MOF-based porous carbon positive electrode material, preparation method thereof and application of MOF-based porous carbon positive electrode material in lithium battery
By preparing MOF-based porous carbon cathode materials, the problems of low self-discharge and cycle life of lithium-sulfur batteries were solved. Through the design of mesoporous carbon structure and COF coating material, the cycle performance and rate performance of lithium-sulfur batteries were improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-03
- Publication Date
- 2026-04-14
AI Technical Summary
The industrialization of lithium-sulfur batteries is hampered by self-discharge and low cycle life, mainly due to the shuttle behavior of lithium polysulfides and the slow chemical kinetics of sulfur in the sulfur cathode.
The MOF-based porous carbon cathode material is prepared by coating porous carbon/S composite material with COF, combined with conductive agent and binder, onto the surface of aluminum foil to form MOF-based porous carbon cathode material.
It improves the cycle performance and rate performance of lithium-sulfur batteries. The mesoporous carbon structure provides sulfur-carrying space, and the high porosity and ultra-small pore size of the COF structure inhibit the shuttle of polysulfides. The nitrogen and cobalt-nickel elements on the porous carbon material work together to provide chemical interaction and catalytic sites, inhibiting the dissolution and diffusion of polysulfides.
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Figure CN121849914A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of battery cathode material technology, specifically to a MOF-based porous carbon cathode material, its preparation method, and its application in lithium batteries. Background Technology
[0002] With the advent of the information age and rapid social development, the energy crisis caused by the depletion of fossil fuels has become a topic of particular concern. Electrochemical energy storage is one of the important means to alleviate the energy crisis. Secondary batteries, as a medium for storing and converting electrical and chemical energy, have high energy conversion efficiency and have become a research hotspot among many new renewable energy sources. Among them, lithium-ion secondary batteries, as a representative of secondary batteries, have advantages such as high specific energy, long cycle life, light weight, and small size, and are widely used in portable electronic products, electric vehicles, and spacecraft, showing very promising application prospects.
[0003] However, the industrialization of lithium-sulfur batteries is largely hindered by severe self-discharge and low cycle life, mainly due to the shuttle behavior of lithium polysulfides and the slow sulfur chemical kinetics in the sulfur cathode. Therefore, developing cathode materials that can suppress the shuttle effect, inhibit polysulfide dissolution, and buffer their volume expansion is key to developing high-performance lithium-sulfur batteries and realizing their practical applications. Summary of the Invention
[0004] The purpose of this invention is to provide a MOF-based porous carbon cathode material, its preparation method, and its application in lithium batteries, so as to solve the problems existing in the prior art.
[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:
[0006] A MOF-based porous carbon cathode material is prepared by coating a mixture of COF-coated porous carbon / S composite material, conductive agent, and binder onto the surface of aluminum foil.
[0007] As an optimization, the COF-coated porous carbon / S composite material is prepared by mixing COF-coated porous carbon material with sublimed sulfur, followed by grinding and heating.
[0008] As an optimization, the COF-coated porous carbon material is prepared by reacting porous carbon material with trialdehyde phloroglucinol and (4,6-diamino-1,3,5-triazine-2-yl)methanethiol.
[0009] As an optimization, the porous carbon material is prepared by reacting cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and 2-methylimidazole, followed by high-temperature carbonization.
[0010] A method for preparing a MOF-based porous carbon cathode material includes the following preparation steps:
[0011] (1) Cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and deionized water were mixed evenly to prepare a metal solution; the metal solution and 2-methylimidazole solution were mixed evenly, and the mixture was allowed to stand at room temperature for 20-24 hours. The mixture was then centrifuged, washed, and dried to obtain Co / Ni-MOF material; under an argon atmosphere, the Co / Ni-MOF material was placed in a tube furnace, heated to 800℃, carbonized for 3 hours, and cooled to room temperature to obtain porous carbon material;
[0012] (2) The porous carbon material, trialdehyde phloroglucinol, (4,6-diamino-1,3,5-triazine-2-yl)methanethiol, 1,4-dioxane, mesitylene, and acetic acid aqueous solution were mixed evenly, ultrasonically dispersed for 20-40 min, rapidly frozen in liquid nitrogen, degassed and sealed, kept in an oil bath at 120℃ for 40-48 h, cooled to room temperature, filtered, washed, and dried to obtain COF-coated porous carbon material;
[0013] (3) COF-coated porous carbon material and sublimed sulfur were mixed and ground, and heated at 155°C for 24 hours under argon atmosphere and then at 185°C for 24 hours to obtain COF-coated porous carbon / S composite material.
[0014] (4) Mix COF-coated porous carbon / S composite material, conductive agent and binder in a mass ratio of 7:2:1. Add N-methylpyrrolidone at a mass ratio of 2 to 3 times that of COF-coated porous carbon / S composite material, stir magnetically to form a uniform slurry, coat it on aluminum foil, and vacuum dry it at 80°C for 10 to 12 hours to obtain MOF-based porous carbon cathode material.
[0015] As an optimization, the preparation steps of the porous carbon material in step (1) are as follows: cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and deionized water are mixed evenly at a mass ratio of 1:(0.3~0.4):(100~150) to obtain a metal solution; 2-methylimidazole and deionized water are mixed evenly at a mass ratio of 1:(80~100) to obtain a 2-methylimidazole solution; the metal solution and 2-methylimidazole solution are mixed evenly at a mass ratio of 1:(1~1.2), allowed to stand at room temperature for 20~24h, centrifuged, and the resulting precipitate is washed 2~4 times with anhydrous ethanol and dried under vacuum at 70~80℃ for 4~6h to obtain Co / Ni-MOF material; under an argon atmosphere, the Co / Ni-MOF material is placed in a tube furnace, heated to 800℃ at a heating rate of 4℃ / min, carbonized for 3h, and cooled to room temperature to obtain porous carbon material.
[0016] As an optimization, the preparation steps of the COF-coated porous carbon material in step (2) are as follows: the porous carbon material, trialdehyde phloroglucinol, (4,6-diamino-1,3,5-triazine-2-yl)methanethiol, 1,4-dioxane, mesitylene, and aqueous acetic acid are mixed evenly in a mass ratio of 1:(0.3~0.33):(0.3~0.34):(20~25):(20~25):(5~10), ultrasonically dispersed for 20~40 min, rapidly frozen in liquid nitrogen, degassed and sealed, kept in an oil bath at 120℃ for 40~48 h, cooled to room temperature, filtered and washed 3~5 times each with tetrahydrofuran and methanol, and vacuum dried at 50~60℃ for 10~12 h to obtain the COF-coated porous carbon material.
[0017] As an optimization, the preparation steps of the COF-coated porous carbon / S composite material in step (3) are as follows: COF-coated porous carbon material and sublimed sulfur are mixed at a mass ratio of 1:(1.5~2), ground in a mortar for 20~40 min, heated at 155℃ for 24 h under an argon atmosphere, and then heated at 185℃ for 24 h to obtain the COF-coated porous carbon / S composite material.
[0018] As an optimization, the conductive agent in step (4) is acetylene black with a median diameter of 1~3 μm.
[0019] As an optimization, the adhesive in step (4) is polyvinylidene fluoride, model Kynar 741.
[0020] As an optimization, the concentration of the acetic acid aqueous solution is 3 mol / L.
[0021] As an optimization, the number of iterations is 3.
[0022] Application of MOF-based porous carbon cathode material prepared according to the aforementioned method in lithium batteries.
[0023] Compared with the prior art, the beneficial effects achieved by the present invention are:
[0024] In preparing MOF-based porous carbon cathode materials, this invention involves reacting cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and 2-methylimidazole to obtain Co / Ni-MOF material; carbonizing the Co / Ni-MOF material at high temperature to obtain porous carbon material; reacting the porous carbon material with trialdehyde-based phloroglucinol and (4,6-diamino-1,3,5-triazine-2-yl)methanethiol to obtain COF-coated porous carbon material; mixing the COF-coated porous carbon material with sublimed sulfur, grinding, and heating to obtain COF-coated porous carbon / S composite material; and mixing the COF-coated porous carbon / S composite material, conductive agent, and binder, then coating it onto the surface of aluminum foil to obtain MOF-based porous carbon cathode material.
[0025] First, porous carbon materials are prepared by reacting cobalt nitrate hexahydrate and nickel nitrate hexahydrate with 2-methylimidazole and then carbonizing them at high temperature. The regular framework of the MOF precursor forms a mesoporous carbon structure after high-temperature carbonization. The high specific surface area of the mesoporous carbon structure provides ample space for sulfur loading, and the mesoporous channels facilitate electrolyte penetration and rapid ion transport, thereby improving rate performance. At the same time, the nitrogen and cobalt-nickel elements on the porous carbon material work synergistically to provide strong chemical interactions and catalytic sites for the capture and conversion of polysulfides, thereby improving cycle stability. Furthermore, as a sulfur carrier, the porous carbon material can physically limit the dissolution and diffusion of lithium polysulfides, alleviate volume expansion during cycling, and thus improve cycle performance and rate performance.
[0026] Secondly, porous carbon materials were reacted with trialdehyde-based phloroglucinol and (4,6-diamino-1,3,5-triazin-2-yl)methanethiol to prepare COF-coated porous carbon materials. These were then mixed with sublimed sulfur, ground, and heated to obtain COF-coated porous carbon / S composite materials. The trialdehyde-based phloroglucinol and (4,6-diamino-1,3,5-triazin-2-yl)methanethiol underwent a Schiff base reaction to generate a COF structure containing triazine and thiol groups, which coated the porous carbon materials. Due to the high porosity and ultra-small pore size of the COF, it possesses ion sieving and sulfur-limiting capabilities. Simultaneously, the COF acts as an external protective barrier, further reducing polysulfide shuttle and improving the battery's cycle performance and rate performance. The triazine groups on the COF-coated porous carbon materials react with Li... + The good dipole interaction between them improves the cycle performance and rate performance of the battery; the thiol groups on the COF-coated porous carbon material can be covalently linked with sublimed sulfur, suppressing the shuttle effect and promoting the conversion kinetics of polysulfides, thereby improving the cycle performance and rate performance. Attached Figure Description
[0027] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0028] Figure 1 The graph shows the rate performance of coin cells at room temperature obtained by using the MOF-based porous carbon cathode materials prepared in Example 2 and Comparative Examples 1-4 of this application as cathodes for lithium-sulfur batteries. Detailed Implementation
[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0030] Example 1
[0031] A method for preparing a MOF-based porous carbon cathode material includes the following preparation steps:
[0032] (1) Cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and deionized water were mixed evenly at a mass ratio of 1:0.3:100 to prepare a metal solution; 2-methylimidazole and deionized water were mixed evenly at a mass ratio of 1:80 to prepare a 2-methylimidazole solution; the metal solution and the 2-methylimidazole solution were mixed evenly at a mass ratio of 1:1, allowed to stand at room temperature for 20 h, centrifuged, and the resulting precipitate was washed twice with anhydrous ethanol and dried under vacuum at 70 °C for 4 h to obtain Co / Ni-MOF material; under an argon atmosphere, the Co / Ni-MOF material was placed in a tube furnace and heated to 800 °C at a heating rate of 4 °C / min for 3 h, and then cooled to room temperature to obtain porous carbon material;
[0033] (2) The porous carbon material, trialdehyde phloroglucinol, (4,6-diamino-1,3,5-triazine-2-yl)methanethiol, 1,4-dioxane, mesitylene, and acetic acid aqueous solution were mixed evenly in a mass ratio of 1:0.3:0.3:20:20:5, ultrasonically dispersed for 20 min, rapidly frozen in liquid nitrogen, degassed three times and sealed, kept in an oil bath at 120℃ for 40 h, cooled to room temperature, filtered and washed three times each with tetrahydrofuran and methanol, and vacuum dried at 50℃ for 10 h to obtain COF-coated porous carbon material;
[0034] (3) After mixing COF-coated porous carbon material and sublimed sulfur at a mass ratio of 1:1.5, grind them in a mortar for 20 min, heat them at 155℃ for 24 h under an argon atmosphere, and then heat them at 185℃ for 24 h to obtain COF-coated porous carbon / S composite material.
[0035] (4) COF-coated porous carbon / S composite material, acetylene black and polyvinylidene fluoride are mixed evenly in a mass ratio of 7:2:1. N-methylpyrrolidone with a mass of 2 times that of COF-coated porous carbon / S composite material is added and magnetically stirred to form a uniform slurry. The slurry is coated on aluminum foil and vacuum dried at 80°C for 10 h to obtain MOF-based porous carbon cathode material.
[0036] Example 2
[0037] A method for preparing a MOF-based porous carbon cathode material includes the following preparation steps:
[0038] (1) Cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and deionized water were mixed evenly at a mass ratio of 1:0.35:125 to prepare a metal solution; 2-methylimidazole and deionized water were mixed evenly at a mass ratio of 1:90 to prepare a 2-methylimidazole solution; the metal solution and the 2-methylimidazole solution were mixed evenly at a mass ratio of 1:1.1, allowed to stand at room temperature for 22 h, centrifuged, and the resulting precipitate was washed three times with anhydrous ethanol and dried under vacuum at 75 °C for 5 h to obtain Co / Ni-MOF material; under an argon atmosphere, the Co / Ni-MOF material was placed in a tube furnace and heated to 800 °C at a heating rate of 4 °C / min for 3 h, and then cooled to room temperature to obtain porous carbon material;
[0039] (2) The porous carbon material, trialdehyde phloroglucinol, (4,6-diamino-1,3,5-triazine-2-yl)methanethiol, 1,4-dioxane, mesitylene, and acetic acid aqueous solution were mixed evenly in a mass ratio of 1:0.315:0.32:23:23:8, ultrasonically dispersed for 30 min, rapidly frozen in liquid nitrogen, degassed three times and sealed, kept in an oil bath at 120℃ for 44 h, cooled to room temperature, filtered and washed four times each with tetrahydrofuran and methanol, and vacuum dried at 55℃ for 11 h to obtain COF-coated porous carbon material;
[0040] (3) After mixing COF-coated porous carbon material and sublimed sulfur at a mass ratio of 1:1.8, grind them in a mortar for 30 min, heat them at 155℃ for 24 h under an argon atmosphere, and then heat them at 185℃ for 24 h to obtain COF-coated porous carbon / S composite material.
[0041] (4) COF-coated porous carbon / S composite material, acetylene black and polyvinylidene fluoride are mixed evenly in a mass ratio of 7:2:1. N-methylpyrrolidone with a mass of 2.5 times that of COF-coated porous carbon / S composite material is added and magnetically stirred to form a uniform slurry. The slurry is coated on aluminum foil and vacuum dried at 80°C for 11 hours to obtain MOF-based porous carbon cathode material.
[0042] Example 3
[0043] A method for preparing a MOF-based porous carbon cathode material includes the following preparation steps:
[0044] (1) Cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and deionized water were mixed evenly at a mass ratio of 1:0.4:150 to prepare a metal solution; 2-methylimidazole and deionized water were mixed evenly at a mass ratio of 1:100 to prepare a 2-methylimidazole solution; the metal solution and the 2-methylimidazole solution were mixed evenly at a mass ratio of 1:1.2, allowed to stand at room temperature for 24 h, centrifuged, and the resulting precipitate was washed 4 times with anhydrous ethanol and dried under vacuum at 80℃ for 6 h to obtain Co / Ni-MOF material; under an argon atmosphere, the Co / Ni-MOF material was placed in a tube furnace and heated to 800℃ at a heating rate of 4℃ / min for 3 h, and then cooled to room temperature to obtain porous carbon material;
[0045] (2) The porous carbon material, trialdehyde phloroglucinol, (4,6-diamino-1,3,5-triazine-2-yl)methanethiol, 1,4-dioxane, mesitylene, and acetic acid aqueous solution were mixed evenly in a mass ratio of 1:0.33:0.34:25:25:10, ultrasonically dispersed for 40 min, rapidly frozen in liquid nitrogen, degassed 3 times and sealed, kept in an oil bath at 120℃ for 48 h, cooled to room temperature, filtered and washed 5 times each with tetrahydrofuran and methanol, and vacuum dried at 60℃ for 12 h to obtain COF-coated porous carbon material;
[0046] (3) After mixing COF-coated porous carbon material and sublimed sulfur at a mass ratio of 1:2, grind them in a mortar for 40 min, heat them at 155℃ for 24 h under an argon atmosphere, and then heat them at 185℃ for 24 h to obtain COF-coated porous carbon / S composite material.
[0047] (4) COF-coated porous carbon / S composite material, acetylene black and polyvinylidene fluoride are mixed evenly in a mass ratio of 7:2:1. N-methylpyrrolidone with a mass of 3 times that of COF-coated porous carbon / S composite material is added and magnetically stirred to form a uniform slurry. The slurry is coated on aluminum foil and vacuum dried at 80°C for 12 hours to obtain MOF-based porous carbon cathode material.
[0048] Comparative Example 1
[0049] The preparation method of MOF-based porous carbon cathode material in Comparative Example 1 differs from that in Example 2 in that step (1) is omitted, and step (2) is modified as follows: trialdehyde phloroglucinol, (4,6-diamino-1,3,5-triazine-2-yl)methanethiol, 1,4-dioxane, mesitylene, and aqueous acetic acid are mixed evenly in a mass ratio of 0.315:0.32:23:23:8, ultrasonically dispersed for 30 min, rapidly frozen in liquid nitrogen, degassed three times and sealed, kept in an oil bath at 120°C for 44 h, cooled to room temperature, filtered and washed four times each with tetrahydrofuran and methanol, and vacuum dried at 55°C for 11 h. COF material was prepared; step (3) was modified as follows: COF material and sublimed sulfur were mixed at a mass ratio of 1:1.8, ground in a mortar for 30 min, heated at 155°C for 24 h under an argon atmosphere, and then heated at 185°C for 24 h to obtain COF / S composite material; step (4) was modified as follows: COF / S composite material, acetylene black, and polyvinylidene fluoride were mixed evenly at a mass ratio of 7:2:1, and N-methylpyrrolidone with a mass ratio of 2.5 times that of COF-coated porous carbon / S composite material was added. The mixture was magnetically stirred to form a uniform slurry, coated on aluminum foil, and vacuum dried at 80°C for 11 h to obtain positive electrode material. The remaining steps were the same as in Example 2.
[0050] Comparative Example 2
[0051] The difference between the preparation method of MOF-based porous carbon cathode material in Comparative Example 2 and Example 2 lies in step (2). Step (2) is modified as follows: porous carbon material, trialdehyde-based phloroglucinol, 6-methyl-1,3,5-triazine-2,4-diamine, 1,4-dioxane, mesitylene, and aqueous acetic acid are mixed evenly at a mass ratio of 1:0.315:0.32:23:23:8, ultrasonically dispersed for 30 min, rapidly frozen in liquid nitrogen, degassed three times, sealed, kept in an oil bath at 120°C for 44 h, cooled to room temperature, filtered, and washed four times each with tetrahydrofuran and methanol, and vacuum dried at 55°C for 11 h to obtain COF-coated porous carbon material. The remaining steps are the same as in Example 2.
[0052] Comparative Example 3
[0053] The difference between the preparation method of MOF-based porous carbon cathode material in Comparative Example 3 and Example 2 lies in step (2). Step (2) is modified as follows: porous carbon material, trialdehyde-based phloroglucinol, 3,5-diamino-4-methylbenzenethiol, 1,4-dioxane, mesitylene, and aqueous acetic acid are mixed evenly in a mass ratio of 1:0.315:0.32:23:23:8, ultrasonically dispersed for 30 min, rapidly frozen in liquid nitrogen, degassed three times and sealed, kept in an oil bath at 120°C for 44 h, cooled to room temperature, filtered and washed four times each with tetrahydrofuran and methanol, and vacuum dried at 55°C for 11 h to obtain COF-coated porous carbon material. The remaining steps are the same as in Example 2.
[0054] Comparative Example 4
[0055] The preparation method of MOF-based porous carbon cathode material in Comparative Example 4 differs from that in Example 2 in that step (2) is omitted, and step (3) is modified as follows: porous carbon material and sublimed sulfur are mixed at a mass ratio of 1:1.8, ground in a mortar for 30 min, heated at 155°C for 24 h under an argon atmosphere, and then heated at 185°C for 24 h to obtain porous carbon / S composite material; step (4) is modified as follows: porous carbon / S composite material, acetylene black, and polyvinylidene fluoride are mixed evenly at a mass ratio of 7:2:1, N-methylpyrrolidone (2.5 times the mass of COF-coated porous carbon / S composite material) is added, magnetically stirred to form a uniform slurry, coated on aluminum foil, and vacuum dried at 80°C for 11 h to obtain MOF-based porous carbon cathode material. The remaining steps are the same as in Example 2.
[0056] Test Example 1
[0057] Cyclic performance and rate performance testing:
[0058] The MOF-based porous carbon cathode materials prepared in the various examples and comparative examples were used to form circular samples with a diameter of 16 mm as the cathode, lithium metal sheets as the anode, porous polyethylene membranes as the separator, and a mixed solution of 1 mol / L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in ethylene glycol dimethyl ether (DOL) / hexane oxide (DEM) (volume ratio 1:1) and 1% LiNO3 as the electrolyte. CR2032 coin cells were fabricated using the same battery assembly process. The entire assembly process of the coin cells was carried out in a sealed argon glove box.
[0059] A CT-4800 multi-channel battery tester was used. The voltage test range was 1.7~2.8V, the temperature was 25℃, and the humidity was less than 30%. The current density for cycle testing was 1C, defined as 1675mAh / g. 500 cycles were performed at room temperature, and the discharge specific capacity retention rate after 500 cycles was recorded. For rate performance testing, the current density settings were sequentially 0.2C, 0.5C, 1C, 2C, and 3C, finally returning to 0.2C. Each current density was tested for 10 cycles, and the discharge specific capacity was recorded.
[0060] The results are shown in Table 1 and... Figure 1 .
[0061] Table 1
[0062] Capacity retention Capacity retention Example 1 88.62% Comparative Example 1 81.43% Example 2 89.06% Comparative Example 2 83.15% Example 3 88.89% Comparative Example 3 84.65% Comparative Example 4 78.23%
[0063] from Figure 1 Comparison with the experimental data of Examples 1-3 and Comparative Examples 1-4 in Table 1 reveals that the MOF-based porous carbon cathode material prepared by this invention has good cycle performance and rate performance.
[0064] By comparison Figure 1 The data from Example 2 and Comparative Example 1 in Table 1 illustrate that the regular framework of the MOF precursor forms a mesoporous carbon structure after high-temperature carbonization. The high specific surface area of the mesoporous carbon structure provides ample space for sulfur loading, and the mesoporous channels facilitate electrolyte penetration and rapid ion transport, thereby improving rate performance. At the same time, the nitrogen and cobalt-nickel elements on the porous carbon material work synergistically to provide strong chemical interactions and catalytic sites for the capture and conversion of polysulfides, thereby improving cycle stability. Furthermore, the porous carbon material, as a sulfur carrier, can physically limit the dissolution and diffusion of lithium polysulfides, alleviate volume expansion during cycling, and thus improve cycle performance and rate performance.
[0065] By comparison Figure 1 The data from Example 2 and Comparative Examples 2-4 in Table 1 illustrate that trialdehyde phloroglucinol reacts with (4,6-diamino-1,3,5-triazine-2-yl)methanethiol via a Schiff base reaction to generate a COF structure containing triazine and thiol groups, which coats the outside of porous carbon materials. Due to the high porosity and ultra-small pore size of the COF, it possesses ion sieving and sulfur-limiting capabilities. Simultaneously, the COF acts as an external protective barrier, further reducing polysulfide shuttle behavior and improving the battery's cycle performance and rate performance. The triazine groups on the COF-coated porous carbon material react with Li... + The good dipole interaction between them improves the cycle performance and rate performance of the battery; the thiol groups on the COF-coated porous carbon material can be covalently linked with sublimed sulfur, suppressing the shuttle effect and promoting the conversion kinetics of polysulfides, thereby improving the cycle performance and rate performance.
[0066] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A MOF-based porous carbon cathode material, characterized in that, The MOF-based porous carbon cathode material is prepared by coating a mixture of COF-coated porous carbon / S composite material, conductive agent, and binder onto the surface of aluminum foil. The COF-coated porous carbon / S composite material is prepared by mixing COF-coated porous carbon material with sublimed sulfur, followed by grinding and heating. The COF-coated porous carbon material is prepared by reacting porous carbon material with trialdehyde phloroglucinol and (4,6-diamino-1,3,5-triazin-2-yl)methanethiol; The porous carbon material is prepared by reacting cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and 2-methylimidazole, followed by high-temperature carbonization.
2. A method for preparing a MOF-based porous carbon cathode material, characterized in that, The preparation steps include the following: (1) Cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and deionized water were mixed evenly to prepare a metal solution; the metal solution and 2-methylimidazole solution were mixed evenly, and the mixture was allowed to stand at room temperature for 20-24 hours. The mixture was then centrifuged, washed, and dried to obtain Co / Ni-MOF material; under an argon atmosphere, the Co / Ni-MOF material was placed in a tube furnace, heated to 800℃, carbonized for 3 hours, and cooled to room temperature to obtain porous carbon material; (2) The porous carbon material, trialdehyde phloroglucinol, (4,6-diamino-1,3,5-triazine-2-yl)methanethiol, 1,4-dioxane, mesitylene, and acetic acid aqueous solution were mixed evenly, ultrasonically dispersed for 20-40 min, rapidly frozen in liquid nitrogen, degassed and sealed, kept in an oil bath at 120℃ for 40-48 h, cooled to room temperature, filtered, washed, and dried to obtain COF-coated porous carbon material; (3) COF-coated porous carbon material and sublimed sulfur were mixed and ground, and heated at 155°C for 24 hours under argon atmosphere and then at 185°C for 24 hours to obtain COF-coated porous carbon / S composite material. (4) Mix COF-coated porous carbon / S composite material, conductive agent and binder in a mass ratio of 7:2:
1. Add N-methylpyrrolidone at a mass ratio of 2 to 3 times that of COF-coated porous carbon / S composite material, stir magnetically to form a uniform slurry, coat it on aluminum foil, and vacuum dry it at 80°C for 10 to 12 hours to obtain MOF-based porous carbon cathode material.
3. The method for preparing a MOF-based porous carbon cathode material according to claim 2, characterized in that, The preparation steps of the porous carbon material in step (1) are as follows: Cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and deionized water are mixed evenly at a mass ratio of 1:(0.3~0.4):(100~150) to obtain a metal solution; 2-methylimidazole and deionized water are mixed evenly at a mass ratio of 1:(80~100) to obtain a 2-methylimidazole solution; the metal solution and 2-methylimidazole solution are mixed evenly at a mass ratio of 1:(1~1.2), allowed to stand at room temperature for 20~24h, centrifuged, and the resulting precipitate is washed 2~4 times with anhydrous ethanol and dried under vacuum at 70~80℃ for 4~6h to obtain Co / Ni-MOF material; under an argon atmosphere, the Co / Ni-MOF material is placed in a tube furnace, heated to 800℃ at a heating rate of 4℃ / min, carbonized for 3h, and cooled to room temperature to obtain porous carbon material.
4. The method for preparing a MOF-based porous carbon cathode material according to claim 2, characterized in that, The preparation steps of the COF-coated porous carbon material in step (2) are as follows: the porous carbon material, trialdehyde phloroglucinol, (4,6-diamino-1,3,5-triazine-2-yl)methanethiol, 1,4-dioxane, mesitylene, and aqueous acetic acid are mixed evenly in a mass ratio of 1:(0.3~0.33):(0.3~0.34):(20~25):(20~25):(5~10), ultrasonically dispersed for 20~40 min, rapidly frozen in liquid nitrogen, degassed and sealed, kept in an oil bath at 120℃ for 40~48 h, cooled to room temperature, filtered and washed 3~5 times each with tetrahydrofuran and methanol, and vacuum dried at 50~60℃ for 10~12 h to obtain the COF-coated porous carbon material.
5. The method for preparing a MOF-based porous carbon cathode material according to claim 2, characterized in that, The preparation steps of the COF-coated porous carbon / S composite material in step (3) are as follows: COF-coated porous carbon material and sublimed sulfur are mixed at a mass ratio of 1:(1.5~2), ground in a mortar for 20~40 min, heated at 155℃ for 24 h under an argon atmosphere, and then heated at 185℃ for 24 h to obtain the COF-coated porous carbon / S composite material.
6. The method for preparing a MOF-based porous carbon cathode material according to claim 2, characterized in that, The conductive agent in step (4) is acetylene black with a median diameter of 1~3 μm.
7. The method for preparing a MOF-based porous carbon cathode material according to claim 2, characterized in that, The adhesive used in step (4) is polyvinylidene fluoride, model Kynar 741.
8. The method for preparing a MOF-based porous carbon cathode material according to claim 4, characterized in that, The cycle is repeated 3 times.
9. The application of the MOF-based porous carbon cathode material prepared by the method according to any one of claims 2 to 8 in lithium batteries.