A lithium extraction electrode, its preparation method and application

Abstract

The present disclosure provides a lithium extraction electrode and a preparation method and application thereof, the preparation method comprising the following steps: mixing an active material, a conductive agent, a binder, a foaming agent and a solvent to obtain a slurry, and then coating the slurry on a current collector, and after drying and water immersion treatment, the lithium extraction electrode is obtained; wherein the foaming agent comprises a composite silicone oil, an inhibitor and a catalyst. The present disclosure forms micropores with uniform pores inside the lithium extraction electrode by using a foaming agent containing a composite silicone oil, an inhibitor and a catalyst, 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 higher cycle service life.

Description

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

[0002] As a main component of batteries, efficient acquisition and stable supply of lithium resources are the top priority for the development of new energy industries. At present, salt lake lithium extraction has a natural cost advantage in acquiring lithium resources, but the working conditions of different salt lakes around the world differ greatly. The direct lithium extraction technology based on electrochemical deintercalation has become one of the important lithium extraction research and development routes due to its efficient magnesium-lithium performance and wide adaptability.

[0003] The electrochemical deintercalation technology is one of the direct lithium extraction schemes, that is, lithium ions are selectively intercalated by active materials under the driving of electric current. In view of the low charge-discharge specific capacity and capacity attenuation of the current electrochemical deintercalation lithium extraction technology, the porosity of the electrode plate can be improved to improve the charge-discharge performance of the electrode plate.

[0004] Therefore, it is urgent to design a preparation method of a lithium extraction electrode, so that the lithium extraction electrode has high porosity, excellent charge-discharge performance and high cycle service life. SUMMARY

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

[0006] In view of the deficiencies of the prior art, the purpose of the present disclosure is to provide a lithium extraction electrode and a preparation method and application thereof. The present disclosure forms uniform micropores with high connectivity between micropores, large specific surface area and high porosity in the lithium extraction electrode by using a foaming agent containing composite silicone oil, inhibitor and catalyst, so that the prepared lithium extraction electrode has excellent charge-discharge performance and high cycle service life.

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

[0008] In a first aspect, the present disclosure provides a preparation method of a lithium extraction electrode, which comprises the following steps:

[0009] Mixing an active material, a conductive agent, a binder, a foaming agent and a solvent to obtain a slurry, and then coating the slurry on a current collector to obtain the lithium extraction electrode after drying and water immersion treatment;

[0010] The foaming agent comprises a composite silicone oil, an inhibitor and a catalyst.

[0011] The present disclosure forms micro-pores with uniform porosity and stronger connectivity between the micro-pores in the lithium extraction electrode by using a foaming agent containing composite silicone oil, an inhibitor and a catalyst, so that the prepared lithium extraction electrode has excellent charge-discharge performance and higher cycle life.

[0012] In the present disclosure, the role of the composite silicone oil is to form pores.

[0013] In the present disclosure, the role of the inhibitor is to control the rate and size of foaming.

[0014] In the present disclosure, the role of the catalyst is to promote the decomposition of the foaming agent into gas to generate bubbles.

[0015] In the present disclosure, the purpose of water immersion treatment is to dissolve and replace water-soluble substances in the electrode plate.

[0016] As an optional technical solution of the present disclosure, the composite silicone oil comprises vinyl silicone oil, hydroxyl silicone oil and hydrogen-containing silicone oil.

[0017] In the present disclosure, the composite silicone oil comprises vinyl silicone oil, hydroxyl silicone oil and hydrogen-containing silicone oil, wherein the role of the vinyl silicone oil is to adjust the viscosity of the composite silicone oil, and the roles of the hydroxyl silicone oil and the hydrogen-containing silicone oil are to form pores.

[0018] In an embodiment, the mass fraction of the vinyl silicone oil is 6%-30% based on the mass of the foaming agent, for example, it can be 6%, 8%, 10%, 15%, 20%, 25% or 30%, and further optionally 20%-25%.

[0019] 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.

[0020] In an embodiment, the total mass content of the hydroxyl silicone oil and the hydrogen-containing silicone oil is 5%-15% based on the mass of the foaming agent, for example, it can be 5%, 10% or 15%, and further optionally 11%-13%.

[0021] In the present disclosure, if the total mass content of the hydroxyl silicone oil and the hydrogen-containing silicone oil is too low, the porosity of the prepared lithium extraction electrode is low; if the total mass content of the hydroxyl silicone oil and the hydrogen-containing silicone oil is too high, the porosity of the prepared lithium extraction electrode is high.

[0022] In an embodiment, the mass ratio of the hydroxyl silicone oil to the hydrogen-containing silicone oil is (2-9):(1-8), wherein the selected range "2-9" of the hydroxyl silicone oil can be 2, 3, 4, 5, 6, 7, 8 or 9, and the selected range "1-8" of the hydrogen-containing silicone oil can be 1, 2, 3, 4, 5, 6, 7 or 8.

[0023] In the present disclosure, if the mass ratio of the hydroxyl silicone oil and the hydrogen-containing silicone oil is too low, i.e., the mass content of the hydrogen-containing silicone oil is too high, the micropores account for a large proportion in the lithium extraction electrode prepared; if the mass ratio of the hydroxyl silicone oil and the hydrogen-containing silicone oil is too high, i.e., the mass content of the hydrogen-containing silicone oil is too low, the mesopores and macropores account for a large proportion in the lithium extraction electrode.

[0024] As an optional technical solution of the present disclosure, the inhibitor is an alcohol substance, and the alcohol substance includes cyclohexanol.

[0025] In the present disclosure, cyclohexanol is used as the inhibitor, which can inhibit the speed of foaming, prevent the pores from being unevenly formed due to the rapid generation of bubbles, and affect the uniformity of the internal pores.

[0026] In an embodiment, the mass fraction of the inhibitor is 40%-70% based on the mass of the foaming agent, for example, can be 40%, 50%, 60% or 70%, and further can be selected as 60%-65%.

[0027] In the present disclosure, the mass fraction of the inhibitor is 40%-70%, which can ensure the uniform distribution of the porosity of the lithium extraction electrode.

[0028] As an optional technical solution of the present disclosure, the catalyst includes chloroplatinic acid.

[0029] In the present disclosure, the chloroplatinic acid catalyst can catalyze the decomposition of the foaming agent into bubbles for pore formation.

[0030] In an embodiment, the mass fraction of the catalyst is 0.1%-1% based on the mass of the foaming agent, for example, can be 0.1%, 0.3%, 0.5%, 0.7% or 0.9%, and further can be selected as 0.3%-0.7%.

[0031] In the present disclosure, if the mass fraction of the catalyst is too low, the number of bubbles is too small, and the pore porosity is too low; if the mass fraction of the catalyst is too high, the pore formation speed is too fast, and the pore distribution is uneven.

[0032] As an optional technical solution of the present disclosure, the active substance includes lithium iron phosphate.

[0033] In an embodiment, the conductive agent includes any one or a combination of at least two of white carbon black, carbon nanotubes or acetylene black.

[0034] In an embodiment, the binder includes any one or a combination of at least two of polyamide, polyimide, polysulfone, polyvinylidene fluoride or polydimethylsiloxane.

[0035] In one embodiment, the current collector comprises a porous metal titanium mesh, a porous titanium alloy or stainless steel mesh, or the like.

[0036] As an optional technical solution of the present disclosure, 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), wherein the selection range "70-75" of the active material may be 70, 71, 72, 73, 74 or 75, etc., the selection range "5-10" of the conductive agent may be 5, 6, 7, 8, 9 or 10, etc., the selection range "5-15" of the binder may be 5, 7, 10, 12 or 15, etc., and the selection range "5-10" of the foaming agent may be 5, 6, 7, 8, 9 or 10, etc.

[0037] In the present disclosure, if the mass ratio of the active material and the foaming agent is too small, i.e., the mass content of the foaming agent is too high, there is too little active material in the electrode plate and too many pores, which is not conducive to subsequent lithium extraction, and if the mass ratio of the active material and the foaming agent is too large, i.e., the mass content of the foaming agent is too low, the porosity is not enough, and the subsequent oxidative delithiation is not complete, resulting in a low initial specific capacity.

[0038] In one embodiment, the ratio of the total mass of the active material, the conductive agent, the binder and the foaming agent to the mass of the solvent is (0.8-1.2):1, which may be 0.8:1, 0.9:1, 1:1, 1.1:1 or 1.2:1, etc.

[0039] As an optional technical solution of the present disclosure, the drying method is multistage drying.

[0040] In one embodiment, the multistage drying process comprises: one-time heating from room temperature to a primary temperature for primary drying, then two-time heating to a secondary temperature for secondary drying, and finally cooling to room temperature.

[0041] In the present disclosure, the use of the above drying method helps to more fully realize the drying of the slurry, so that the pore distribution is uniform.

[0042] It should be noted that the present disclosure does not specifically limit the room temperature, which may be 25±℃, for example, 20℃, 25℃ or 30℃, etc.

[0043] In one embodiment, the one-time heating time is 0.8-1.2h, which may be 0.8h, 0.9h, 1h, 1.1h or 1.2h, etc.

[0044] In one embodiment, the primary temperature is 55-65℃, which may be 55℃, 57℃, 60℃, 63℃ or 65℃, etc., and the primary drying time is 4-8h, which may be 4h, 5h, 6h, 7h or 8h, etc.

[0045] In the present disclosure, the first drying at 55-65℃ for 4-8h helps to achieve a more complete drying of the slurry, resulting in a uniform pore distribution.

[0046] In one embodiment, the secondary temperature is 75-85℃, for example, it can be 75℃, 77℃, 80℃, 83℃ or 85℃, etc., and the secondary drying time is 14-18h, for example, it can be 14h, 15h, 16h, 17h or 18h, etc.

[0047] In one embodiment, the secondary temperature is 75-85℃, for example, it can be 75℃, 77℃, 80℃, 83℃ or 85℃, etc., and the secondary drying time is 14-18h, for example, it can be 14h, 15h, 16h, 17h or 18h, etc.

[0048] In the present disclosure, the secondary drying at 75-85℃ for 14-18h helps to achieve a more complete drying of the slurry, resulting in a uniform pore distribution.

[0049] In one embodiment, the water immersion time is 4-8h, for example, it can be 4h, 5h, 6h, 7h or 8h, etc.

[0050] In one embodiment, after the water immersion treatment, an oxidation treatment is further performed.

[0051] In the present disclosure, through the oxidation treatment, the cracks on the surface of the lithium extraction electrode can be reduced, and the strength and use durability of the lithium extraction electrode can be improved.

[0052] In one embodiment, during the oxidation treatment, the oxidizing agent solution used includes any one or a combination of at least two of hydrogen peroxide, sodium persulfate solution, sodium hypochlorite solution or sodium chlorate solution.

[0053] As an optional technical solution of the present disclosure, the preparation method comprises the following steps:

[0054] (1) The active material, conductive agent, binder and foaming agent are stirred and mixed with the solvent according to the mass ratio of (70-75):(5-10):(5-15):(5-10) to obtain a slurry;

[0055] In the present disclosure, the foaming agent includes vinyl silicone oil, hydroxyl silicone oil, hydrogen-containing silicone oil, inhibitor and catalyst, and the mass fraction of the vinyl silicone oil is 6%-30% based on the mass of the foaming agent, the total mass content of the hydroxyl silicone oil and hydrogen-containing silicone oil is 5%-15%, the mass fraction of the inhibitor is 40%-70%, and 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).

[0056] (2) coating the slurry on the current collector, then performing multi-stage drying, then immersing in water for 4-8h, and finally immersing in an oxidant solution at 30-50℃ for 0.5-2h (for example, it can be 0.5h, 1h, 1.5h or 2h, etc.) for oxidation treatment, to obtain the lithium extraction electrode.

[0057] In a second aspect, the present disclosure provides a lithium extraction electrode prepared by the preparation method of the first aspect, the lithium extraction electrode comprising a current collector and a porous active layer arranged on at least one surface of the current collector.

[0058] In the present disclosure, the porous active layer has uniform micropores, stronger connectivity between micropores, larger specific surface area and higher porosity, so that the prepared lithium extraction electrode has excellent charge-discharge performance and higher cycle service life.

[0059] As an optional technical solution of the present disclosure, the thickness of the porous active layer is 1-7mm, for example, it can be 1mm, 2mm, 3mm, 4mm, 5mm, 6mm or 7mm, etc.

[0060] In the present disclosure, if the thickness of the porous active layer is too thin, the amount of active components of the single electrode plate is low, and the lithium extraction efficiency is low; if the thickness of the porous active layer is too thick, the electrode polarization phenomenon is serious, and the capacity attenuation is fast.

[0061] In an 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.

[0062] In the present disclosure, the porous active layer with a porosity of 10%-60% and an average pore size of 0.1nm-1μm can make the prepared lithium extraction electrode have excellent charge-discharge performance and higher cycle service life.

[0063] In a third aspect, the present disclosure provides an application of the lithium extraction electrode of the second aspect, and the lithium extraction electrode is applied to lithium extraction from salt lakes.

[0064] The lithium extraction electrode prepared by the present disclosure increases the porosity of the active material in the electrode plate, and creates micropores, mesopores and macropores, thereby facilitating the transmission of lithium ions in the salt lake to improve the charge-discharge capacity and cycle life.

[0065] The numerical range in the present disclosure not only includes the above-mentioned point values, but also includes any point values between the above-mentioned numerical ranges which are not mentioned. Due to the limited space and for the sake of simplicity, the present disclosure does not enumerate the specific point values included in the range.

[0066] Compared with the prior art, the present disclosure has the following beneficial effects:

[0067] (2) The present disclosure forms uniform micropores with strong connectivity between the micropores in the lithium extraction electrode by using a foaming agent containing composite silicone oil, an inhibitor and a catalyst, and 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 higher cycle service life.

[0068] (2) The lithium extraction electrode prepared by the preparation method provided by the present disclosure has an initial specific capacity of 101.68 mAh / g and a specific capacity of 97.36 mAh / g after 200 cycles, and a capacity retention rate of 95.75%.

[0069] Other aspects can be apparent after reading and understanding the detailed description. DETAILED DESCRIPTION

[0070] The technical solutions of the present disclosure will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present disclosure and should not be regarded as specific limitations on the present disclosure.

[0071] Embodiment 1

[0072] The present embodiment provides a preparation method of a lithium extraction electrode, which comprises the following steps:

[0073] (1) mixing and stirring vinyl silicone oil, hydroxyl silicone oil, hydrogen-containing silicone oil, an inhibitor and a catalyst for 2 hours to obtain a foaming agent;

[0074] wherein the inhibitor is cyclohexanol and the catalyst is chloroplatinic acid, the mass fraction of the vinyl silicone oil is 24% based on the mass of the foaming agent, 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;

[0075] (2) fully dissolving a binder polyvinylidene fluoride (PVDF) in N-methyl pyrrolidone (NMP) to form a polymer solution, then adding an active material lithium iron phosphate, a conductive agent white carbon black and the foaming agent to the polymer solution and fully stirring to obtain a slurry;

[0076] wherein the mass ratio of lithium iron phosphate, white carbon black, polyvinylidene fluoride and the foaming agent is 72:8:12:8, and the ratio of the total mass of lithium iron phosphate, white carbon black, polyvinylidene fluoride and the foaming agent to the mass of the NMP is 1:1;

[0077] (3) using a template to blade the slurry on the current collector porous titanium mesh, and then placing the obtained electrode in an oven with a set temperature curve to dry for 24 h (the drying process includes: once heating from room temperature 25 °C to a primary temperature 60 °C for 1 h, primary drying for 6 h, twice heating from 0.5 h to a secondary temperature 80 °C, secondary drying for 16 h, and finally cooling to room temperature 25 °C), then immersing in deionized water and standing for 4 h, after which, immersing in a sodium persulfate solution at 40 °C for 1 h for oxidation treatment, then rinsing under water flow, and immersing in deionized water for 3 h, to obtain the lithium extraction electrode.

[0078] The embodiment also provides a lithium extraction electrode prepared by the preparation method, the lithium extraction electrode comprising a current collector and a porous active layer arranged on at least one surface of the current collector, the thickness of the porous active layer being 3 mm, the porosity of the porous active layer being 30%, and the average pore size being 0.5 μm.

[0079] Embodiment 2

[0080] The embodiment provides a preparation method of a lithium extraction electrode, the preparation method comprising the following steps:

[0081] (1) mixing and stirring vinyl silicone oil, hydroxyl silicone oil, hydrogen-containing silicone oil, an inhibitor and a catalyst for 2 h to obtain a foaming agent;

[0082] In the embodiment, the inhibitor is cyclohexanol, the catalyst is chloroplatinic acid, the mass fraction of the vinyl silicone oil is 15% based on the mass of the foaming agent, 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.

[0083] (2) fully dissolving a binder polyvinylidene fluoride (PVDF) in N-methyl pyrrolidone (NMP) to form a polymer solution, and then adding an active substance lithium iron phosphate, a conductive agent white carbon black and the foaming agent into the polymer solution and fully stirring to obtain a slurry;

[0084] In the embodiment, the mass ratio of the lithium iron phosphate, the white carbon black, the polyvinylidene fluoride and the foaming agent is 75:5:15:5, and the ratio of the total mass of the lithium iron phosphate, the white carbon black, the polyvinylidene fluoride and the foaming agent to the mass of the NMP is 1:1.

[0085] (3) using a template to blade coat the slurry on the current collector porous titanium mesh, then placing the obtained electrode in an oven with a set temperature curve to dry for 24 h (the drying process includes: once heating from room temperature 25℃ to a primary temperature 55℃ for 1 h, primary drying for 6 h, then twice heating from 0.5 h to a secondary temperature 75℃, secondary drying for 14 h, and finally cooling to room temperature 25℃), then immersing in deionized water and standing for 6 h, after which, immersing in a sodium hypochlorite solution at 30℃ for 2 h for oxidation treatment, then rinsing under water flow, and immersing in deionized water for 3 h, to obtain the lithium extraction electrode.

[0086] The embodiment also provides a lithium extraction electrode prepared by the preparation method, the lithium extraction electrode comprising a current collector and a porous active layer arranged on at least one surface of the current collector, the thickness of the porous active layer being 1 mm, the porosity of the porous active layer being 60%, and the average pore size being 1 nm.

[0087] Embodiment 3

[0088] The embodiment provides a preparation method of a lithium extraction electrode, the preparation method comprising the following steps:

[0089] (1) mixing and stirring vinyl silicone oil, hydroxyl silicone oil, hydrogen-containing silicone oil, an inhibitor and a catalyst for 2 h to obtain a foaming agent;

[0090] In the embodiment, the inhibitor is cyclohexanol, and the catalyst is chloroplatinic acid; 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%, and the mass fraction of the catalyst is 0.1%, based on the mass of the foaming agent; and the mass ratio of the hydroxyl silicone oil to the hydrogen-containing silicone oil is 8.9:1.

[0091] (2) fully dissolving a binder polyvinylidene fluoride (PVDF) in N-methyl pyrrolidone (NMP) to form a polymer solution, then adding an active substance lithium iron phosphate, a conductive agent white carbon black and the foaming agent into the polymer solution and fully stirring to obtain a slurry;

[0092] In the embodiment, the mass ratio of the lithium iron phosphate, the white carbon black, the polyvinylidene fluoride and the foaming agent is 70:10:10:10, and the ratio of the total mass of the lithium iron phosphate, the white carbon black, the polyvinylidene fluoride and the foaming agent to the mass of the NMP is 1:1.

[0093] (3) using a template to blade coat the slurry on the current collector porous titanium mesh, then placing the obtained electrode in an oven with a set temperature curve to dry for 24 h (the drying process includes: once heating from room temperature 25℃ to a primary temperature 65℃ for 1 h, primary drying for 4 h, then twice heating from 0.5 h to a secondary temperature 85℃, secondary drying for 18 h, and finally cooling to room temperature 25℃), then immersing in deionized water and standing for 8 h, after which, immersing in hydrogen peroxide at 50℃ for 0.5 h for oxidation treatment, then rinsing under water flow, and immersing in deionized water for 3 h, to obtain the lithium extraction electrode.

[0094] The embodiment also provides a lithium extraction electrode prepared by the preparation method, the lithium extraction electrode comprising a current collector and a porous active layer arranged on at least one surface of the current collector, the thickness of the porous active layer being 7 mm, the porosity of the porous active layer being 10%, and the average pore size being 1 μm.

[0095] Embodiment 4

[0096] The embodiment differs from embodiment 1 in 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%.

[0097] The rest of the preparation method and parameters remain the same as those in embodiment 1.

[0098] Embodiment 5

[0099] The embodiment differs from embodiment 1 in 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%.

[0100] The rest of the preparation method and parameters remain the same as those in embodiment 1.

[0101] Embodiment 6

[0102] The embodiment differs from embodiment 1 in that the total mass content of the hydroxyl silicone oil and the hydrogen-containing 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%.

[0103] The rest of the preparation method and parameters remain the same as those in embodiment 1.

[0104] Embodiment 7

[0105] The embodiment differs from embodiment 1 in that the total mass content of the hydroxyl silicone oil and the hydrogen-containing silicone oil in step (1) is 20%, and the mass fraction of the inhibitor is adaptively adjusted to 55.5%.

[0106] The rest of the preparation method and parameters remain the same as those in embodiment 1.

[0107] Example 8

[0108] The difference between this example and Example 1 is that the mass ratio of the hydroxyl silicone oil and the hydrogen-containing silicone oil in step (1) is 2:10.

[0109] The rest of the preparation method and parameters remain the same as in Example 1.

[0110] Example 9

[0111] The difference between this example and Example 1 is that the mass ratio of the hydroxyl silicone oil and the hydrogen-containing silicone oil in step (1) is 10:1.

[0112] The rest of the preparation method and parameters remain the same as in Example 1.

[0113] Example 10

[0114] The difference between this example and Example 1 is that the hydrogen-containing silicone oil in step (1) is replaced by an equal mass of hydroxyl silicone oil.

[0115] The rest of the preparation method and parameters remain the same as in Example 1.

[0116] Example 11

[0117] The difference between this example and Example 1 is that the mass fraction of the catalyst in step (1) is 0.05%, and the mass fraction of the inhibitor is adjusted to 63.95% adaptively.

[0118] The rest of the preparation method and parameters remain the same as in Example 1.

[0119] Example 12

[0120] The difference between this example and Example 1 is that the mass fraction of the catalyst in step (1) is 1.5%, and the mass fraction of the inhibitor is adjusted to 62.5% adaptively.

[0121] The rest of the preparation method and parameters remain the same as in Example 1.

[0122] Example 13

[0123] The difference between this example and Example 1 is that the mass ratio of lithium iron phosphate, white carbon black, polyvinylidene fluoride and foaming agent in step (2) is 75:8:14:3.

[0124] The rest of the preparation method and parameters remain the same as in Example 1.

[0125] Example 14

[0126] The difference between this embodiment and embodiment 1 is that the mass ratio of lithium iron phosphate, white carbon black, polyvinylidene fluoride and foaming agent in step (2) is 70:8:10:12.

[0127] The rest of the preparation method and parameters remain the same as in embodiment 1.

[0128] Example 15

[0129] The difference between this embodiment and embodiment 1 is that the thickness of the porous active layer in the lithium extraction electrode obtained by adjusting the process parameters of step (3) is 0.5 mm.

[0130] The rest of the preparation method and parameters remain the same as in embodiment 1.

[0131] Example 16

[0132] The difference between this embodiment and embodiment 1 is that the thickness of the porous active layer in the lithium extraction electrode obtained by adjusting the process parameters of step (3) is 8 mm.

[0133] The rest of the preparation method and parameters remain the same as in embodiment 1.

[0134] Comparative Example 1

[0135] The difference between this comparative example and embodiment 1 is that the vinyl silicone oil, hydroxyl silicone oil and hydrogen-containing silicone oil in step (1) are replaced with the same mass of inhibitor, i.e. no composite silicone oil is added.

[0136] The rest of the preparation method and parameters remain the same as in embodiment 1.

[0137] Comparative Example 2

[0138] The difference between this comparative example and embodiment 1 is that step (1) is not performed, i.e. no foaming agent is added in step (2).

[0139] The rest of the preparation method and parameters remain the same as in embodiment 1.

[0140] Performance test

[0141] The lithium extraction electrodes prepared in the above examples and comparative examples were subjected to electrochemical deintercalation test, and the specific steps included:

[0142] (1) pre-stored for 20 min;

[0143] (2) stand for 10 min;

[0144] (3) constant current charging, rate is 0.1C, current is 0.0168A, cutoff voltage is 0.35V;

[0145] (4) constant voltage charging, the rate is 0.1C, the current is 0.0168A, the voltage is 0.35V, the cut-off rate is 0.025C, and the cut-off current is 0.0042A;

[0146] (5) rest for 10 min;

[0147] (6) constant current discharging, the rate is 0.1C, the current is 0.0168A, and the cut-off voltage is -0.35V;

[0148] (7) rest for 1 min;

[0149] (8) constant current discharging, the rate is 0.05C, the current is 0.0084A, and the cut-off voltage is -0.35V;

[0150] (9) rest for 1 min;

[0151] (10) constant current discharging, the rate is 0.025C, the current is 0.0042A, and the cut-off voltage is -0.35V;

[0152] (11) cycle steps (2)-(10) for 200 times.

[0153] The test results are shown in Table 1.

[0154] Table 1

[0155]

[0156]

[0157] Analysis:

[0158] It can be seen from the above table that the initial specific capacity of the lithium extraction electrode prepared by the preparation method provided in the present disclosure can reach 101.68 mAh / g, the specific capacity after 200 cycles can reach 97.36 mAh / g, and the capacity retention rate can reach 95.75%.

[0159] It can be seen from Example 1 and Examples 4-5 that if the mass fraction of the vinyl silicone oil is too small, the viscosity of the foaming agent is too low, which can cause low adhesion and low specific capacity of the electrode plate; if the mass fraction of the vinyl silicone oil is too large, the viscosity of the foaming agent is too high, which can cause uneven dispersion in the pulping process and low specific capacity of the electrode plate.

[0160] It can be seen from Example 1 and Examples 6-7 that if the total mass content of the hydroxyl silicone oil and the hydrogen-containing silicone oil is too small, the porosity of the lithium extraction electrode can decrease, and the specific capacity can be low; if the total mass content of the hydroxyl silicone oil and the hydrogen-containing silicone oil is too large, the electrode plate can crack, the voids can be too many and too large, and the specific capacity can be low.

[0161] From Example 1 and Examples 8-9, if the mass ratio of hydroxyl silicone oil and hydrogen-containing silicone oil is too small, the formed pores are mainly micropores, which can lead to subsequent difficulty in oxidative delithiation and low specific capacity; if the mass ratio of hydroxyl silicone oil and hydrogen-containing silicone oil is too large, the formed pores are mainly macropores, which can lead to rapid attenuation of the electrode plate in electrical cycle.

[0162] From Example 1 and Example 10, a certain amount of hydrogen-containing silicone oil needs to be added to the foaming agent, so that the prepared lithium extraction electrode has a certain amount of pore structure, which is beneficial to the uniformity of subsequent oxidation treatment.

[0163] From Example 1 and Examples 11-12, if the mass fraction of the catalyst is too small, the pore forming speed is slow, which can lead to low porosity; if the mass fraction of the catalyst is too large, the pore forming speed is fast, which can lead to difficulty in controlling the pore forming process.

[0164] From Example 1 and Examples 13-14, if the mass ratio of active material and foaming agent is too small, i.e., the mass content of the foaming agent is too high, the active material in the electrode plate is too little and the pores are too many, which is not conducive to subsequent lithium extraction; if the mass ratio of active material and foaming agent is too large, i.e., the mass content of the foaming agent is too low, the porosity is not enough, the subsequent oxidative delithiation is not complete, and the initial specific capacity is low.

[0165] From Example 1 and Examples 15-16, if the thickness of the porous active layer is too thin, the active material mass of the electrode plate is low, which can lead to low specific capacity; if the thickness of the porous active layer is too thick, the electrode plate polarization is serious, which can lead to difficulty in delithiation, low specific capacity, and rapid attenuation of electrical performance.

[0166] From Example 1 and Comparative Example 1, if no composite silicone oil is added to the foaming agent, the pore forming inside the electrode plate is not uniform, which can lead to low specific capacity.

[0167] From Example 1 and Comparative Example 2, adding a foaming agent in the preparation process of the lithium extraction electrode can prepare an electrode deintercalation plate with high porosity, and the prepared lithium extraction electrode has excellent performance.

Claims

1. A method for preparing a lithium extraction electrode, comprising the following steps: (1) mixing an active material, a conductive agent, a binder and a foaming agent with a solvent by stirring to obtain a slurry, 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) ; wherein the foaming agent comprises vinyl silicone oil, hydroxyl silicone oil, hydrogen-containing silicone oil, an inhibitor and a catalyst, the mass fraction of the vinyl silicone oil is 6-30% based on the mass of the foaming agent, 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) ; the inhibitor is an alcohol substance, and the alcohol substance comprises cyclohexanol; the catalyst comprises chloroplatinic acid; (2) coating the slurry on a current collector, then performing multi-stage drying, then immersing in water for 4-8 hours, and finally immersing in an oxidant solution at 30-50℃ for 0.5-2 hours for oxidation treatment to obtain the lithium extraction electrode.

2. The production method according to claim 1, wherein, The mass fraction of the vinyl silicone oil is 20-25% based on the mass of the foaming agent.

3. The production method according to claim 1, wherein, The total mass content of the hydroxyl silicone oil and the hydrogen-containing silicone oil is 11-13% based on the mass of the foaming agent.

4. The production method according to claim 1, wherein The mass fraction of the inhibitor is 60-65% based on the mass of the foaming agent.

5. The production method according to claim 1, wherein The mass fraction of the catalyst is 0.3-0.7% based on the mass of the foaming agent.

6. The production method according to claim 1, wherein The multi-stage drying process comprises: one-time heating from room temperature to a first-stage temperature for first-stage drying, then two-time heating to a second-stage temperature for second-stage drying, and finally cooling to room temperature.

7. The production method according to claim 6, wherein The first-stage temperature is 55-65℃, and the time for the first-stage drying is 4-8 hours.

8. The production method according to claim 6, wherein The second-stage temperature is 75-85℃, and the time for the second-stage drying is 14-18 hours. 9.A lithium extraction electrode prepared by the method of any one of claims 1-8, comprising a current collector and a porous active layer arranged on at least one surface of the current collector.

10. The lithium extraction electrode of claim 9, wherein, The thickness of the porous active layer is 1-7 mm.

11. The lithium extraction electrode of claim 9, wherein, The porosity of the porous active layer is 10-60%, and the average pore size is 0.1 nm-1 μm. 12.The use of the lithium extraction electrode of any one of claims 9-11 for lithium extraction from a salt lake.

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