Fe7s8-cnts / s composite lithium-sulfur battery cathode material and preparation method thereof
By introducing a Fe7S8-CNTs/S composite structure into the cathode material of lithium-sulfur batteries, the high conductivity of CNTs and the catalytic effect of Fe7S8 are utilized to solve the problem of polysulfide dissolution and migration in lithium-sulfur batteries, thereby improving the electrochemical performance and cycle life of the batteries.
Patent Information
- Application Number
- CN202210404891.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-04-18
- Publication Date
- 2025-12-12
- Estimated Expiration
- 2042-04-18
AI Technical Summary
The short cycle life of lithium-sulfur batteries, self-discharge caused by the dissolution and migration of polysulfides, and the electronic insulation and volume expansion problems of sulfur limit their commercial application.
The Fe7S8-CNTs/S composite lithium-sulfur battery cathode material utilizes carbon nanotubes (CNTs) to provide high conductivity and physical adsorption capacity, while Fe7S8 acts as a catalyst to promote the redox reaction of polysulfides and inhibits the dissolution and migration of polysulfides through chemical adsorption.
It significantly improves the electrochemical performance of lithium-sulfur batteries, enhances capacity and cycle stability, reduces the shuttle effect of polysulfides, and improves sulfur utilization and battery charge-discharge efficiency.
Smart Images
Figure CN114678516B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of preparation of lithium-sulfur battery electrode materials, and particularly relates to a Fe7S8-CNTs / S composite lithium-sulfur battery positive electrode material and a preparation method thereof. BACKGROUND
[0002] The rapid development of the economic society and the increasing energy consumption have brought about serious environmental pollution and energy crisis. Renewable energy technologies such as wind energy and solar energy other than traditional fossil energy have effectively alleviated the current energy shortage. However, due to the intermittent characteristics of geographical environment and natural conditions, such energy cannot be continuously supplied. In order to cope with this situation, electrochemical energy technologies, especially rechargeable lithium-sulfur batteries (LSBs), have attracted extensive attention.
[0003] Lithium-sulfur batteries (LSBs) have attracted great interest in the academic community due to their extremely high theoretical energy density (2600 Wh kg -1 ). The high theoretical capacity (1675 mAh g -1 ) of elemental sulfur completely offsets the relatively low operating voltage (2.2 V). In addition, the natural abundance and cost-effectiveness of sulfur also provide the possibility for large-scale application of LSBs. Unfortunately, the long-term development of LSBs has been restricted by the poor cycle life, which has led to the commercial failure of LSBs. The dissolution and migration of lithium polysulfides (LiPSs) in the organic electrolyte from the cathode to the anode lead to poor cycle stability. In addition, the migration of dissolved LiPSs will cause self-discharge even in storage and resting state. At the same time, the intrinsic electronic insulation of sulfur (5 x 10 -30 S cm −1 ) and lithium sulfide (Li2S) (3 x 10 −7 Scm −1 ) also leads to low sulfur utilization and poor desulfurization ability. In addition, the sulfur cathode based on the conversion mechanism produces 80% volume expansion during discharge / charge, which leads to the crushing of active materials and the falling off from the current collector.
[0004] In order to solve the above problems, many scholars have applied various strategies such as element doping and structure design to improve the problems of lithium-sulfur batteries. Generally, conductive carbon materials are used to enhance the electrical conductivity of the sulfur cathode, and metal polar materials are used to improve the chemical affinity to lithium polysulfide and improve the shuttle effect.
[0005] On this basis, the structure and function of the sulfur carrier material can be designed. For example, hollow carbon nanotubes are used to improve the problem of low electrical conductivity, and metal compounds are doped to promote the conversion of polysulfides in the redox reaction. In this way, the electrochemical performance of lithium-sulfur batteries is improved. SUMMARY
[0006] To address the aforementioned problems, this invention provides a Fe7S8-CNTs / S composite lithium-sulfur battery cathode material. This cathode material uses carbon nanotubes (CNTs) as the conductive carbon material and iron sulfide (Fe7S8) as the catalyst. Fe7S8 is attached to the walls of the CNTs, and sulfur (S) is supported on the composite material. Based on this structure, the highly conductive CNTs can achieve both rapid and efficient lithium-ion and electron transport, and also have the ability to adsorb polysulfides. Furthermore, the Fe7S8 uniformly dispersed on the surface of the CNTs can act as a catalyst in the redox process, thereby improving the electrochemical performance of the lithium-sulfur battery.
[0007] The present invention also provides a method for preparing the above-mentioned Fe7S8-CNTs / S composite lithium-sulfur battery cathode material. The preparation method is simple and easy to operate, and the preparation process is easy to control.
[0008] The technical solution of this invention is as follows:
[0009] A Fe7S8-CNTs / S composite lithium-sulfur battery cathode material is disclosed, wherein the CNTs are carbon materials, Fe7S8 is attached to the CNT wall, and sulfur is loaded on the Fe7S8-CNTs. The highly conductive CNTs enable rapid and efficient lithium-ion and electron transport, and also have the ability to physically adsorb polysulfides; the Fe7S8 uniformly attached to the CNT surface accelerates the redox process, thereby improving the electrochemical performance of the lithium-sulfur battery.
[0010] CNTs can restrict the shuttle effect of LiPSs through physical confinement. On the one hand, Fe7S8 effectively suppresses the "shuttle effect" by chemically adsorbing LiPSs, and on the other hand, it lowers the activation energy of LiPS conversion to Li2S2 and Li2S. Due to the special structure of the electrode and the perfect combination of CNTs and Fe7S8, the Fe7S8-CNTs / S cathode has excellent electrochemical performance.
[0011] The preparation method of the above-mentioned Fe7S8-CNTs / S composite lithium-sulfur battery cathode material specifically includes the following steps:
[0012] (1) After mixing and stirring CNTs, iron salts, urea and ethylene glycol, the mixture is placed in a high-pressure reactor for reaction, and then centrifuged, vacuum dried and calcined in sequence to obtain iron-doped carbon nanotube precursors.
[0013] (2) The precursor obtained in step (1) and sublimed sulfur were placed in a tube furnace and calcined under an inert gas to obtain Fe7S8-CNTs;
[0014] (3) The Fe7S8-CNTs obtained in step (2) are mixed with sublimed sulfur and ground evenly, and then annealed under an inert atmosphere to obtain Fe7S8-CNTs / S composite lithium-sulfur battery cathode material, with sulfur uniformly loaded on Fe7S8-CNTs.
[0015] The cathode material prepared by this invention possesses adsorption, catalytic, and high conductivity properties. Fe7S8 can adsorb polysulfides and also acts as a catalyst. Carbon materials (CNTs) can also adsorb these compounds and further improve conductivity.
[0016] According to a preferred embodiment of the present invention, in step (1), the iron salt is ferric nitrate nonahydrate, the molar ratio of iron salt to CNTs is (0.4-0.8):(5-9), unit, mmol / g; the molar ratio of iron salt to urea is (0.4-0.8):(15-18); the molar ratio of CNTs to ethylene glycol is (0.005-0.009):(1-3), unit, mol / g.
[0017] Further preferred, the molar mass ratio of iron salt to CNTs is 0.74:8.3 (mmol / g); the molar ratio of iron salt to urea is 0.74:17; and the mass-volume ratio of CNTs to ethylene glycol is 0.0083:1.26 (g / mL).
[0018] According to a preferred embodiment of the present invention, in step (1), the reaction temperature in the high-pressure reactor is 180-250°C and the reaction time is 1-3 h; more preferably, the reaction temperature is 200°C and the reaction time is 2 h.
[0019] According to a preferred embodiment of the present invention, in step (1), the calcination temperature is 400-550℃ and the calcination time is 3-6h; more preferably, the calcination temperature is 500℃ and the calcination time is 2h. This calcination temperature can maintain the material morphology without significant changes while ensuring the reaction proceeds.
[0020] According to a preferred embodiment of the present invention, in step (2), the mass ratio of CNTs to sublimed sulfur is (0.1-0.3):(0.2-0.6), the calcination temperature is 350 ℃-550 ℃, and the calcination time is 1-3 h; more preferably, the mass ratio of CNTs to sublimed sulfur is 0.1:0.2, the calcination temperature is 500 ℃, and the calcination time is 2 h.
[0021] According to a preferred embodiment of the present invention, in step (3), the annealing temperature is 100-200℃ and the annealing time is 12-15 h; more preferably, the annealing temperature is 155℃ and the annealing time is 12 h.
[0022] Beneficial effects
[0023] This invention discloses a Fe7S8-CNTs / S composite lithium-sulfur battery cathode material and its preparation method. Compared with the prior art, this invention has the following advantages:
[0024] 1. This invention provides a Fe7S8-CNTs / S composite material. Fe7S8 not only provides adsorption for polysulfides but also offers strong chemisorption and activation sites for the adsorption and catalytic conversion of polysulfides through Fe7S8. The polarity of Fe7S8 can inhibit the dissolution of polysulfides in organic electrolytes, thereby mitigating the shuttle effect and accelerating the redox reaction kinetics of polysulfides, which can significantly improve the battery capacity and cycle performance. Furthermore, CNTs, while providing a highly conductive structure, also have a physical adsorption effect on polysulfides.
[0025] 2. The material prepared by this invention retains the initial morphology of carbon nanotubes and Fe7S8 is prepared on this basis. The space between these layers can have a certain slow-release effect on the volume change during the charging and discharging process.
[0026] 3. The lithium-sulfur battery cathode material prepared by this invention exhibits high electron and ion transport properties and good electrochemical performance. At 1C, its capacity remains essentially stable after 500 cycles, reaching 277 mAh g⁻¹. -1 .
[0027] 4. The preparation method provided by this invention is simple and readily available; and the raw materials are relatively inexpensive and widely available compared to other metal compounds (such as Au, Ag, etc.); the preparation process does not generate any unmanageable waste liquid or waste material, has low energy consumption, is environmentally friendly, and is highly operable, providing a new direction for the preparation of lithium-sulfur battery cathode materials. Attached Figure Description
[0028] Figure 1 The XRD pattern of Fe7S8-CNTs prepared in Example 1;
[0029] Figure 2 These are SEM images of the Fe7S8-CNTs prepared in Example 1;
[0030] Figure 3 This is a schematic diagram comparing the long-cycle performance curves of the lithium-sulfur battery using the Fe7S8-CNTs / S cathode material prepared in Example 1. Detailed Implementation
[0031] The present invention will now be described in detail. Before proceeding with the description, it should be understood that the terminology used in this specification and the appended claims should not be construed as limited to its general or dictionary meaning, but rather should be interpreted according to the meaning and concept corresponding to the technical aspects of the invention, based on the principle that the inventors are allowed to appropriately define the terms for the best interpretation. Therefore, the description presented herein is merely a preferred example for illustrative purposes and is not intended to limit the scope of the invention. It should be understood that other equivalents or modifications can be obtained from it without departing from the spirit and scope of the invention.
[0032] The following embodiments are merely examples illustrating implementations of the present invention and do not constitute any limitation on the present invention. Those skilled in the art will understand that modifications made without departing from the spirit and concept of the present invention fall within the protection scope of the present invention. Unless otherwise specified, the reagents and instruments used in the following embodiments are commercially available products.
[0033] Example 1
[0034] A method for preparing Fe7S8-CNTs / S composite lithium-sulfur battery cathode material
[0035] Specifically, the following steps are included:
[0036] (1) After stirring 0.3g of ferric nitrate nonahydrate, 1.0g of urea, 0.1g of CNTs and 50mL of ethylene glycol evenly, the mixture was transferred to a high-pressure reactor and reacted at 200°C for 1h. After centrifugation, it was freeze-dried for 18h to obtain a precursor with iron ions loaded on the surface of carbon nanotubes. The precursor was prepared by solvothermal method.
[0037] (2) The precursor obtained in step (1) was calcined at 500 °C under argon for 2 h, and then 0.24 g of sublimed sulfur was added in a tube furnace and calcined again at 500 °C under argon for 2 h to obtain Fe7S8-CNTs.
[0038] (3) The Fe7S8-CNTs obtained in step (2) are mixed with sublimed sulfur at a mass ratio of 3:7 and ground evenly. The mixture is then annealed at 150°C for 12 hours under an inert atmosphere to obtain Fe7S8-CNTs / S composite lithium-sulfur battery cathode material.
[0039] The Fe7S8-CNTs / S composite lithium-sulfur battery cathode material was prepared through the above steps. The Fe7S8-CNTs in the cathode material are nanostructures, and S is loaded on Fe7S8-CNTs.
[0040] This invention provides a Fe7S8-CNTs / S composite material. Firstly, the unique Fe7S8-CNTs nanostructure in this cathode material not only provides chemical adsorption for polysulfides, mitigating the shuttle effect, but also accelerates the redox reaction kinetics of polysulfides, significantly improving battery capacity and cycle performance. Secondly, CNTs, while providing a highly conductive structure, also have a physical adsorption effect on polysulfides, thereby improving battery capacity and cycle performance.
[0041] The XRD pattern of the Fe7S8-CNTs prepared in this embodiment is as follows: Figure 1 As shown, from Figure 1 As can be seen, the Fe7S8-CNTs we prepared exhibited the diffraction characteristic peak pattern of Fe7S8, and a characteristic diffraction peak appeared at the 22° position in the diffraction peak pattern of the Fe7S8-CNTs material, corresponding to the unique tubular structure of carbon nanotubes, indicating the presence of carbon nanotubes in the composite material; the SEM image of the Fe7S8-CNTs prepared in this embodiment is shown below. Figure 2 As shown, from Figure 2 As can be seen, Fe7S8 is uniformly attached to the carbon nanotubes, with a particle size of approximately 100-150 nm. The uniform dispersion and interfacial growth of Fe7S8 ensure the Li... + There are sufficient channels for transport. In addition, due to its small particle size, it can also mitigate the volume change of the positive electrode during the discharge process of lithium-sulfur batteries.
[0042] Example 2
[0043] A method for preparing Fe7S8-CNTs / S composite lithium-sulfur battery cathode material
[0044] Specifically, the following steps are included:
[0045] (1) After stirring 0.1 g of ferric nitrate nonahydrate, 1.0 g of urea, 0.1 g of CNTs and 50 mL of ethylene glycol evenly, the mixture was transferred to a high-pressure reactor and reacted at 200°C for 1 h. After centrifugation, the mixture was freeze-dried for 18 h to obtain a precursor with iron ions loaded on the surface of carbon nanotubes. The precursor was prepared by solvothermal method.
[0046] (2) The precursor obtained in step (1) was calcined at 500°C under argon for 2 hours, and then 0.24 g of sublimed sulfur was added in a tube furnace and calcined again at 500°C under argon for 2 hours to obtain Fe7S8-CNTs.
[0047] (3) The Fe7S8-CNTs obtained in step (2) are mixed with sublimed sulfur at a mass ratio of 3:7 and ground evenly. The mixture is then annealed at 150°C for 12.5 h under an inert atmosphere to obtain the Fe7S8-CNTs / S composite lithium-sulfur battery cathode material.
[0048] Example 3
[0049] A method for preparing Fe7S8-CNTs / S composite lithium-sulfur battery cathode material
[0050] Specifically, the following steps are included:
[0051] (1) After stirring 0.2g of ferric nitrate nonahydrate, 1.0g of urea, 0.1g of CNTs and 50mL of ethylene glycol evenly, the mixture was transferred to a high-pressure reactor and reacted at 200°C for 1h. After centrifugation, the mixture was freeze-dried for 18h to obtain a precursor with iron ions loaded on the surface of carbon nanotubes. The precursor was prepared by solvothermal method.
[0052] (2) The precursor obtained in step (1) was calcined at 500 °C under argon for 2 h, and then 0.24 g of sublimed sulfur was added in a tube furnace and calcined again at 500 °C under argon for 2 h to obtain Fe7S8-CNTs.
[0053] (3) The Fe7S8-CNTs obtained in step (2) are mixed with sublimed sulfur at a mass ratio of 3:7 and ground evenly. The mixture is then annealed at 150°C for 12.5 h under an inert atmosphere to obtain the Fe7S8-CNTs / S composite lithium-sulfur battery cathode material.
[0054] The Fe7S8-CNTs / S composite lithium-sulfur battery cathode material was prepared through the above steps. The Fe7S8-CNTs in the cathode material are nanostructures, and S is loaded on the Fe7S8-CNTs.
[0055] Experimental Example
[0056] The Fe7S8-CNTs prepared in Example 1 were used to prepare the positive electrode of a lithium-sulfur battery, and the lithium-sulfur battery was assembled. The performance of the lithium-sulfur battery was tested, as follows:
[0057] Test method: Cyclic stability was tested on the Newway testing system, with a charge / discharge voltage range of 1.7-2.8V. At 1C, the capacity was 277 mAh g after 500 cycles. -1 .
[0058] Test Results: A comparative schematic diagram of the long-cycle performance curves of the lithium-sulfur battery using the Fe7S8-CNTs / S cathode material prepared in Example 1 is shown below. Figure 3 As shown, from Figure 3 The results show that the discharge specific capacity of lithium-sulfur batteries decreases with increasing cycle number. At a current density of 1 C, the initial discharge specific capacity of the lithium-sulfur battery assembled with Fe7S8-CNTs / S cathode material is 938 mAhg. -1After 500 cycles, it remained at 277 mAh g. -1 It exhibits high utilization of active materials and excellent cycle performance. This indicates that Fe7S8-CNTs / S cathode material can improve battery charge-discharge performance and cycle performance.
[0059] Fe7S8 acts as a catalyst to promote the redox reaction of polysulfides and provides efficient polysulfide chemisorption. CNTs, as highly conductive carbon materials, enable rapid and efficient lithium-ion and electron transport, improving sulfur utilization and accelerating the redox reaction. The synergistic effect of these two materials significantly improves the capacity and cycle performance of lithium-sulfur batteries.
[0060] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions claimed by the present invention.
Claims
1. A preparation method of Fe7S8-CNTs / S composite lithium-sulfur battery cathode material, characterized in that, The positive electrode material has a space structure between layers, and Fe7S8 is attached to hollow carbon nanotubes (CNTs) to obtain nanostructured Fe7S8-CNTs, and sulfur is uniformly loaded on the Fe7S8-CNTs. The preparation method specifically comprises the following steps: (1) CNTs, iron salt, urea and ethylene glycol are mixed and stirred uniformly, and then are placed in a reaction container for reaction, and then are subjected to centrifugation, vacuum drying and calcination to obtain an iron-doped carbon nanotube precursor; (2) The precursor obtained in step (1) and sublimed sulfur are placed in a tube furnace, and are calcined under inert gas to obtain Fe7S8-CNTs; (3) Fe7S8-CNTs obtained in step (2) and sublimed sulfur are mixed and ground uniformly, and are annealed under an inert atmosphere to obtain a Fe7S8-CNTs / S composite lithium-sulfur battery positive electrode material, wherein sulfur is uniformly loaded on the Fe7S8-CNTs.
2. The production method according to claim 1, characterized by, In step (1), the iron salt is ferric nitrate nonahydrate, the molar ratio of the iron salt to CNTs is (0.4-0.8):(5-9), the molar ratio of the iron salt to urea is (0.4-0.8):(15-18), and the molar ratio of CNTs to ethylene glycol is (0.005-0.009):(1-3).
3. The preparation method according to claim 1, characterized in that, In step (1), the reaction temperature in the reaction container is 180-250°C, and the reaction time is 1-3h.
4. The method of claim 1, wherein, In step (1), the calcination temperature is 450-550°C, and the calcination time is 2-3h.
5. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of CNTs to sublimed sulfur is (0.1-0.3):(0.2-0.6).
6. The method of claim 1, wherein, In step (2), the calcination temperature is 350-550°C, and the calcination time is 1-3h.
7. The preparation method according to claim 1, characterized in that, In step (3), the annealing temperature is 100-200°C, and the annealing time is 12-15h.
8. Use of Fe7S8-CNTs / S composite lithium-sulfur battery cathode material, characterized in that, The material is used for manufacturing a positive electrode sheet of a lithium-sulfur battery.