Iron monatomic-sulfur positive electrode material with controllable nitrogen and sulfur coordination ratio and preparation method thereof
Patent Information
- Application Number
- CN202310875626.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-07-17
- Publication Date
- 2026-09-29
- Estimated Expiration
- 2043-07-17
AI Technical Summary
然而，目前应用于锂硫电池的铁单原子催化剂的配位框架主要为Fe-N4-C，该类结构稳定性良好，但其对称结构在一定程度上限制了主-客体相互作用和催化性能；因此，亟需进一步调控铁单原子的配位环境，定量分析配位环境对其催化活性和硫正极电化学行为的作用规律
[0024]本发明的氮、硫配位占比可控的铁单原子-硫正极材料主要包括S@FeN4S2、S@FeN3S2、S@FeN2S2、S@FeN1S1；首先将配位原子定量化，合成了具有不同氮、硫配位占比的铁单原子，研究了不同配位占比对铁单原子电子结构、电子密度、电子分布等微观特性的影响，揭示其配位占比与催化性能间的构效关系，为高性能锂硫电池硫正极用铁单原子催化剂的设计提供理论指导；更为重要的是，将活性物质硫与不同氮、硫配位占比的铁单原子复合，优化了氮、硫配位占比可控的铁单原子材料与硫物质间的相互作用，获得了优异的倍率性能；另外，本发明的方法为锂硫电池硫正极提供了多种具有新型的配位结构的铁单原子。
Smart Images
Figure CN116845204B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-sulfur secondary battery technology, and relates to iron single-atom-sulfur cathode materials (at least one of S@FeN4S2, S@FeN3S2, S@FeN2S2, and S@FeN1S1) with controllable nitrogen and sulfur coordination ratios and their preparation methods. Background Technology
[0002] Lithium-sulfur batteries mainly consist of a sulfur cathode, an ether-based or carbonate-based electrolyte, a polymer-based separator, and a lithium metal anode. The overall reaction is: S₈ + 16Li = 8Li₂S. Based on this electrochemical reaction, the sulfur cathode exhibits high energy density (2600 Wh / kg) and high theoretical specific capacity (1672 mAh / g), making it one of the important development directions for next-generation energy storage / power batteries. However, the severe shuttle effect and slow reaction kinetics in the sulfur cathode significantly reduce rate performance. Therefore, designing and developing sulfur host materials with excellent adsorption energy and high catalytic activity to improve the electrochemical performance of lithium-sulfur batteries is urgently needed.
[0003] Iron single-atom catalysts are highly favored by the scientific and industrial communities due to their unique electronic structure and high catalytic activity. They not only provide strong anchoring sites for polysulfides, mitigating their shuttle effect, but also effectively promote the transformation of different intermediate phases, enhancing the reaction kinetics of the sulfur cathode. However, the coordination framework of iron single-atom catalysts currently used in lithium-sulfur batteries is mainly Fe-N4-C. While this structure exhibits good stability, its symmetrical structure limits host-guest interactions and catalytic performance to some extent. Therefore, it is urgent to further regulate the coordination environment of iron single atoms and quantitatively analyze the influence of the coordination environment on its catalytic activity and the electrochemical behavior of the sulfur cathode. Summary of the Invention
[0004] The purpose of this invention is to provide a variety of iron single-atom-sulfur cathode materials with controllable nitrogen and sulfur coordination ratios, which have the characteristics of improving the rate performance of sulfur cathodes and quantitatively studying the effect of coordination environment on the catalytic activity of iron single atoms and the electrochemical behavior of sulfur cathodes.
[0005] Another objective of this invention is to provide a method for preparing iron single-atom-sulfur cathode materials with controllable nitrogen and sulfur coordination ratios.
[0006] The first technical solution adopted in this invention is an iron single-atom-sulfur cathode material with controllable nitrogen and sulfur coordination ratio. The cathode material specifically includes nitrogen and sulfur coordinated iron single atoms and elemental sulfur.
[0007] The first technical solution of this invention is also characterized by:
[0008] Among them, the iron single atom with nitrogen and sulfur coordination ratio is the sulfur host, and elemental sulfur is the active substance;
[0009] The iron single atoms with nitrogen and sulfur coordination ratios are at least one of FeN4S2, FeN3S2, FeN2S2, and FeN1S1.
[0010] The second technical solution adopted in this invention is a method for preparing an iron single-atom-sulfur cathode material with controllable nitrogen and sulfur coordination ratios. The method utilizes an iron single-atom-sulfur cathode material with controllable nitrogen and sulfur coordination ratios, and is implemented according to the following steps:
[0011] Step 1: Prepare precursor powder of iron single atoms with controllable nitrogen and sulfur coordination ratio;
[0012] Step 2 involves pyrolyzing the precursor powder obtained in Step 1 at high temperatures to obtain iron single atoms with controllable nitrogen and sulfur coordination ratios containing templates and unstable substances.
[0013] Step 3: The material obtained in Step 2 is subjected to acid and alkali etching and drying to obtain iron single atoms with controllable nitrogen and sulfur coordination ratios;
[0014] Step 4: The iron single atom and elemental sulfur with controllable nitrogen and sulfur coordination ratios obtained in Step 3 are used to obtain an iron single atom-sulfur cathode material with controllable nitrogen and sulfur coordination ratios through liquid phase method and electrode coating method.
[0015] The second technical solution of the present invention is further characterized by:
[0016] Step 1 specifically involves weighing the raw material, dispersing it in a solvent, heating and stirring it, drying it, and grinding it to obtain a precursor powder of iron single atoms with a controllable nitrogen and sulfur coordination ratio.
[0017] The raw materials specifically include allyl thiourea as the carbon, nitrogen, and sulfur source; ferric nitrate as the iron source; silicon dioxide as the template; and deionized water as the solvent. The mass ratio of allyl thiourea, silicon dioxide, and ferric nitrate is 40:40:1.
[0018] In step 1, the stirring temperature is 70–90°C and the drying temperature is 50–70°C.
[0019] The high-temperature pyrolysis process in step 2 is as follows: First, the precursor powder is heated to 900℃ and held for 3 hours to form iron single atoms with a coordination structure of Fe-N4S2-C; then it is heated to 1000~1150℃ and held for 0.5~2 hours to obtain iron single atoms with controllable nitrogen and sulfur coordination ratios containing unstable substances.
[0020] Among them, the iron single atoms containing unstable substances with controllable nitrogen and sulfur coordination ratios are at least one of FeN4S2, FeN3S2, FeN2S2, and FeN1S1.
[0021] The alkali and acid treatment process in step 3 is as follows: the material obtained in step 2 is placed in a 2M hot sodium hydroxide solution at a temperature of 80-100℃ for 12-48 hours, and washed until the solution is neutral; then the sample is dispersed in a 6M hot hydrochloric acid solution at a temperature of 80-100℃ for 12-48 hours, washed again until the solution is neutral, and then vacuum dried;
[0022] In step 4, the iron single-atom material with controllable nitrogen and sulfur coordination ratio obtained in step 3 is dispersed with elemental sulfur in a mass ratio of 1:3 in a mixed solution of carbon disulfide and N-methylpyrrolidone. After spontaneous solvent evaporation and subsequent heating and drying, an iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is obtained. Then, the iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is coated with conductive carbon black and polyvinylidene fluoride in a ratio of 7:2:1 to obtain an iron single-atom-sulfur cathode material with controllable nitrogen and sulfur coordination ratio. The iron single-atom-sulfur cathode material with controllable nitrogen and sulfur coordination ratio is at least one of S@FeN4S2, S@FeN3S2, S@FeN2S2, and S@FeN1S1.
[0023] The beneficial effects of this invention are:
[0024] The iron single-atom-sulfur cathode materials with controllable nitrogen and sulfur coordination ratios of the present invention mainly include S@FeN4S2, S@FeN3S2, S@FeN2S2, and S@FeN1S1. First, the coordination atoms were quantified, and iron single atoms with different nitrogen and sulfur coordination ratios were synthesized. The effects of different coordination ratios on the microscopic properties of iron single atoms, such as electronic structure, electron density, and electron distribution, were studied, revealing the structure-activity relationship between the coordination ratio and catalytic performance, providing theoretical guidance for the design of iron single-atom catalysts for high-performance lithium-sulfur battery sulfur cathodes. More importantly, by compositing the active material sulfur with iron single atoms of different nitrogen and sulfur coordination ratios, the interaction between the iron single-atom materials with controllable nitrogen and sulfur coordination ratios and sulfur substances was optimized, resulting in excellent rate performance. Furthermore, the method of the present invention provides a variety of iron single atoms with novel coordination structures for lithium-sulfur battery sulfur cathodes. Attached Figure Description
[0025] Figure 1 This is a dark-field image of an iron single atom with controllable nitrogen and sulfur coordination ratio in Example 2 of the present invention, obtained by spherical aberration electron microscopy.
[0026] Figure 2 This is a transmission electron microscope image of iron single atoms with controllable nitrogen and sulfur coordination ratio in Example 4 of the present invention;
[0027] Figure 3 This is the X-ray diffraction pattern of iron single atoms with controllable nitrogen and sulfur coordination ratio in Example 10 of the present invention;
[0028] Figure 4 This is a rate performance diagram of the iron single-atom-sulfur cathode material with controllable nitrogen and sulfur coordination ratio in Example 11 of the present invention. Detailed Implementation
[0029] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.
[0030] This invention provides an iron single-atom-sulfur cathode material with controllable nitrogen and sulfur coordination ratio, comprising iron single atoms (at least one of FeN4S2, FeN3S2, FeN2S2, and FeN1S1) with controllable nitrogen and sulfur coordination ratio and elemental sulfur, wherein the iron single atoms with controllable nitrogen and sulfur coordination ratio are sulfur hosts and elemental sulfur is the active material.
[0031] This invention also provides a method for preparing iron single-atom-sulfur cathode materials with controllable nitrogen and sulfur coordination ratios, as described in the following examples:
[0032] Example 1
[0033] Step 1: Weigh allyl thiourea, silicon dioxide and ferric nitrate in a mass ratio of 40:40:1, disperse them in deionized water, and stir continuously at 80°C for 2 hours; then dry slowly at low temperature and grind to obtain precursor powder of iron single atoms with controllable nitrogen and sulfur coordination ratio.
[0034] Step 2: Take the precursor powder obtained in Step 1, heat it to 900℃ under an argon atmosphere, hold it for 3 hours to form iron single atoms with a coordination structure of Fe-N4S2-C; then heat it to 1000℃, hold it for 0.5 hours, and cool it to room temperature with the furnace to obtain iron single atoms (at least one of FeN4S2, FeN3S2, FeN2S2, and FeN1S1) with controllable nitrogen and sulfur coordination ratios containing unstable substances.
[0035] Step 3: Place the material obtained in Step 2 in a 2M sodium hydroxide solution at 90℃ for 12–48 h and wash until the solution is neutral; then disperse the sample in a 6M hydrochloric acid solution at 80℃ for the same time, wash again until the solution is neutral, and vacuum dry.
[0036] Step 4: The iron single-atom material with controllable nitrogen and sulfur coordination ratio obtained in Step 3 is dispersed with elemental sulfur in a mass ratio of 1:3 in a mixed solution of carbon disulfide and N-methylpyrrolidone. After spontaneous solvent evaporation and subsequent heating and drying, an iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is obtained. Then, the iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is mixed with conductive carbon black and polyvinylidene fluoride in a ratio of 7:2:1, and an electrode coating method is used to obtain an iron single-atom-sulfur cathode material (at least one of S@FeN4S2, S@FeN3S2, S@FeN2S2, and S@FeN1S1) with controllable nitrogen and sulfur coordination ratio.
[0037] Example 2
[0038] Step 1: Weigh allyl thiourea, silicon dioxide and ferric nitrate in a mass ratio of 40:40:1, disperse them in deionized water, and stir continuously at 80°C for 2 hours; then dry slowly at low temperature and grind to obtain precursor powder of iron single atoms with controllable nitrogen and sulfur coordination ratio.
[0039] Step 2: Take the precursor powder obtained in Step 1, heat it to 900℃ under an argon atmosphere, hold it for 3 hours to form iron single atoms with a coordination structure of Fe-N4S2-C; then heat it to 1000℃, hold it for 1 hour, and cool it to room temperature in the furnace to obtain iron single atoms (at least one of FeN4S2, FeN3S2, FeN2S2, and FeN1S1) with controllable nitrogen and sulfur coordination ratios containing unstable substances.
[0040] Step 3: Place the material obtained in Step 2 in a 2M sodium hydroxide solution at 90℃ for 12–48 h and wash until the solution is neutral; then disperse the sample in a 6M hydrochloric acid solution at 80℃ for the same time, wash again until the solution is neutral, and vacuum dry.
[0041] Step 4: The iron single-atom material with controllable nitrogen and sulfur coordination ratio obtained in Step 3 is dispersed with elemental sulfur in a mass ratio of 1:3 in a mixed solution of carbon disulfide and N-methylpyrrolidone. After spontaneous solvent evaporation and subsequent heating and drying, an iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is obtained. Then, the iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is mixed with conductive carbon black and polyvinylidene fluoride in a ratio of 7:2:1, and an electrode coating method is used to obtain an iron single-atom-sulfur cathode material (at least one of S@FeN4S2, S@FeN3S2, S@FeN2S2, and S@FeN1S1) with controllable nitrogen and sulfur coordination ratio.
[0042] Example 3
[0043] Step 1: Weigh allyl thiourea, silicon dioxide and ferric nitrate in a mass ratio of 40:40:1, disperse them in deionized water, and stir continuously at 80°C for 2 hours; then dry slowly at low temperature and grind to obtain precursor powder of iron single atoms with controllable nitrogen and sulfur coordination ratio.
[0044] Step 2: Take the precursor powder obtained in Step 1, heat it to 900℃ under an argon atmosphere, hold it for 3 hours to form iron single atoms with a coordination structure of Fe-N4S2-C; then heat it to 1000℃, hold it for 2 hours, and cool it to room temperature in the furnace to obtain iron single atoms (at least one of FeN4S2, FeN3S2, FeN2S2, and FeN1S1) with controllable nitrogen and sulfur coordination ratios containing unstable substances.
[0045] Step 3: Place the material obtained in Step 2 in a 2M sodium hydroxide solution at 90℃ for 12–48 h and wash until the solution is neutral; then disperse the sample in a 6M hydrochloric acid solution at 80℃ for the same time, wash again until the solution is neutral, and vacuum dry.
[0046] Step 4, the iron single-atom material with controllable nitrogen and sulfur coordination ratio obtained in Step 3 (such as...) Figure 1 The sample was dispersed with elemental sulfur in a mass ratio of 1:3 in a mixed solution of carbon disulfide and N-methylpyrrolidone. After spontaneous solvent evaporation and subsequent heating and drying, an iron single-atom sulfur composite material with controllable nitrogen and sulfur coordination ratio was obtained. Then, the iron single-atom sulfur composite material with controllable nitrogen and sulfur coordination ratio was mixed with conductive carbon black and polyvinylidene fluoride in a ratio of 7:2:1, and an electrode coating method was used to obtain an iron single-atom sulfur cathode material (at least one of S@FeN4S2, S@FeN3S2, S@FeN2S2, and S@FeN1S1) with controllable nitrogen and sulfur coordination ratio.
[0047] Example 4
[0048] Step 1: Weigh allyl thiourea, silicon dioxide and ferric nitrate in a mass ratio of 40:40:1, disperse them in deionized water, and stir continuously at 80°C for 2 hours; then dry slowly at low temperature and grind to obtain precursor powder of iron single atoms with controllable nitrogen and sulfur coordination ratio.
[0049] Step 2: Take the precursor powder obtained in Step 1, heat it to 900℃ under an argon atmosphere, hold it for 3 hours to form iron single atoms with a coordination structure of Fe-N4S2-C; then heat it to 1050℃, hold it for 0.5 hours, and cool it to room temperature with the furnace to obtain iron single atoms (at least one of FeN4S2, FeN3S2, FeN2S2, and FeN1S1) with a controllable ratio of nitrogen and sulfur coordination containing unstable substances.
[0050] Step 3: Place the material obtained in Step 2 in a 2M sodium hydroxide solution at 90℃ for 12–48 hours, and wash until the solution is neutral. Then disperse the sample in a 6M hydrochloric acid solution at 80℃ for the same time, wash again until the solution is neutral, and vacuum dry. Its microstructure is as follows: Figure 2 As shown;
[0051] Step 4: The iron single-atom material with controllable nitrogen and sulfur coordination ratio obtained in Step 3 is dispersed with elemental sulfur in a mass ratio of 1:3 in a mixed solution of carbon disulfide and N-methylpyrrolidone. After spontaneous solvent evaporation and subsequent heating and drying, an iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is obtained. Then, the iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is mixed with conductive carbon black and polyvinylidene fluoride in a ratio of 7:2:1, and an electrode coating method is used to obtain an iron single-atom-sulfur cathode material (at least one of S@FeN4S2, S@FeN3S2, S@FeN2S2, and S@FeN1S1) with controllable nitrogen and sulfur coordination ratio.
[0052] Example 5
[0053] Step 1: Weigh allyl thiourea, silicon dioxide and ferric nitrate in a mass ratio of 40:40:1, disperse them in deionized water, and stir continuously at 80°C for 2 hours; then dry slowly at low temperature and grind to obtain precursor powder of iron single atoms with controllable nitrogen and sulfur coordination ratio.
[0054] Step 2: Take the precursor powder obtained in Step 1, heat it to 900℃ under an argon atmosphere, hold it for 3 hours to form iron single atoms with a coordination structure of Fe-N4S2-C; then heat it to 1050℃, hold it for 1 hour, and cool it to room temperature in the furnace to obtain iron single atoms (at least one of FeN4S2, FeN3S2, FeN2S2, and FeN1S1) with controllable nitrogen and sulfur coordination ratios containing unstable substances.
[0055] Step 3: Place the material obtained in Step 2 in a 2M sodium hydroxide solution at 90℃ for 12–48 h and wash until the solution is neutral; then disperse the sample in a 6M hydrochloric acid solution at 80℃ for the same time, wash again until the solution is neutral, and vacuum dry.
[0056] Step 4: The iron single-atom material with controllable nitrogen and sulfur coordination ratio obtained in Step 3 is dispersed with elemental sulfur in a mass ratio of 1:3 in a mixed solution of carbon disulfide and N-methylpyrrolidone. After spontaneous solvent evaporation and subsequent heating and drying, an iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is obtained. Then, the iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is mixed with conductive carbon black and polyvinylidene fluoride in a ratio of 7:2:1, and an electrode coating method is used to obtain an iron single-atom-sulfur cathode material (at least one of S@FeN4S2, S@FeN3S2, S@FeN2S2, and S@FeN1S1) with controllable nitrogen and sulfur coordination ratio.
[0057] Example 6
[0058] Step 1: Weigh allyl thiourea, silicon dioxide and ferric nitrate in a mass ratio of 40:40:1, disperse them in deionized water, and stir continuously at 80°C for 2 hours; then dry slowly at low temperature and grind to obtain precursor powder of iron single atoms with controllable nitrogen and sulfur coordination ratio.
[0059] Step 2: Take the precursor powder obtained in Step 1, heat it to 900℃ under an argon atmosphere, hold it for 3 hours to form iron single atoms with a coordination structure of Fe-N4S2-C; then heat it to 1050℃, hold it for 2 hours, and cool it to room temperature in the furnace to obtain iron single atoms (at least one of FeN4S2, FeN3S2, FeN2S2, and FeN1S1) with controllable nitrogen and sulfur coordination ratios containing unstable substances.
[0060] Step 3: Place the material obtained in Step 2 in a 2M sodium hydroxide solution at 90℃ for 12–48 h and wash until the solution is neutral; then disperse the sample in a 6M hydrochloric acid solution at 80℃ for the same time, wash again until the solution is neutral, and vacuum dry.
[0061] Step 4: The iron single-atom material with controllable nitrogen and sulfur coordination ratio obtained in Step 3 is dispersed with elemental sulfur in a mass ratio of 1:3 in a mixed solution of carbon disulfide and N-methylpyrrolidone. After spontaneous solvent evaporation and subsequent heating and drying, an iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is obtained. Then, the iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is mixed with conductive carbon black and polyvinylidene fluoride in a ratio of 7:2:1, and an electrode coating method is used to obtain an iron single-atom-sulfur cathode material (at least one of S@FeN4S2, S@FeN3S2, S@FeN2S2, and S@FeN1S1) with controllable nitrogen and sulfur coordination ratio.
[0062] Example 7
[0063] Step 1: Weigh allyl thiourea, silicon dioxide and ferric nitrate in a mass ratio of 40:40:1, disperse them in deionized water, and stir continuously at 80°C for 2 hours; then dry slowly at low temperature and grind to obtain precursor powder of iron single atoms with controllable nitrogen and sulfur coordination ratio.
[0064] Step 2: Take the precursor powder obtained in Step 1, heat it to 900℃ under an argon atmosphere, hold it for 3 hours to form iron single atoms with a coordination structure of Fe-N4S2-C; then heat it to 1100℃, hold it for 0.5 hours, and cool it to room temperature with the furnace to obtain iron single atoms (at least one of FeN4S2, FeN3S2, FeN2S2, and FeN1S1) with controllable nitrogen and sulfur coordination ratios containing unstable substances.
[0065] Step 3: Place the material obtained in Step 2 in a 2M sodium hydroxide solution at 90℃ for 12–48 h and wash until the solution is neutral; then disperse the sample in a 6M hydrochloric acid solution at 80℃ for the same time, wash again until the solution is neutral, and vacuum dry.
[0066] Step 4: The iron single-atom material with controllable nitrogen and sulfur coordination ratio obtained in Step 3 is dispersed with elemental sulfur in a mass ratio of 1:3 in a mixed solution of carbon disulfide and N-methylpyrrolidone. After spontaneous solvent evaporation and subsequent heating and drying, an iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is obtained. Then, the iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is mixed with conductive carbon black and polyvinylidene fluoride in a ratio of 7:2:1, and an electrode coating method is used to obtain an iron single-atom-sulfur cathode material (at least one of S@FeN4S2, S@FeN3S2, S@FeN2S2, and S@FeN1S1) with controllable nitrogen and sulfur coordination ratio.
[0067] Example 8
[0068] Step 1: Weigh allyl thiourea, silicon dioxide and ferric nitrate in a mass ratio of 40:40:1, disperse them in deionized water, and stir continuously at 80°C for 2 hours; then dry slowly at low temperature and grind to obtain precursor powder of iron single atoms with controllable nitrogen and sulfur coordination ratio.
[0069] Step 2: Take the precursor powder obtained in Step 1, heat it to 900℃ under an argon atmosphere, hold it for 3 hours to form iron single atoms with a coordination structure of Fe-N4S2-C; then heat it to 1100℃, hold it for 1 hour, and cool it to room temperature in the furnace to obtain iron single atoms (at least one of FeN4S2, FeN3S2, FeN2S2, and FeN1S1) with controllable nitrogen and sulfur coordination ratios containing unstable substances.
[0070] Step 3: The material obtained in Step 2 was placed in a 2M sodium hydroxide solution at 90℃ for 12–48 hours and washed until the solution was neutral. Then, the sample was dispersed in a 6M hydrochloric acid solution at 80℃ for the same duration, washed again until the solution was neutral, and then vacuum dried. X-ray diffraction analysis preliminarily determined that its main component was carbon material. Figure 3 As shown;
[0071] Step 4: The iron single-atom material with controllable nitrogen and sulfur coordination ratio obtained in Step 3 is dispersed with elemental sulfur in a mass ratio of 1:3 in a mixed solution of carbon disulfide and N-methylpyrrolidone. After spontaneous solvent evaporation and subsequent heating and drying, an iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is obtained. Then, the iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is mixed with conductive carbon black and polyvinylidene fluoride in a ratio of 7:2:1, and an electrode coating method is used to obtain an iron single-atom-sulfur cathode material (at least one of S@FeN4S2, S@FeN3S2, S@FeN2S2, and S@FeN1S1) with controllable nitrogen and sulfur coordination ratio.
[0072] Example 9
[0073] Step 1: Weigh allyl thiourea, silicon dioxide and ferric nitrate in a mass ratio of 40:40:1, disperse them in deionized water, and stir continuously at 80°C for 2 hours; then dry slowly at low temperature and grind to obtain precursor powder of iron single atoms with controllable nitrogen and sulfur coordination ratio.
[0074] Step 2: Take the precursor powder obtained in Step 1, heat it to 900℃ under an argon atmosphere, hold it for 3 hours to form iron single atoms with a coordination structure of Fe-N4S2-C; then heat it to 1100℃, hold it for 2 hours, and cool it to room temperature in the furnace to obtain iron single atoms (at least one of FeN4S2, FeN3S2, FeN2S2, and FeN1S1) with controllable nitrogen and sulfur coordination ratios containing unstable substances.
[0075] Step 3: Place the material obtained in Step 2 in a 2M sodium hydroxide solution at 90℃ for 12–48 h and wash until the solution is neutral; then disperse the sample in a 6M hydrochloric acid solution at 80℃ for the same time, wash again until the solution is neutral, and vacuum dry.
[0076] Step 4: The iron single-atom material with controllable nitrogen and sulfur coordination ratio obtained in Step 3 is dispersed with elemental sulfur in a mass ratio of 1:3 in a mixed solution of carbon disulfide and N-methylpyrrolidone. After spontaneous solvent evaporation and subsequent heating and drying, an iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is obtained. Then, the iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is mixed with conductive carbon black and polyvinylidene fluoride in a ratio of 7:2:1, and an electrode coating method is used to obtain an iron single-atom-sulfur cathode material (at least one of S@FeN4S2, S@FeN3S2, S@FeN2S2, and S@FeN1S1) with controllable nitrogen and sulfur coordination ratio.
[0077] Example 10
[0078] Step 1: Weigh allyl thiourea, silicon dioxide and ferric nitrate in a mass ratio of 40:40:1, disperse them in deionized water, and stir continuously at 80°C for 2 hours; then dry slowly at low temperature and grind to obtain precursor powder of iron single atoms with controllable nitrogen and sulfur coordination ratio.
[0079] Step 2: Take the precursor powder obtained in Step 1, heat it to 900℃ under an argon atmosphere, hold it for 3 hours to form iron single atoms with a coordination structure of Fe-N4S2-C; then heat it to 1150℃, hold it for 0.5 hours, and cool it to room temperature with the furnace to obtain iron single atoms (at least one of FeN4S2, FeN3S2, FeN2S2, and FeN1S1) with controllable nitrogen and sulfur coordination ratios containing unstable substances.
[0080] Step 3: Place the material obtained in Step 2 in a 2M sodium hydroxide solution at 90℃ for 12–48 h and wash until the solution is neutral; then disperse the sample in a 6M hydrochloric acid solution at 80℃ for the same time, wash again until the solution is neutral, and vacuum dry.
[0081] Step 4: The iron single-atom material with controllable nitrogen and sulfur coordination ratio obtained in Step 3 is dispersed with elemental sulfur in a mass ratio of 1:3 in a mixed solution of carbon disulfide and N-methylpyrrolidone. After spontaneous solvent evaporation and subsequent heating and drying, an iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is obtained. Then, the iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is mixed with conductive carbon black and polyvinylidene fluoride in a ratio of 7:2:1, and an electrode coating method is used to obtain an iron single-atom-sulfur cathode material (at least one of S@FeN4S2, S@FeN3S2, S@FeN2S2, and S@FeN1S1) with controllable nitrogen and sulfur coordination ratio.
[0082] Example 11
[0083] Step 1: Weigh allyl thiourea, silicon dioxide and ferric nitrate in a mass ratio of 40:40:1, disperse them in deionized water, and stir continuously at 80°C for 2 hours; then dry slowly at low temperature and grind to obtain precursor powder of iron single atoms with controllable nitrogen and sulfur coordination ratio.
[0084] Step 2: Take the precursor powder obtained in Step 1, heat it to 900℃ under an argon atmosphere, hold it for 3 hours to form iron single atoms with a coordination structure of Fe-N4S2-C; then heat it to 1150℃, hold it for 1 hour, and cool it to room temperature in the furnace to obtain iron single atoms (at least one of FeN4S2, FeN3S2, FeN2S2, and FeN1S1) with controllable nitrogen and sulfur coordination ratios containing unstable substances.
[0085] Step 3: Place the material obtained in Step 2 in a 2M sodium hydroxide solution at 90℃ for 12–48 h and wash until the solution is neutral; then disperse the sample in a 6M hydrochloric acid solution at 80℃ for the same time, wash again until the solution is neutral, and vacuum dry.
[0086] Step 4: The iron single-atom material with controllable nitrogen and sulfur coordination ratio obtained in Step 3 is dispersed with elemental sulfur in a mass ratio of 1:3 in a mixed solution of carbon disulfide and N-methylpyrrolidone. After spontaneous solvent evaporation and subsequent heating and drying, an iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is obtained. Then, the iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is mixed with conductive carbon black and polyvinylidene fluoride in a ratio of 7:2:1, and an electrode coating method is used to obtain an iron single-atom-sulfur cathode material (at least one of S@FeN4S2, S@FeN3S2, S@FeN2S2, and S@FeN1S1) with controllable nitrogen and sulfur coordination ratio.
[0087] Figure 4 The rate performance diagram of the iron single-atom-sulfur cathode material with controllable nitrogen and sulfur coordination ratio involved in Example 11 shows that the discharge specific capacity can reach 911, 771, 690, 680, 574 and 540 mAh / g at current densities of 0.2, 0.5, 1.0, 2.0, 4.0 and 5.0C (1C = 1672 mA / g).
[0088] Example 12
[0089] Step 1: Weigh allyl thiourea, silicon dioxide and ferric nitrate in a mass ratio of 40:40:1, disperse them in deionized water, and stir continuously at 80°C for 2 hours; then dry slowly at low temperature and grind to obtain precursor powder of iron single atoms with controllable nitrogen and sulfur coordination ratio.
[0090] Step 2: Take the precursor powder obtained in Step 1, heat it to 900℃ under an argon atmosphere, hold it for 3 hours to form iron single atoms with a coordination structure of Fe-N4S2-C; then heat it to 1150℃, hold it for 2 hours, and cool it to room temperature in the furnace to obtain iron single atoms (at least one of FeN4S2, FeN3S2, FeN2S2, and FeN1S1) with controllable nitrogen and sulfur coordination ratios containing unstable substances.
[0091] Step 3: Place the material obtained in Step 2 in a 2M sodium hydroxide solution at 90℃ for 12–48 h and wash until the solution is neutral; then disperse the sample in a 6M hydrochloric acid solution at 80℃ for the same time, wash again until the solution is neutral, and vacuum dry.
[0092] Step 4: The iron single-atom material with controllable nitrogen and sulfur coordination ratio obtained in Step 3 is dispersed with elemental sulfur in a mass ratio of 1:3 in a mixed solution of carbon disulfide and N-methylpyrrolidone. After spontaneous solvent evaporation and subsequent heating and drying, an iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is obtained. Then, the iron single-atom-sulfur composite material with controllable nitrogen and sulfur coordination ratio is mixed with conductive carbon black and polyvinylidene fluoride in a ratio of 7:2:1, and an electrode coating method is used to obtain an iron single-atom-sulfur cathode material (at least one of S@FeN4S2, S@FeN3S2, S@FeN2S2, and S@FeN1S1) with controllable nitrogen and sulfur coordination ratio.
[0093] The iron single-atom-sulfur cathode materials with controllable nitrogen and sulfur coordination ratios of this invention mainly include S@FeN4S2, S@FeN3S2, S@FeN2S2, and S@FeN1S1. This invention quantifies the coordination atoms, synthesizing iron single atoms with different nitrogen and sulfur coordination ratios. The effects of different coordination ratios on the microscopic properties of iron single atoms, such as electronic structure, electron density, and electron distribution, are studied, revealing the structure-activity relationship between coordination ratios and catalytic performance. This provides theoretical guidance for the design of iron single-atom catalysts for high-performance lithium-sulfur battery sulfur cathodes. More importantly, by compositing the active material sulfur with iron single atoms of different nitrogen and sulfur coordination ratios, the interaction between the iron single-atom materials with controllable nitrogen and sulfur coordination ratios and sulfur is optimized, resulting in excellent rate performance. Furthermore, the method of this invention provides a variety of iron single atoms with novel coordination structures for lithium-sulfur battery sulfur cathodes.
Claims
1. A method for preparing an iron single-atom-sulfur cathode material with controllable nitrogen and sulfur coordination ratio, characterized in that, The specific steps are as follows: Step 1: Weigh the raw materials, disperse them in a solvent, and obtain precursor powder of iron single atoms with controllable nitrogen and sulfur coordination ratio by heating, stirring, drying and grinding. Step 2: The precursor powder obtained in Step 1 is pyrolyzed at high temperature to obtain iron single atoms with controllable nitrogen and sulfur coordination ratios containing templates and unstable substances. Step 3: The material obtained in Step 2 is subjected to alkaline etching, acid etching, and drying to obtain iron single atoms with controllable nitrogen and sulfur coordination ratios. Step 4: The iron single atom and elemental sulfur with controllable nitrogen and sulfur coordination ratios obtained in Step 3 are used to obtain an iron single atom-sulfur composite material with controllable nitrogen and sulfur coordination ratios through a liquid phase method. Then, the iron single atom-sulfur composite material with controllable nitrogen and sulfur coordination ratios is mixed with conductive carbon black and polyvinylidene fluoride in a ratio of 7:2:1 and an electrode coating method is used to obtain an iron single atom-sulfur cathode material with controllable nitrogen and sulfur coordination ratios. In step 1, the raw materials include allyl thiourea as a carbon, nitrogen, and sulfur source; ferric nitrate as an iron source; silicon dioxide as a template; and deionized water as a solvent; the mass ratio of allyl thiourea, silicon dioxide, and ferric nitrate is 40:40:
1. In step 1, the stirring temperature is 70–90℃, and the drying temperature is 50–70℃; In step 2, the high-temperature pyrolysis process is as follows: First, the precursor powder is heated to 900℃ and held for 3 hours to form iron single atoms with a coordination structure of Fe-N4S2-C; then it is heated to 1000~1150℃ and held for 0.5~2 hours to obtain iron single atoms with controllable nitrogen and sulfur coordination ratios containing unstable substances. In the iron single-atom-sulfur cathode material with controllable nitrogen and sulfur coordination ratio, the iron single atom with controllable nitrogen and sulfur coordination ratio is the sulfur host, and elemental sulfur is the active material; the iron single atom with controllable nitrogen and sulfur coordination ratio is at least one of FeN4S2, FeN3S2, FeN2S2, and FeN1S1.
2. The method for preparing the iron single-atom-sulfur cathode material with controllable nitrogen and sulfur coordination ratio according to claim 1, characterized in that, In step 3, the alkaline etching and acid etching processes are as follows: the material obtained in step 2 is placed in a 2M hot sodium hydroxide solution at a temperature of 80-100°C for 12-48 hours, and washed until the solution is neutral; then it is dispersed in a 6M hot hydrochloric acid solution at a temperature of 80-100°C for 12-48 hours, washed again until the solution is neutral, and then vacuum dried.
3. The method for preparing the iron single-atom-sulfur cathode material with controllable nitrogen and sulfur coordination ratio according to claim 1, characterized in that, In step 4, the steps for obtaining the iron single-atom-sulfur cathode composite material with controllable nitrogen and sulfur coordination ratios by liquid phase method are as follows: The iron single-atom material with controllable nitrogen and sulfur coordination ratios obtained in step 3 and elemental sulfur are dispersed in a mixed solution of carbon disulfide and N-methylpyrrolidone at a mass ratio of 1:
3. The iron single-atom material with controllable nitrogen and sulfur coordination ratios is obtained by spontaneous solvent evaporation and subsequent heating and drying.