PI / CNTS / FES ternary composite electrode material and preparation and application thereof

Abstract

This invention relates to the field of lithium-sulfur battery electrode materials technology, providing a PI / CNTS / FES ternary composite electrode material and its preparation and application. This material uses polyimide, carbon nanotubes, and aminated ferrous sulfide as its core components, forming an integrated functional system of adsorption, catalysis, and conductivity through APTES-mediated chemical bonding. This addresses the core problems of polysulfide shuttle and poor cycle stability in lithium-sulfur batteries from the source. Through the synergistic effect of strong PI adsorption, FeS-NH2 catalytic conversion, and high CNT conductivity, this invention strengthens the electrode interface bonding, improves charge transport efficiency and reaction kinetics, and enables lithium-sulfur batteries to possess both excellent rate performance and long-term cycle stability, showing broad application prospects in consumer electronics, electric vehicles, and large-scale energy storage.

Description

Technical Field

[0001] This invention relates to the field of lithium-sulfur battery electrode materials technology, specifically a PI / CNTS / FES ternary composite electrode material and its preparation and application. Background Technology

[0002] With the rapid rise of the new energy industry, the performance upgrade of energy storage systems has become a key demand for industry development. Lithium-sulfur batteries, with their outstanding advantages such as a high theoretical energy density of 2600 Wh / kg, abundant and low-cost sulfur resources, and environmental friendliness, are considered one of the core candidates for next-generation high-performance energy storage batteries, and have broad application prospects in electric vehicles, portable electronic devices, and large-scale energy storage power stations. However, the commercialization of lithium-sulfur batteries still faces insurmountable technical bottlenecks: First, the poor conductivity of elemental sulfur and its discharge product, lithium sulfide, leads to low electrode charge transfer efficiency, limiting battery rate performance; second, soluble lithium polysulfides (LiPSs) generated during charging and discharging easily dissolve and diffuse in the electrolyte, triggering a "shuttle effect," which not only causes loss of active materials but also leads to corrosion of the negative electrode lithium sheet, ultimately resulting in rapid capacity decay and severely insufficient cycle stability.

[0003] To address the aforementioned issues, existing technologies primarily employ single strategies such as carbon material composites, metal compound catalysis, or polymer coating to optimize electrode performance. However, these strategies still suffer from problems like weak interfacial bonding and insufficient functional synergy, failing to fundamentally suppress the shuttle effect and improve long-cycle stability. Therefore, there is an urgent need to provide a PI / CNTS / FES ternary composite electrode material, along with its preparation and application, to overcome the shortcomings in current practical applications. Summary of the Invention

[0004] The purpose of this invention is to provide a PI / CNTS / FES ternary composite electrode material and its preparation and application. Through multi-component synergistic design and precise process control, it solves the core problems of polysulfide shuttle and poor cycle stability in lithium-sulfur batteries.

[0005] The present invention is achieved as follows: a PI / CNTS / FES ternary composite electrode material comprising polyimide (PI), carbon nanotubes (CNTs) and aminated ferrous sulfide (FeS-NH2).

[0006] The PI, CNTs, and FeS-NH2 form a stable composite structure through chemical bonding mediated by γ-aminopropyltriethoxysilane (APTES), constituting a cathode material system that integrates polysulfide adsorption, catalytic conversion, and electronic conduction functions.

[0007] The present invention also provides a method for preparing the PI / CNTs / FeS ternary composite electrode material as described above, the method comprising the following steps:

[0008] Step S1: Synthesis of aminated FeS (FeS-NH2)

[0009] S11: Weigh ferrous sulfate heptahydrate and sodium sulfide nonahydrate, add deionized water and stir until completely dissolved to obtain ferrous sulfate solution and sodium sulfide solution. While stirring continuously, slowly add sodium sulfide solution to ferrous sulfate solution to generate black FeS precipitate.

[0010] S12: Transfer the mixed solution to a centrifuge tube and centrifuge to separate the precipitate. Wash with deionized water first, then with ethanol.

[0011] S13: Disperse FeS in ethanol by ultrasonication, add APTES and stir until homogeneous, transfer to an oil bath for reflux reaction, cool and centrifuge to separate the solid product, wash with ethanol several times, and vacuum dry until the product mass is constant to obtain FeS-NH2.

[0012] S2: Synthetic polyamic acid (PAA)

[0013] S21: Under nitrogen protection, 4,4'-diaminodiphenyl ether (ODA) is dissolved in N-methylpyrrolidone (NMP) and stirred until completely dissolved. The solution is then transferred to an ice bath, and pyromellitic dianhydride (PMDA) is added in batches according to the ratio while stirring and controlling the temperature ≤10℃. The reaction yields a PAA solution.

[0014] S3: Preparation of PI / CNTs / FeS ternary composite slurry

[0015] S31: Weigh CNTs and add them to NMP to form a suspension by sonication. Then add PAA solution, stir at room temperature under nitrogen protection, and vacuum dry to obtain polyamic acid powder. Calcine the polyamic acid powder in a tube furnace under nitrogen atmosphere to obtain PI / CNTs powder.

[0016] S32: Weigh PI / CNTs powder and add it to NMP and stir to disperse. Weigh FeS-NH2 and add it to NMP and sonicate to form a suspension. Slowly add the FeS-NH2 suspension to the PI / CNTs solution, heat and stir, then add APTES and degas under vacuum to obtain ternary composite slurry.

[0017] S4: Preparation of PI / CNTs / FeS ternary composite electrode

[0018] S41: The ternary composite slurry is uniformly coated on aluminum foil, vacuum dried, and then cut into circular pieces to obtain the PI / CNTs / FeS ternary composite electrode.

[0019] As a further aspect of the present invention: in step S11, the mass ratio of ferrous sulfate heptahydrate to sodium sulfide nonahydrate is 1.39 g:1.56 g, and the volume ratio of the corresponding deionized water is 1.39 g:20 mL and 1.56 g:20 mL.

[0020] As a further aspect of the present invention: in step S11, the sodium sulfide solution is slowly added to the ferrous sulfate solution with continuous stirring at a rate of 1-2 mL / min;

[0021] In step S12, the centrifugation speed is 3500-4500 rpm, the centrifugation time is 4-6 minutes, and the washing with deionized water and ethanol is no less than 5 times, with each washing time being no less than 3 minutes.

[0022] As a further aspect of the present invention: in step S13, the ultrasonic power for ultrasonic dispersion of FeS in ethanol is 100-150 W, and the dispersion time is 30 minutes.

[0023] The oil bath reflux temperature is 75-85℃, and the reaction time is 3-5 hours;

[0024] The vacuum drying temperature is 25-35℃.

[0025] As a further aspect of the present invention: in step S21, the mass ratio of PMDA to ODA is 1.089:1, and PMDA is added in 3-5 batches with an interval of 15-20 minutes between each batch.

[0026] Nitrogen purity ≥ 99.99%, gas flow rate 10-20 mL / min, NMP is anhydrous.

[0027] As a further aspect of the present invention: in step S31, the CNTs are multi-walled carbon nanotubes with a length of 5-15 micrometers, a diameter of 20-40 nanometers, and a purity of ≥95%;

[0028] The ultrasonic dispersion power is 150-200 W, and the dispersion time is 30 minutes;

[0029] The vacuum drying temperature is 55-65℃, the vacuum degree is ≤-0.09 MPa, and the drying time is 3 hours.

[0030] As a further aspect of the present invention: in step S31, the polyamic acid powder is calcined in a tube furnace under a nitrogen atmosphere, wherein the nitrogen gas flow rate is 20-30 mL / min, the heating rate is 2-3℃ / min, the calcination temperature is 300-320℃, and the calcination time is 8 hours.

[0031] The mass ratio of PI / CNTs to FeS-NH2 is 0.8:1-1.2:1;

[0032] In step S32, the heating temperature is 75-85℃, and the stirring time is 2 hours;

[0033] The amount of APTES added is 1-2% of the total mass of the reaction system;

[0034] The vacuum degree of vacuum degassing is ≤-0.095MPa, and the degassing time is 30 minutes.

[0035] The present invention also provides a lithium-sulfur battery cathode, wherein the active material layer of the lithium-sulfur battery cathode is composed of the above-mentioned PI / CNTs / FeS ternary composite electrode material or the PI / CNTs / FeS ternary composite electrode material prepared by the above method.

[0036] The present invention also provides a lithium-sulfur battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode is the positive electrode of the lithium-sulfur battery described above;

[0037] The negative electrode is a thin sheet of metallic lithium, and the separator is Celgard 2400;

[0038] The electrolyte is composed of 1 mol / L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) dissolved in a solvent consisting of 1,3-dioxolane and 1,2-dimethoxyethane in a volume ratio of 1:1.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] (1) The strong adsorption of PI, the catalytic activity of FeS-NH2 and the conductive network of CNTs form an integrated system of adsorption, catalysis and conduction, which greatly reduces the dissolution and migration of polysulfides;

[0041] (2) By using APTES to mediate chemical bonding, the interaction between components is strengthened, preventing peeling and shedding during use, and significantly improving the stability of the electrode structure and cycle life;

[0042] (3) The three factors work together to optimize charge transport efficiency and reaction kinetics, taking into account high conductivity, strong catalytic activity and stable structure, so that the battery can have both excellent rate performance and long cycle stability. Attached Figure Description

[0043] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0044] Figure 1SEM image and elemental mapping of the PI / CNTs / FeS sample prepared in Example 1;

[0045] Figure 2 The XRD pattern of the PI / CNTs / FeS sample prepared in Example 1;

[0046] Figure 3 Raman spectrum of the PI / CNTs / FeS sample prepared in Example 1;

[0047] Figure 4 The TG curve of the PI / CNTs / FeS sample prepared in Example 1;

[0048] Figure 5 XPS image of the PI / CNTs / FeS sample prepared in Example 1;

[0049] Figure 6 XPS image of the PI / CNTs / FeS sample prepared in Example 1;

[0050] Figure 7 XPS image of the PI / CNTs / FeS sample prepared in Example 1;

[0051] Figure 8 XPS image of the PI / CNTs / FeS sample prepared in Example 1;

[0052] Figure 9 XPS image of the PI / CNTs / FeS sample prepared in Example 1;

[0053] Figure 10 XPS image of the PI / CNTs / FeS sample prepared in Example 1;

[0054] Figure 11 The image shows the polysulfide adsorption chromatogram of the PI / CNTs / FeS sample prepared in Example 1.

[0055] Figure 12 Peel strength diagram of the PI / CNTs / FeS sample prepared in Example 1;

[0056] Figure 13 The differential CV plot of the PI / CNTs / FeS sample prepared in Example 1;

[0057] Figure 14 The CV diffusion coefficient diagram of the PI / CNTs / FeS sample prepared in Example 1;

[0058] Figure 15 The figure shows the galvanostatic intermittent titration (GITT) curve of the PI / CNTs / FeS sample prepared in Example 1.

[0059] Figure 16 Internal resistance diagram of the electrode relative to normalized discharge-charge time for the PI / CNTs / FeS sample prepared in Example 1;

[0060] Figure 17 CV chromatogram of the PI / CNTs / FeS sample prepared in Example 1;

[0061] Figure 18 The constant current discharge / charge curve of the PI / CNTs / FeS sample prepared in Example 1 at 0.1C during the first cycle.

[0062] Figure 19 Impedance spectroscopy of the PI / CNTs / FeS sample prepared in Example 2;

[0063] Figure 20 The differential rate performance diagram of the PI / CNTs / FeS sample prepared in Example 1;

[0064] Figure 21 The image shows a 0.2C long-cycle diagram of the PI / CNTs / FeS sample prepared in Example 1.

[0065] Figure 22 The 1C long cycle diagram of the PI / CNTs / FeS sample prepared in Example 2;

[0066] Figure 23 The constant current discharge / charge curves of the PI / CNTs / FeS sample prepared in Example 1 under different current densities during the first cycle are shown. Detailed Implementation

[0067] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0068] The present invention will be further explained below with reference to specific embodiments.

[0069] The present invention provides a PI / CNTS / FES ternary composite electrode material comprising polyimide (PI), carbon nanotubes (CNTs) and aminated ferrous sulfide (FeS-NH2).

[0070] The PI, CNTs, and FeS-NH2 form a stable composite structure through chemical bonding mediated by γ-aminopropyltriethoxysilane (APTES), constituting a cathode material system that integrates polysulfide adsorption, catalytic conversion, and electronic conduction functions.

[0071] By leveraging the synergistic effect of each component, the performance bottleneck of lithium-sulfur batteries can be overcome. The synergistic effect of the three components suppresses the shuttle effect from the source, solving the core problems of polysulfide shuttle and poor cycle stability in lithium-sulfur batteries.

[0072] This invention also provides a method for preparing a PI / CNTS / FES ternary composite electrode material, comprising the following steps:

[0073] Step S1: Synthesis of aminated FeS (FeS-NH2)

[0074] Step S11: Weigh ferrous sulfate heptahydrate (FeSO4·7H2O), add deionized water and stir until completely dissolved to obtain a ferrous sulfate solution. Weigh sodium sulfide nonahydrate (Na2S·9H2O), add deionized water and stir until completely dissolved to obtain a sodium sulfide solution. While continuously stirring, slowly add the sodium sulfide solution dropwise to the ferrous sulfate solution, forming a black FeS precipitate.

[0075] The ratio of ferrous sulfate heptahydrate, sodium sulfide nonahydrate, and deionized water is 1.39 g:1.56 g:20 mL:20 mL. The ratio can be reduced or increased accordingly. The dropping rate of the sodium sulfide solution is 1-2 mL / min to ensure uniform reaction and avoid excessive local concentration that could lead to precipitation and agglomeration.

[0076] Step S12: Transfer the mixed solution to a centrifuge tube, centrifuge, separate the precipitate, wash with deionized water first, and then wash with ethanol.

[0077] The centrifugation speed can be adjusted within the range of 3500-4500 rpm, and the centrifugation time is 4-6 minutes to ensure that the precipitate and solution are fully separated. The washing with deionized water and ethanol should be done by soaking and shaking, and each washing time should be no less than 3 minutes to thoroughly remove residual sodium ions, sulfate ions and other impurities.

[0078] Step S13: Disperse FeS in ethanol by ultrasonication for 30 minutes, slowly add APTES and stir until homogeneous, then transfer to an oil bath for reflux reaction. After cooling, centrifuge to separate the solid product, wash several times with ethanol, and vacuum dry to constant weight to obtain FeS-NH2.

[0079] The ultrasonic dispersion power is 100-150W to ensure uniform dispersion of FeS without agglomeration; the mass ratio of APTES to FeS is 0.5 mL:0.8 g (calculated based on the theoretical mass of FeS produced), which can be adjusted proportionally according to the actual FeS yield; the oil bath reflux temperature is controlled at 75-85℃, and the reaction time is 3-5 hours; the vacuum drying temperature is 25-35℃, and the drying time is 8-12 hours, until the product quality is constant.

[0080] Step S2: Synthesis of polyamic acid (PAA)

[0081] Step S21: Under nitrogen protection, dissolve 0.4 g of 4,4'-diaminodiphenyl ether (ODA) in 10 mL of N-methylpyrrolidone (NMP) and stir until completely dissolved. Transfer the solution to an ice bath, and add 0.436 g of pyromellitic dianhydride (PMDA) in portions at a PMDA to ODA mass ratio of 1.089, stirring continuously while adding the solution. Control the temperature to ≤10℃ and react for 4 hours to obtain a PAA solution.

[0082] The nitrogen gas must be ≥99.99% pure and flow rate 10-20 mL / min to ensure the reaction system is isolated from air; NMP must be anhydrous (moisture content ≤0.05%) to avoid affecting the polymerization reaction; PMDA must be added in 3-5 batches, with an interval of 15-20 minutes between each batch, and the reaction temperature must be strictly controlled not to exceed 10℃ to prevent premature imidization due to excessive temperature; the stirring rate must be 300-500 rpm to ensure the monomer reacts fully.

[0083] Step S3: Preparation of PI / CNTs / FeS ternary composite slurry

[0084] Step S31: Weigh 0.8 g of CNTs and add them to 10 mL of NMP. Sonicate for 30 minutes to form a suspension. Slowly add the above PAA solution to the CNTs suspension. Stir at room temperature for 2 hours under nitrogen protection, then dry in a vacuum drying oven at 60°C for 3 hours to obtain polyamic acid powder. Place the polyamic acid powder in a tube furnace and calcine at 310°C for 8 hours under a nitrogen atmosphere to obtain PI / CNTs powder.

[0085] The CNTs are multi-walled carbon nanotubes with a length of 5-15 micrometers, a diameter of 20-40 nanometers, and a purity of ≥95%. The ultrasonic dispersion power is 150-200 W to ensure that the CNTs are uniformly dispersed in NMP without agglomeration. The PAA solution is added at a rate of 2-3 mL / min, and the stirring rate is 400-600 rpm. The vacuum drying temperature is 55-65℃, and the vacuum degree is ≤-0.09 MPa. The nitrogen gas flow rate for tube furnace calcination is 20-30 mL / min, the heating rate is 2-3℃ / min, and the calcination temperature is controlled at 300-320℃ to ensure complete imidization of polyamic acid to form PI.

[0086] Step S32: Weigh 0.05 g of PI / CNTs and add them to 2 mL of NMP. Stir for 30 minutes until fully dissolved and dispersed. Weigh 0.05 g of FeS-NH2 and add it to 1 mL of NMP. Sonicate for 15 minutes to form a suspension. Slowly add the FeS-NH2 suspension dropwise to the PI / CNTs solution. Stir at 80°C for 2 hours. Add 0.1 mL of APTES to promote chemical bonding. Degas under vacuum for 30 minutes to obtain the ternary composite slurry.

[0087] The mass ratio of PI / CNTs to FeS-NH2 is 1:1, which can be adjusted within the range of 0.8:1-1.2:1; the ultrasonic power of the FeS-NH2 suspension is 80-120 W, and the dropping acceleration rate is 0.5-1 mL / min; the temperature fluctuation range of stirring at 80℃ is ±5℃, and the stirring speed is 500-700 rpm; the amount of APTES added is 1-2% of the total mass of the reaction system, and the vacuum degree of vacuum degassing is ≤-0.095 MPa to ensure that there are no residual bubbles in the slurry.

[0088] Step S4: Assemble a lithium-sulfur battery using a PI / CNTs / FeS ternary composite electrode material.

[0089] Step S41: The above ternary composite slurry is uniformly coated onto aluminum foil, vacuum dried at 80°C for 12 hours, and then cut into 12 mm diameter discs as positive electrodes. Using lithium metal sheets as negative electrodes, Celgard 2400 as separators, and 1 mol / L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) electrolyte (prepared by dissolving equal volumes of 1,3-dioxosilane and 1,2-dimethoxyethane in a mixed solvent), the lithium-sulfur battery is assembled in an argon-atmosphere glove box.

[0090] In this embodiment, the method sequentially includes the synthesis of aminated FeS, the synthesis of polyamic acid, the preparation of PI / CNTs / FeS ternary composite slurry, and the molding of composite electrode. The process parameters of each step are precisely controllable, the raw material ratio can be scaled proportionally, and the preparation process is highly compatible with existing lithium battery production lines.

[0091] This invention also provides a lithium-sulfur battery cathode, wherein the active material layer of the lithium-sulfur battery cathode is composed of the above-mentioned PI / CNTs / FeS ternary composite electrode material or the PI / CNTs / FeS ternary composite electrode material prepared by the above method.

[0092] This invention also provides a lithium-sulfur battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode is the lithium-sulfur battery positive electrode according to claim 8;

[0093] The negative electrode is a thin sheet of metallic lithium, and the separator is Celgard 2400;

[0094] The electrolyte is composed of 1 mol / L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) dissolved in a solvent consisting of 1,3-dioxolane and 1,2-dimethoxyethane in a volume ratio of 1:1.

[0095] In summary, the working principle of this invention is to achieve efficient capture and rapid conversion of polysulfides through the synergistic effect of the strong adsorption characteristics of PI, the high conductivity network of CNTs, and the catalytic conversion effect of FeS, aiming to solve the core problems of polysulfide shuttle and poor cycle stability in lithium-sulfur batteries.

[0096] Example 1

[0097] Please see Figures 1-18 , Figure 20 , Figure 21 as well as Figure 23 A method for preparing a PI / CNTS / FES ternary composite electrode material includes the following steps:

[0098] Step S1: Synthesis of aminated FeS (FeS-NH2)

[0099] Step S11: Weigh 1.39 g of ferrous sulfate heptahydrate (FeSO4·7H2O), add 20 mL of deionized water and stir until completely dissolved to obtain a ferrous sulfate solution. Weigh 1.56 g of sodium sulfide nonahydrate (Na2S·9H2O), add 20 mL of deionized water and stir until completely dissolved to obtain a sodium sulfide solution. While continuously stirring, slowly add the sodium sulfide solution dropwise to the ferrous sulfate solution at a rate of 1 mL / min, forming a black FeS precipitate.

[0100] Step S12: Transfer the mixed solution to a centrifuge tube and centrifuge at 4000 rpm for 6 minutes. After separating the precipitate, wash it 5 times with deionized water and then 5 times with ethanol, with each washing time being no less than 3 minutes.

[0101] Step S13: Disperse 0.8 g of FeS in ethanol by ultrasonication for 30 minutes, slowly add 0.5 mL of APTES and stir until homogeneous, then transfer to an 80°C oil bath for reflux reaction for 3 hours. After cooling, centrifuge to separate the solid product, wash several times with ethanol, and vacuum dry at 30°C for 8 hours until the product mass is constant, obtaining FeS-NH2.

[0102] Step S2: Synthesis of polyamic acid (PAA)

[0103] Step S21: Under nitrogen protection (purity ≥ 99.99%) and a gas flow rate of 20 mL / min, dissolve 0.4 g of 4,4'-diaminodiphenyl ether (ODA) in 10 mL of N-methylpyrrolidone (NMP, water content ≤ 0.05%) and stir until completely dissolved. Transfer the solution to an ice bath. Add 0.436 g of pyromellitic dianhydride (PMDA) in three batches at 15-minute intervals, maintaining a PMDA to ODA mass ratio of 1.089. Stir continuously while adding the PMDA, controlling the temperature to ≤ 10℃ and the stirring rate at 400 rpm. React for 4 hours to obtain a PAA solution.

[0104] Step S3: Preparation of PI / CNTs / FeS ternary composite slurry

[0105] Step S31: Weigh 0.8 g of CNTs and add them to 10 mL of NMP. Sonicate for 30 minutes to form a suspension. Slowly add the above PAA solution to the CNTs suspension at a rate of 2 mL / min. Stir at room temperature for 2 hours under nitrogen protection at a stirring rate of 400 rpm. Then dry in a vacuum drying oven at 60℃ for 3 hours with a vacuum degree ≤-0.09 MPa to obtain polyamic acid powder. Place the polyamic acid powder in a tube furnace. Calcinate the powder at a nitrogen gas flow rate of 20 mL / min, a heating rate of 3℃ / min, a calcination temperature of 300℃, and a calcination time of 8 hours to obtain PI / CNTs powder.

[0106] Step S32: Weigh 0.05 g of PI / CNTs and add them to 2 mL of NMP. Stir for 30 minutes until fully dissolved and dispersed. Weigh 0.05 g of FeS-NH2 and add it to 1 mL of NMP. Sonicate for 15 minutes to form a suspension. Slowly add the FeS-NH2 suspension to the PI / CNTs solution at a dropping rate of 1 mL / min. Stir at 80℃ for 2 hours with a temperature fluctuation range of ±5℃ and a stirring rate of 500 rpm. Add 0.1 mL of APTES to promote chemical bonding. Degas under vacuum for 30 minutes to obtain the ternary composite slurry.

[0107] Step S4: Assemble a lithium-sulfur battery using a PI / CNTs / FeS ternary composite electrode material.

[0108] Step S41: The above ternary composite slurry is uniformly coated onto aluminum foil, vacuum dried at 80°C for 12 hours, and then cut into 12 mm diameter discs as positive electrodes. Using lithium metal sheets as negative electrodes, Celgard 2400 as separators, and 1 mol / L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) electrolyte (prepared by dissolving equal volumes of 1,3-dioxosilane and 1,2-dimethoxyethane in a mixed solvent), the lithium-sulfur battery is assembled in an argon-atmosphere glove box.

[0109] Example 2

[0110] Please see Figure 19 and Figure 22 A method for preparing a PI / CNTS / FES ternary composite electrode material includes the following steps:

[0111] Step S1: Synthesis of aminated FeS (FeS-NH2)

[0112] Step S11: Weigh 6.95 g of ferrous sulfate heptahydrate (FeSO4·7H2O), add 100 mL of deionized water and stir until completely dissolved to obtain a ferrous sulfate solution. Weigh 7.8 g of sodium sulfide nonahydrate (Na2S·9H2O), add 100 mL of deionized water and stir until completely dissolved to obtain a sodium sulfide solution. While continuously stirring, slowly add the sodium sulfide solution dropwise to the ferrous sulfate solution at a rate of 1 mL / min, forming a black FeS precipitate.

[0113] Step S21: Transfer the mixed solution to a centrifuge tube and centrifuge at 4000 rpm for 6 minutes. After separating the precipitate, wash it 5 times with deionized water and then 5 times with ethanol, with each washing time being no less than 3 minutes.

[0114] Step S31: Disperse 4 g of FeS in ethanol by ultrasonication for 30 minutes, slowly add 2.5 mL of APTES and stir until homogeneous, then transfer to an 80°C oil bath for reflux reaction for 5 hours. After cooling, centrifuge to separate the solid product, wash several times with ethanol, and dry under vacuum at 30°C for 12 hours until the product mass is constant, obtaining FeS-NH2.

[0115] Step S2: Synthesis of polyamic acid (PAA)

[0116] Step S21: Under nitrogen protection (purity ≥ 99.99%) and a gas flow rate of 20 mL / min, dissolve 0.4 g of 4,4'-diaminodiphenyl ether (ODA) in 10 mL of N-methylpyrrolidone (NMP, water content ≤ 0.05%) and stir until completely dissolved. Transfer the solution to an ice bath. Add 0.436 g of pyromellitic dianhydride (PMDA) in 5 batches at 20-minute intervals, maintaining a PMDA to ODA mass ratio of 1.089. Stir continuously while adding the PMDA, controlling the temperature to ≤ 10℃ and the stirring rate at 400 rpm. React for 4 hours to obtain a PAA solution.

[0117] Step S3: Preparation of PI / CNTs / FeS ternary composite slurry

[0118] Step S31: Weigh 0.8 g of CNTs and add them to 10 mL of NMP. Sonicate for 30 minutes to form a suspension. Slowly add the above PAA solution to the CNTs suspension at a rate of 2 mL / min. Stir at room temperature for 2 hours under nitrogen protection at a stirring rate of 400 rpm. Then dry in a vacuum drying oven at 60℃ for 3 hours with a vacuum degree ≤-0.09 MPa to obtain polyamic acid powder. Place the polyamic acid powder in a tube furnace. Calcinate the powder at a nitrogen gas flow rate of 30 mL / min, a heating rate of 2℃ / min, a calcination temperature of 310℃, and a calcination time of 8 hours to obtain PI / CNTs powder.

[0119] Step S32: Weigh 0.25 g of PI / CNTs and add them to 10 mL of NMP. Stir for 30 minutes until fully dissolved and dispersed. Weigh 0.25 g of FeS-NH2 and add it to 5 mL of NMP. Sonicate for 15 minutes to form a suspension. Slowly add the FeS-NH2 suspension to the PI / CNTs solution at a dropping rate of 0.5 mL / min. Stir at 80℃ for 2 hours, with a temperature fluctuation range of ±5℃ and a stirring speed of 600 rpm. Add 0.5 mL of APTES to promote chemical bonding. Degas under vacuum for 30 minutes to obtain the ternary composite slurry.

[0120] Step S4: Assemble a lithium-sulfur battery using a PI / CNTs / FeS ternary composite electrode material.

[0121] Step S41: The above ternary composite slurry is uniformly coated onto aluminum foil, vacuum dried at 80°C for 12 hours, and then cut into 12 mm diameter discs as positive electrodes. Using lithium metal sheets as negative electrodes, Celgard 2400 as separators, and 1 mol / L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) electrolyte (prepared by dissolving equal volumes of 1,3-dioxosilane and 1,2-dimethoxyethane in a mixed solvent), the lithium-sulfur battery is assembled in an argon-atmosphere glove box.

[0122] Example 3

[0123] A method for preparing a PI / CNTS / FES ternary composite electrode material includes the following steps:

[0124] Step S1: Synthesis of aminated FeS (FeS-NH2)

[0125] Step S11: Weigh 1.39 g of ferrous sulfate heptahydrate (FeSO4·7H2O), add 20 mL of deionized water and stir until completely dissolved to obtain a ferrous sulfate solution. Weigh 1.56 g of sodium sulfide nonahydrate (Na2S·9H2O), add 20 mL of deionized water and stir until completely dissolved to obtain a sodium sulfide solution. While continuously stirring, slowly add the sodium sulfide solution dropwise to the ferrous sulfate solution at a rate of 2 mL / min, forming a black FeS precipitate.

[0126] Step S21: Transfer the mixed solution to a centrifuge tube and centrifuge at 4600 rpm for 4 minutes. After separating the precipitate, wash it 5 times with deionized water and then 5 times with ethanol, with each washing time not less than 3 minutes.

[0127] Step S31: Disperse 0.8 g of FeS in ethanol by ultrasonication for 30 minutes, slowly add 0.5 mL of APTES and stir until homogeneous, then transfer to an 80°C oil bath for reflux reaction for 3 hours. After cooling, centrifuge to separate the solid product, wash several times with ethanol, and vacuum dry at 30°C for 8 hours until the product mass is constant, obtaining FeS-NH2.

[0128] Step S2: Synthesis of polyamic acid (PAA)

[0129] Step S21: Under nitrogen protection (purity ≥ 99.99%) and a gas flow rate of 20 mL / min, dissolve 0.4 g of 4,4'-diaminodiphenyl ether (ODA) in 10 mL of N-methylpyrrolidone (NMP, water content ≤ 0.05%) and stir until completely dissolved. Transfer the solution to an ice bath. Add 0.436 g of pyromellitic dianhydride (PMDA) in three batches at 15-minute intervals, maintaining a PMDA to ODA mass ratio of 1.089. Stir continuously while adding the PMDA, controlling the temperature to ≤ 10℃ and the stirring rate at 500 rpm. React for 4 hours to obtain a PAA solution.

[0130] Step S3: Preparation of PI / CNTs / FeS ternary composite slurry

[0131] Step S31: Weigh 0.8 g of CNTs and add them to 10 mL of NMP. Sonicate for 30 minutes to form a suspension. Slowly add the above PAA solution to the CNTs suspension at a rate of 3 mL / min. Stir at room temperature for 2 hours under nitrogen protection at a stirring rate of 600 rpm. Then dry in a vacuum drying oven at 60℃ for 3 hours with a vacuum degree ≤-0.09 MPa to obtain polyamic acid powder. Place the polyamic acid powder in a tube furnace. Calcinate the powder at a nitrogen flow rate of 20 mL / min, a heating rate of 3℃ / min, a calcination temperature of 320℃, and a calcination time of 8 hours to obtain PI / CNTs powder.

[0132] Step S32: Weigh 0.05 g of PI / CNTs and add them to 2 mL of NMP. Stir for 30 minutes until fully dissolved and dispersed. Weigh 0.05 g of FeS-NH2 and add it to 1 mL of NMP. Sonicate for 15 minutes to form a suspension. Slowly add the FeS-NH2 suspension to the PI / CNTs solution at a dropping rate of 1 mL / min. Stir at 80℃ for 2 hours, with a temperature fluctuation range of ±5℃ and a stirring speed of 700 rpm. Add 0.1 mL of APTES to promote chemical bonding. Degas under vacuum for 30 minutes to obtain the ternary composite slurry.

[0133] Step S4: Assemble a lithium-sulfur battery using a PI / CNTs / FeS ternary composite electrode material.

[0134] Step S41: The above ternary composite slurry is uniformly coated onto aluminum foil, vacuum dried at 80°C for 12 hours, and then cut into 12 mm diameter discs as positive electrodes. Using lithium metal sheets as negative electrodes, Celgard 2400 as separators, and 1 mol / L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) electrolyte (prepared by dissolving equal volumes of 1,3-dioxosilane and 1,2-dimethoxyethane in a mixed solvent), the lithium-sulfur battery is assembled in an argon-atmosphere glove box.

[0135] The instruments used for material characterization and electrochemical performance testing in the above embodiments are as follows:

[0136] Morphological characterization: Observation was performed using a Thermo Fisher Apreo 2S high-resolution field emission scanning electron microscope.

[0137] Surface chemical analysis: Tests were performed using a ThermoFisher Nexsa G2 X-ray photoelectron spectroscopy system.

[0138] Crystal structure analysis: Characterized by Bruker D8 Advance X-ray powder diffractometer.

[0139] Thermal performance testing: performed on a Netzsch STA449 F5 synchronous thermal analyzer.

[0140] Interface peel strength test: The test was conducted using a Jinan Langguang XLW(PC) 180-degree peel tester.

[0141] Molecular structure analysis: conducted using a Horiba LabRAM HR Evolution Raman spectrometer from Japan.

[0142] Electrochemical performance testing: The CHI6600E electrochemical workstation manufactured by Shanghai Chenhua Co., Ltd. was used to test the cyclic voltammetry characteristics and AC impedance of the battery.

[0143] Charge and discharge test: The Wuhan Landian Battery Testing System was used, which has a current range of 20 mA and a voltage range of 5 V.

[0144] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A PI / CNTS / FES ternary composite electrode material, characterized in that, Including polyimide (PI), carbon nanotubes (CNTs) and aminated ferrous sulfide (FeS-NH2). The PI, CNTs, and FeS-NH2 form a stable composite structure through chemical bonding mediated by γ-aminopropyltriethoxysilane (APTES), constituting a cathode material system that integrates polysulfide adsorption, catalytic conversion, and electronic conduction functions.

2. A method for preparing the PI / CNTs / FeS ternary composite electrode material as described in claim 1, characterized in that, The method includes the following steps: Step S1: Synthesis of aminated FeS (FeS-NH2) S11: Weigh ferrous sulfate heptahydrate and sodium sulfide nonahydrate, add deionized water and stir until completely dissolved to obtain ferrous sulfate solution and sodium sulfide solution. While stirring continuously, slowly add sodium sulfide solution to ferrous sulfate solution to generate black FeS precipitate. S12: Transfer the mixed solution to a centrifuge tube and centrifuge to separate the precipitate. Wash with deionized water first, then with ethanol. S13: Disperse FeS in ethanol by ultrasonication, add APTES and stir until homogeneous, transfer to an oil bath for reflux reaction, cool and centrifuge to separate the solid product, wash with ethanol several times, and vacuum dry until the product mass is constant to obtain FeS-NH2. S2: Synthetic polyamic acid (PAA) S21: Under nitrogen protection, 4,4'-diaminodiphenyl ether (ODA) is dissolved in N-methylpyrrolidone (NMP) and stirred until completely dissolved. The solution is then transferred to an ice bath, and pyromellitic dianhydride (PMDA) is added in batches according to the ratio while stirring and controlling the temperature ≤10℃. The reaction yields a PAA solution. S3: Preparation of PI / CNTs / FeS ternary composite slurry S31: Weigh CNTs and add them to NMP to form a suspension by sonication. Then add PAA solution, stir at room temperature under nitrogen protection, and vacuum dry to obtain polyamic acid powder. Calcine the polyamic acid powder in a tube furnace under nitrogen atmosphere to obtain PI / CNTs powder. S32: Weigh PI / CNTs powder and add it to NMP and stir to disperse. Weigh FeS-NH2 and add it to NMP and sonicate to form a suspension. Slowly add the FeS-NH2 suspension to the PI / CNTs solution, heat and stir, then add APTES and degas under vacuum to obtain ternary composite slurry. S4: Preparation of PI / CNTs / FeS ternary composite electrode S41: The ternary composite slurry is uniformly coated on aluminum foil, vacuum dried, and then cut into circular pieces to obtain the PI / CNTs / FeS ternary composite electrode.

3. The method for preparing the PI / CNTS / FES ternary composite electrode material according to claim 2, characterized in that, In step S11, the mass ratio of ferrous sulfate heptahydrate to sodium sulfide nonahydrate is 1.39 g:1.56 g, and the volume ratio of the corresponding deionized water is 1.39 g:20 mL and 1.56 g:20 mL.

4. The method for preparing the PI / CNTS / FES ternary composite electrode material according to claim 2, characterized in that, In step S11, the sodium sulfide solution is slowly added dropwise to the ferrous sulfate solution with continuous stirring at a rate of 1-2 mL / min. In step S12, the centrifugation speed is 3500-4500 rpm, the centrifugation time is 4-6 minutes, and the washing with deionized water and ethanol is no less than 5 times, with each washing time being no less than 3 minutes.

5. The method for preparing the PI / CNTS / FES ternary composite electrode material according to claim 2, characterized in that, In step S13, the ultrasonic power for ultrasonic dispersion of FeS in ethanol is 100-150 W, and the dispersion time is 30 minutes. The oil bath reflux temperature is 75-85℃, and the reaction time is 3-5 hours; The vacuum drying temperature is 25-35℃.

6. The method for preparing the PI / CNTS / FES ternary composite electrode material according to claim 2, characterized in that, In step S21, the mass ratio of PMDA to ODA is 1.089:1, and PMDA is added in 3-5 batches with an interval of 15-20 minutes between each batch. Nitrogen purity ≥ 99.99%, gas flow rate 10-20 mL / min, NMP is anhydrous.

7. The method for preparing the PI / CNTS / FES ternary composite electrode material according to claim 2, characterized in that, In step S31, the CNTs are multi-walled carbon nanotubes with a length of 5-15 micrometers, a diameter of 20-40 nanometers, and a purity of ≥95%. The ultrasonic dispersion power is 150-200 W, and the dispersion time is 30 minutes; The vacuum drying temperature is 55-65℃, the vacuum degree is ≤-0.09 MPa, and the drying time is 3 hours.

8. The method for preparing the PI / CNTS / FES ternary composite electrode material according to claim 2, characterized in that, In step S31, the polyamic acid powder is calcined in a tube furnace under a nitrogen atmosphere, wherein the nitrogen gas flow rate is 20-30 mL / min, the heating rate is 2-3℃ / min, the calcination temperature is 300-320℃, and the calcination time is 8 hours. The mass ratio of PI / CNTs to FeS-NH2 is 0.8:1-1.2:1; In step S32, the heating temperature is 75-85℃, and the stirring time is 2 hours; The amount of APTES added is 1-2% of the total mass of the reaction system; The vacuum degree of vacuum degassing is ≤-0.095MPa, and the degassing time is 30 minutes.

9. A lithium-sulfur battery cathode, characterized in that, The active material layer of the positive electrode of the lithium-sulfur battery is composed of the PI / CNTs / FeS ternary composite electrode material as described in claim 1 or the PI / CNTs / FeS ternary composite electrode material prepared by the method described in any one of claims 2-8.

10. A lithium-sulfur battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode is the positive electrode of the lithium-sulfur battery according to claim 9; The negative electrode is a thin sheet of metallic lithium, and the separator is Celgard 2400; The electrolyte is composed of 1 mol / L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) dissolved in a solvent consisting of 1,3-dioxolane and 1,2-dimethoxyethane in a volume ratio of 1:1.

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