Fe nano-modified carbon-sulfur composite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of carbon-sulfur composite materials, and particularly discloses a Fe nano-modified carbon-sulfur composite material and a preparation method and application thereof.The preparation method comprises the following steps that ketjen black and an iron source are added into deionized water under stirring, then an alcoholic solution is added, ultrasonic treatment is conducted, and suspension liquid is obtained; the suspension liquid is dried and then sintered, and the Fe-KB composite material is obtained; and mixing the Fe-KB composite material with elemental sulfur, and sintering to obtain the Fe nano-modified carbon-sulfur composite material. The carbon-sulfur composite material is subjected to nano-iron doping modification treatment, and in-situ grown Fe nano-particles have high conductivity and high-activity sites, so that rapid transfer of charges is promoted, the oxidation-reduction reaction of sulfur is effectively catalyzed, the utilization efficiency and oxidation-reduction kinetics of sulfur are improved, and the carbon-sulfur composite material is prepared. Therefore, the electrochemical performance of the carbon-sulfur composite material is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon-sulfur composite materials, and particularly to an Fe nanomodified carbon-sulfur composite material, a preparation method thereof, and an application thereof. Background Art

[0002] The Global Sustainable Energy Transitions Initiative for power batteries has witnessed a major shift towards advanced energy storage technologies, with solid-state batteries leading the way in this field. Existing technologies face energy density and safety issues in practical applications, and there is an urgent need for advanced energy storage technologies. Solid-state batteries use solid electrolyte materials and have greater capabilities compared to traditional batteries, such as higher energy density, higher specific energy, and better safety. These characteristics have received more attention globally, especially in the automotive and energy sectors, as they pave the way for sustainable future solutions.

[0003] Lithium-sulfur batteries have attracted much attention as a new generation of high-energy density batteries. The cathode material, elemental sulfur, has a theoretical specific capacity as high as 1675 mAh / g, which is much higher than that of the cathode materials of traditional lithium-ion batteries. However, lithium-sulfur batteries still face many challenges. First, active substances such as elemental sulfur and its discharge products, polysulfides, have poor electronic conductivity and reaction inertness, resulting in low discharge specific capacity, low Coulomb efficiency, poor electrochemical reversibility, and poor cycle stability of the battery. Second, polysulfides in the liquid electrolyte are easily dissolved and undergo a shuttle effect, causing loss of active substances and affecting the cycle performance of the battery. In addition, there are safety hazards such as the growth of lithium dendrites on the lithium metal anode.

[0004] To solve the above problems, all-solid-state lithium-sulfur batteries have become a research hotspot. As a next-generation high-energy density energy storage technology, although all-solid-state lithium-sulfur batteries have broad prospects, they still face multiple technical challenges. Therefore, it is necessary to modify carbon-sulfur composite materials to improve the performance of all-solid-state lithium-sulfur batteries, promote their large-scale application, and ultimately achieve commercialization goals. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide an Fe nanomodified carbon-sulfur composite material, a preparation method thereof, and an application thereof. By doping and modifying the carbon-sulfur composite material with nano-iron, the in-situ grown Fe nanoparticles have high conductivity and high active sites, which not only promote the rapid transfer of charges but also effectively catalyze the redox reaction of sulfur, improving the utilization efficiency of sulfur and the redox kinetics, thereby enhancing the electrochemical performance of the carbon-sulfur composite material.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: The present invention first provides a preparation method for an Fe nanomodified carbon-sulfur composite material, which includes the following steps: S1. Under stirring, add Ketjen black and iron source into deionized water, then add alcohol solution, and perform ultrasonic treatment to obtain a suspension; S2. After drying the suspension, sinter it to obtain an Fe-KB composite material; S3. Mix the Fe-KB composite material with sulfur and sinter it to obtain an Fe nano-modified carbon-sulfur composite material.

[0007] In the present invention, through the nano-iron doping modification treatment of the carbon-sulfur composite material, the in-situ grown Fe nanoparticles have high conductivity and high active sites, which not only promote the rapid transfer of charges, but also effectively catalyze the redox reaction of sulfur, improve the utilization efficiency of sulfur and the redox kinetics, thereby improving the electrochemical performance of the carbon-sulfur composite material; in addition, the Fe nano-modified carbon-sulfur composite material can effectively alleviate the volume expansion problem of sulfur during charge and discharge.

[0008] As a further improvement of the above solution of the present invention, in step S1, the iron source is at least one of FeCl3, Fe2(SO4)3, Fe(NO3)3, and Fe(ClO4)3; in the suspension, the concentration of Fe 3+ is 20 - 30 g / L.

[0009] As a further improvement of the above solution of the present invention, in step S1, the alcohol solution is at least one of ethanol and isopropanol; the time of ultrasonic treatment is 40 - 60 min.

[0010] As a further improvement of the above solution of the present invention, in step S2, the drying is first carried out in a vacuum drying oven at 120 - 150 °C for 7 - 9 h, and then in a vacuum drying oven at 75 - 85 °C for 23 - 25 h.

[0011] As a further improvement of the above solution of the present invention, in step S2, the sintering is carried out under a protective atmosphere, and the heating rate is 5 °C / min to rise to 810 - 850 °C and hold for 1 - 3 h.

[0012] As a further improvement of the above solution of the present invention, in step S3, the mass ratio of the Fe-KB composite material to sulfur is 1:(2.3 - 2.5).

[0013] As a further improvement of the above solution of the present invention, in step S3, the sintering is carried out under a protective atmosphere. First, the heating rate is 2 °C / min to rise to 150 - 160 °C and hold for 7 - 10 h, and then the heating rate is 2 °C / min to rise to 300 - 350 °C and hold for 1 - 3 h.

[0014] The present invention also provides an Fe nano-modified carbon-sulfur composite material, which is prepared by the preparation method as described above.

[0015] The present invention also provides an application of the Fe nano-modified carbon-sulfur composite material as described above, which is used as a cathode material for preparing an all-solid-state lithium-sulfur battery.

[0016] As a further improvement of the above solution of the present invention, the steps for preparing the all-solid-state lithium-sulfur battery are as follows: Mix Li2S powder, lithium chloride powder, and P2S5 powder, ball-mill, and sinter to obtain a Li6PS5Cl solid electrolyte. Add the Fe nano-modified carbon-sulfur composite material, the Li6PS5Cl solid electrolyte, carbon nanotubes, and ethyl cellulose into 1,3-dioxane to obtain a positive electrode slurry; coat the positive electrode slurry on carbon-coated aluminum foil and dry to obtain a positive electrode sheet. Assemble the positive electrode sheet, the Li6PS5Cl solid electrolyte, and the lithium negative electrode sheet into an all-solid-state lithium-sulfur battery.

[0017] Compared with the prior art, the present invention has the following beneficial effects: By doping and modifying the carbon-sulfur composite material with nano-iron, the in-situ grown Fe nanoparticles have high conductivity and high active sites, which not only promote the rapid transfer of charges, but also effectively catalyze the redox reaction of sulfur, improve the utilization efficiency of sulfur and the redox kinetics, thereby improving the electrochemical performance of the carbon-sulfur composite material; in addition, the Fe nano-modified carbon-sulfur composite material can effectively alleviate the volume expansion problem of sulfur during charge and discharge.

[0018] The Fe nano-modified carbon-sulfur composite material provided by the present invention still maintains a discharge specific capacity of 520 mAh / g after 150 cycles at a current density of 50 mA / g, showing excellent cycle stability. Description of the Drawings

[0019] Figure 1 SEM image of the Fe-KB composite material obtained in step S2 of Example 1 of the present invention; Figure 2 TEM and EDS mapping images of the Fe-KB composite material obtained in step S2 of Example 1 of the present invention; Figure 3 XRD patterns of Fe-KB / S prepared in Example 1, KB / S prepared in the comparative example, the Fe-KB composite material prepared in Example 1, and Ketjen black KB; Figure 4 Cycling performance and charge-discharge curve of the Fe nano-modified carbon-sulfur cathode material Fe-KB / S prepared in Example 1 at a current density of 50 mA / g; Figure 5Cycling performance and charge-discharge curve of the sulfur-carbon cathode material KB / S prepared as a comparative example at a current density of 50 mA / g; Figure 6 SEM image of the Fe-nanomodified carbon-sulfur cathode material Fe-KB / S prepared in Example 1 after the first discharge; Figure 7 SEM image of the sulfur-carbon cathode material KB / S prepared as a comparative example after the first discharge. Detailed implementation manners

[0020] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0022] Example 1 This example presents a Fe-nanomodified carbon-sulfur composite material, and its preparation method includes the following steps: S1. Under stirring conditions, 9 g of Ketjen black (KB) and 6 g of anhydrous Fe2(SO4)3 are slowly added to 60 mL of deionized water, then 15 mL of anhydrous ethanol is added, and after stirring and mixing for 30 s, ultrasonic treatment is carried out for 50 min to form a KB suspension; during this process, Fe 3+ can penetrate into the pores of KB, which helps to form highly dispersed Fe nanoparticles; S2. The suspension obtained in step S1 is dried in a vacuum drying oven at 150 °C for 8 h, then dried in a vacuum drying oven at 75 °C for 25 h. The dried powder is placed in a tube furnace, and under an argon atmosphere, it is heated to 850 °C at a heating rate of 5 °C / min and held for 2 hours to obtain a Fe-KB composite material; S3. The Fe-KB composite material obtained in step S2 and sulfur are ball-milled and mixed for 30 min according to a mass ratio of 1:2.5. Under an argon atmosphere, it is heated to 150 °C at a heating rate of 2 °C / min and held for 10 h. Subsequently, the mixture is continuously heated to 300 °C at a heating rate of 2 °C / min and held for 3 h to obtain a Fe-nanomodified carbon-sulfur cathode material (Fe-KB / S).

[0023] Example 2 This embodiment provides a Fe nanomodified carbon-sulfur composite material, and its preparation method includes the following steps: S1. Under stirring conditions, 2 g of Ketjen black (KB) and 5.44 g of anhydrous FeCl3 are slowly added to 60 ml of deionized water, then 15 ml of isopropanol is added, and after stirring and mixing for 30 s, ultrasonic treatment is carried out for 60 min to form a KB suspension; in this process, Fe 3+ can penetrate into the pores of KB, which helps to form highly dispersed Fe nanoparticles; S2. The suspension obtained in step S1 is dried in a vacuum drying oven at 120 °C for 9 h, then dried in a vacuum drying oven at 80 °C for 24 h. The dried powder is placed in a tubular furnace, and under an argon atmosphere, it is heated at a heating rate of 5 °C / min to 810 °C and held for 3 h to obtain a Fe-KB composite material; S3. The Fe-KB composite material obtained in step S2 and sulfur are ball-milled and mixed at a mass ratio of 1:2.5 for 30 min, and under an argon atmosphere, it is heated at a heating rate of 2 °C / min to 160 °C and held for 7 h. Subsequently, the mixture is continuously heated at a heating rate of 2 °C / min to 350 °C and held for 1 h to obtain a Fe nanomodified carbon-sulfur cathode material.

[0024] Example 3 This embodiment provides a Fe nanomodified carbon-sulfur composite material, and its preparation method includes the following steps: S1. Under stirring conditions, 2 g of Ketjen black (KB) and 7.0 g of Fe(NO3)3 are slowly added to 50 mL of deionized water, then 15 mL of absolute ethanol is added, and after stirring and mixing for 30 s, ultrasonic treatment is carried out for 40 min to form a KB suspension; in this process, Fe 3+ can penetrate into the pores of KB, which helps to form highly dispersed Fe nanoparticles; S2. The suspension obtained in step S1 is dried in a vacuum drying oven at 130 °C for 7 h, then dried in a vacuum drying oven at 85 °C for 23 h. The dried powder is placed in a tubular furnace, and under an argon atmosphere, it is heated at a heating rate of 5 °C / min to 840 °C and held for 2.5 h to obtain a Fe-KB composite material; S3. The Fe-KB composite material obtained in step S2 and sulfur are ball-milled and mixed at a mass ratio of 1:2.4 for 30 min, and under an argon atmosphere, it is heated at a heating rate of 2 °C / min to 155 °C and held for 8 h. Subsequently, the mixture is continuously heated at a heating rate of 2 °C / min to 320 °C and held for 2 h to obtain a Fe nanomodified carbon-sulfur cathode material.

[0025] Example 4 This embodiment provides a Fe nano-modified carbon-sulfur composite material, and its preparation method includes the following steps: S1. Under stirring conditions, 2 g of Ketjenblack (KB) and 11.9 g of Fe(ClO4)3 are slowly added to 60 mL of deionized water, then 12 mL of absolute ethanol is added, and after stirring and mixing for 30 s, ultrasonic treatment is carried out for 50 min to form a KB suspension; during this process, Fe 3+ can penetrate into the pores of KB, which helps to form highly dispersed Fe nanoparticles; S2. The suspension obtained in step S1 is dried in a vacuum drying oven at 140 °C for 8 h, and then dried in a vacuum drying oven at 80 °C for 24 h. The dried powder is placed in a tube furnace, and under an argon atmosphere, it is heated to 850 °C at a heating rate of 5 °C / min and held for 1 h to obtain a Fe-KB composite material; S3. The Fe-KB composite material obtained in step S2 and sulfur are ball-milled and mixed at a mass ratio of 1:2.3 for 30 min. Under an argon atmosphere, it is heated to 160 °C at a heating rate of 2 °C / min and held for 7 h. Subsequently, the mixture is continuously heated to 330 °C at a heating rate of 2 °C / min and held for 2 h to obtain a Fe nano-modified carbon-sulfur cathode material.

[0026] Comparative example This comparative example provides a carbon-sulfur cathode material, and its preparation method includes the following steps: S1. Under stirring conditions, 9 g of Ketjenblack (KB) is slowly added to 60 mL of deionized water, then 15 mL of absolute ethanol is added, and after stirring and mixing for 30 s, ultrasonic treatment is carried out for 50 min to form a KB suspension; S2. The suspension obtained in step S1 is dried in a vacuum drying oven at 150 °C for 8 h, and then dried in a vacuum drying oven at 85 °C for 24 h. The dried powder is placed in a tube furnace, and under an argon atmosphere, it is heated to 840 °C at a heating rate of 5 °C / min and held for 2 h to obtain a KB material; S3. The KB material obtained in step S2 and sulfur are ball-milled and mixed at a mass ratio of 1:2.5 for 30 min. Under an argon atmosphere, it is heated to 150 °C at a heating rate of 2 °C / min and held for 10 h; subsequently, the mixture is continuously heated to 300 °C at a heating rate of 2 °C / min and held for 3 h to obtain a carbon-sulfur cathode material (KB / S).

[0027] Test example (1) The Fe-KB composite material obtained in step S2 of Example 1 is characterized by using a scanning electron microscope and a transmission electron microscope respectively, and the obtained Figure 1 SEM images are as shown, and the Figure 2The TEM images and EDS mappings are shown as follows. The results show that no obvious metallic Fe nanoparticles and clusters were detected by SEM, which may be because the Fe nanoparticles were embedded in the pores of KB, and the overall original morphology of KB was retained in the Fe-KB / S composite, and this morphology ensured abundant contact sites and high electron transfer ability. From Figure 2 it can be seen that the Fe nanoparticles are uniformly distributed in KB, indicating that Fe 3+ was embedded in the pores of KB during the preparation process and reduced to carbon-containing Fe monomers at high temperature; combined with the elemental distribution in the EDS mapping, it can be found that the Fe nanoparticles are uniformly distributed in the composite material.

[0028] (2) The Fe nanoparticle-modified carbon-sulfur cathode material Fe-KB / S prepared in Example 1, the sulfur-carbon cathode material KB / S prepared in the comparative example, the Fe-KB composite material obtained in step S2 of Example 1, and Ketjenblack KB were respectively subjected to X-ray diffraction to obtain the XRD patterns as shown in Figure 3 follows. From Figure 3 it can be seen that compared with KB, an obvious diffraction peak can be observed at 44.7° for Fe-KB, corresponding to the (110) crystal plane of the Fe crystal phase, and a small diffraction peak appears at 65.0°, belonging to the (200) crystal plane of the Fe crystal phase, which confirms that Fe atoms were successfully embedded in the KB material; the diffraction peaks of S are clearly visible in KB / S and Fe-KB / S, indicating that S was successfully loaded on the carbon matrix material.

[0029] Application Example The Fe nanoparticle-modified carbon-sulfur cathode material Fe-KB / S prepared in Example 1 and the sulfur-carbon cathode material KB / S prepared in the comparative example were respectively used to prepare button batteries. The method is as follows: 1.25 g of lithium hydride and 2.5 g of sulfur were mixed and ball-milled at a speed of 500 revolutions per minute for 12 h, and vacuum was pumped every 6 h to remove HS gas, so as to obtain 3.59 g of Li2S powder; the prepared Li2S powder, 1.75 g of lithium chloride powder and 3.63 g of P2S5 powder were mixed and ball-milled at a speed of 500 revolutions per minute for 12 h, and then kept at 530 °C for 12 h in an argon atmosphere to obtain the Li6PS5Cl solid electrolyte; 8 g of the carbon-sulfur cathode material, 8 g of the Li6PS5Cl solid electrolyte, 3 g of carbon nanotubes and 1 g of ethyl cellulose were uniformly dispersed in 55 g of 1,3-dioxane (DOL) to obtain the positive electrode slurry; the positive electrode slurry was applied at 1.5 mg / cm 2The load was evenly coated on carbon-coated aluminum foil and kept at 60 °C in an argon atmosphere for 12 h to obtain the positive electrode sheet. The positive electrode sheet was covered on 100 mg of LPSC solid electrolyte powder and pressed into a customized mold under a pressure of 20 MPa. The lithium negative electrode sheet was pressed on the other side of the LPSC solid electrolyte to obtain a button battery.

[0030] The prepared button battery was subjected to electrochemical performance tests: cyclic voltammetry (CV) tests were carried out on a CHI660E electrochemical workstation with a voltage range of 1.5 - 3 V; on a button battery test system with a voltage range of 1.5 - 3 V, charge-discharge cycles and constant current intermittent tests were carried out on KB / S and Fe-KB / S button batteries; and Figure 4 、 Figure 5 。Results showed that at a current density of 50 mA / g, after 150 cycles, the Fe-KB / S battery of Example 1 maintained a discharge specific capacity of 520 mAh / g, much higher than 282 mAh / g of the KB / S battery of the comparative example. It was also observed that the coulombic efficiency of the KB / S battery of the comparative example had significant fluctuations, while the Fe-KB / S battery of Example 1 showed excellent cycle stability and redox kinetics.

[0031] Figure 6 、 Figure 7 are SEM images of the sulfur-carbon positive electrode materials prepared in Example 1 and the comparative example after the first discharge, respectively; the results clearly showed that more cracks appeared in the sulfur-carbon positive electrode material KB / S prepared in the comparative example, indicating that volume expansion and interface degradation of S occurred during cycling. Fortunately, there were no obvious cracks formed on the surface of the Fe nanomodified carbon-sulfur positive electrode material Fe-KB / S prepared in Example 1. This enhancement was due to the in-situ grown Fe nanoparticles, which provided more active sites, promoted the conversion of S to Li2S, and anchored the conversion of S at certain intervals to mitigate the swelling effect.

[0032] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0033] The above-described embodiments only represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A method for preparing a Fe nano-modified carbon-sulfur composite material, characterized in that: It includes the following steps: S1. Under stirring, Ketjen black and an iron source are added to deionized water, and then an alcohol solution is added, and ultrasonic treatment is performed to obtain a suspension; S2. After the suspension is dried, sintered to obtain a Fe-KB composite material; S3. Mixing the Fe-KB composite material with sulfur element and sintering them to obtain Fe nano-modified carbon-sulfur composite material.

2. The method for preparing the Fe nano-modified carbon-sulfur composite material according to claim 1, characterized in that: In step S1, the iron source is at least one of FeCl3, Fe2(SO4)3, Fe(NO3)3, and Fe(ClO4)3; in the suspension, Fe 3+ The concentration is 20-30 g / L.

3. The method for preparing the Fe nano-modified carbon-sulfur composite material according to claim 1, characterized in that: In step S1, the alcohol solution is at least one of anhydrous ethanol and isopropanol; and the ultrasonic treatment time is 40-60 minutes.

4. The method for preparing the Fe nano-modified carbon-sulfur composite material according to claim 1, characterized in that: In step S2, the drying is first carried out in a vacuum drying oven at 120-150°C for 7-9 hours, and then in a vacuum drying oven at 75-85°C for 23-25 ​​hours.

5. The method for preparing the Fe nano-modified carbon-sulfur composite material according to claim 1, characterized in that: In step S2, the sintering is carried out under a protective atmosphere, with the temperature being raised to 810-850°C at a heating rate of 5°C / min and kept at that temperature for 1-3h.

6. The method for preparing the Fe nano-modified carbon-sulfur composite material according to claim 1, characterized in that: In step S3, the mass ratio of the Fe-KB composite material to sulfur is 1:(2.3-2.5).

7. The method for preparing the Fe nano-modified carbon-sulfur composite material according to claim 1, characterized in that: In step S3, the sintering is carried out under a protective atmosphere, firstly heating the temperature to 150-160°C at a heating rate of 2°C / min and keeping the temperature for 7-10h, and then heating the temperature to 300-350°C at a heating rate of 2°C / min and keeping the temperature for 1-3h.

8. A Fe nano-modified carbon-sulfur composite material, characterized in that: The invention is prepared by the preparation method described in any one of claims 1 to 7.

9. An application of the Fe nano-modified carbon-sulfur composite material as claimed in claim 8, characterized in that: It is used as a positive electrode material to prepare all-solid-state lithium-sulfur batteries.

10. The use according to claim 9, characterized in that: The steps of preparing the all-solid-state lithium-sulfur battery are: Li2S powder, lithium chloride powder and P2S5 powder are mixed, ball-milled and sintered to obtain Li6PS5Cl solid electrolyte; The Fe nano-modified carbon-sulfur composite material, the Li6PS5Cl solid electrolyte, carbon nanotubes and ethyl cellulose are added into 1,3-dioxane to obtain a positive electrode slurry; the positive electrode slurry is coated on a carbon-coated aluminum foil and dried to obtain a positive electrode sheet; The positive electrode plate, the Li6PS5Cl solid electrolyte and the lithium negative electrode plate are assembled into an all-solid-state lithium-sulfur battery.

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