Lithium extraction electrode, and preparation method therefor and use thereof

Abstract

A lithium extraction electrode, and a preparation method therefor and the use thereof. The preparation method comprises the following steps: mixing an active material, a conductive agent, a binder, a foaming agent and a solvent to obtain a slurry, then coating a current collector with the slurry, and conducting drying and water immersion treatments, so as to obtain the lithium extraction electrode, wherein the foaming agent comprises composite silicone oil, an inhibitor and a catalyst. The foaming agent containing composite silicone oil, an inhibitor and a catalyst is used to form, in the lithium extraction electrode, micropores with a uniform pore size, and moreover the connectivity between the micropores is stronger, the specific surface area of the electrode is larger, and the porosity is higher; therefore, the prepared lithium extraction electrode has good charge-discharge performance and relatively long cycle life.

Description

A lithium extraction electrode and its preparation method and application Technical Field

[0001] The present disclosure belongs to the technical field of lithium extraction from salt lakes, and particularly relates to a lithium extraction electrode and a preparation method and application thereof. Background Art

[0002] As a primary component of batteries, efficient acquisition and stable supply of lithium resources are paramount to the development of the new energy industry. Currently, extracting lithium from salt lakes offers inherent cost advantages, but operating conditions vary significantly across salt lakes globally. Direct lithium extraction via electro-deintercalation has become a key research and development approach for lithium extraction from salt lakes due to its efficient magnesium-lithium performance and wide adaptability.

[0003] Electrochemical deintercalation is a direct lithium extraction method that uses active materials to selectively intercalate lithium ions under current. To address the low charge / discharge capacity and capacity decay associated with current electrochemical deintercalation, increasing the porosity of the electrode plates can improve their charge / discharge performance.

[0004] Therefore, it is urgent to design a preparation method for lithium extraction electrodes so that the lithium extraction electrodes have a higher porosity, excellent charge and discharge performance, and a longer cycle life.

[0005] Summary of the Invention

[0006] 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.

[0007] To address the shortcomings of the prior art, the present invention aims to provide a lithium extraction electrode, its preparation method, and its application. By using a foaming agent containing composite silicone oil, an inhibitor, and a catalyst, the present invention forms uniform micropores within the lithium extraction electrode. The micropores are more interconnected, resulting in a larger specific surface area and higher porosity. This results in the prepared lithium extraction electrode having excellent charge-discharge performance and a long cycle life.

[0008] To achieve this goal, the present disclosure adopts the following technical solutions:

[0009] In a first aspect, the present disclosure provides a method for preparing a lithium extraction electrode, the preparation method comprising the following steps:

[0010] The active material, the conductive agent, the binder, the foaming agent and the solvent are mixed to obtain a slurry, and the slurry is then coated on a current collector, and after drying and water immersion treatment, the lithium extraction electrode is obtained;

[0011] The foaming agent includes composite silicone oil, inhibitor and catalyst.

[0012] The present invention adopts a foaming agent containing composite silicone oil, an inhibitor and a catalyst to form micropores with uniform pores inside the lithium extraction electrode, and the connectivity between the micropores is stronger, the specific surface area of ​​the electrode is larger, and the porosity is higher, so that the prepared lithium extraction electrode has excellent charge and discharge performance and a long cycle life.

[0013] In the present disclosure, the function of the composite silicone oil is to create pores.

[0014] In the present disclosure, the role of the inhibitor is to control the rate of foaming and the size of the foams.

[0015] In the present disclosure, the role of the catalyst is to promote the decomposition of the blowing agent into gas, thereby generating bubbles.

[0016] In the present disclosure, the purpose of the water immersion treatment is to dissolve and replace the water-soluble substances in the electrode plates.

[0017] As an optional technical solution of the present disclosure, the composite silicone oil includes vinyl silicone oil, hydroxyl silicone oil and hydrogen-containing silicone oil.

[0018] In the present disclosure, the composite silicone oil includes vinyl silicone oil, hydroxy silicone oil and hydrogen silicone oil, wherein the vinyl silicone oil is used to adjust the viscosity of the composite silicone oil, and the hydroxy silicone oil and hydrogen silicone oil are used to form pores.

[0019] In one embodiment, based on the mass of the foaming agent, the mass fraction of the vinyl silicone oil is 6%-30%, for example, it can be 6%, 8%, 10%, 15%, 20%, 25% or 30%, and can further be 20%-25%.

[0020] In the present disclosure, if the mass fraction of the vinyl silicone oil is too low, the viscosity of the foaming agent is low; if the mass fraction of the vinyl silicone oil is too high, the viscosity of the foaming agent is high.

[0021] In one embodiment, based on the mass of the foaming agent, the total mass content of the hydroxy silicone oil and hydrogen silicone oil is 5%-15%, for example, 5%, 10% or 15%, and further optionally 11%-13%.

[0022] In the present disclosure, if the total mass content of hydroxyl silicone oil and hydrogen-containing silicone oil is too low, the porosity of the prepared lithium extraction electrode is low; if the total mass content of hydroxyl silicone oil and hydrogen-containing silicone oil is too high, the porosity of the prepared lithium extraction electrode is high.

[0023] In one embodiment, the mass ratio of the hydroxyl silicone oil to the hydrogen-containing silicone oil is (2-9): (1-8), wherein the selection range of the hydroxyl silicone oil "2-9" can be, for example, 2, 3, 4, 5, 6, 7, 8 or 9, and the selection range of the hydrogen-containing silicone oil "1-8" can be, for example, 1, 2, 3, 4, 5, 6, 7 or 8, etc.

[0024] In the present disclosure, if the mass ratio of hydroxyl silicone oil and hydrogen-containing silicone oil is too low, that is, the mass content of hydrogen-containing silicone oil is too high, then the proportion of micropores in the prepared lithium extraction electrode is relatively large; if the mass ratio of hydroxyl silicone oil and hydrogen-containing silicone oil is too high, that is, the mass content of hydrogen-containing silicone oil is too low, then the proportion of mesopores and macropores in the lithium extraction electrode is relatively large.

[0025] As an optional technical solution of the present disclosure, the inhibitor is an alcohol substance, and the alcohol substance includes cyclohexanol.

[0026] In the present disclosure, cyclohexanol is used as an inhibitor to inhibit the foaming speed, prevent bubbles from being generated too quickly, resulting in uneven pore formation and affecting the uniformity of the internal pores.

[0027] In one embodiment, based on the mass of the foaming agent, the mass fraction of the inhibitor is 40%-70%, for example, 40%, 50%, 60% or 70%, and further optionally 60%-65%.

[0028] In the present disclosure, the mass fraction of the inhibitor is 40%-70%, which can ensure that the porosity of the lithium extraction electrode is evenly distributed.

[0029] As an optional technical solution of the present disclosure, the catalyst includes chloroplatinic acid.

[0030] In the present disclosure, the chloroplatinic acid catalyst can catalyze the decomposition of the foaming agent into bubbles to form pores.

[0031] In one embodiment, based on the mass of the foaming agent, the mass fraction of the catalyst is 0.1%-1%, for example, 0.1%, 0.3%, 0.5%, 0.7% or 0.9%, and can further be 0.3%-0.7%.

[0032] In the present disclosure, if the mass fraction of the catalyst is too low, the number of bubbles is too small and the pore-forming porosity is too low; if the mass fraction of the catalyst is too high, the pore-forming speed is too fast and the pore distribution is uneven.

[0033] As an optional technical solution of the present disclosure, the active material includes lithium iron phosphate.

[0034] In one embodiment, the conductive agent includes any one of white carbon black, carbon nanotubes, or acetylene black, or a combination of at least two thereof.

[0035] In one embodiment, the binder includes any one of polyamide, polyimide, polysulfone, polyvinylidene fluoride, or polydimethylsiloxane, or a combination of at least two thereof.

[0036] In one embodiment, the current collector includes a porous metal titanium mesh, a porous titanium alloy or a stainless steel mesh.

[0037] As an optional technical solution of the present invention, the mass ratio of the active material, conductive agent, binder and foaming agent is (70-75): (5-10): (5-15): (5-10), wherein the selection range of the active material "70-75" can be, for example, 70, 71, 72, 73, 74 or 75, etc., the selection range of the conductive agent "5-10" can be, for example, 5, 6, 7, 8, 9 or 10, etc., the selection range of the binder "5-15" can be, for example, 5, 7, 10, 12 or 15, etc., and the selection range of the foaming agent "5-10" can be, for example, 5, 6, 7, 8, 9 or 10, etc.

[0038] In the present disclosure, if the mass ratio of the active substance to the foaming agent is too small, that is, the mass content of the foaming agent is too high, then there will be too little active substance in the plate and too many pores, which is not conducive to subsequent lithium extraction. If the mass ratio of the active substance to the foaming agent is too large, that is, the mass content of the foaming agent is too low, then the porosity is insufficient, the subsequent oxidation delithiation is incomplete, and the initial gram capacity is low.

[0039] In one embodiment, the ratio of the total mass of the active material, conductive agent, binder and foaming agent to the mass of the solvent is (0.8-1.2):1, for example, it can be 0.8:1, 0.9:1, 1:1, 1.1:1 or 1.2:1.

[0040] As an optional technical solution of the present disclosure, the drying method is multi-stage drying.

[0041] In one embodiment, the multi-stage drying process includes: heating from room temperature to a first temperature for primary drying, then heating to a second temperature for secondary drying, and finally cooling to room temperature.

[0042] In the present disclosure, the above-mentioned drying method is adopted to help achieve more complete drying of the slurry, so that the pore distribution is uniform.

[0043] It should be noted that the present disclosure does not specifically limit the room temperature. For example, it can be 25±°C, such as 20°C, 25°C or 30°C.

[0044] In one embodiment, the time for the first heating is 0.8-1.2 h, for example, 0.8 h, 0.9 h, 1 h, 1.1 h or 1.2 h.

[0045] In one embodiment, the primary temperature is 55-65°C, for example, 55°C, 57°C, 60°C, 63°C or 65°C, and the primary drying time is 4-8h, for example, 4h, 5h, 6h, 7h or 8h.

[0046] In the present disclosure, the primary drying is performed at 55-65° C. for 4-8 hours in advance, which helps to achieve more complete drying of the slurry and make the pore distribution uniform.

[0047] In one embodiment, the secondary heating time is 0.3-0.7 h, for example, 0.3 h, 0.4 h, 0.6 h or 0.7 h.

[0048] In one embodiment, the secondary temperature is 75-85°C, for example, 75°C, 77°C, 80°C, 83°C or 85°C, and the secondary drying time is 14-18h, for example, 14h, 15h, 16h, 17h or 18h.

[0049] In the present disclosure, secondary drying at 75-85° C. for 14-18 hours helps to achieve more complete drying of the slurry and make the pore distribution uniform.

[0050] In one embodiment, the immersion time is 4-8 hours, for example, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours.

[0051] In one embodiment, the water immersion treatment is followed by an oxidation treatment.

[0052] In the present disclosure, oxidation treatment can reduce cracks on the surface of the lithium extraction electrode and improve the strength and durability of the lithium extraction electrode.

[0053] In one embodiment, during the oxidation treatment, the oxidant solution used includes any one of hydrogen peroxide, sodium persulfate solution, sodium hypochlorite solution or sodium chlorate solution, or a combination of at least two thereof.

[0054] As an optional technical solution of the present disclosure, the preparation method includes the following steps:

[0055] (1) mixing an active material, a conductive agent, a binder, and a foaming agent with a solvent in a mass ratio of (70-75):(5-10):(5-15):(5-10) to obtain a slurry;

[0056] Wherein, the foaming agent includes vinyl silicone oil, hydroxyl silicone oil, hydrogen-containing silicone oil, an inhibitor and a catalyst. Based on the mass of the foaming agent, the mass fraction of the vinyl silicone oil is 6%-30%, the total mass content of the hydroxyl silicone oil and the hydrogen-containing silicone oil is 5%-15%, the mass fraction of the inhibitor is 40%-70%, the mass fraction of the catalyst is 0.1%-1%, and the mass ratio of the hydroxyl silicone oil to the hydrogen-containing silicone oil is (2-9):(1-8);

[0057] (2) The slurry is coated on a current collector, and then multi-stage dried, and then immersed in water for 4-8 hours, and finally immersed in an oxidant solution at 30-50°C for 0.5-2 hours (for example, 0.5 hours, 1 hour, 1.5 hours or 2 hours, etc.) for oxidation treatment to obtain the lithium extraction electrode.

[0058] In a second aspect, the present disclosure provides a lithium extraction electrode prepared by the preparation method described in the first aspect, wherein the lithium extraction electrode comprises a current collector and a porous active layer disposed on at least one surface of the current collector.

[0059] In the present disclosure, the porous active layer has micropores with uniform porosity, and the connectivity between the micropores is stronger, the electrode has a larger specific surface area and a higher porosity, so that the prepared lithium extraction electrode has excellent charge and discharge performance and a longer cycle life.

[0060] As an optional technical solution of the present disclosure, the thickness of the porous active layer is 1-7 mm, for example, it can be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm or 7 mm.

[0061] In the present disclosure, if the porous active layer is too thin, the amount of active components in a single plate is low and the lithium extraction efficiency is low; if the porous active layer is too thick, the plate polarization phenomenon is serious and the specific capacity decays quickly.

[0062] In one embodiment, the porosity of the porous active layer is 10%-60%, for example, it can be 10%, 20%, 30%, 40%, 50% or 60%, etc., and the average pore size is 0.1nm-1μm, for example, it can be 0.1nm, 1nm, 10nm, 100nm, 500nm or 1μm, etc.

[0063] In the present disclosure, the porous active layer with a porosity of 10%-60% and an average pore diameter of 0.1 nm-1 μm can enable the prepared lithium extraction electrode to have excellent charge and discharge performance and a long cycle life.

[0064] In a third aspect, the present disclosure provides an application of the lithium extraction electrode as described in the second aspect, wherein the lithium extraction electrode is applied to extract lithium from a salt lake.

[0065] The lithium extraction electrode prepared in the present invention is prepared by increasing the porosity of the active material in the electrode plate and creating small pores, mesopores and macropores, thereby facilitating the transmission of lithium ions in the salt lake to improve the charge and discharge capacity and cycle life.

[0066] 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.

[0067] Compared with the prior art, the present disclosure has the following beneficial effects:

[0068] (2) The present invention adopts a foaming agent containing composite silicone oil, an inhibitor and a catalyst to form micropores with uniform pores inside the lithium extraction electrode, and the connectivity between the micropores is stronger, the specific surface area of ​​the electrode is larger, and the porosity is higher, so that the prepared lithium extraction electrode has excellent charge and discharge performance and a long cycle life.

[0069] (2) The lithium-extraction electrode prepared by the preparation method provided in the present disclosure has an initial specific capacity of 101.68 mAh / g, a specific capacity of 97.36 mAh / g after 200 cycles, and a capacity retention rate of 95.75%.

[0070] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0071] The technical solution of the present disclosure is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present disclosure and should not be regarded as specific limitations of the present disclosure.

[0072] Example 1

[0073] This embodiment provides a method for preparing a lithium extraction electrode, the preparation method comprising the following steps:

[0074] (1) vinyl silicone oil, hydroxy silicone oil, hydrogen silicone oil, inhibitor and catalyst were mixed and stirred for 2 hours to obtain a foaming agent;

[0075] The inhibitor is cyclohexanol, the catalyst is chloroplatinic acid, and based on the mass of the foaming agent, the mass fraction of the vinyl silicone oil is 24%, the total mass content of the hydroxyl silicone oil and the hydrogen-containing silicone oil is 12%, the mass fraction of the inhibitor is 63.5%, the mass fraction of the catalyst is 0.5%, and the mass ratio of the hydroxyl silicone oil to the hydrogen-containing silicone oil is 8.4:3.6;

[0076] (2) fully dissolving the binder polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) to form a polymer solution, and then adding the active material lithium iron phosphate, the conductive agent white carbon black and the foaming agent to the polymer solution and stirring them thoroughly to obtain a slurry;

[0077] The mass ratio of lithium iron phosphate, white carbon black, polyvinylidene fluoride and foaming agent is 72:8:12:8, and the ratio of the total mass of lithium iron phosphate, white carbon black, polyvinylidene fluoride and foaming agent to the mass of NMP is 1:1.

[0078] (3) The slurry is scraped onto the current collector porous titanium mesh using a template, and then the obtained electrode is placed in an oven set with a heating curve and dried for 24 hours (the drying process includes: heating from room temperature 25°C to a primary temperature of 60°C for 1 hour, performing primary drying for 6 hours, then heating to a secondary temperature of 80°C for 0.5 hours, performing secondary drying for 16 hours, and finally cooling to room temperature 25°C), then immersed in deionized water and allowed to stand for 4 hours. After the end, it is placed in a sodium persulfate solution at 40°C and immersed for 1 hour for oxidation treatment, and then rinsed under water and immersed in deionized water for 3 hours to obtain the lithium extraction electrode.

[0079] This embodiment also provides a lithium extraction electrode prepared using the above-mentioned preparation method, wherein the lithium extraction electrode includes a current collector and a porous active layer arranged on at least one surface of the current collector, wherein the thickness of the porous active layer is 3 mm, the porosity of the porous active layer is 30%, and the average pore diameter is 0.5 μm.

[0080] Example 2

[0081] This embodiment provides a method for preparing a lithium extraction electrode, the preparation method comprising the following steps:

[0082] (1) vinyl silicone oil, hydroxy silicone oil, hydrogen silicone oil, inhibitor and catalyst were mixed and stirred for 2 hours to obtain a foaming agent;

[0083] The inhibitor is cyclohexanol, the catalyst is chloroplatinic acid, and based on the mass of the foaming agent, the mass fraction of the vinyl silicone oil is 15%, the total mass content of the hydroxyl silicone oil and the hydrogen-containing silicone oil is 14%, the mass fraction of the inhibitor is 70%, the mass fraction of the catalyst is 1%, and the mass ratio of the hydroxyl silicone oil to the hydrogen-containing silicone oil is 6:8;

[0084] (2) fully dissolving the binder polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) to form a polymer solution, and then adding the active material lithium iron phosphate, the conductive agent white carbon black and the foaming agent to the polymer solution and stirring them thoroughly to obtain a slurry;

[0085] The mass ratio of lithium iron phosphate, white carbon black, polyvinylidene fluoride and foaming agent is 75:5:15:5, and the ratio of the total mass of lithium iron phosphate, white carbon black, polyvinylidene fluoride and foaming agent to the mass of NMP is 1:1.

[0086] (3) The slurry is scraped onto the current collector porous titanium mesh using a template, and then the obtained electrode is placed in an oven set with a heating curve and dried for 24 hours (the drying process includes: heating from room temperature 25°C to a first-level temperature of 55°C for 1 hour, performing first-level drying for 6 hours, then heating to a second-level temperature of 75°C for 0.5 hours, performing second-level drying for 14 hours, and finally cooling to room temperature 25°C), then immersed in deionized water and allowed to stand for 6 hours. After the end, it is placed in a sodium hypochlorite solution at 30°C and immersed for 2 hours for oxidation treatment, and then rinsed under water and immersed in deionized water for 3 hours to obtain the lithium extraction electrode.

[0087] This embodiment also provides a lithium extraction electrode prepared using the above-mentioned preparation method, wherein the lithium extraction electrode includes a current collector and a porous active layer arranged on at least one surface of the current collector, wherein the thickness of the porous active layer is 1 mm, the porosity of the porous active layer is 60%, and the average pore diameter is 1 nm.

[0088] Example 3

[0089] This embodiment provides a method for preparing a lithium extraction electrode, the preparation method comprising the following steps:

[0090] (1) vinyl silicone oil, hydroxy silicone oil, hydrogen silicone oil, inhibitor and catalyst were mixed and stirred for 2 hours to obtain a foaming agent;

[0091] The inhibitor is cyclohexanol, the catalyst is chloroplatinic acid, and based on the mass of the foaming agent, the mass fraction of the vinyl silicone oil is 30%, the total mass content of the hydroxyl silicone oil and the hydrogen-containing silicone oil is 9.9%, the mass fraction of the inhibitor is 60%, the mass fraction of the catalyst is 0.1%, and the mass ratio of the hydroxyl silicone oil to the hydrogen-containing silicone oil is 8.9:1;

[0092] (2) fully dissolving the binder polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) to form a polymer solution, and then adding the active material lithium iron phosphate, the conductive agent white carbon black and the foaming agent to the polymer solution and stirring them thoroughly to obtain a slurry;

[0093] Wherein, the mass ratio of lithium iron phosphate, white carbon black, polyvinylidene fluoride and foaming agent is 70:10:10:10, and the ratio of the total mass of lithium iron phosphate, white carbon black, polyvinylidene fluoride and foaming agent to the mass of the NMP is 1:1;

[0094] (3) The slurry is scraped onto the current collector porous titanium mesh using a template, and then the obtained electrode is placed in an oven set with a heating curve and dried for 24 hours (the drying process includes: heating from room temperature 25°C to a first-level temperature of 65°C for 1 hour, performing first-level drying for 4 hours, then heating to a second-level temperature of 85°C for 0.5 hours, performing second-level drying for 18 hours, and finally cooling to room temperature 25°C), then immersed in deionized water and allowed to stand for 8 hours. After the end, it is placed in hydrogen peroxide at 50°C for 0.5 hours for oxidation treatment, and then rinsed under water and soaked in deionized water for 3 hours to obtain the lithium extraction electrode.

[0095] This embodiment also provides a lithium extraction electrode prepared using the above-mentioned preparation method, wherein the lithium extraction electrode includes a current collector and a porous active layer arranged on at least one surface of the current collector, wherein the thickness of the porous active layer is 7 mm, the porosity of the porous active layer is 10%, and the average pore size is 1 μm.

[0096] Example 4

[0097] The difference between this embodiment and embodiment 1 is that the mass fraction of the vinyl silicone oil in step (1) is 5%, and the mass fraction of the inhibitor is adaptively adjusted to 82.9%.

[0098] The rest of the preparation methods and parameters remained the same as in Example 1.

[0099] Example 5

[0100] The difference between this embodiment and embodiment 1 is that the mass fraction of the vinyl silicone oil in step (1) is 35%, and the mass fraction of the inhibitor is adaptively adjusted to 52.5%.

[0101] The rest of the preparation methods and parameters remained the same as in Example 1.

[0102] Example 6

[0103] The difference between this embodiment and embodiment 1 is that the total mass content of hydroxy silicone oil and hydrogen silicone oil in step (1) is 3%, and the mass fraction of the inhibitor is adaptively adjusted to 70%, and the mass fraction of the vinyl silicone oil is 26.5%.

[0104] The rest of the preparation methods and parameters remained the same as in Example 1.

[0105] Example 7

[0106] The difference between this embodiment and embodiment 1 is that the total mass content of hydroxy silicone oil and hydrogen silicone oil in step (1) is 20%, and the mass fraction of the inhibitor is adaptively adjusted to 55.5%.

[0107] The rest of the preparation methods and parameters remained the same as in Example 1.

[0108] Example 8

[0109] The difference between this embodiment and embodiment 1 is that the mass ratio of hydroxy silicone oil to hydrogen silicone oil in step (1) is 2:10.

[0110] The rest of the preparation methods and parameters remained the same as in Example 1.

[0111] Example 9

[0112] The difference between this embodiment and embodiment 1 is that the mass ratio of hydroxy silicone oil to hydrogen silicone oil in step (1) is 10:1.

[0113] The rest of the preparation methods and parameters remained the same as in Example 1.

[0114] Example 10

[0115] The difference between this embodiment and embodiment 1 is that the hydrogenated silicone oil in step (1) is replaced by hydroxyl silicone oil of equal mass.

[0116] The rest of the preparation methods and parameters remained the same as in Example 1.

[0117] Example 11

[0118] The difference between this embodiment and embodiment 1 is that the mass fraction of the catalyst in step (1) is 0.05%, and the mass fraction of the inhibitor is adaptively adjusted to 63.95%.

[0119] The rest of the preparation methods and parameters remained the same as in Example 1.

[0120] Example 12

[0121] The difference between this embodiment and embodiment 1 is that the mass fraction of the catalyst in step (1) is 1.5%, and the mass fraction of the inhibitor is adaptively adjusted to 62.5%.

[0122] The rest of the preparation methods and parameters remained the same as in Example 1.

[0123] Example 13

[0124] The difference between this embodiment and embodiment 1 is that in step (2), the mass ratio of lithium iron phosphate, white carbon black, polyvinylidene fluoride and foaming agent is 75:8:14:3.

[0125] The rest of the preparation methods and parameters remained the same as in Example 1.

[0126] Example 14

[0127] The difference between this embodiment and embodiment 1 is that in step (2), the mass ratio of lithium iron phosphate, white carbon black, polyvinylidene fluoride and foaming agent is 70:8:10:12.

[0128] The rest of the preparation methods and parameters remained the same as in Example 1.

[0129] Example 15

[0130] The difference between this embodiment and embodiment 1 is that by adjusting the process parameters of step (3), the thickness of the porous active layer in the obtained lithium extraction electrode is 0.5 mm.

[0131] The rest of the preparation methods and parameters remained the same as in Example 1.

[0132] Example 16

[0133] The difference between this embodiment and embodiment 1 is that by adjusting the process parameters of step (3), the thickness of the porous active layer in the obtained lithium extraction electrode is 8 mm.

[0134] The rest of the preparation methods and parameters remained the same as in Example 1.

[0135] Comparative Example 1

[0136] The difference between this comparative example and Example 1 is that in step (1), the vinyl silicone oil, hydroxy silicone oil and hydrogen silicone oil are replaced by inhibitors of equal mass, that is, no composite silicone oil is added.

[0137] The rest of the preparation methods and parameters remained the same as in Example 1.

[0138] Comparative Example 2

[0139] The difference between this comparative example and Example 1 is that step (1) is not performed, that is, no foaming agent is added in step (2).

[0140] The rest of the preparation methods and parameters remained the same as in Example 1.

[0141] Performance Testing

[0142] The lithium extraction electrodes prepared in the above examples and comparative examples were subjected to electrochemical deintercalation tests, and the specific steps included:

[0143] (1) Pre-stand for 20 minutes;

[0144] (2) Set aside for 10 minutes;

[0145] (3) Constant current charging, rate 0.1C, current 0.0168A, cut-off voltage 0.35V;

[0146] (4) Constant voltage charging, rate is 0.1C, current is 0.0168A, voltage is 0.35V, cut-off rate is 0.025C, cut-off current is 0.0042A;

[0147] (5) Set aside for 10 minutes;

[0148] (6) Constant current discharge, rate 0.1C, current 0.0168A, cut-off voltage -0.35V;

[0149] (7) Set aside for 1 minute;

[0150] (8) Constant current discharge, rate of 0.05C, current of 0.0084A, cut-off voltage of -0.35V; (9) Stand for 1 min;

[0151] (10) Constant current discharge, rate of 0.025C, current of 0.0042A, cut-off voltage of -0.35V; (11) Cycle steps (2) to (10) for 200 cycles.

[0152] The test results are shown in Table 1.

[0153] Table 1

[0154] analyze:

[0155] As can be seen from the above table, the initial specific capacity of the lithium-extraction electrode prepared by the preparation method provided by the present disclosure can reach 101.68 mAh / g, the specific capacity can reach 97.36 mAh / g after 200 cycles, and the capacity retention rate can reach 95.75%.

[0156] It can be seen from Examples 1 and 4-5 that if the mass fraction of vinyl silicone oil is too small, the viscosity of the foaming agent is too low, resulting in low adhesion and low plate specific capacity; if the mass fraction of vinyl silicone oil is too large, the viscosity of the foaming agent is too high, resulting in uneven dispersion during the pulping process and low plate specific capacity.

[0157] It can be seen from Examples 1 and 6-7 that if the total mass content of hydroxyl silicone oil and hydrogen-containing silicone oil is too small, the porosity of the lithium extraction electrode will decrease and the gram capacity will be low; if the total mass content of hydroxyl silicone oil and hydrogen-containing silicone oil is too large, the electrode plate will crack, the voids will be too large, and the gram capacity will be low.

[0158] It can be seen from Examples 1 and 8-9 that if the mass ratio of hydroxyl silicone oil to hydrogen-containing silicone oil is too small, the pores formed are mainly micropores, which will make subsequent oxidation and delithiation difficult and result in low specific capacity; if the mass ratio of hydroxyl silicone oil to hydrogen-containing silicone oil is too large, the pores formed are mostly macropores, which will cause the electrical cycle energy of the plate to decay too quickly.

[0159] It can be seen from Examples 1 and 10 that a certain amount of hydrogenated silicone oil needs to be added to the foaming agent so that the prepared lithium extraction electrode can have a certain amount of pore structure, which facilitates the uniformity of the subsequent oxidation treatment.

[0160] It can be seen from Examples 1 and 11-12 that if the mass fraction of the catalyst is too small, the pore-forming speed is slow, resulting in low porosity; if the mass fraction of the catalyst is too large, the pore-forming speed is fast, making the pore-forming process difficult to control.

[0161] It can be seen from Examples 1 and 13-14 that if the mass ratio of the active substance to the foaming agent is too small, that is, the mass content of the foaming agent is too high, there will be too little active substance in the plate and too many pores, which is not conducive to subsequent lithium extraction; if the mass ratio of the active substance to the foaming agent is too large, that is, the mass content of the foaming agent is too low, the porosity is insufficient, the subsequent oxidation delithiation is incomplete, and the initial gram capacity is low.

[0162] It can be seen from Examples 1 and 15-16 that if the thickness of the porous active layer is too thin, the active material mass of the electrode plate is low, resulting in low specific capacity; if the thickness of the porous active layer is too thick, the polarization phenomenon of the electrode plate is serious, and it is difficult to remove lithium, resulting in low specific capacity and rapid degradation of electrical performance.

[0163] It can be seen from Example 1 and Comparative Example 1 that if composite silicone oil is not added to the foaming agent, the pores inside the plate will be uneven, resulting in a decrease in gram capacity.

[0164] It can be seen from Example 1 and Comparative Example 2 that adding a foaming agent during the preparation of a lithium extraction electrode can produce an electro-deintercalation plate with high porosity, and the prepared lithium extraction electrode has excellent performance.

Claims

1. A preparation method of a lithium extraction electrode, comprising the following steps: Mix an active material, a conductive agent, a binder, a foaming agent and a solvent to obtain a slurry, and then coat the slurry on a current collector. After drying and water immersion treatment, the lithium extraction electrode is obtained; Wherein, the foaming agent includes a composite silicone oil, an inhibitor and a catalyst.

2. The preparation method according to claim 1, wherein The composite silicone oil includes vinyl silicone oil, hydroxy silicone oil and hydrogen-containing silicone oil.

3. The preparation method according to claim 2, wherein, Based on the mass of the foaming agent, the mass fraction of the vinyl silicone oil is 6%-30%, and further optionally 20%-25%.

4. The preparation method according to claim 2 or 3, wherein Based on the mass of the foaming agent, the total mass content of the hydroxy silicone oil and the hydrogen-containing silicone oil is 5%-15%, and further optionally 11%-13%.

5. The preparation method according to any one of claims 2-4, wherein, The mass ratio of the hydroxy silicone oil to the hydrogen-containing silicone oil is (2-9):(1-8).

6. The preparation method according to any one of claims 1-5, wherein, The inhibitor is an alcohol substance, and the alcohol substance includes cyclohexanol.

7. The preparation method according to any one of claims 1-6, wherein, Based on the mass of the foaming agent, the mass fraction of the inhibitor is 40%-70%, and further optionally 60-65%.

8. The preparation method according to any one of claims 1 to 7, wherein, The catalyst includes chloroplatinic acid.

9. The preparation method according to any one of claims 1-8, wherein, Based on the mass of the foaming agent, the mass fraction of the catalyst is 0.1%-1%, and further optionally 0.3%-0.7%.

10. The preparation method according to any one of claims 1-9, wherein, The mass ratio of the active material, the conductive agent, the binder and the foaming agent is (70-75):(5-10):(5-15):(5-10).

11. According to the preparation method described in any one of claims 1-10, wherein, The drying method is multi-stage drying.

12. The preparation method according to claim 11, wherein The process of the multi-stage drying includes: heating from room temperature to the first-stage temperature at one time for the first-stage drying, then heating to the second-stage temperature for the second-stage drying, and finally cooling to room temperature; Optionally, the first-stage temperature is 55-65°C, and the time for the first-stage drying is 4-8h; Optionally, the second-stage temperature is 75-85°C, and the time for the second-stage drying is 14-18h.

13. The preparation method according to any one of claims 1-12, wherein, The time for water immersion is 4-8h; Optionally, after the water immersion treatment, an oxidation treatment is further performed.

14. The preparation method according to any one of claims 1-13, wherein, The preparation method includes the following steps: (1) Stir and mix an active material, a conductive agent, a binder and a foaming agent with a solvent according to a mass ratio of (70-75):(5-10):(5-15):(5-10) to obtain a slurry; Wherein, the foaming agent includes vinyl silicone oil, hydroxy silicone oil, hydrogen-containing silicone oil, an inhibitor and a catalyst. Based on the mass of the foaming agent, the mass fraction of the vinyl silicone oil is 6%-30%, the total mass content of the hydroxy silicone oil and the hydrogen-containing silicone oil is 5-15%, the mass fraction of the inhibitor is 40%-70%, the mass fraction of the catalyst is 0.1-1%, and the mass ratio of the hydroxy silicone oil to the hydrogen-containing silicone oil is (2-9):(1-8); (2) Coat the slurry on a current collector, then perform multi-stage drying, then immerse it in water for 4-8h, and finally soak it in an oxidant solution at 30-50°C for 0.5-2h for oxidation treatment to obtain the lithium extraction electrode.

15. A lithium extraction electrode prepared by the preparation method according to any one of claims 1-14, comprising a current collector and a porous active layer provided on at least one surface of the current collector.

16. The lithium extraction electrode according to claim 15, wherein, The thickness of the porous active layer is 1-7mm; Optionally, the porosity of the porous active layer is 10%-60%, and the average pore diameter is 0.1 nm-1 μm.

17. An application of the lithium extraction electrode as described in claim 15 or 16 for extracting lithium from salt lakes.

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