulfate to be 2:1, and react at room temperature for 6 hours, then filter, wash and dry to obtain under-lithiated iron phosphate.

[0131] (2) Lithium-deficient iron phosphate, acetylene black and polyvinylidene fluoride were added into N-methylpyrrolidone solvent in a mass ratio of 8:1:1, and a mixed homogenate was obtained after stirring for 10 hours by using a double planetary mixer, thereby obtaining a lithium-deficient iron phosphate slurry; polypyrole, conductive agent acetylene black and binder PVDF were added into N-methylpyrrolidone solvent in a mass ratio of 7:2:1, and a mixed homogenate was obtained after stirring for 10 hours by using a double planetary mixer, thereby obtaining a ppy slurry;

[0132] (3) The lithium-deficient iron phosphate slurry and the polypyrole slurry of (2) were respectively coated on two surfaces of a 50x50cm titanium sheet, and the coating density was 200mg / cm 2 , and dried at 80°C for 12 hours to obtain a bipolar electrode.

[0133] (4) The lithium-deficient iron phosphate slurry and the polypyrole slurry were respectively coated on two surfaces of two 50x50cm titanium sheets, and the coating density was 200mg / cm 2 , and dried at 80°C for 12 hours to obtain a lithium-deficient iron phosphate end electrode and a polypyrole anion active end electrode, respectively.

[0134] (5) A lithium extraction electrolytic cell was assembled by using the lithium-deficient iron phosphate end electrode, the polypyrole anion active end electrode, nine bipolar electrodes and a water distribution net, and the electrode distance between the electrodes was 1-2mm; the lithium-deficient iron phosphate end electrode was connected to the negative electrode of a power supply, and the polypyrole end electrode was connected to the positive electrode of the power supply.

[0135] Method for extracting lithium from solution by using a membrane-free bipolar electrode (using an anion balance layer):

[0136] (1) Lithium extraction: continuously circulating injection of salt lake brine (total volume of brine 250L) into the electrolytic cell was performed, and the power supply was turned on. During the lithium extraction process, constant current electrolysis was first performed at a current of 6A, and when the cell voltage reached 4.0V, constant voltage electrolysis was performed until the current decreased to 0.6A, and the process was ended. After electrolysis, the brine was discharged, and 30L of clean water was injected into the electrolytic cell in three times (10L each time) for circulation cleaning, and after each cleaning for 5 minutes, the washing water was discharged;

[0137] (2) Lithium extraction: 15L of NaCl solution with a concentration of 5g / L was injected into the electrolytic cell as a supporting electrolyte, and the positive and negative electrodes in the lithium extraction process were reversed, and constant voltage electrolysis was performed at a voltage of 5.0V. When the current was less than 10% of the initial current, the electrolysis process was ended, and then the lithium-rich liquid obtained in the second cycle electrolysis was discharged.

[0138] (3) The system can be operated in a cycle by repeating steps (1) and (2).

[0139] The changes in lithium concentration of the brine during the lithium extraction process and the lithium concentration of the lithium-rich liquid during the lithium extraction process are shown in Table 5 and Figure 6 Table 6, and the changes in cell voltage during the lithium extraction process are shown inFigure 7 The adsorption capacity change in the cycle is shown in Figure 2. Figure 8 The adsorption capacity change in the cycle is shown in Figure 2.

[0140] Table 5 Main components of the salt lake brine and the lithium-rich solution in the lithium extraction process (g / L)

[0141] solution Li Na Mg K B SO4 2- ]]> initial brine 0.55 59.34 86.36 5.34 1.74 18.53 brine after lithium extraction 0.04 59.10 86.01 5.32 1.73 18.44 lithium-rich solution 8.43 3.16 1.44 0.09 0.03 0.31

[0142] From Table 5 and Figure 6 It can be seen that the lithium extraction mode using bipolar electrodes can effectively achieve lithium extraction. After 8 hours of electrolytic lithium extraction, the lithium concentration in the brine can be reduced from the initial 0.55 g / L to 0.04 g / L, and the lithium extraction rate can be more than 90%, and the rejection rate of impurity ions in the process is more than 99%, showing good selectivity. In addition, the lithium extraction can be basically completed within 4 hours, and the lithium concentration in the lithium-rich solution can reach 8.4 g / L, and the impurity ions are relatively low. The Na / Li and Mg / Li ratios in the lithium-rich solution are reduced from 107:1 and 157:1 in the original brine to 0.37:1 and 0.17:1. In fact, during the desorption process, sodium, magnesium and other impurities are mainly the brine adsorbed and entrained by the electrode plate. If a low-concentration LiCl solution is used as the supporting electrolyte, the Na / Li in the lithium-rich solution can be reduced to a lower value.

[0143] From Figure 7 It can be seen that the entire lithium extraction process can be divided into three stages, namely the spontaneous lithium extraction process, the constant-current lithium extraction process and the constant-voltage lithium extraction process. Lithium extraction can be achieved without external power supply in the spontaneous lithium extraction process. In addition, from the cycle performance shown in Figure 8 It can be seen that the lithium adsorption capacity of the lithium active electrode material is basically maintained at 25 mg (Li) / g (active material) during the lithium extraction process, and the cycle performance is excellent.

[0144] Example 9

[0145] The same electrode preparation method and process as in Example 8 are used, and the lithium active electrode material is changed to LiMn2O4, and the brine volume is changed to 200 L. In the lithium extraction process, first, a constant current of 10 A is used for electrolysis, and when the cell voltage reaches 7.0 V, constant voltage electrolysis is used, and the process ends until the current decreases to 1 A. In the lithium desorption process, constant voltage electrolysis is used at a cell voltage of 7.0 V, and the process ends until the current decreases to 1 / 10 of the initial value.

[0146] From Table 6, it can be seen that using the LiMn2O4-pyrrole system, the lithium concentration in the brine can be reduced to 0.08 g / L, and the lithium concentration in the lithium-rich solution can also be enriched to 6.67 g / L, and the rejection rate of other impurity ions remains at about 99%. From the lithium concentration change graph and Figure 9 Figure 10 ​The cycle performance shown can be seen that the lithium adsorption capacity of the material can be basically stabilized at 20 mg (Li) / g (active material), and the cycle performance is excellent.

[0147] Table 6 Main components of salt lake brine and lithium-rich solution during lithium extraction process (g / L)

[0148] solution Li Na Mg K B SO4 2- ]]> Cl - ]] initial brine 0.55 59.34 86.36 5.34 1.74 18.53 223.5 brine after lithium extraction 0.08 59.16 86.10 5.32 1.73 18.46 / lithium-rich solution 6.67 3.11 1.35 0.08 0.02 0.19 /

[0149] Examples 10-19

[0150] Examples 10-19 have similar operation as Example 8, the number of bipolar electrodes is also 9, and the electrode coating size is the same, the process uses constant voltage electrolysis to extract lithium and delithiate, the brine and electrolyte used are the same as in the example, and other specific parameters change as shown in Table 7.

[0151] The solution composition after lithium extraction in different lithium extraction systems is shown in Table 8, and the ion composition of the obtained lithium-rich solution is shown in Table 9.

[0152] Table 7 Parameter table of lithium extraction device in Examples 10-19

[0153]

[0154]

[0155] Table 8 Solution composition of brine after lithium extraction in Examples 10-19 (g / L)

[0156]

[0157] Table 9 Composition of lithium-rich solution in Examples 10-19 (g / L)

[0158]

[0159]

[0160] From Tables 8 and 9, it can be seen that the electrochemical lithium extraction systems composed of lithium iron phosphate, lithium manganate and ternary material matched with different anion electrode materials all have good lithium extraction performance, and the impurity content of the obtained lithium-rich solution is low. In addition, whether in the lithium extraction process or in the lithium release process, the current is mostly about 6-8 A.

[0161] Comparative Example 2

[0162] (1) Lithium iron phosphate material was added to a 0.1 mol / L sodium persulfate solution, and the molar ratio of lithium iron phosphate to sodium persulfate was controlled at 2:1. After reacting at room temperature for 6 hours, filtration, washing and drying were performed to obtain a pre-delithiated lithium-deficient lithium iron phosphate.

[0163] (2) The same method as in Example 1 was used to prepare the iron phosphate slurry and the polypyrrole slurry. The lithium iron phosphate slurry and the polypyrrole slurry were coated on both sides of a titanium sheet (titanium sheet size 50 x 50 cm 2 , both sides were of the same material) to prepare an iron phosphate electrode and a polypyrrole anion electrode, respectively, using the same coating density and drying conditions as in the example.

[0164] (3) Five iron phosphate electrodes and five polypyrrole electrodes were alternately placed in the electrolytic cell, and the electrodes were separated and watered using a water distribution net. Each iron phosphate electrode was connected to the negative pole of the power supply through a wire, and each polypyrrole electrode was connected to the positive pole of the power supply. A membrane stack lithium extraction electrolytic cell was formed in a conventional connection mode and working mode.

[0165] (4) Lithium extraction: The salt lake brine (total volume of brine 250 L) was continuously circulated into the electrolytic cell, and the power supply was turned on. The lithium extraction process was carried out using a cell voltage of 0.4 V for constant voltage electrolysis, and the process was stopped when the current decreased to 10% of the initial current. After electrolysis, the brine was discharged, and 30 L of clean water was injected into the electrolytic cell in three cycles (10 L each time) for cleaning. After each cleaning cycle, the washing water was discharged.

[0166] (5) Lithium extraction: 15 L of NaCl solution with a concentration of 5 g / L was injected as a supporting electrolyte between the electrodes, and the positive and negative electrodes of the lithium extraction process were reversed. The process was carried out using a voltage of 0.4 V for constant voltage electrolysis, and the process was stopped when the current was less than 10% of the initial current. Subsequently, the lithium-rich solution obtained in the second cycle of electrolysis was discharged.

[0167] (6) The system can be operated in a cyclic manner by repeating steps (4) to (5).

[0168] Comparative Example 3

[0169] The difference between this comparative example and Comparative Example 2 is that in step (1) of Comparative Example 1, lithium iron phosphate is replaced by LiMn2O4, and polypyrrole is replaced by polyaniline. The lithium extraction process is carried out using a voltage of 0.6 V for electrolysis.

[0170] Comparative Example 4

[0171] The difference between this comparative example and Comparative Example 2 is that in step (1) of Comparative Example 1, lithium iron phosphate is replaced by LiNi 0.6 Co 0.2 Mn 0.2 O2, and polypyrrole is replaced by polyferrocene. The lithium extraction process is carried out using a voltage of 0.7 V for electrolysis.

[0172] The lithium concentration in the brine before and after lithium extraction and the main ion concentration in the lithium-rich solution in Comparative Examples 2 to 4 are shown in Table 10.

[0173] Table 10 Main ion concentration (g / L) in brine and lithium-rich solution after lithium extraction

[0174]

[0175] Compared with the lithium extraction modes of Example 8, Example 15 and Example 18, the lithium extraction effect of Comparative Examples 2-4 is equivalent. However, it can be obviously seen from the comparison of the process current that the voltage used in Example 8, 18 and 15 is about 10 times of that of the comparative examples, using the same number of electrodes; but the current of the comparative examples is as high as about 80 A, which is about 10 times of that of the corresponding system of Example 8, Example 15 and Example 18. It can be seen that the original low-voltage mode can be converted to a conventional voltage by using the example scheme, and the high current in the comparative examples is converted to a low current.

[0176] In actual production process, in order to ensure the number of lithium extraction of each membrane stack electrolytic cell, the number of electrode assembly in unit electrolytic cell often needs to reach 100-200. In this way, the current of the working mode of Comparative Examples 2-4 will be about 100 times of that of the present patent. This will cause the current of the lithium extraction system to be too large, not only the cost of power supply, but also the busbar pressure drop caused by large current operation will have a great impact on the working condition of the electrolytic cell electrode.

[0177] In addition, the power supply used in the comparative examples is a low-voltage-high-current special power supply system, which has high processing cost. However, by using the bipolar electrode working mode of the present patent, it can be converted to a conventional voltage (about 20-100 V is required for 100 bipolar electrolytic cells)-low current (about 20-50 A current for 1 square meter of bipolar electrode), not only the power supply system can use conventional power supply, but also the current passing through each bipolar electrode is consistent, which can fundamentally solve the problems of power supply system, electrode reaction consistency and other problems faced by the traditional lithium extraction mode.

[0178] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An apparatus for extracting lithium from a solution by a membraneless bipolar electrode, characterized in that, The electrolytic cell comprises an electrolytic cell, end electrodes, and one or more conductive separators. The end electrodes comprise a first end electrode and a second end electrode respectively arranged at two ends of the electrolytic cell; the conductive separators are arranged inside the electrolytic cell and between the two end electrodes; the first end electrode and the second end electrode are respectively connected to the positive electrode and the negative electrode of a power supply. The surface of the conductive separator facing the first end electrode is coated with a lithium extraction layer; the lithium extraction layer is a lithium electroactive material that can extract lithium but is in a state of lithium deficiency; the surface of the conductive separator facing the second end electrode is coated with an ion balance layer material; the ion balance layer maintains the ion charge balance in the lithium-containing solution through a chemical reaction; the conductive separator is coated with a lithium electroactive material that can extract lithium but is in a state of lithium deficiency and an ion balance layer material on both surfaces to form a bipolar electrode.

2. The apparatus for extracting lithium from solution using a membraneless bipolar electrode according to claim 1, wherein, The ion balance layer is a cation balance layer, and the cation balance layer material comprises an electroactive material for adsorbing or desorbing cations other than lithium ions.

3. The apparatus for extracting lithium from solution using a membraneless bipolar electrode according to claim 2, wherein, The cationic balancing layer material is at least one material of the chemical formula (M1) x Fe y (M2) z (CN)6, wherein 0≤x≤2, 0 y≤2, 0≤z≤2, the valence of Fe is +2 or +3, M1 is selected from Na, K, and M2 is selected from Cr, Ti, Ni, Co, Mn, Cu, and Zn.

4. The apparatus for extracting lithium from solution using a membraneless bipolar electrode of claim 1, wherein, The ion balance layer is an anion balance layer, and the anion balance layer material comprises an electroactive material for adsorbing or desorbing anions.

5. The apparatus for extracting lithium from solution using a membraneless bipolar electrode of claim 4, wherein, The anion balance layer material uses at least one of polyferrocene, polypyrrole, polyaniline, polythiophene, porous carbon material, antimony, silver, bismuth.

6. The device for extracting lithium from solution with a membraneless bipolar electrode according to any one of claims 1-5, characterized in that, The surface of the first end electrode facing the conductive separator is coated with the ion balance layer material, and the surface of the second end electrode facing the conductive separator is coated with the lithium extraction layer material.

7. The device for extracting lithium from solution using a membraneless bipolar electrode according to any one of claims 1-5, wherein, It also includes one more insulating water distribution network than the number of conductive separators, and the water distribution network is arranged in the electrolytic cell and distributed on both sides of the conductive separator.

8. The apparatus for extracting lithium from solution using a membraneless bipolar electrode of claim 7, wherein, The conductive separator is an electrochemically inert electronic conductor, which is made of dense carbon paper, dense carbon fiber sintered cloth, graphite, corrosion-resistant intermetallic compound, ruthenium-coated titanium, gold, platinum group metal and / or its alloy, or titanium, zirconium, hafnium, tantalum, niobium and / or their alloys.

9. The apparatus for extracting lithium from solution using a membraneless bipolar electrode according to any one of claims 1-5, wherein, The lithium extraction layer material is a mixture of one or more of LiFePO4, LiMn2O4, LiMeO2 and its doped derivatives, wherein Me is one or more of Ni, Co, Mn, and is prepared by removing part or all of the lithium after chemical oxidation or electrochemical oxidation.

10. A method for extracting lithium from a solution by a membrane-free bipolar electrode, comprising the following steps: Step 1, lithium extraction; taking the device for extracting lithium from a solution by a membrane-free bipolar electrode according to any one of claims 1-9, connecting the first end electrode to the positive electrode of a power supply, connecting the second end electrode to the negative electrode of a power supply, and injecting a lithium-containing solution to be extracted into the electrolytic cell; turning on the power supply, and current flows into the first end electrode and flows out of the second end electrode, while the following changes occur: The lithium ions in the solution to be extracted enter the lithium extraction layer and are extracted by being embedded into the lithium electroactive material in a state of lithium deficiency; the electroactive material in the ion balance layer maintains the ion charge balance in the solution to be extracted by adsorbing anions or releasing cations other than lithium; Step 2, lithium liquid discharge; After the reaction in step 1, the solution to be extracted is converted into a lithium-depleted solution, the power supply is turned off, the lithium-depleted solution is discharged, and the electrolytic cell is cleaned; Step 3, lithium enrichment; The supporting electrolyte is injected into the electrolytic cell in step 3, the power supply is turned on with the positive and negative poles exchanged, and the current flows from the second end electrode to the first end electrode, while the following changes occur: The lithium electroactive material in the lithium extraction layer is oxidized, thereby releasing the adsorbed lithium ions into the supporting electrolyte; The electroactive material in the ion balance layer maintains the ion charge balance in the supporting electrolyte by releasing anions or adsorbing cations other than lithium; Step 4, discharge of the lithium-enriched solution; After the reaction in step 3, the supporting electrolyte is converted into a lithium-enriched solution, the power supply is turned off, and the lithium-enriched solution is discharged and collected; the device for extracting lithium from the solution by the bipolar electrode returns to the state before step 1, ready for reuse.

11. The method of extracting lithium from solution with a membraneless bipolar electrode of claim 10, wherein, When the ion balance layer is a cation balance layer, In step 1, the electroactive material in the cation balance layer is oxidized to release other cations other than lithium ions that have been adsorbed and released into the solution to be extracted; In step 3, the electroactive material in the cation balance layer is reduced, and other cations in the supporting electrolyte are inserted into the electroactive material; Or, when the ion balance layer is an anion balance layer, In step 1, anions in the solution to be extracted enter the anion balance layer and are solidified; In step 3, the adsorbed anions in the anion balance layer are desorbed and released into the supporting electrolyte.

12. The method of extracting lithium from solution with a membraneless bipolar electrode of claim 10, wherein, The solution to be extracted is any one or a mixture of several of the following: salt lake brine, underground brine, oilfield brine, ore decomposition, and lithium-containing solution obtained from secondary resource recovery, and lithium-depleted mother liquor.

13. The method of extracting lithium from solution with a membraneless bipolar electrode of claim 12, wherein, The lithium concentration in the solution to be extracted is not less than 0.05 g / L.

14. The method of extracting lithium from solution with a membraneless bipolar electrode of claim 11, wherein, The molar amount of cations adsorbed by the cation balance layer material in the supporting electrolyte is greater than the molar amount of lithium released from the lithium electroactive material, which is 1.1-1.2 times the molar amount of lithium released.

15. The method of extracting lithium from solution with a membraneless bipolar electrode of claim 14, wherein, The power supply voltage is (0.05-0.8) × (n+1) volts, where n is the number of conductive separators.

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