Electrode material and preparation method and application thereof
By preparing electrode materials with carbon nanofiber cores and metal sulfides shells, the problems of poor conductivity and structural stability of transition metal sulfides were solved, achieving high conductivity and excellent rate performance while reducing energy consumption.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-11
- Publication Date
- 2026-04-14
AI Technical Summary
Existing sodium-ion battery anode materials, particularly transition metal sulfides, exhibit poor electronic conductivity and structural stability during cycling. Furthermore, current preparation methods are energy-intensive and prone to particle agglomeration, which negatively impacts rate performance.
A composite nanofiber with a carbon nanofiber core and a metal compound shell is first prepared, and then in-situ sulfidation is carried out by immersing it in a sulfur source solution to form an electrode material with a carbon nanofiber core and a metal sulfide shell.
It improves the conductivity and structural stability of the electrode material, enhances rate performance, reduces energy consumption, and avoids particle agglomeration problems during high-temperature vulcanization.
Smart Images
Figure CN121849926A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of battery technology, and relates to an electrode material, its preparation method and application. Background Technology
[0002] Currently, polyanionic compounds, layered metal oxides, and Prussian blue analogues have been successfully used as cathode materials for sodium-ion batteries. However, due to the large ionic radius of sodium ions, graphite electrodes used in commercial lithium-ion anode materials have difficulty effectively accommodating sodium ions. Therefore, there is an urgent need to develop anode materials with excellent rate performance, high specific capacity, and long cycle life.
[0003] Transition metal sulfides have proven to be promising anode materials for sodium-ion batteries due to their wide variety, high theoretical capacity, low cost, and environmental friendliness. However, transition metal sulfides exhibit poor electronic conductivity and structural stability during cycling, resulting in less than ideal rate performance.
[0004] In existing technologies, metal sulfides are often combined with carbon nanofibers to improve the aforementioned defects of metal sulfides. However, metal sulfides in existing technologies are usually grown on carbon substrates by hydrothermal reaction, and the bond between the metal sulfide and the carbon substrate is weak. Under repeated high-rate cycling, the metal sulfides on the surface are easy to fall off. Moreover, the preparation of metal sulfides uses high-temperature sulfidation, which not only increases the energy consumption in the preparation process, but also easily causes the metal sulfide particles on the surface to agglomerate, reducing the rate performance of the material.
[0005] Based on the above research, there is a need to provide a method for preparing electrode materials. This method can obtain electrode materials with high conductivity, reaction kinetics and structural stability, overcoming the drawbacks of metal sulfides being generated through hydrothermal growth and high-temperature sulfidation. Summary of the Invention
[0006] The purpose of this invention is to provide an electrode material, its preparation method, and its application. The preparation method involves first preparing composite nanofibers with a core of carbon nanofibers and a shell of metal compounds, and then immersing the composite nanofibers in a sulfur source solution for sulfidation, thereby causing the metal compounds to sulfide in situ, thus obtaining an electrode material with a core of carbon nanofibers and a shell of metal sulfides. The obtained electrode material has excellent conductivity and rate performance.
[0007] To achieve this objective, the present invention adopts the following technical solution:
[0008] In a first aspect, the present invention provides a method for preparing an electrode material, the method comprising the following steps:
[0009] (1) Mix the polymer, solvent and metal source and electrospin to obtain spun fibers;
[0010] (2) Carbonize the spun fibers described in step (1) to obtain composite nanofibers;
[0011] (3) The composite nanofibers described in step (2) are immersed in a sulfur source solution for sulfidation and then dried to obtain the electrode material; the sulfur source solution includes a metal sulfide solution and / or a non-metal sulfide solution, wherein the non-metal sulfide in the non-metal sulfide solution is an ionic compound.
[0012] Preferably, the concentration of the sulfur source solution in step (3) is 2.0-5.0 mol / L.
[0013] Preferably, the vulcanization temperature in step (3) is 10-50℃ and the time is 1-10h.
[0014] Preferably, the metal sulfide solution in step (3) includes alkali metal sulfides.
[0015] Preferably, the alkali metal sulfide includes any one or a combination of at least two of sodium sulfide, potassium sulfide, or rubidium sulfide.
[0016] Preferably, the non-metallic sulfide solution in step (3) includes ammonium sulfide.
[0017] Preferably, the drying temperature in step (3) is 25-70°C and the time is 10-24 hours.
[0018] Preferably, after vulcanization in step (3) and before drying, the product is washed with water.
[0019] Preferably, the carbonization temperature in step (2) is 500-800℃ and the time is 2-12h.
[0020] Preferably, the spun fibers in step (1) are pre-oxidized before carbonization.
[0021] Preferably, the polymer in step (1) includes a first polymer and a second polymer.
[0022] Preferably, the first polymer comprises any one or a combination of at least two of polypropylene, polyethylene, polystyrene, polyamide, polylactic acid, or polyacrylonitrile, and is preferably polyacrylonitrile.
[0023] Preferably, the second polymer comprises polyvinylpyrrolidone.
[0024] Preferably, in the polymer of step (1), the content of the first polymer is 70-95 wt%, and the content of the second polymer is 5-30 wt%.
[0025] Preferably, the solvent in step (1) includes N,N-dimethylformamide.
[0026] Preferably, the metal source in step (1) includes any one or a combination of at least two of the following: nickel source, cobalt source, copper source or iron source.
[0027] As a preferred embodiment of the present invention, the preparation method includes the following steps:
[0028] (1) Mix the polymer, solvent and metal source and electrospin to obtain spun fibers;
[0029] The polymer comprises 70-95 wt% of a first polymer and 5-30 wt% of a second polymer, wherein the first polymer comprises any one or a combination of at least two of polypropylene, polyethylene, polystyrene, polyamide, polylactic acid or polyacrylonitrile, and the second polymer comprises polyvinylpyrrolidone.
[0030] (2) The spun fibers described in step (1) are first pre-oxidized and then carbonized at 500-800℃ to obtain composite nanofibers;
[0031] (3) The composite nanofibers described in step (2) are immersed in a sulfur source solution with a concentration of 2.0-5.0 mol / L, and sulfurized at 20-35°C for 1-3 hours. Then, they are washed with water and dried at 50-70°C for 10-14 hours to obtain the electrode material.
[0032] The sulfur source solution includes any one or a combination of at least two of sodium sulfide, potassium sulfide, rubidium sulfide, or ammonium sulfide.
[0033] In a second aspect, the present invention provides an electrode material, which is prepared by the preparation method described in the first aspect.
[0034] Preferably, the electrode material comprises a core and a shell, the core comprising carbon nanofibers and the shell comprising metal sulfides.
[0035] Preferably, the content of the outer shell in the electrode material is 30-70 wt%.
[0036] Thirdly, the present invention provides a battery comprising the electrode material as described in the second aspect, or comprising the electrode material prepared by the preparation method described in the first aspect.
[0037] Compared with the prior art, the present invention has the following beneficial effects:
[0038] This invention first prepares composite nanofibers with a carbon nanofiber core and a metal compound shell, then immerses the composite nanofibers in a sulfur source solution for in-situ sulfurization. The metal compound in the shell reacts with the sulfur source to obtain a metal sulfide, thus obtaining an electrode material with a carbon nanofiber core and a metal sulfide shell. The sulfurization described in this invention can be achieved at room temperature by ion exchange between the sulfur source and the metal compound on the composite nanofiber, allowing the metal sulfide to grow in situ on the nanofiber. This greatly improves the structural stability of the material, significantly enhances its rate performance, reduces energy consumption, and avoids the problem of particle agglomeration during high-temperature sulfurization. Attached Figure Description
[0039] Figure 1 This is a SEM image of the composite nanofibers obtained in step (2) of Example 1 of the present invention;
[0040] Figure 2 This is a SEM image of the electrode material obtained in Example 1 of the present invention;
[0041] Figure 3 This is a SEM image of the composite nanofibers obtained in step (2) of Example 6 of the present invention;
[0042] Figure 4 This is a SEM image of the electrode material obtained in Example 6 of the present invention;
[0043] Figure 5 This is a SEM image of the composite nanofibers obtained in step (2) of Example 7 of the present invention;
[0044] Figure 6 This is a SEM image of the electrode material obtained in Example 7 of the present invention. Detailed Implementation
[0045] For metal sulfide / carbon composites, metal sulfides are generally grown on a carbon substrate through hydrothermal reaction. The bond between the two is weak, making the metal sulfides easy to fall off. In addition, the metal sulfide sulfidation method is high-temperature sulfidation, which not only consumes a lot of energy, but also easily causes the metal sulfide particles on the surface to agglomerate, reducing the rate performance of the material.
[0046] Therefore, in order to solve the above problems, the present invention adopts a sulfurization method by immersion in a sulfur source solution, which not only improves the stability of the electrode material, but also significantly improves the conductivity and rate performance of the electrode material.
[0047] The technical solution of the present invention will be further illustrated below through specific embodiments.
[0048] In one specific embodiment, a method for preparing an electrode material is provided, the method comprising the following steps:
[0049] (1) Mix the polymer, solvent and metal source and electrospin to obtain spun fibers;
[0050] (2) Carbonize the spun fibers described in step (1) to obtain composite nanofibers;
[0051] (3) The composite nanofibers described in step (2) are immersed in a sulfur source solution for sulfidation and then dried to obtain the electrode material; the sulfur source solution includes a metal sulfide solution and / or a non-metal sulfide solution, wherein the non-metal sulfide in the non-metal sulfide solution is an ionic compound.
[0052] The preparation method of this invention involves adding a metal source to the raw materials for preparing spun fibers to prepare spun fibers. The spun fibers are then carbonized to obtain composite nanofibers with a carbon nanofiber core and a metal compound shell. The composite nanofibers are then immersed in a sulfur source solution to allow the metal compounds on the composite nanofibers to undergo in-situ sulfurization. Therefore, this invention uses an immersion sulfur source solution for sulfurization, which not only reduces energy consumption but also avoids the problem of particle agglomeration during high-temperature sulfurization, resulting in an electrode material with a carbon nanofiber core and a metal sulfide shell. The sulfur source solution of this invention includes a metal sulfide solution and / or a non-metal sulfide solution. The principle of sulfurization is that the sulfur source undergoes ion exchange with the metal compounds on the composite nanofibers, allowing the metal sulfides to grow in-situ on the nanofibers, greatly improving the structural stability of the material and enhancing the rate performance of the electrode material.
[0053] Preferably, the concentration of the sulfur source solution in step (3) is 2.0-5.0 mol / L, for example, it can be 2.0 mol / L, 3.0 mol / L, 4.0 mol / L or 5.0 mol / L, but is not limited to the listed values. Other unlisted values within the range are also applicable.
[0054] This invention involves sulfidation in a high-concentration sulfur source solution, resulting in an excess of sulfur source in the solution. This promotes ion exchange between the sulfur source and the metal compounds on the surface of the composite nanofibers, leading to thorough sulfidation. If the concentration of the sulfur source solution is too low, the sulfidation effect will decrease. If the concentration of the sulfur source solution is too high, sodium sulfide crystals are easily precipitated and adhere to the surface of the composite nanofibers, introducing impurities.
[0055] Preferably, the vulcanization temperature in step (3) is 10-50℃, for example, 10℃, 20℃, 30℃, 40℃ or 50℃, and the time is 1-10h, for example, 1h, 3h, 5h, 7h, 9h or 10h, but not limited to the listed values. Other unlisted values within the range are also applicable.
[0056] Existing vulcanization techniques require heat treatment at high temperatures, while the vulcanization of this invention can be achieved simply by immersing the composite nanofibers in a sulfur source solution at 10-50°C. Therefore, the vulcanization method of this invention is a vulcanization process close to room temperature, eliminating the need for high-temperature heat treatment. This demonstrates that the vulcanization temperature required by this invention is low, saving energy and simplifying operation. However, the vulcanization temperature should not be too low; if the temperature is too low, the reaction rate will be too low, hindering vulcanization and affecting the vulcanization effect. Conversely, the vulcanization temperature should not be too high; if the temperature is too high, the sulfur source solution is prone to deterioration, which will also affect the vulcanization effect.
[0057] Preferably, the metal sulfide solution in step (3) includes alkali metal sulfides.
[0058] Preferably, the alkali metal sulfide includes any one or a combination of at least two of sodium sulfide, potassium sulfide, or rubidium sulfide.
[0059] Preferably, the non-metallic sulfide solution in step (3) includes ammonium sulfide.
[0060] Preferably, the drying temperature in step (3) is 25-70°C, for example, 25°C, 30°C, 40°C, 50°C, 60°C or 70°C, and the drying time is 10-24h, for example, 10h, 15h, 20h or 24h, but not limited to the listed values. Other unlisted values within the range are also applicable.
[0061] The sulfidation of this invention is achieved by immersing composite nanofibers in a sulfur source solution, followed by ordinary drying. High-temperature calcination is not required for sulfidation. If the drying temperature is too high, it will cause the metal sulfide to oxidize.
[0062] Preferably, after vulcanization in step (3) and before drying, the product is washed with water.
[0063] Preferably, the water washing is performed 4-5 times.
[0064] Preferably, after the composite nanofibers described in step (2) are immersed in the sulfur source solution, they are sealed and left to stand for vulcanization.
[0065] Preferably, the carbonization temperature in step (2) is 500-800℃, for example, 500℃, 600℃, 700℃ or 800℃, and the time is 2-12h, for example, 2h, 4h, 6h, 8h, 10h or 12h, but not limited to the listed values. Other unlisted values within the range are also applicable.
[0066] The present invention can optimize the kinetic performance of the electrode material by controlling the carbonization temperature and adjusting the content and size of the generated metal sulfides.
[0067] Preferably, the spun fibers in step (1) are pre-oxidized before carbonization.
[0068] This invention improves the thermal stability of spun fibers by pre-oxidizing them to include hydroxyl and carbonyl groups in the fibers and forming hydrogen bonds between and within molecules.
[0069] Preferably, the pre-oxidation temperature is 150-350℃, for example, 150℃, 250℃ or 350℃, and the time is 1-3h, for example, 1h, 2h or 3h, but not limited to the listed values. Other unlisted values within the range are also applicable.
[0070] Preferably, the polymer in step (1) includes a first polymer and a second polymer.
[0071] Preferably, the first polymer comprises any one or a combination of at least two of polypropylene, polyethylene, polystyrene, polyamide, polylactic acid, or polyacrylonitrile, and is preferably polyacrylonitrile.
[0072] Preferably, the second polymer comprises polyvinylpyrrolidone.
[0073] The preferred polymers used in the electrospinning process of this invention are polyacrylonitrile (PA) and polyvinylpyrrolidone (PVP). Since PPVP has a strong coordination ability with metal ions, and PA and PPVP are incompatible in electrospinning solvents such as N,N-dimethylformamide (the incompatibility is due to the inherent properties of polymers, such as viscosity and interfacial tension), PA or PPVP will undergo phase separation from the metal solution formed by the metal source and solvent. Because PPVP has an even stronger coordination ability with metal ions, highly stretched PA core-shell structured fiber materials coated with PPVP and metal compounds can be formed during electrospinning, providing feasibility for subsequent room-temperature in-situ vulcanization.
[0074] Preferably, in the polymer of step (1), the content of the first polymer is 70-95 wt%, for example, it can be 70 wt%, 80 wt%, 90 wt% or 95 wt%, and the content of the second polymer is 5-30 wt%, for example, it can be 5 wt%, 10 wt%, 20 wt% or 30 wt%, but is not limited to the listed values, and other unlisted values within the range are also applicable.
[0075] Preferably, the solvent in step (1) includes N,N-dimethylformamide.
[0076] Preferably, the mass ratio of the solvent to the polymer in step (1) is (10-15):1, for example, it can be 10:1, 12:1, 14:1 or 15:1, but is not limited to the listed values. Other unlisted values within the range are also applicable.
[0077] Preferably, the metal source in step (1) includes any one or a combination of at least two of nickel, cobalt, copper or iron sources, and is preferably nickel and cobalt sources.
[0078] Preferably, the metal source in step (1) includes any one or a combination of at least two of Ni(Ac)2, Co(Ac)2, Cu(Ac)2, NiSO4, CoSO4, FeSO4 or CoCl2.
[0079] Preferably, the mixing of the polymer, solvent and metal source in step (1) includes first heating and mixing the solvent with the polymer to dissolve the polymer, then adding the metal source and stirring after cooling to obtain a mixed solution.
[0080] Preferably, after cooling, a nickel source of 0.1-1 mmol / L is added, such as 0.1 mmol / L, 0.3 mmol / L, 0.5 mmol / L, 0.7 mmol / L, 0.9 mmol / L, or 1 mmol / L, and a cobalt source of 0.1-1 mmol / L are added, such as 0.1 mmol / L, 0.3 mmol / L, 0.5 mmol / L, 0.7 mmol / L, 0.9 mmol / L, or 1 mmol / L, but not limited to the listed values. Other unlisted values within the range are also applicable.
[0081] Preferably, after cooling, the metal source is added and stirred for 10-14 hours, for example, 10 hours, 11 hours, 12 hours, 13 hours or 14 hours, but not limited to the listed values. Other unlisted values within the range are also applicable.
[0082] As a preferred embodiment of the preparation method of the present invention, the preparation method includes the following steps:
[0083] (1) Mix the polymer, solvent and metal source and electrospin to obtain spun fibers;
[0084] The polymer comprises 70-95 wt% of a first polymer and 5-30 wt% of a second polymer, wherein the first polymer comprises any one or a combination of at least two of polypropylene, polyethylene, polystyrene, polyamide, polylactic acid or polyacrylonitrile, and the second polymer comprises polyvinylpyrrolidone.
[0085] (2) The spun fibers described in step (1) are first pre-oxidized and then carbonized at 500-800℃ to obtain composite nanofibers;
[0086] (3) The composite nanofibers described in step (2) are immersed in a sulfur source solution with a concentration of 2.0-5.0 mol / L, and sulfurized at 20-35°C for 1-3 hours. Then, they are washed with water and dried at 50-70°C for 10-14 hours to obtain the electrode material.
[0087] The sulfur source solution includes any one or a combination of at least two of sodium sulfide, potassium sulfide, rubidium sulfide, or ammonium sulfide.
[0088] In one specific embodiment, an electrode material is provided, which is prepared by the preparation method described above.
[0089] Preferably, the electrode material comprises a core and a shell, the core comprising carbon nanofibers and the shell comprising metal sulfides.
[0090] In addition to providing high conductivity, the carbon nanofibers described in this invention also enable the in-situ growth of metal sulfides on the carbon nanofibers, which greatly enhances the structural stability of the material and improves its rate performance.
[0091] Preferably, the content of the outer shell in the electrode material is 30-70 wt%, for example, it can be 30 wt%, 40 wt%, 50 wt%, 60 wt% or 70 wt%, but is not limited to the listed values. Other unlisted values within the range are also applicable.
[0092] In the electrode material described in this invention, if the shell content is too low, the active material content will decrease, resulting in a lower overall specific capacity of the electrode material; if the content is too high, the carbon nanofiber content will be too low, and it will not be able to effectively play a supporting role.
[0093] In one specific embodiment, a battery is provided, the battery comprising the electrode material, or comprising the electrode material prepared by the preparation method.
[0094] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.
[0095] Example 1
[0096] This embodiment provides a method for preparing an electrode material, the method comprising the following steps:
[0097] (1) Add 0.4g of polyacrylonitrile and 0.05g of polyvinylpyrrolidone to 4.5g of N,N-dimethylformamide, and heat and stir at 60℃ for 2h to fully dissolve polyacrylonitrile and polyvinylpyrrolidone. After the solution is cooled to room temperature, add 0.5mmol / L Ni(Ac)2 and 1mmol / L Co(Ac)2 in sequence, and stir at room temperature for 12h to obtain a mixed solution. Then transfer the above mixed solution to a 5mL syringe and perform electrospinning to obtain spun fibers.
[0098] The mass ratio of polyacrylonitrile to polyvinylpyrrolidone is 88.9:11.1;
[0099] (2) After thoroughly drying the spun fibers described in step (1), heat them at 1°C·min. -1 The temperature was increased to 260℃ for pre-oxidation at a heating rate of 1℃·min for 2 hours, and then increased to 260℃ for 2 hours for pre-oxidation. -1 The temperature was increased to 500℃ and carbonized for 7 hours to obtain composite nanofibers.
[0100] (3) The composite nanofibers described in step (2) are immersed in a Na2S solution with a concentration of 2.0 mol / L, sealed and left to stand at 25°C for 2 hours for sulfidation. Then, after rinsing with deionized water 4 times, they are dried in a constant temperature drying oven at 60°C for 12 hours to obtain the electrode material. The electrode material includes a core of 50 wt% and a shell of 50 wt%. The core includes carbon nanofibers and the shell includes nickel cobalt sulfide.
[0101] The SEM image of the composite nanofibers obtained in step (2) of this embodiment is shown below. Figure 1 As shown, the SEM image of the obtained electrode material is as follows: Figure 2 As shown.
[0102] Example 2
[0103] This embodiment provides a method for preparing an electrode material, the method comprising the following steps:
[0104] (1) Add 0.28g of polyacrylonitrile and 0.12g of polyvinylpyrrolidone to 5g of N,N-dimethylformamide, and heat and stir at 60℃ for 2h to fully dissolve polyacrylonitrile and polyvinylpyrrolidone. After the solution is cooled to room temperature, add 1mmol / L Ni(Ac)2 and 1mmol / L Co(Ac)2 in sequence, and stir at room temperature for 14h to obtain a mixed solution. Then transfer the above mixed solution to a 5mL syringe and perform electrospinning to obtain spun fibers.
[0105] The mass ratio of polyacrylonitrile to polyvinylpyrrolidone is 70:30;
[0106] (2) After thoroughly drying the spun fibers described in step (1), heat them at 1°C·min. -1 The temperature was increased to 350℃ for pre-oxidation at a heating rate of 1℃·min for 1 hour, and then increased to 1℃·min. -1 The temperature was increased to 500℃ and carbonized for 12 hours to obtain composite nanofibers.
[0107] (3) The composite nanofibers described in step (2) are immersed in a Na2S solution with a concentration of 2.0 mol / L, sealed and left to stand at 50°C for 1 hour for sulfidation. Then, after rinsing with deionized water 4 times, they are dried in a constant temperature drying oven at 70°C for 10 hours to obtain the electrode material. The electrode material includes a core of 30 wt% and a shell of 70 wt%. The core includes carbon nanofibers and the shell includes nickel cobalt sulfide.
[0108] Example 3
[0109] This embodiment provides a method for preparing an electrode material, the method comprising the following steps:
[0110] (1) Add 0.42g of polyacrylonitrile and 0.03g of polyvinylpyrrolidone to 4.5g of N,N-dimethylformamide, and heat and stir at 60℃ for 2h to fully dissolve polyacrylonitrile and polyvinylpyrrolidone. After the solution cools to room temperature, add 0.1mmol / L Ni(Ac)2 and 0.1mmol / L Co(Ac)2 in sequence, and stir at room temperature for 10h to obtain a mixed solution. Then transfer the above mixed solution to a 5mL syringe and perform electrospinning to obtain spun fibers.
[0111] The mass ratio of polyacrylonitrile to polyvinylpyrrolidone is 93.3:6.7;
[0112] (2) After thoroughly drying the spun fibers described in step (1), heat them at 1°C·min. -1 The temperature was increased to 150℃ for pre-oxidation at a heating rate of 3 h, and then increased at 1℃·min. -1 The temperature was increased to 500℃ and carbonized for 2 hours to obtain composite nanofibers.
[0113] (3) The composite nanofibers described in step (2) are immersed in an ammonium sulfide solution with a concentration of 2.0 mol / L, sealed and left to stand at 10°C for 10 h for sulfidation. Then, after rinsing with deionized water 5 times, they are dried in a constant temperature drying oven at 50°C for 10 h to obtain the electrode material. The electrode material includes a core of 70 wt% and a shell of 30 wt%. The core includes carbon nanofibers and the shell includes nickel cobalt sulfide.
[0114] Example 4
[0115] This embodiment provides a method for preparing an electrode material. The method is the same as in Example 1 except that the equimolar replacement of Ni(Ac)2 with NiSO4 and the equimolar replacement of Co(Ac)2 with CoSO4 in step (1) changes the adaptability of the obtained electrode material.
[0116] Example 5
[0117] This embodiment provides a method for preparing an electrode material. The method is the same as in Example 1, except that the polyacrylonitrile and polyvinylpyrrolidone in step (1) are replaced with polypropylene in equal mass to change the adaptability of the resulting electrode material.
[0118] Example 6
[0119] This embodiment provides a method for preparing an electrode material. Except for the carbonization temperature of 650°C in step (2) and the concentration of Na2S solution of 3.0 mol / L in step (3) to change the adaptability of the obtained electrode material, the preparation method is the same as that in Example 1.
[0120] The SEM image of the composite nanofibers obtained in step (2) of this embodiment is shown below. Figure 3 As shown, the SEM image of the obtained electrode material is as follows: Figure 4 As shown.
[0121] Example 7
[0122] This embodiment provides a method for preparing an electrode material. Except for the carbonization temperature of 800℃ in step (2) and the concentration of Na2S solution of 5.0mol / L in step (3) to change the adaptability of the obtained electrode material, the preparation method is the same as that in Example 1.
[0123] The SEM image of the composite nanofibers obtained in step (2) of this embodiment is shown below. Figure 5 As shown, the SEM image of the obtained electrode material is as follows: Figure 6 As shown.
[0124] Example 8
[0125] This embodiment provides a method for preparing an electrode material. Except for step (3), where the concentration of the Na2S solution is 1 mol / L to change the adaptability of the obtained electrode material, the preparation method is the same as in Example 1.
[0126] Example 9
[0127] This embodiment provides a method for preparing an electrode material. Except for step (3), where the concentration of the Na2S solution is 6 mol / L to change the adaptability of the obtained electrode material, the preparation method is the same as in Example 1.
[0128] Example 10
[0129] This embodiment provides a method for preparing an electrode material. Except for step (3), where the sulfidation temperature is 5°C to allow the electrode material to adapt to changes, the preparation method is the same as in Example 1.
[0130] Example 11
[0131] This embodiment provides a method for preparing an electrode material. Except for step (3), where the sulfidation temperature is 60°C to allow the electrode material to adapt to changes, the preparation method is the same as in Example 1.
[0132] Comparative Example 1
[0133] This comparative example provides a method for preparing an electrode material. The method is the same as in Example 1 except that the Na2S solution of equal concentration in step (3) is replaced with carbon sulfide solution to change the adaptability of the obtained electrode material.
[0134] Comparative Example 2
[0135] This comparative example provides a method for preparing an electrode material. The method is the same as in Example 1 except that the Na2S solution of equal concentration in step (3) is replaced with carbon sulfide solution, and after drying, it is heat-treated at 150°C for 12 hours under an argon atmosphere to change the adaptability of the obtained electrode material.
[0136] The electrode materials obtained in the above embodiments and comparative examples are used to prepare coin cells. The method for preparing coin cells includes the following steps:
[0137] First, the prepared sample was mixed with conductive carbon black and sodium carboxymethyl cellulose at a weight ratio of 7:2:1, and stirred in deionized water to obtain a homogeneous slurry. The slurry was then coated onto a 20 μm copper foil, vacuum dried overnight at 60 °C, and cut into 12 mmol / L diameter electrodes to obtain the working electrodes. The electrode loading was approximately 1.0–1.5 mg·cm³. -2Then, half-cells were assembled in an argon-atmospheric glove box, using sodium sheets and glass fiber membranes as reference electrodes and membranes, respectively. The electrolyte was prepared by dissolving 1 mol / L NaClO4 in ethylene carbonate and diethyl carbonate. The assembled cells were left to stand overnight to allow the electrolyte to fully wet the membranes. Subsequently, constant current charge-discharge tests of the coin cells were performed on a CHI 660D electrochemical workstation with an electrochemical window of 0.01-3V to obtain the specific capacity at different rates, with the test rates being 1 A·g -1 and 10A·g -1 The conductivity of the electrode materials obtained in the above embodiments and comparative examples was tested using a four-probe tester.
[0138] The test results are shown in Table 1:
[0139] Table 1
[0140]
[0141] As can be seen from Table 1:
[0142] (1) As can be seen from Example 1 and Comparative Examples 1-2, the present invention can achieve sulfidation by immersion in a specific sulfur source solution. However, if the sulfided carbon solution of Comparative Example 1 is used, sulfidation cannot be effectively achieved. Sulfidation is required by the heat treatment described in Comparative Example 2. Therefore, the sulfidation method of the present invention can reduce energy consumption, avoid high-temperature particle agglomeration, and achieve in-situ sulfidation, thereby improving the rate performance of the material. As can be seen from Example 1 and Example 5, the polymers in step (1) of the present invention are preferably polyacrylonitrile and polyvinylpyrrolidone, which can promote subsequent in-situ sulfidation, thereby improving the conductivity and rate performance of the electrode material. As can be seen from Example 1, Examples 6-7, and Examples 10-11, the present invention can optimize the conductivity and rate performance of the electrode material by controlling the carbonization temperature and the concentration of the sulfur source solution, thereby controlling the content and particle size of the metal sulfide.
[0143] (2) As can be seen from Examples 1 and 8-9, the concentration of the sulfur source solution of the present invention will affect the sulfidation effect and the content of metal sulfides in the electrode material, thereby affecting the conductivity and rate performance of the electrode material. As can be seen from Examples 1 and 10-11, if the sulfidation temperature of the present invention is too low, the sulfidation rate will be reduced and the content of metal sulfides will be reduced. If the sulfidation temperature is too high, the sulfide solution will deteriorate and the content of metal sulfides will also be reduced, thereby affecting the conductivity and rate performance of the electrode material.
[0144] In summary, this invention provides an electrode material, its preparation method, and its application. The preparation method involves first preparing composite nanofibers with a carbon nanofiber core and a metal compound shell, and then immersing the composite nanofibers in a sulfur source solution for sulfidation, thereby causing the metal compound to sulfide in situ, thus obtaining an electrode material with a carbon nanofiber core and a metal sulfide shell. The obtained electrode material possesses excellent conductivity and rate performance.
[0145] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.
Claims
1. A method for preparing an electrode material, characterized in that, The preparation method includes the following steps: (1) Mix the polymer, solvent and metal source and electrospin to obtain spun fibers; (2) Carbonize the spun fibers described in step (1) to obtain composite nanofibers; (3) The composite nanofibers described in step (2) are immersed in a sulfur source solution for sulfurization, and then dried to obtain the electrode material; The sulfur source solution includes a metal sulfide solution and / or a non-metal sulfide solution, wherein the non-metal sulfide in the non-metal sulfide solution is an ionic compound.
2. The preparation method according to claim 1, characterized in that, The concentration of the sulfur source solution in step (3) is 2.0-5.0 mol / L; Preferably, the vulcanization temperature in step (3) is 10-50℃ and the time is 1-10h.
3. The preparation method according to claim 1 or 2, characterized in that, The metal sulfide solution in step (3) includes alkali metal sulfides; Preferably, the alkali metal sulfide includes any one or a combination of at least two of sodium sulfide, potassium sulfide, or rubidium sulfide; Preferably, the non-metallic sulfide solution in step (3) comprises ammonium sulfide; Preferably, the drying temperature in step (3) is 25-70℃ and the drying time is 10-24h; Preferably, after vulcanization in step (3) and before drying, the product is washed with water.
4. The preparation method according to claim 1 or 2, characterized in that, The carbonization temperature in step (2) is 500-800℃, and the time is 2-12h; Preferably, the spun fibers in step (1) are pre-oxidized before carbonization.
5. The preparation method according to claim 1 or 2, characterized in that, The polymer in step (1) includes a first polymer and a second polymer; Preferably, the first polymer comprises any one or a combination of at least two of polypropylene, polyethylene, polystyrene, polyamide, polylactic acid, or polyacrylonitrile, and is preferably polyacrylonitrile; Preferably, the second polymer comprises polyvinylpyrrolidone; Preferably, in the polymer of step (1), the content of the first polymer is 70-95 wt%, and the content of the second polymer is 5-30 wt%.
6. The preparation method according to claim 1 or 2, characterized in that, The solvent in step (1) includes N,N-dimethylformamide; Preferably, the metal source in step (1) includes any one or a combination of at least two of the following: nickel source, cobalt source, copper source or iron source.
7. The preparation method according to claim 1 or 2, characterized in that, The preparation method includes the following steps: (1) Mix the polymer, solvent and metal source and electrospin to obtain spun fibers; The polymer comprises 70-95 wt% of a first polymer and 5-30 wt% of a second polymer, wherein the first polymer comprises any one or a combination of at least two of polypropylene, polyethylene, polystyrene, polyamide, polylactic acid or polyacrylonitrile, and the second polymer comprises polyvinylpyrrolidone. (2) The spun fibers described in step (1) are first pre-oxidized and then carbonized at 500-800℃ to obtain composite nanofibers; (3) The composite nanofibers described in step (2) are immersed in a sulfur source solution with a concentration of 2.0-5.0 mol / L, and sulfurized at 20-35°C for 1-3 hours. Then, they are washed with water and dried at 50-70°C for 10-14 hours to obtain the electrode material. The sulfur source solution includes any one or a combination of at least two of sodium sulfide, potassium sulfide, rubidium sulfide, or ammonium sulfide.
8. An electrode material, characterized in that, The electrode material is prepared by the preparation method according to any one of claims 1-7.
9. The electrode material according to claim 8, characterized in that, The electrode material includes a core and a shell, the core comprising carbon nanofibers and the shell comprising metal sulfides; Preferably, the content of the outer shell in the electrode material is 30-70 wt%.
10. A battery, characterized in that, The battery comprises the electrode material as described in claim 8 or 9, or the electrode material prepared by the preparation method as described in any one of claims 1-7.