Preparation of a functional lithium-sulfur battery separator constructed by cobalt diselenide nanoparticles embedded nitrogen-selenium co-doped carbon nanocages
By loading CoSe2@NSeC nanoparticles onto a lithium-sulfur battery separator to form a hollow nanocage structure, the problems of conductivity, volume expansion, and shuttle effect in lithium-sulfur batteries were solved, resulting in a significant improvement in battery performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- FUZHOU UNIV
- Filing Date
- 2023-06-20
- Publication Date
- 2026-06-05
Smart Images
Figure CN116505190B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of preparation of modified separators for lithium-sulfur batteries, specifically relating to a functional separator CoSe2@NSeC / PP for lithium-sulfur batteries, its preparation method, and its application. Background Technology
[0002] Traditional lithium-ion batteries have reached their capacity limit and are expensive. Lithium-sulfur batteries, with their ultra-high theoretical energy density (2600 Wh / kg), low cost, and environmental friendliness, have become candidates for the next generation of energy storage systems. However, some thorny issues restrict the practical application and commercial development of lithium-sulfur batteries: (1) elemental sulfur and its discharge product Li2S are both electronic / ionic insulators; (2) sulfur undergoes nearly 80% volume expansion during charging and discharging, which can easily lead to electrode structure collapse and rapid capacity decay; (3) the reaction kinetics of the active material sulfur are slow; (4) the intermediate product of discharge, soluble lithium polysulfide, undergoes a shuttle effect, resulting in low utilization of the active material sulfur and deterioration of electrochemical performance. In general, lithium-sulfur batteries suffer from low discharge capacity and poor cycle stability.
[0003] Transition metal selenides (TMSEs) have attracted considerable attention from researchers due to their superior conductivity and structural tunability compared to oxides and sulfides. The numerous chalcophilic sites on the surface of TMSEs can chemisorb lithium polysulfides and reduce Li-2 levels. + A diffusion barrier is created, thus promoting the rapid conversion of LiPSs into Li2S2 / Li2S. Simultaneously, relevant literature confirms that Se atoms possess lithium-philic properties, enabling them to form Li-Se bonds and interact with polysulfides. Since cathode materials still have significant limitations in further suppressing the "shuttle effect," developing TMSEs materials and applying them to modified separators can fully leverage the advantages of TMSEs, thereby significantly improving the electrochemical performance of high-sulfur-loaded lithium-sulfur batteries.
[0004] Currently, commercially available polypropylene (PP) separators have numerous pores that allow electrolyte and ions to permeate. However, lithium polysulfides dissolved in the electrolyte can also pass through and reach the negative electrode surface, causing irreversible loss of active materials and performance degradation. Therefore, the concept of functionalizing polypropylene separators has been proposed, namely, loading an additional layer of functional material onto the polypropylene separator to block lithium polysulfides and accelerate their redox transformation. This invention loads CoSe2@NSeC onto a conventional polypropylene separator using a simple coating method to prepare a CoSe2@NSeC / PP functional separator, which is then applied to lithium-sulfur batteries. Summary of the Invention
[0005] To address the aforementioned problems, the present invention aims to provide a functional lithium-sulfur battery separator CoSe2@NSeC / PP, its preparation method, and its applications. The functional lithium-sulfur battery separator comprises CoSe2@NSeC and a polypropylene separator. The CoSe2@NSeC has a highly hollow nanocage structure with an average particle size of approximately 250 nm and a large specific surface area. By applying this selenide composite to the modification of lithium-sulfur battery separators, a functional lithium-sulfur battery separator can be prepared through a simple process. Lithium-sulfur batteries assembled using this functional separator exhibit significantly improved rate performance and cycle performance.
[0006] To achieve the above objectives, the present invention adopts the following technical solution:
[0007] A method for preparing a functional separator CoSe2@NSeC / PP for lithium-sulfur batteries includes the following steps:
[0008] (1) Weigh out zinc salt, cobalt salt, and hexadecyltrimethylammonium bromide and add them to deionized water. Stir until completely dissolved to obtain solution A.
[0009] (2) Weigh 2-methylimidazole and add it to deionized water, stir until completely dissolved, to obtain solution B;
[0010] (3) Mix solution A and solution B and stir until the reaction is uniform; centrifuge the resulting suspension to obtain the solid product, wash with anhydrous ethanol, and dry to obtain purple powder CoZn-ZIF;
[0011] (4) Add the purple powder CoZn-ZIF from step (3) to methanol, then add dopamine hydrochloride and stir until the reaction is uniform; centrifuge the resulting suspension to obtain the solid product, wash with methanol, and dry to obtain a brown powder.
[0012] (5) Place the brown powder from step (4) in a quartz boat and carbonize it under a nitrogen atmosphere to obtain Co@NC;
[0013] (6) Place the Co@NC from step (5) in the downstream quartz boat and place the selenium powder in the upstream quartz boat. Selenize under a nitrogen atmosphere to obtain CoSe2@NSeC;
[0014] (7) The reaction products of step (6), conductive carbon black and polyvinylidene fluoride are added to N-methylpyrrolidone respectively. The mixed solution is ultrasonically vibrated until the solute is uniformly dispersed in the solution. Then, the slurry is uniformly loaded onto a commercial polypropylene separator by a scraper. After that, the prepared separator is placed in a vacuum drying oven for drying to obtain the functional separator CoSe2@NSeC / PP for lithium-sulfur batteries.
[0015] Further, in step (1), the zinc salt concentration in solution A is 0.002-2 mol / L; the zinc salt is one or more of Zn(NO3)2, ZnSO4, Zn(CH3COO)2, and ZnCl2. The cobalt salt concentration is 0.002-2 mol / L; the cobalt salt is one or more of Co(NO3)2, CoSO4, Co(CH3COO)2, and CoCl2, and the mass of hexadecyltrimethylammonium bromide is 0.01-0.05 g.
[0016] Furthermore, the concentration of 2-methylimidazole in solution B in step (2) is 0.05-5 mol / L.
[0017] Furthermore, the reaction time in step (3) is 4-16 h.
[0018] Furthermore, in step (4), the mass ratio of dopamine hydrochloride to CoZn-ZIF is 5:3-2:1, the volume of methanol is 30-120 mL, and the reaction time is 4-16 h.
[0019] Furthermore, the carbonization temperature in step (5) is 700-1300 ℃, the heating rate is 1-10 ℃ / min, and the reaction time is 2 hours.
[0020] Furthermore, in step (6), the selenization temperature is 300-500 ℃, the heating rate is 1-10 ℃ / min, and the reaction time is 2 hours.
[0021] Further, in step (7), the mass of CoSe2@NSeC is 70 mg, the mass of conductive carbon black is 20 mg, the mass of polyvinylidene fluoride is 10 mg, and the volume of N-methylpyrrolidone is 10~100 mL.
[0022] Application: The use of CoSe2@NSeC / PP functional separator in the assembly of lithium-sulfur batteries.
[0023] The significant advantages of this invention are:
[0024] This invention provides a method for preparing a functional separator CoSe2@NSeC / PP for lithium-sulfur batteries. The excellent conductivity of CoSe2@NSeC effectively promotes electron / ion migration and increases the electrochemical reaction rate. The hollow porous structure of CoSe2@NSeC provides a large specific surface area, increasing the contact area between the material and the electrolyte, and also promoting the uniform deposition of the discharge product Li2S. The transition metal selenides contained in CoSe2@NSeC have a strong chemisorption effect on lithium polysulfides, effectively anchoring soluble lithium polysulfides and suppressing the shuttle effect. CoSe2@NSeC possesses high catalytic activity, accelerating the conversion of lithium polysulfides and improving electrochemical reaction kinetics. Therefore, lithium-sulfur batteries assembled using the functional separator of this invention exhibit significantly improved rate performance and cycle performance. Attached Figure Description
[0025] Figure 1 The X-ray diffraction pattern and specific surface area and pore size analysis diagram of the functional separator modification layer material for lithium-sulfur batteries prepared in Example 1 are shown.
[0026] Figure 2 The image shows a scanning electron microscope image of the functional separator modification layer material for lithium-sulfur batteries prepared in Example 1.
[0027] Figure 3 The charge-discharge curves of a lithium-sulfur battery assembled from the lithium-sulfur battery functional separator prepared in Example 1 are shown.
[0028] Figure 4 The graph shows the cycle performance of a lithium-sulfur battery assembled from the lithium-sulfur battery functional separator prepared in Example 1.
[0029] Figure 5 The rate performance diagram is shown for a lithium-sulfur battery assembled from the lithium-sulfur battery functional separator prepared in Example 1.
[0030] Figure 6 This is a comparison chart of the electrochemical performance of lithium-sulfur batteries assembled from the functional separator of lithium-sulfur battery prepared in Example 1 and the modified separator of lithium-sulfur battery prepared in Comparative Example 1. Detailed Implementation
[0031] To make the above-mentioned features and advantages of the present invention more apparent and understandable, specific embodiments are described below in detail. Unless otherwise specified, the methods of the present invention are conventional methods in the art. Example 1
[0032] A method for preparing a functional separator CoSe2@NSeC / PP for lithium-sulfur batteries, comprising the following steps:
[0033] (1) Weigh zinc nitrate hexahydrate, cobalt nitrate hexahydrate, and 0.02 g cetyltrimethylammonium bromide into a beaker, add 40 mL of deionized water and stir until completely dissolved to form solution A (the concentration of zinc salt in solution A is 0.1 mol / L, and the concentration of cobalt salt is 0.007 mol / L). Weigh 2-methylimidazole into another beaker, add 280 mL of deionized water and stir until completely dissolved to form solution B (the concentration of 2-methylimidazole in solution B is 0.78 mol / L). Then slowly add solution A to solution B, stir and mix at room temperature to form a light purple solution, continue stirring for 12 h to form a dark purple suspension and then stop the reaction. Wash three times with anhydrous ethanol and centrifuge to obtain a light purple precipitate, then vacuum dry and grind to obtain CoZn-ZIF;
[0034] (2) The reaction product CoZn-ZIF from step (1) was added to 60 mL of methanol and ultrasonically stirred until uniformly dispersed. Then, 120 mg of dopamine hydrochloride was added and the reaction was stirred continuously at room temperature for 12 h. The product was washed three times with methanol and centrifuged to obtain a brown precipitate. Then, it was vacuum dried and ground to obtain CoZn-ZIF@PDA nanocubes.
[0035] (3) Place the reaction product CoZn-ZIF@PDA from step (2) in a quartz boat, then place the quartz boat in a tube furnace, and react at 5 °C / min to 900 °C for 2 h under an inert atmosphere to obtain Co@NC powder;
[0036] (4) Place the reaction product Co@NC and selenium powder from step (3) into two quartz boats respectively. Place the quartz boat containing selenium powder at the upper air vent of the tube furnace and place the quartz boat containing Co@NC in the center of the tube furnace. Heat under an inert gas atmosphere. After reacting at 400 ℃ for 2 h at a rate of 5 ℃ / min under an inert atmosphere, CoSe2@NSeC powder is obtained.
[0037] (5) The reaction products of step (4), conductive carbon black and polyvinylidene fluoride are added to N-methylpyrrolidone. The mixed solution is ultrasonically vibrated until the solute is uniformly dispersed in the solution. Then, CoSe2@NSeC in the solution is loaded onto a commercial polypropylene separator by a scraper. The prepared separator is then placed in a vacuum drying oven for drying to obtain the functional separator CoSe2@NSeC / PP for lithium-sulfur batteries.
[0038] Figure 1The X-ray diffraction pattern and specific surface area and pore size analysis of the CoSe2@NSeC material, a functional separator modification layer for lithium-sulfur batteries prepared in Example 1, are shown. The diffraction peaks are very clear and distinct, indicating high crystallinity. The diffraction peaks correspond to the PDF card, demonstrating the accuracy of the phase composition and the correct synthesis of the material. Furthermore, the specific surface area of CoSe2@NSeC reaches 79.73 m². 2 g -1 Micropores and mesopores are the main components of its pore structure. The diameter of micropores is mainly concentrated in 0.8-1 nm, and the size of mesopores is 20-35 nm, indicating that it has a large specific surface area, which is beneficial to increasing the contact area between the material and the electrolyte. Figure 2 The image shows a scanning electron microscope image of the functional separator modification layer material for lithium-sulfur batteries prepared in Example 1. The material has a particle size of about 250 nm and the particles exhibit a highly hollow porous nanocage structure.
[0039] Electrochemical performance testing
[0040] The CoSe2@NSeC / PP prepared by the above method was used as the separator, lithium sheet was used as the negative electrode, and commercial conductive carbon black Super Li / S was used as the positive electrode. The battery was assembled in a glove box using a CR2025 battery case. Figure 3 The graph shows the charge-discharge curves of a lithium-sulfur battery assembled from the functional separator prepared in Example 1. It can be observed that Q in Comparative Example 1... H Q L -1 The value is 2.74, and the polarization potential is 123.1 mV. Q in Example 1 H Q L -1 The value is 3.16 and the polarization potential is 108.8 mV, indicating that the modified membrane of Example 1 is beneficial for the efficient capture and catalysis of LiPSs conversion, can significantly reduce the "shuttle effect" and improve the utilization rate of active materials; Figure 4 The graph shows the cycle performance of a lithium-sulfur battery assembled from the functional separator prepared in Example 1. It can be seen that the battery capacity decreases gradually, the coulombic efficiency remains above 98% throughout the cycle, and its initial specific capacity is 1378 mAh g⁻¹. -1 The reversible specific capacity after 100 cycles is 1050 mAh g. -1 The capacity decay rate is 0.238% per cycle, indicating good cycling stability. Figure 5 The graph shows the rate performance of a lithium-sulfur battery assembled from the functional separator prepared in Example 1. It can be seen that the battery still maintains a capacity of 764.0 mAh g⁻¹ at a high current density of 8 C. -1The discharge specific capacity remains at 1375 mAh g⁻¹, and it is still able to maintain this capacity when the current density returns to 0.2 C. -1 It has excellent discharge capacity and rate performance.
[0041] Comparative Example 1
[0042] Method for preparing Co@NC / PP modified separator for lithium-sulfur batteries:
[0043] (1) Weigh zinc nitrate hexahydrate, cobalt nitrate hexahydrate, and 0.02 g cetyltrimethylammonium bromide into a beaker, add 40 mL of deionized water and stir until completely dissolved to form solution A (the concentration of zinc salt in solution A is 0.1 mol / L, and the concentration of cobalt salt is 0.007 mol / L). Weigh 2-methylimidazole into another beaker, add 280 mL of deionized water and stir until completely dissolved to form solution B (the concentration of 2-methylimidazole in solution B is 0.78 mol / L). Then slowly add solution A to solution B, stir and mix at room temperature to form a light purple solution, continue stirring for 12 h to form a dark purple suspension and then stop the reaction. Wash three times with anhydrous ethanol and centrifuge to obtain a light purple precipitate, then vacuum dry and grind to obtain CoZn-ZIF;
[0044] (2) The reaction product CoZn-ZIF from step (1) was added to 60 mL of methanol and ultrasonically stirred until uniformly dispersed. Then, 120 mg of dopamine hydrochloride was added and the reaction was stirred continuously at room temperature for 12 h. The product was washed three times with methanol and centrifuged to obtain a brown precipitate. Then, it was vacuum dried and ground to obtain CoZn-ZIF@PDA nanocubes.
[0045] (3) Place the reaction product CoZn-ZIF@PDA from step (2) in a quartz boat, then place the quartz boat in a tube furnace, and react at 5 °C / min to 900 °C for 2 h under an inert atmosphere to obtain Co@NC powder;
[0046] (4) The reaction products of step (3), conductive carbon black and polyvinylidene fluoride are added to N-methylpyrrolidone. The mixed solution is ultrasonically vibrated until the solute is uniformly dispersed in the solution. Then, Co@NC in the solution is loaded onto a commercial polypropylene membrane by a scraper. The prepared membrane is then placed in a vacuum drying oven for drying to obtain a functional membrane Co@NC / PP for lithium-sulfur batteries.
[0047] The lithium-sulfur battery assembled with the modified lithium-sulfur battery separator prepared by the above method was subjected to electrochemical performance testing in the same manner as described above. Figure 6This is a comparison of the electrochemical performance of lithium-sulfur batteries assembled from the functional separator prepared in Example 1 and the modified separator prepared in Comparative Example 1. It can be seen that the initial specific capacity and reversible specific capacity of Comparative Example 1 are only 1256 and 871 mAh g, respectively. -1 The capacity decay rate was 0.307%, and the coulombic efficiency in the later stages of cycling was less than 98%, indicating that Example 1 has better cycling stability than Comparative Example 1. Furthermore, Example 1 achieved current densities of 1488, 1368, 1246, 1090, 986, 903, 838, and 764 mAh g⁻¹ at current densities of 0.2, 0.5, 1.0, 2.0, 3.0, 5.0, 6.0, and 8.0 C, respectively. -1 The specific capacity can recover to 1375 mAh g when the current density returns to 0.2 C. -1 The reversible specific capacity of the sample is significantly higher than that of Comparative Example 1 at various rate rates. The comparison demonstrates that the functional separator CoSe2@NSeC / PP for lithium-sulfur batteries can effectively catalyze the conversion of lithium polysulfides, accelerate reaction kinetics, and improve the electrochemical performance of the battery.
[0048] Example 1 exhibits superior performance compared to Comparative Example 1 primarily due to the highly hollow internal structure of the synthesized CoSe2@NSeC nanocages. Its shell contains numerous micropores and mesopores, which, combined with Se atom doping, construct a dense conductive network. This not only facilitates efficient interfacial charge transport but also promotes thorough electrolyte wetting and smooth lithium ion passage. Secondly, compared to Co@NC, the CoSe2 nanoparticles and N, Se co-doped carbon matrix provide a more effective adsorption capacity for capturing polysulfides and a more efficient catalytic ability to accelerate the redox transformation of polysulfides, thus significantly suppressing the negative effects of the "shuttle effect."
[0049] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.
Claims
1. A method for preparing a functional separator for lithium-sulfur batteries, characterized in that: Includes the following steps: (1) Weigh zinc salt, cobalt salt and hexadecyltrimethylammonium bromide, add deionized water and stir until completely dissolved to form solution A; weigh 2-methylimidazole, add deionized water and stir until completely dissolved to form solution B; then slowly add solution A to solution B, stir and mix at room temperature to form a light purple solution, continue stirring to form a dark purple suspension and then stop the reaction, wash three times with anhydrous ethanol and centrifuge to obtain a light purple precipitate, then vacuum dry and grind to obtain CoZn-ZIF; (2) The reaction product CoZn-ZIF from step (1) was added to methanol and ultrasonically stirred until it was uniformly dispersed. Then, dopamine hydrochloride was added and stirred continuously at room temperature to form a dark brown suspension. The reaction was stopped, washed three times with methanol and centrifuged to obtain a brown precipitate. Then, it was vacuum dried and ground to obtain CoZn-ZIF@PDA nanocubes. (3) Place the reaction product CoZn-ZIF@PDA from step (2) into a quartz boat, then place the quartz boat into a tube furnace and carbonize it under a nitrogen atmosphere to obtain Co@NC powder; (4) Place the reaction product Co@NC and selenium powder from step (3) into two quartz boats respectively. Place the quartz boat containing selenium powder at the upper air vent of the tube furnace and place the quartz boat containing Co@NC in the center of the tube furnace. Heat under an inert gas atmosphere and perform chemical vapor deposition to obtain CoSe2@NSeC powder. (5) The reaction products of step (4), conductive carbon black and polyvinylidene fluoride are added to N-methylpyrrolidone. The mixed solution is ultrasonically vibrated until the solute is uniformly dispersed in the solution. Then, CoSe2@NSeC in the solution is loaded onto a commercial polypropylene separator by a scraper. The prepared separator is then placed in a vacuum drying oven for drying to obtain the functional separator CoSe2@NSeC / PP for lithium-sulfur batteries.
2. The preparation method according to claim 1, characterized in that: In step (1), the concentration of zinc salt in solution A is 0.002-2 mol / L; the zinc salt is one or more of Zn(NO3)2, ZnSO4, (CH3COO)2Zn and ZnCl2; the concentration of cobalt salt is 0.002-2 mol / L; the cobalt salt is one or more of Co(NO3)2, CoSO4, Co(CH3COO)2 and CoCl2; the mass of hexadecyltrimethylammonium bromide is 0.01-0.05 g; the concentration of 2-methylimidazole in solution B is 0.05-5 mol / L; and the stirring time is 4-16 hours.
3. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of dopamine hydrochloride and CoZn-ZIF is 5:3-2:1, and the stirring time is 4-16 hours.
4. The preparation method according to claim 1, characterized in that: The carbonization reaction temperature in step (3) is 700-1300 ℃, the heating rate is 1-10 ℃ / min, and the reaction time is 2 hours.
5. The preparation method according to claim 1, characterized in that: In step (4), the mass ratio of selenium powder to Co@NC is 1:1-10:1, the reaction temperature of vapor deposition is 300-500 ℃, the heating rate is 1-10 ℃ / min, and the reaction time is 2 hours.
6. The preparation method according to claim 1, characterized in that: In step (5), the mass of CoSe2@NSeC is 70 mg, the mass of conductive carbon black is 20 mg, the mass of polyvinylidene fluoride is 10 mg, and the volume of N-methylpyrrolidone is 10~100 mL.
7. A functional separator for lithium-sulfur batteries prepared by the method according to any one of claims 1-6.
8. The application of the lithium-sulfur battery functional separator as described in claim 7 in the assembly of lithium-sulfur batteries.