A two-dimensional functional material of polymer-based dynamic double ion coordination conjugated chain segments and its preparation method and application

Abstract

The present invention belongs to the technical field of lithium-sulfur batteries, and specifically relates to a two-dimensional functional material comprising a polymer-based dynamic diionic coordination conjugated chain segment, its preparation method, and application. The two-dimensional functional material comprises a conjugated chain segment polymer with zwitterionic functional groups grafted onto the molecular chain, and a two-dimensional material serving as a substrate for the conjugated chain segment growth. The present invention proposes a dynamic conjugated diionic coordination strategy to in situ grow the conjugated chain segment polymer on the surface of the two-dimensional material, successfully growing a flexible electronic pathway and a polymer segment rich in zwitterionic functional groups on the surface of the two-dimensional material. The combination of the flexible conjugated chain segment rich in zwitterionic functional groups with the substrate two-dimensional nanomaterial takes into account both homogeneous and heterogeneous phases, ensuring the mobility of the active sites and providing rapid conversion efficiency for homogeneous electrocatalysis. This effectively accelerates polysulfide conversion, inhibits the shuttle effect, and improves the cycle life, specific capacity, and cycle stability of the lithium-sulfur battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-sulfur batteries, and specifically relates to a two-dimensional functional material of a polymer-based dynamic double-ion coordinated conjugated chain segment, and a preparation method and application thereof. Background Art

[0002] The limited specific capacity of traditional lithium-ion batteries has limited the development of next-generation energy storage devices. In contrast, conversion electrode materials that have undergone characteristic structural evolution or multiphase redox reactions have surpassed the capacity limitations of intercalation electrode materials and are expected to achieve high-energy-density battery systems. By pairing a metallic lithium anode with a constructed lithium-sulfur (Li-S) battery, sulfur and lithium undergo a step-by-step redox reaction to generate soluble lithium polysulfides (LiPSs), which in turn generate solid-state lithium sulfide (Li2S). On the one hand, through the complete rupture of SS bonds and the formation of Li-S bonds, a capacity of 1672 mAh g was achieved. -1 On the other hand, the complex multi-electron and multi-phase redox reaction kinetics are slow, resulting in low active material utilization and rapid capacity decay.

[0003] To address the aforementioned sluggish sulfur redox kinetics, numerous electrocatalysts have been proposed to accelerate reaction kinetics and modulate heterogeneous redox reactions, including transition metal compounds, heteroatom-doped carbon, and their composites. Despite these achievements, the design of rational electrocatalysts to regulate the unique electrochemical properties of sulfur redox reactions has received little attention. The sulfur redox reaction in Li-S batteries involves both heterogeneous and homogeneous processes. Heterogeneous interfacial processes between solid S8, soluble LiPSs, and solid Li2S involve interfacial electron transfer and solid-liquid phase transitions, which are highly dependent on the conductive substrate to ensure the necessary electron pathways. Simultaneously, homogeneous processes occur in the electrolyte, such as liquid-liquid conversion between soluble LiPSs and neutralization reactions and disproportionation reactions occurring in the electrolyte. In a working Li-S battery, these heterogeneous and homogeneous processes are highly coupled, synergistically impacting the overall battery performance. Both processes require kinetically promoted and targeted, efficient electrocatalysts.

[0004] Based on the above considerations, synergistic regulation of heterogeneous and homogeneous processes is a reasonable strategy to comprehensively improve the electrochemical performance of working Li-S batteries. Specifically, electrocatalytic active sites can not only be effectively integrated onto conductive substrates to provide electrocatalytic functions for heterogeneous processes, but also exhibit mobility, extending the electrocatalytic function to the bulk electrolyte of homogeneous processes. However, for sulfur redox reactions with fixed electrocatalytic active sites, conventional electrocatalysts have limited electrocatalytic functions and unsatisfactory electrocatalytic activities, especially in high-sulfur-loading and lean electrolyte LS cells facing a large amount of sulfur derivatives. In addition, the fixed electrocatalytic active sites are easily covered by deposited insulators S8 and Li2S and deactivated, hindering the long-term electrocatalytic function of the working battery. Therefore, conventional electrocatalysts cannot meet the requirements of sulfur redox reactions in working Li-S batteries. To this end, emerging nanostructured electrocatalysts with heterogeneous and homogeneous electrocatalytic functions are urgently needed. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a dynamic dual ion coordination strategy, which in situ grows conjugated chain segment polymers on the surface of two-dimensional materials, and through an intermediate containing -SH at one end and -COOH at the other end, -COOH undergoes a condensation reaction with -NH on the conjugated chain segment, and -SH undergoes a thiol-ene click chemistry reaction with the C=C of the zwitterion, successfully growing a flexible electronic pathway and a polymer segment rich in zwitterionic functional groups on the surface of the two-dimensional material. The base material with excellent conductivity is combined with the flexible conjugated chain segment to ensure the basic mobility of the active site and provide rapid conversion efficiency for the homogeneous electrocatalytic function. The flexible electronic pathway is combined with the zwitterionic functional group at zero distance to ensure efficient polysulfide conversion. In addition, due to the lithium affinity of -SO3- and the flexibility of the electronic pathway, Li can be transported by the swing of the flexible dual ion conjugated chain segment. + , replacing traditional pore transport, avoiding the irreversible loss of electrolyte due to large amounts of electrolyte infiltration, and ultimately achieving both the cycle stability and high energy density of lithium-sulfur batteries under low E / S ratio conditions.

[0006] The technical solutions of the present invention are as follows:

[0007] A two-dimensional functional material of a polymer-based dynamic diionic coordinated conjugated chain segment comprises a conjugated chain segment polymer with zwitterionic functional groups grafted onto the molecular chain and a two-dimensional material serving as a growth substrate for the conjugated chain segment.

[0008] The two-dimensional material is one or a mixture of two or more of surface-modified graphene and MXene materials.

[0009] The MXene material refers to a two-dimensional layered material derived from transition metal carbides, transition metal nitrides or transition metal carbonitrides, specifically a type of MXene material with n+1 Xn T x A material system composed of elements, where M represents an early transition metal element, X represents one or both of C and N, T represents a group or modification on the surface of the material, and n is 1-3; for example, Ti3C2T x 、Ti3CNT x , Ti 1.6 Nb 0.4 CT x 、V2CT x 、Nb2CT x etc., which can be one or a mixture of two or more;

[0010] The surface-modified graphene refers to a product obtained by modifying functional groups on the graphene surface through chemical or physical treatment; for example, graphene oxide, carboxylated graphene, etc., which can be one or a mixture of two or more.

[0011] The conjugated chain segment polymer with zwitterionic functional groups grafted onto the molecular chain refers to a polymer obtained by polymerizing conjugated monomers to obtain conjugated chain segments, and grafting zwitterionic small molecules onto the conjugated chain segments with the aid of intermediates.

[0012] The conjugated monomer is pyrrole.

[0013] The zwitterionic small molecule is one or a mixture of two or more of 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, 3-(1-vinyl-3-imidazolyl)propane sulfonate, and 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate.

[0014] The intermediate is a small molecule with -SH at one end and -COOH at the other end, such as one or a mixture of two or more of thioglycolic acid, cysteine, mercaptopropionic acid, dimercaptosuccinic acid, thioglycolic acid, 2-mercapto-3-pyridinecarboxylic acid, and mercapto-triethylene glycol-carboxylic acid.

[0015] The preparation method of the above-mentioned polymer-based two-dimensional functional material with flexible conjugated diionic coordination dynamic swinging effect comprises the following specific steps:

[0016] Step (1): The two-dimensional material is uniformly dispersed in a solvent by ultrasound to obtain a solution A.

[0017] Step (2): dissolving the conjugated monomer and the initiator APS in a solvent by ultrasonication, respectively, to obtain solutions B and C.

[0018] In step (3), solution A is mixed with solution B to obtain a mixed solution E, which is stored at 4-10° C.; solution C is added dropwise to the mixed solution E under continuous stirring to obtain a mixed solution F; the mixed solution F is stirred at 4-10° C. for more than 24 hours; the filtered solid is washed with water 3-5 times, washed with ethanol 3-5 times, and dried at 50-75° C. overnight.

[0019] Step (4): dissolving the intermediate in a solvent to obtain an intermediate solution, then adding SOCl2 to obtain a mixed solution G, and ultrasonicating for 30-60 min to ensure that the carboxyl group is fully converted into an acid chloride; then, adding DMAP and ultrasonicating for 10-30 min to form a solution D.

[0020] Step (5): mixing the solid obtained in step (3) with triethylamine and a solvent, and ultrasonically treating the mixture for 30-90 minutes to form a uniform suspension; gradually adding the solution D obtained in step (4) dropwise to the suspension under continuous stirring; continuously stirring the obtained mixture at 50-120° C. for 12-36 hours, and then naturally cooling to room temperature; after suction filtration, the product is ultrasonically dispersed and washed in a solvent for 3-5 times, then washed with ethanol for 2-5 times, and then dried at 50-75° C. overnight to obtain a product with successfully grafted thiol groups.

[0021] Step (6), sequentially mixing the product obtained in step (5) with zwitterionic small molecules, solvent, and AlBN, ultrasonically degassing for 10-30 minutes, and stirring at 50-100° C. in a nitrogen atmosphere for 15 hours to 20 hours; washing the product with deionized water and methanol to remove residual zwitterionic small molecules, and then vacuum drying at 50-100° C. for 4-12 hours to obtain a polymer-based two-dimensional functional material with flexible conjugated diionic coordination and dynamic swinging effect.

[0022] The solvent in steps (2), (4), (5) and (6) is one or a mixture of two or more of water, anhydrous ethanol, acetone, DMF and NMP.

[0023] In the step (1), the concentration of solution A is 1-20 mg mL -1 .

[0024] In the step (2), the concentration of solution B is 0.5-6 mg mL -1 , the concentration of solution C is 1.5-15 mg mL -1 ; Ultrasonic time is 3-30min.

[0025] In the step (3), the mass ratio of the two-dimensional material to the conjugated monomer in the mixed solution E is 0.5-10, and the mass ratio of the conjugated monomer to the initiator APS in the mixed solution F is 0.5-10.

[0026] In the step (4), the concentration of the intermediate solution is 5-20 mg mL -1 In mixed solution G, the concentration of SOCl2 relative to the solvent is 5-10 mg mL -1 ; The amount of DMAP relative to the concentration of the solvent is 5-10 mg mL -1 ;

[0027] In the step (5), the amount of solid obtained in step (3) added relative to the concentration of the solvent is 2-8 mg mL -1 The amount of triethylamine relative to the concentration of the solvent is 2-8 mg mL -1 ;

[0028] In the step (6), the amount of the product successfully grafted with thiol groups is 2-10 mg mL relative to the concentration of the solvent. -1 The concentration of zwitterionic small molecules relative to the solvent is 1-5 mg mL -1 The amount of AlBN added was 1% of the total mass of the successfully grafted thiol product and the zwitterionic small molecules.

[0029] The above-mentioned two-dimensional functional material of polymer-based dynamic double-ion coordination conjugated chain segments is applied to the positive electrode of lithium-sulfur batteries and can be used as core energy in new energy vehicles, communication devices, laptop computers and other electronic products.

[0030] Beneficial effects of the present invention:

[0031] (1) The present invention proposes a dynamic conjugated diionic coordination strategy to in situ grow conjugated chain segment polymers on the surface of two-dimensional materials, successfully growing flexible electronic pathways and polymer segments rich in zwitterionic functional groups on the surface of two-dimensional materials; the combination of flexible conjugated segments rich in zwitterionic functional groups and the base two-dimensional nanomaterials takes into account both homogeneous and heterogeneous phases, ensures the mobility of active sites, and provides rapid conversion efficiency for homogeneous electrocatalytic functions; thereby efficiently accelerating the conversion of polysulfides, inhibiting the shuttle effect, and improving the cycle life, specific capacity and cycle stability of lithium-sulfur batteries.

[0032] (2) The zwitterionic functional groups are grafted onto the conjugated chain segments through intermediates, achieving zero-distance combination of the active sites and the electron pathways, thereby improving the polysulfide conversion efficiency.

[0033] (3) Rich in lithium-philic sites - SO3 - The conjugated chain segments can transport Li + , replacing traditional pore transport, avoiding the large amount of electrolyte infiltration caused by pore transport. Ensure the stable cycle of lithium-sulfur batteries under the condition of poor electrolyte in soft-pack batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1This is a scanning electron microscope image of the graphene-conjugated diionic chain segment of the present invention;

[0035] Figure 2 Graph (cycle) showing the electrochemical performance of the carboxylated graphene / graphene-conjugated dual ion segments in Examples 1 and 2 of the present invention.

[0036] Figure 3 is the Ti3C2T in Examples 3 and 7 of the present invention x / Nb2CT x -Charge platform curve (voltage-specific capacity) of conjugated diionic chain segment.

[0037] Figure 4 This is the electrochemical performance diagram of graphene oxide-conjugated double ion chain segments in Example 5 of the present invention (magnification).

[0038] Figure 5 This is the graphene oxide-conjugated double ion segment charging platform curve (voltage-specific capacity) in Example 5 of the present invention. DETAILED DESCRIPTION

[0039] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0040] In the following examples, different two-dimensional functional materials were prepared and used as positive electrode materials for lithium-sulfur batteries to prepare corresponding lithium-sulfur batteries.

[0041] Example 1:

[0042] (1) 400 mg of single-layer graphene was dispersed in 20 mL of NMP and ultrasonicated for 30 min to form a uniform suspension.

[0043] (2) 300 mg of pyrrole and 375 mg of APS were dissolved in 50 and 25 mL of deionized water, respectively.

[0044] (3) The resulting graphene suspension was mixed with the pyrrole solution and stored at 4°C. The APS solution was added dropwise to the mixed solution under continuous stirring. The resulting mixture was stirred continuously at 4°C for 24 h. After filtration, the mixture was washed three times with water and three times with ethanol, and dried overnight at 50°C.

[0045] (4) Dissolve 100 mg of mercaptopropionic acid in 5 mL of DMF, add 50 mg of SOCl2, and sonicate for 30 min. Then, add 50 mg of DMAP and sonicate for 10 min.

[0046] (5) 120 mg of the final solid obtained in step (3) was mixed with 120 mg of triethylamine and 15 mL of DMF and ultrasonicated for 90 min to form a uniform suspension. Under continuous stirring, the final solution obtained in step (4) was added dropwise to the suspension. Stirring was continued at 50°C for 12 h, and then naturally cooled to room temperature. The product was filtered, washed three times with DMF, and then washed twice with ethanol. Drying was done at 50°C overnight to obtain a product with successfully grafted thiol groups.

[0047] (6) 200 mg of the product successfully grafted with thiol groups in step (5), 100 mg of 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, 20 mL of deionized water, and 1 wt% of AlBN were mixed thoroughly. Then, ultrasonic degassing was performed for 10 min and the mixture was kept at 50°C in a nitrogen atmosphere for 15 h. The product was washed three times with DMF, deionized water, and methanol to remove residual monomers, and then vacuum dried at 50°C for 4 h. A two-dimensional functional material with a flexible conjugated diionic coordination dynamic swing effect was obtained.

[0048] (7) A simple melt diffusion method was used to mix the obtained two-dimensional functional material and sulfur powder in a mass ratio of 1:3 and heated at 155 °C for 12 h.

[0049] (8) Grind the obtained powder evenly, grind it in a ratio of powder: conductive agent: binder of 7:2:1, add an appropriate amount of NMP to assist in grinding, and form a uniformly dispersed slurry. Then, coat the slurry on aluminum foil and dry it under vacuum.

[0050] (9) The aluminum foil from the previous step was slivered to form an electrode sheet. The electrode sheet and lithium metal sheet were assembled into a CR2032 button cell and the electrochemical performance was tested. The electrolyte was 1.0M LiTFSI in DOL:DME = 1:1 Vol% with 2.0% LiNO3, a lithium-sulfur battery electrolyte.

[0051] Example 2:

[0052] (1) 25 mg of carboxylated graphene was dispersed in 25 mL of NMP and ultrasonicated for 30 min to form a uniform suspension.

[0053] (2) Dissolve 25 mg of pyrrole and 37.5 mg of APS in 50 and 25 mL of deionized water, respectively.

[0054] (3) The resulting graphene suspension was mixed with the pyrrole solution and stored at 10°C. The APS solution was added dropwise to the mixed solution under continuous stirring. The resulting mixture was stirred continuously at 10°C for 24 h. After filtration, the mixture was washed five times with water and five times with ethanol, and dried overnight at 75°C.

[0055] (4) Dissolve 25 mg of cysteine in 5 mL of DMF, add 25 mg of SOCl2, and sonicate for 60 min. Then, add 25 mg of DMAP and sonicate for 30 min.

[0056] (5) 30 mg of the final solid obtained in step (3) was mixed with 30 mg of triethylamine and 15 mL of DMF and ultrasonicated for 90 min to form a uniform suspension. Under continuous stirring, the final solution obtained in step (4) was added dropwise to the suspension. Stirring was continued at 120°C for 36 h, and then naturally cooled to room temperature. The product was filtered, washed with DMF 5 times, and then washed with ethanol 5 times. Drying was done at 75°C overnight to obtain a product with successfully grafted thiol groups.

[0057] (6) 40 mg of the product successfully grafted with thiol groups in step (5), 20 mg of 3-(1-vinyl-3-imidazolyl)propane sulfonate, 20 mL of deionized water, and 1 wt% of AlBN were mixed thoroughly. The mixture was then ultrasonically degassed for 10 min and maintained at 60°C under a nitrogen atmosphere for 16 h. The product was washed three times with DMF, deionized water, and methanol to remove residual monomers, and then dried in vacuo at 60°C for 8 h. A two-dimensional functional material with a flexible conjugated diionic coordination dynamic swinging effect was obtained.

[0058] (7) A simple melt diffusion method was used to mix the obtained two-dimensional functional material and sulfur powder in a mass ratio of 1:3 and heated at 155 °C for 12 h.

[0059] (8) Grind the obtained powder evenly, grind it in a ratio of powder: conductive agent: binder of 7:2:1, add an appropriate amount of NMP to assist in grinding, and form a uniformly dispersed slurry. Then, coat the slurry on aluminum foil and dry it under vacuum.

[0060] (9) The aluminum foil from the previous step was slivered to form an electrode sheet. The electrode sheet and lithium metal sheet were assembled into a CR2032 button cell and the electrochemical performance was tested. The electrolyte was 1.0M LiTFSI in DOL:DME = 1:1 Vol% with 2.0% LiNO3, a lithium-sulfur battery electrolyte.

[0061] Example 3:

[0062] (1) 100 mg of Ti3C2T xThe mixture was dispersed in 25 mL of deionized water and ultrasonicated for 30 min to form a uniform suspension.

[0063] (2) Dissolve 200 mg of pyrrole and 50 mg of APS in 50 and 25 mL of deionized water, respectively.

[0064] (3) The resulting graphene suspension was mixed with the pyrrole solution and stored at 5°C. The APS solution was added dropwise to the mixed solution under continuous stirring. The resulting mixture was stirred continuously at 5°C for 24 h. After filtration, the mixture was washed three times with water and three times with ethanol, and dried overnight at 60°C.

[0065] (4) Dissolve 50 mg of thioglycolic acid in 5 mL of DMF, add 35 mg of SOCl2, and sonicate for 40 min. Then, add 40 mg of DMAP and sonicate for 15 min.

[0066] (5) 60 mg of the final solid obtained in step (3) was mixed with 30 mg of triethylamine and 15 mL of DMF and ultrasonicated for 90 min to form a uniform suspension. The final solution obtained in step (4) was added dropwise to the suspension under continuous stirring. Stirring was continued at 100°C for 18 h, and then naturally cooled to room temperature. The product was filtered, washed with DMF 5 times, and then washed with ethanol 3 times. Drying was done at 55°C overnight to obtain a product with successfully grafted thiol groups.

[0067] (6) 40 mg of the product successfully grafted with thiol groups in step (5), 40 mg of 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate, 20 mL of deionized water, and 1 wt% of AlBN were mixed thoroughly. The mixture was then ultrasonically degassed for 15 min and maintained at 65°C under a nitrogen atmosphere for 17 h. The product was washed three times with DMF, deionized water, and methanol to remove residual monomers, and then dried in vacuo at 70°C for 9 h. A two-dimensional functional material with a flexible conjugated diionic coordination dynamic swinging effect was obtained.

[0068] (7) A simple melt diffusion method was used to mix the obtained two-dimensional functional material and sulfur powder in a mass ratio of 1:3 and heated at 155 °C for 12 h.

[0069] (8) Grind the obtained powder evenly, grind it in a ratio of powder: conductive agent: binder of 7:2:1, add an appropriate amount of NMP to assist in grinding, and form a uniformly dispersed slurry. Then, coat the slurry on aluminum foil and dry it under vacuum.

[0070] (9) The aluminum foil from the previous step was slivered to form an electrode sheet. The electrode sheet and lithium metal sheet were assembled into a CR2032 button cell and the electrochemical performance was tested. The electrolyte was 1.0M LiTFSI in DOL:DME = 1:1 Vol% with 2.0% LiNO3, a lithium-sulfur battery electrolyte.

[0071] Example 4:

[0072] (1) 500 mg of Ti3CNT x Disperse in 25 mL of NMP and sonicate for 30 min to form a uniform suspension.

[0073] (2) Dissolve 50 mg of pyrrole and 50 mg of APS in 50 and 25 mL of deionized water, respectively.

[0074] (3) The resulting graphene suspension was mixed with the pyrrole solution and stored at 6°C. The APS solution was added dropwise to the mixed solution under continuous stirring. The resulting mixture was stirred continuously at 6°C for 24 h. After filtration, the mixture was washed four times with water and three times with ethanol, and dried overnight at 70°C.

[0075] (4) 30 mg of 2-mercapto-3-pyridinecarboxylic acid was dissolved in 5 mL of DMF, 30 mg of SOCl2 was added, and the mixture was sonicated for 45 min. Then, 30 mg of DMAP was added and the mixture was sonicated for 20 min.

[0076] (5) 30 mg of the final solid obtained in step (3) was mixed with 60 mg of triethylamine and 15 mL of DMF and ultrasonicated for 90 min to form a uniform suspension. Under continuous stirring, the final solution obtained in step (4) was added dropwise to the suspension. Stirring was continued at 105°C for 16 h, and then naturally cooled to room temperature. The product was filtered, washed with DMF 5 times, and then washed with ethanol 4 times. Drying was done at 60°C overnight to obtain a product with successfully grafted thiol groups.

[0077] (6) 60 mg of the product successfully grafted with thiol groups in step (5), 20 mg of 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, 20 mL of deionized water, and 1 wt% of AlBN were mixed thoroughly. Then, ultrasonic degassing was performed for 24 min and the mixture was kept at 80°C under nitrogen atmosphere for 20 h. The product was washed three times with DMF, deionized water, and methanol to remove residual monomers, and then vacuum dried at 80°C for 10 h. A two-dimensional functional material with a flexible conjugated diionic coordination dynamic swing effect was obtained.

[0078] (7) A simple melt diffusion method was used to mix the obtained two-dimensional functional material and sulfur powder in a mass ratio of 1:3 and heated at 155 °C for 12 h.

[0079] (8) Grind the obtained powder evenly, grind it in a ratio of powder: conductive agent: binder of 7:2:1, add an appropriate amount of NMP to assist in grinding, and form a uniformly dispersed slurry. Then, coat the slurry on aluminum foil and dry it under vacuum.

[0080] (9) The aluminum foil from the previous step was slivered to form an electrode sheet. The electrode sheet and lithium metal sheet were assembled into a CR2032 button cell and the electrochemical performance was tested. The electrolyte was 1.0M LiTFSI in DOL:DME = 1:1 Vol% with 2.0% LiNO3, a lithium-sulfur battery electrolyte.

[0081] Example 5:

[0082] (1) 270 mg of graphene oxide was dispersed in 25 mL of NMP and ultrasonicated for 30 min to form a uniform suspension.

[0083] (2) 375 mg of pyrrole and 37.5 mg of APS were dissolved in 62.5 and 25 mL of deionized water, respectively.

[0084] (3) The resulting graphene suspension was mixed with the pyrrole solution and stored at 7°C. The APS solution was added dropwise to the mixed solution under continuous stirring. The resulting mixture was stirred continuously at 7°C for 24 h. After filtration, the mixture was washed four times with water and four times with ethanol, and dried overnight at 60°C.

[0085] (4) 90 mg of mercapto-triethylene glycol-carboxylic acid was dissolved in 5 mL of DMF, 30 mg of SOCl2 was added, and the mixture was sonicated for 50 min. Then, 40 mg of DMAP was added and the mixture was sonicated for 25 min.

[0086] (5) 75 mg of the final solid obtained in step (3) was mixed with 60 mg of triethylamine and 15 mL of DMF and ultrasonicated for 90 min to form a uniform suspension. The final solution obtained in step (4) was added dropwise to the suspension under continuous stirring. Stirring was continued at 110°C for 26 h, and then naturally cooled to room temperature. The product was filtered, washed with DMF 5 times, and then washed with ethanol 4 times. Drying was done at 70°C overnight to obtain a product with successfully grafted thiol groups.

[0087] (6) 80 mg of the product successfully grafted with thiol groups in step (5), 45 mg of 3-(1-vinyl-3-imidazolyl)propane sulfonate, 20 mL of deionized water, and 1 wt% of AlBN were mixed thoroughly. The mixture was then ultrasonically degassed for 18 min and maintained at 95°C under a nitrogen atmosphere for 18 h. The product was washed three times with DMF, deionized water, and methanol to remove residual monomers, and then dried under vacuum at 95°C for 11 h. A two-dimensional functional material with a flexible conjugated diionic coordination dynamic swinging effect was obtained.

[0088] (7) A simple melt diffusion method was used to mix the obtained two-dimensional functional material and sulfur powder in a mass ratio of 1:3 and heated at 155 °C for 12 h.

[0089] (8) Grind the obtained powder evenly, grind it in a ratio of powder: conductive agent: binder of 7:2:1, add an appropriate amount of NMP to assist in grinding, and form a uniformly dispersed slurry. Then, coat the slurry on aluminum foil and dry it under vacuum.

[0090] (9) The aluminum foil from the previous step was slivered to form an electrode sheet. The electrode sheet and lithium metal sheet were assembled into a CR2032 button cell and the electrochemical performance was tested. The electrolyte was 1.0M LiTFSI in DOL:DME = 1:1 Vol% with 2.0% LiNO3, a lithium-sulfur battery electrolyte.

[0091] Example 6:

[0092] (1) 200 mg of Ti 1.6 Nb 0.4 CT x The mixture was dispersed in 25 mL of deionized water and ultrasonicated for 30 min to form a uniform suspension.

[0093] (2) Dissolve 250 mg of pyrrole and 300 mg of APS in 50 and 25 mL of deionized water, respectively.

[0094] (3) The resulting graphene suspension was mixed with the pyrrole solution and stored at 8°C. The APS solution was added dropwise to the mixed solution under continuous stirring. The resulting mixture was stirred continuously at 8°C for 24 h. After filtration, the mixture was washed three times with water and three times with ethanol, and dried overnight at 60°C.

[0095] (4) Dissolve 75 mg of dimercaptosuccinic acid in 5 mL of DMF, add 25 mg of SOCl2, and sonicate for 48 min. Then, add 50 mg of DMAP and sonicate for 12 min.

[0096] (5) 105 mg of the final solid obtained in step (3) was mixed with 95 mg of triethylamine and 15 mL of DMF and ultrasonicated for 90 min to form a uniform suspension. Under continuous stirring, the final solution obtained in step (4) was added dropwise to the suspension. Stirring was continued at 115°C for 30 h, and then naturally cooled to room temperature. The product was filtered, washed with DMF 4 times, and then washed with ethanol 2 times. Drying was done at 55°C overnight to obtain a product with successfully grafted thiol groups.

[0097] (6) 120 mg of the product successfully grafted with thiol groups in step (5), 60 mg of 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate, 20 mL of deionized water, and 1 wt% of AlBN were mixed thoroughly. The mixture was then ultrasonically degassed for 15 min and maintained at 80°C under a nitrogen atmosphere for 20 h. The product was washed three times with DMF, deionized water, and methanol to remove residual monomers, and then vacuum-dried at 75°C for 9 h. A two-dimensional functional material with a flexible conjugated diionic coordination dynamic swinging effect was obtained.

[0098] (7) A simple melt diffusion method was used to mix the obtained two-dimensional functional material and sulfur powder in a mass ratio of 1:3 and heated at 155 °C for 12 h.

[0099] (8) Grind the obtained powder evenly, grind it in a ratio of powder: conductive agent: binder of 7:2:1, add an appropriate amount of NMP to assist in grinding, and form a uniformly dispersed slurry. Then, coat the slurry on aluminum foil and dry it under vacuum.

[0100] (9) The aluminum foil from the previous step was slivered to form an electrode sheet. The electrode sheet and lithium metal sheet were assembled into a CR2032 button cell and the electrochemical performance was tested. The electrolyte was 1.0M LiTFSI in DOL:DME = 1:1 Vol% with 2.0% LiNO3, a lithium-sulfur battery electrolyte.

[0101] Example 7:

[0102] (1) 300 mg of Nb2CT x The mixture was dispersed in 25 mL of deionized water and ultrasonicated for 30 min to form a uniform suspension.

[0103] (2) Dissolve 50 mg of pyrrole and 100 mg of APS in 50 and 25 mL of deionized water, respectively.

[0104] (3) The resulting graphene suspension was mixed with the pyrrole solution and stored at 9°C. The APS solution was added dropwise to the mixed solution under continuous stirring. The resulting mixture was stirred continuously at 9°C for 24 h. After filtration, the mixture was washed three times with water and three times with ethanol, and dried overnight at 55°C.

[0105] (4) Dissolve 50 mg of mercaptopropionic acid in 5 mL of DMF, add 50 mg of SOCl2, and sonicate for 60 min. Then, add 25 mg of DMAP and sonicate for 15 min.

[0106] (5) 40 mg of the final solid obtained in step (3) was mixed with 45 mg of triethylamine and 15 mL of DMF and ultrasonicated for 90 min to form a uniform suspension. Under continuous stirring, the final solution obtained in step (4) was added dropwise to the suspension. Stirring was continued at 100°C for 36 h, and then naturally cooled to room temperature. The product was filtered, washed with DMF 5 times, and then washed with ethanol 3 times. Drying was done at 60°C overnight to obtain a product with successfully grafted thiol groups.

[0107] (6) 70 mg of the product successfully grafted with thiol groups in step (5), 30 mg of 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, 20 mL of deionized water, and 1 wt% of AlBN were mixed thoroughly. Then, ultrasonic degassing was performed for 15 min and the mixture was kept at 90°C under nitrogen atmosphere for 20 h. The product was washed three times with DMF, deionized water, and methanol to remove residual monomers, and then vacuum dried at 80°C for 10 h. A two-dimensional functional material with a flexible conjugated diionic coordination dynamic swing effect was obtained.

[0108] (7) A simple melt diffusion method was used to mix the obtained two-dimensional functional material and sulfur powder in a mass ratio of 1:3 and heated at 155 °C for 12 h.

[0109] (8) Grind the obtained powder evenly, grind it in a ratio of powder: conductive agent: binder of 7:2:1, add an appropriate amount of NMP to assist in grinding, and form a uniformly dispersed slurry. Then, coat the slurry on aluminum foil and dry it under vacuum.

[0110] (9) The aluminum foil from the previous step was slivered to form an electrode sheet. The electrode sheet and lithium metal sheet were assembled into a CR2032 button cell and the electrochemical performance was tested. The electrolyte was 1.0M LiTFSI in DOL:DME = 1:1 Vol% with 2.0% LiNO3, a lithium-sulfur battery electrolyte.

[0111] Comparison Examples

[0112] The material preparation method of comparative example 1 is as follows:

[0113] (1) Pure graphene was weighed and ground. The powder was ground in a ratio of powder: conductive agent: binder of 7:2:1. An appropriate amount of NMP was added to assist the grinding to form a uniformly dispersed slurry. The slurry was then coated on aluminum foil and dried under vacuum.

[0114] (2) The aluminum foil from the previous step was slivered to form an electrode sheet. The electrode sheet and lithium metal sheet were assembled into a CR2032 button cell and the electrochemical performance was tested. The electrolyte was 1.0M LiTFSI in DOL:DME = 1:1 Vol% with 2.0% LiNO3, a lithium-sulfur battery electrolyte.

[0115] The material preparation method of comparative example 2 is as follows:

[0116] (1) Weigh pure Ti3C2T x Grind the powder in a ratio of powder: conductive agent: binder of 7:2:1, add an appropriate amount of NMP to assist in grinding, form a uniformly dispersed slurry, and then coat the slurry on aluminum foil and dry it under vacuum.

[0117] (2) The aluminum foil from the previous step was slivered to form an electrode sheet. The electrode sheet and lithium metal sheet were assembled into a CR2032 button cell and the electrochemical performance was tested. The electrolyte was 1.0M LiTFSI in DOL:DME = 1:1 Vol% with 2.0% LiNO3, a lithium-sulfur battery electrolyte.

[0118] Performance Testing

[0119] Taking Examples 1, 2, 3, 5, and 7 as examples and comparing them with Examples 1 and 2, the battery test voltage range is between 1.5V and 3.0V, and the electrochemical test of the battery is performed using a Land CT2001A system. Figure 2 (Example 1, Example 2, Comparative Example 1) shows the cycling performance of the electrode materials as the positive sulfur host of lithium-sulfur batteries at a current density of 1C. It can be found that the capacity and cycling stability of Example 1 and Example 2 are greatly improved compared with Comparative Example 1 at 1C. Figure 3 (Example 3, Example 7, Comparative Example 2) are the charge and discharge platform curves (voltage-specific capacity) of the electrode materials as the positive sulfur host of lithium-sulfur batteries. It can be found that the charge and discharge capacities of Examples 3 and 7 are higher than those of Comparative Example 2, and the voltage polarization is less than that of Comparative Example 2, indicating that the electrochemical performance and kinetics are significantly enhanced. Figure 4 and Figure 5(Example 5) shows the rate performance of the electrode material as the sulfur host of the positive electrode of the lithium-sulfur battery and the corresponding charge-discharge platform curve. It can be found that it can still cycle at a high current density of 3C. The above results show that the two-dimensional functional material of the polymer-based dynamic double ion coordination conjugated chain segment can improve the cycle stability and specific capacity of the lithium-sulfur battery. All of this is attributed to the homogeneous electrocatalytic function and the zero-distance combination of the active site and the electron path to accelerate the conversion kinetics of polysulfide, rich in lithium-philic sites -SO3 - The conjugated chain segments can transport Li + , replacing traditional pore transmission, avoiding the large amount of electrolyte consumption caused by pore transmission. Ensure stable circulation of the battery under lean electrolyte conditions.

[0120] from Figure 1 It can be seen that the graphene-conjugated diionic segment in Example 1 still maintains the graphene morphology, and the polymer segment is evenly distributed.

Claims

1. A two-dimensional functional material of a polymer-based dynamic double ion coordination conjugated chain segment, characterized in that: The two-dimensional functional material includes a conjugated chain segment polymer with zwitterionic functional groups grafted onto the molecular chain and a two-dimensional material serving as a growth substrate for the conjugated chain segment; The two-dimensional material is one or a mixture of two or more of surface-modified graphene and MXene materials; the MXene material refers to a two-dimensional layered material derived from transition metal carbide, transition metal nitride or transition metal carbonitride, specifically refers to a MXene material having n+1 X n T x A material system composed of elements, where M represents an early transition metal element, X represents one or both of C and N, T represents a group or modification on the surface of the material, and n is 1-3; The conjugated chain segment polymer with zwitterionic functional groups grafted onto the molecular chain refers to a polymer obtained by polymerizing conjugated monomers to obtain conjugated chain segments, and grafting zwitterionic small molecules onto the conjugated chain segments with the help of intermediates; The conjugated monomer is pyrrole; the zwitterionic small molecule is one or a mixture of two or more of 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, 3-(1-vinyl-3-imidazolyl)propane sulfonate, and 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate; and the intermediate is one or a mixture of two or more of thioglycolic acid, cysteine, mercaptopropionic acid, dimercaptosuccinic acid, thioglycolic acid, 2-mercapto-3-pyridinecarboxylic acid, and thiol-triethylene glycol-carboxylic acid.

2. The two-dimensional functional material of a polymer-based dynamic double ion coordinated conjugated chain segment according to claim 1, characterized in that: The MXene material is Ti3C2T x 、Ti3CNT x , Ti 1.6 Nb 0.4 CT x 、V2CT x 、Nb2CT x The surface modified graphene is a mixture of one or two or more of graphene oxide and carboxylated graphene.

3. The method for preparing a two-dimensional functional material of a polymer-based dynamic diionic coordinated conjugated chain segment according to claim 1 or 2, characterized in that: The specific steps are as follows: Step (1), the two-dimensional material is uniformly dispersed in a solvent by ultrasound to obtain a solution A; Step (2), dissolving the conjugated monomer and the initiator APS in a solvent by ultrasonication, respectively, to obtain solutions B and C; Step (3), solution A is mixed with solution B to obtain a mixed solution E, which is stored at 4-10°C; Under continuous stirring, solution C is added dropwise to mixed solution E to obtain mixed solution F; mixed solution F is stirred at 4-10°C for more than 24 hours; the filtered solid is washed with water 3-5 times, washed with ethanol 3-5 times, and dried at 50-75°C overnight; Step (4), dissolving the intermediate in a solvent to obtain an intermediate solution, then adding SOCl2 to obtain a mixed solution G, and ultrasonicating for 30-60 minutes to ensure that the carboxyl group is fully converted into an acid chloride; then, adding DMAP and ultrasonicating for 10-30 minutes to form a solution D; Step (5), mixing the solid obtained in step (3) with triethylamine and a solvent, and ultrasonicating for 30-90 minutes to form a uniform suspension; Under continuous stirring, the solution D obtained in step (4) is gradually added dropwise to the suspension; the resulting mixture is continuously stirred at 50-120° C. for 12-36 hours, and then naturally cooled to room temperature; the product is filtered, ultrasonically dispersed and washed in a solvent for 3-5 times, then washed with ethanol for 2-5 times, and then dried at 50-75° C. overnight to obtain a product with successfully grafted thiol groups; Step (6), sequentially mixing the product obtained in step (5) with zwitterionic small molecules, solvent, and AlBN, ultrasonically degassing for 10-30 minutes, and stirring at 50-100° C. in a nitrogen atmosphere for 15 hours to 20 hours; washing the product with deionized water and methanol to remove residual zwitterionic small molecules, and then vacuum drying at 50-100° C. for 4-12 hours to obtain a polymer-based two-dimensional functional material with flexible conjugated diionic coordination and dynamic swinging effect.

4. The method for preparing a two-dimensional functional material of a polymer-based dynamic diionic coordinated conjugated chain segment according to claim 3, characterized in that: The solvent in steps (2), (4), (5) and (6) is one or a mixture of two or more of water, anhydrous ethanol, acetone, DMF and NMP.

5. The method for preparing a two-dimensional functional material of a polymer-based dynamic double ion coordinated conjugated chain segment according to claim 4, characterized in that: In the step (1), the concentration of solution A is 1-20 mg mL -1 ; In the step (2), the concentration of solution B is 0.5-6 mg mL -1 , the concentration of solution C is 1.5-15 mg mL -1 ; Ultrasonication time is 3-30min; In the step (3), the mass ratio of the two-dimensional material to the conjugated monomer in the mixed solution E is 0.5-10, and the mass ratio of the conjugated monomer to the initiator APS in the mixed solution F is 0.5-10.

6. The method for preparing a two-dimensional functional material of a polymer-based dynamic diionic coordinated conjugated segment according to claim 4, characterized in that: In the step (4), the concentration of the intermediate solution is 5-20 mg mL -1 In mixed solution G, the concentration of SOCl2 relative to the solvent is 5-10 mg mL -1 ; The amount of DMAP relative to the concentration of the solvent is 5-10 mg mL -1 .

7. The method for preparing a two-dimensional functional material of a polymer-based dynamic diionic coordinated conjugated segment according to claim 4, characterized in that: In the step (5), the amount of solid obtained in step (3) added relative to the concentration of the solvent is 2-8 mg mL -1 The amount of triethylamine relative to the concentration of the solvent is 2-8 mg mL -1 .

8. The method for preparing a two-dimensional functional material of a polymer-based dynamic diionic coordinated conjugated chain segment according to claim 4, characterized in that: In the step (6), the amount of the product successfully grafted with thiol groups is 2-10 mg mL relative to the concentration of the solvent. -1 The concentration of zwitterionic small molecules relative to the solvent is 1-5 mg mL -1 The amount of AlBN added was 1% of the total mass of the successfully grafted thiol product and the zwitterionic small molecules.

9. A two-dimensional functional material of a polymer-based dynamic double ion coordinated conjugated chain segment prepared by the preparation method according to any one of claims 4 to 8, which is used in the positive electrode of a lithium-sulfur battery.

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