CN111668453A - Flexible self-supporting positive electrode material and preparation method and application thereof - Google Patents
Flexible self-supporting positive electrode material and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a flexible self-supporting cathode material and a preparation method and application thereof. The flexible self-supporting anode material not only has the characteristic of flexibility, but also can remarkably improve the cycling stability and the loading capacity of the battery.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a flexible self-supporting positive electrode material and a preparation method and application thereof.
Background
With the rapid development of various electronic products and electric automobiles, the market has high specific energy densityThe battery with higher degree and high safety has higher and higher requirements, and the existing lithium ion battery can not meet the requirement of rapid development of the market more and more due to the limitation of the theoretical specific capacity of the lithium ion battery. Meanwhile, with the development of intelligent wearable devices and various flexible devices, higher requirements are also put forward on the development of flexible batteries, so that a battery material with high energy density and flexibility is urgently needed to be found. The lithium-sulfur battery has ultrahigh theoretical specific capacity (1672mAh g)-1) And theoretical specific energy (2600Wh kg)-1) The active substance sulfur has the advantages of abundant natural reserves, no toxicity, low cost and the like, and is considered to be the next generation energy storage battery system with the greatest development prospect.
First, elemental sulfur and its discharge product, lithium sulfide, have low conductivity, only 5 × 10 at room temperature-30S·cm-1This makes the utilization of the active substance sulfur low; secondly, lithium polysulfide generated in the process of charging and discharging of the lithium-sulfur battery can be dissolved in electrolyte to cause shuttle effect, which can cause irreversible attenuation of battery capacity; finally, the lithium-sulfur battery undergoes approximately 80% volume expansion during charging and discharging, which easily causes structural damage to the battery, thereby reducing the service life of the battery.
In order to solve the problems, various carbon materials (such as porous carbon, carbon nanofiber, carbon nanotube, graphene and the like), conductive polymers and metal oxides are designed to be compounded with elemental sulfur to prepare a positive electrode material, the conductivity of a sulfur positive electrode can be obviously improved through compounding with the materials, most of the materials have complex morphological structures, a certain adsorption effect on lithium polysulfide generated in the charging and discharging processes of a lithium sulfur battery can be achieved, the internal pore structure can just relieve the volume expansion of the lithium sulfur battery in the charging and discharging processes, and the modification measures are combined together, so that the electrochemical performance of the lithium sulfur battery can be obviously improved. However, most of these materials are complicated to manufacture and need to be used together with a conductive agent, a binder, and a current collector (usually aluminum foil), which inevitably lowers the energy density of the battery as a whole. The development of integrated self-supporting anodes has therefore attracted increasing attention from researchers.
At present, most of the self-supporting anodes are made of various carbon-based materials, for example, anodes prepared by compounding three-dimensional graphene and sulfur can effectively solve the problems of poor conductivity, "shuttle effect", volume expansion and the like of lithium-sulfur batteries; the battery assembled by the bendable composite flexible film consisting of the elemental sulfur, the fibrous molybdenum trioxide and the multi-walled carbon nano tube has the comprehensive advantages of high specific capacity, good rate capability, long cycle life and the like; the positive electrode prepared by compounding nano lithium tantalate and graphene oxide can solve the problem of polysulfide shuttling effect in the lithium-sulfur battery, so that the rate capability and the cycle performance of the battery are improved. However, most of these self-supporting positive electrode schemes can only solve the problems of a certain aspect, such as poor strength and no flexibility of positive electrodes prepared by compounding pure graphene with sulfur and compounding nano lithium tantalate with graphene oxide; the preparation method of the anode prepared from the elemental sulfur, the fibrous molybdenum trioxide and the multi-walled carbon nanotube is complex and difficult to apply on a large scale. In addition, these materials have a limited ability to adsorb polysulfides and do not inhibit them well.
Disclosure of Invention
In view of the above, the present invention needs to provide a flexible self-supporting cathode material, which is composed of an aerogel framework and an active material, wherein the aerogel framework is a transition metal doped carbon nanomaterial reinforced graphene-based aerogel, so that the flexible self-supporting cathode material has a low density and is doped with a transition metal, and has the characteristic of being flexible and self-supporting, so as to solve the above problems.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention firstly provides a flexible self-supporting cathode material which is composed of an active substance material and an aerogel framework, wherein the active substance material is attached to an internal pore structure of the aerogel framework, the active substance material is elemental sulfur, lithium sulfide or sodium sulfide, and the aerogel framework is composed of reduced graphene oxide and a transition metal doped carbon nanomaterial.
Further, in the transition metal doped carbon nanomaterial, the carbon nanomaterial is a carbon nanotube or a carbon nanofiber, and the transition metal includes one of iron, cobalt, nickel, copper, and zinc.
Preferably, the length of the carbon nano tube is between 5 and 100 μm, and the diameter of the carbon nano tube is between 30 and 90 nm;
the carbon nanofiber has a length of 5-15 μm and a diameter of 50-300 nm.
The invention further provides a preparation method of the flexible self-supporting cathode material, which comprises the following steps:
adding a transition metal-doped carbon nanomaterial into the graphene oxide dispersion liquid for uniform dispersion to obtain a uniform suspension, and freeze-drying the suspension and then carrying out self-propagating combustion reduction to obtain a carbon nanomaterial-doped reinforced graphene-based aerogel;
and immersing the enhanced graphene-based aerogel doped with the carbon nano material in a solution in which an active substance material is dissolved, completely volatilizing the solution to obtain an aerogel containing the active substance, and carrying out hot pressing and cutting on the aerogel to obtain the flexible self-supporting cathode material.
Further, the transition metal doped carbon nano-material is a transition metal doped carbon nano-tube, and the preparation method of the transition metal doped carbon nano-tube comprises the following steps: the metal salt is prepared by mixing metal salt and a carbon source, fully grinding and calcining, wherein the metal salt is nitrate, sulfate or chloride of transition metal.
Further, the mass ratio of the metal salt to the carbon source is 1: (5-10).
Further, the specific process of the calcination comprises the following steps: heating to 700-900 ℃ at the heating rate of 2-5 ℃/min in the mixed atmosphere of inert gas and hydrogen, and then preserving the heat for at most 5 hours.
Further, the concentration of the graphene oxide dispersion liquid is 2.5mg/mL-10 mg/mL;
the addition amount of the transition metal doped carbon nanomaterial is 1-5% of the mass of the graphene oxide;
in the solution with the dissolved active substance material, the concentration of the active substance material is 10mg/mL-20 mg/mL.
Further, the hot pressing comprises the following specific processes: heating and insulating the aerogel for 10-24h, and pressing into a film.
The invention also provides the application of the flexible self-supporting cathode material in the preparation of a lithium-sulfur battery or a room-temperature sodium-sulfur battery.
Compared with the prior art, the invention has the following beneficial effects:
the flexible self-supporting anode material is composed of an aerogel framework and an active substance material, wherein the aerogel framework is graphene-based aerogel reinforced by doping a carbon nano material, the carbon nano material can enhance the overall mechanical strength and flexibility of the material, the doping of a transition metal element can play a role in catalysis and chemical adsorption on polysulfide, the shuttling effect of the polysulfide is multiply inhibited under the action of physical adsorption of the material, and the complex hole structure in the flexible self-supporting anode material can play a good role in relieving volume expansion in the charging and discharging processes.
Test results show that the flexible self-supporting cathode material can remarkably improve the cycle stability and the load capacity of the battery, and lays a foundation for the preparation of the flexible battery.
Drawings
Fig. 1 and 2 are optical photographs of the graphene aerogel prepared in example 5 of the present invention;
fig. 3 is an SEM picture of the flexible self-supporting cathode material prepared in example 5 of the present invention, and its internal inset is an optical photograph of the flexible self-supporting cathode material;
FIG. 4 is a graph comparing the cycle performance of the positive electrode materials of example 5 of the present invention and comparative example 3 at 0.1C;
FIG. 5 is a graph comparing the rate capability of example 5 of the present invention and comparative example 3.
Detailed Description
In order that the invention may be more fully understood, reference will now be made to the specific embodiments illustrated. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
The invention discloses a flexible self-supporting cathode material, which is composed of an active substance material and an aerogel skeleton, wherein the active substance material is attached to the internal pore structure of the aerogel skeleton, the active substance material is elemental sulfur, lithium sulfide or sodium sulfide, and the aerogel skeleton is composed of reduced graphene oxide and a transition metal doped carbon nanomaterial.
Aiming at the problems of single solution and limited polysulfide adsorption capacity in the existing flexible self-supporting anode scheme, the invention innovatively provides a flexible self-supporting anode material which is composed of an active substance material and an aerogel framework, wherein the selection of the active substance material can be adjusted according to different applied batteries, and if the anode material is applied to a lithium-sulfur battery, the active substance material can be selected from elemental sulfur or lithium sulfide; if the cathode material is applied to a room-temperature sodium-sulfur battery, the active material can be selected from elemental sulfur or sodium sulfide. Furthermore, the aerogel framework is graphene-based aerogel reinforced by transition metal element-doped carbon nano materials, wherein the carbon nano materials enhance the overall mechanical strength and flexibility of the material, the doping of the transition metal elements plays roles of catalysis and chemical adsorption on polysulfide, and the multiple inhibition on the shuttle effect of the polysulfide is realized by matching with the physical adsorption effect of the material. The anode material can improve the cycling stability and the loading capacity of the battery, has the characteristic of flexible self-support, and lays a foundation for the design of flexible batteries.
Further, as mentioned above, the carbon nano material mainly plays a role in enhancing the mechanical strength and flexibility of the whole material, and preferably, the carbon nano material is a carbon nanotube or a carbon nanofiber; further, transition metals conventional in the art may be used in the present invention, and specific examples include, but are not limited to, one of iron, cobalt, nickel, copper, and zinc.
Further, the size of the carbon nano-material has an influence on the performance of the final cathode material, and preferably, in some exemplary embodiments of the present invention, the carbon nano-tube has a length of between 5 μm and 100 μm and a diameter of between 30nm and 90 nm;
the carbon nanofiber has a length of 5-15 μm and a diameter of 50-300 nm.
The second aspect of the invention discloses a preparation method of the flexible self-supporting cathode material according to the first aspect of the invention, which comprises the following steps:
adding a transition metal-doped carbon nanomaterial into the graphene oxide dispersion liquid for uniform dispersion to obtain a uniform suspension, and freeze-drying the suspension and then carrying out self-propagating combustion reduction to obtain a carbon nanomaterial-doped reinforced graphene-based aerogel;
and immersing the enhanced graphene-based aerogel doped with the carbon nano material in a solution in which an active substance material is dissolved, completely volatilizing the solution to obtain an aerogel containing the active substance, and carrying out hot pressing and cutting on the aerogel to obtain the flexible self-supporting cathode material.
Adding a transition metal element doped carbon nano material into a graphene oxide dispersion liquid to form a suspension, freezing and drying the suspension, and then adopting self-propagating combustion reduction in the reduction process of the graphene oxide, wherein on one hand, the aerogel prepared by the preparation method has an obvious lamellar cross-linked structure, the pore size distribution mainly comprises mesopores and macropores, and almost no micropores; on the other hand, the method is simpler, more convenient and faster than chemical reagent reduction and heating reduction in a tubular furnace, and is suitable for large-scale application.
Further, as mentioned above, the transition metal doped carbon nanomaterial may be a transition metal doped carbon nanotube or carbon nanofiber, and the specific preparation method thereof may be a conventional doping method in the art, for example, the carbon nanotube or carbon nanofiber is prepared by first using methods such as arc discharge and chemical vapor deposition, and then stirred and mixed with the transition metal ion solution, and then subjected to heat treatment to realize doping, so that the transition metal element is uniformly attached to the carbon nanomaterial. Further, in some embodiments of the present invention, the transition metal doped carbon nanomaterial is a transition metal doped carbon nanotube, and preferably, the preparation method thereof is: the method comprises the steps of mixing metal salt and a carbon source, fully grinding and calcining, wherein the metal salt is thermally reduced at a high temperature to generate a metal simple substance, and then the carbon substrate is catalyzed by the metal simple substance to grow to prepare the transition metal element doped carbon nano tube. Further, it is understood that the metal salt herein refers to a nitrate, sulfate or chloride salt of a transition metal, such as cobalt nitrate, iron nitrate, nickel nitrate, cobalt chloride, etc., which are not exemplified herein; the carbon source mainly serves to provide a carbon source in the preparation method, and thus, carbon sources conventionally used in the art may be used in the present invention, and specific examples include, but are not limited to, melamine, glucose, and the like, and preferably, the carbon source is melamine.
Further, the doping amount of the transition metal element has a certain influence on the performance of the final material, and the doping amount is not too high or too low, preferably, in some specific embodiments of the present invention, the mass ratio of the metal salt to the carbon source is 1: (5-10).
Further, in some exemplary embodiments of the present invention, the specific process of the calcination is: raising the temperature to 700-900 ℃ at the temperature raising rate of 2-5 ℃/min in the mixed atmosphere of inert gas and hydrogen, and then preserving the temperature for at most 5 hours. It is to be understood that the inert gas herein may be a conventional choice in the art, and specific examples that may be mentioned include nitrogen, argon, helium, and the like. In the calcination process, the temperature increase rate has an influence on the structure of the final product, and therefore, preferably, the temperature increase rate is 2 to 5 ℃/min, and since the structure of the carbon nanotube is damaged due to a long holding time, it is preferable that the calcination time is not more than 5 hours in the present invention.
In addition, it is understood that the calcination step further includes a step of washing and drying the transition metal doped carbon nanotube, and mainly for removing by-products on the surface of the doped carbon nanotube or raw materials which do not complete the reaction, and the like, the washing and drying processes are performed in a manner conventional in the art, and in some specific embodiments of the present invention, distilled water and absolute ethyl alcohol are respectively washed by centrifugation twice and then placed in a drying device for drying.
Further, the content of graphene in the aerogel skeleton has a certain influence on the performance of a final product, preferably, the concentration of the graphene oxide dispersion liquid is 2.5mg/mL-10mg/mL, more preferably, the concentration of the graphene oxide dispersion liquid is 5mg/mL, the preparation process is a conventional means in the field, and the Graphene Oxide (GO) paste is dispersed in distilled water, which is not described in detail herein;
similarly, the transition metal-doped carbon nanomaterial and the graphene oxide have a proper proportion range, and the performance of the product in the range is better, preferably, the addition amount of the transition metal-doped carbon nanomaterial is 1% -5% of the mass of the graphene oxide, more preferably, the addition amount of the transition metal-doped carbon nanomaterial is 2% of the mass of the graphene oxide, and the transition metal-doped carbon nanomaterial needs to be uniformly dispersed when being added into the graphene oxide dispersion liquid.
Further, the transition metal doped carbon nanomaterial reinforced graphene-based aerogel is immersed in a solution in which an active material is dissolved, and it can be understood that the solution in which the active material is dissolved differs according to the difference of the active material, and when the active material is elemental sulfur, the solution is a carbon disulfide solution, and when the active material is lithium sulfide or sodium sulfide, lithium sulfide or sodium sulfide is extremely sensitive to water and oxygen and is prone to deliquescence reaction, so that the lithium sulfide or sodium sulfide needs to be dispersed in an anaerobic environment such as a glove box in an ethanol solution; further, the concentration of the active material in the solution dissolved with the active material is 10mg/mL-20mg/mL, the preparation process is a conventional means in the field, in some embodiments of the present invention, the active material is dispersed or dissolved in the solution, and the solution is fully stirred until the active material is completely dissolved or uniformly dispersed.
Further, the aerogel containing active substances is hot-pressed and then cut to obtain the flexible self-supporting anode material, and the hot-pressing specific process comprises the following steps: heating and insulating the aerogel for 10-24h, and pressing into a film. Specifically, the heating temperature of the aerogel can be adjusted according to the different active material materials and the requirements of the hot pressing process, and mainly the aerogel is heated to be in a viscous state to meet the requirements of the hot pressing process, so that the heating temperature is not particularly limited herein, for example, if the active material is elemental sulfur, the heating temperature is preferably 155 ℃, and if the active material is lithium sulfide, the heating temperature can be appropriately increased according to the different materials; further, the cutting is not particularly limited, and may be adjusted to an appropriate size according to the need of manufacturing the battery.
In a third aspect of the invention, the use of a flexible self-supporting positive electrode material according to the first aspect of the invention for the preparation of a lithium-sulphur battery or a room temperature sodium-sulphur battery is disclosed. The lithium-sulfur battery or the room-temperature sodium-sulfur battery prepared by adopting the flexible self-supporting anode material has good cycling stability and higher specific discharge capacity.
The technical solution of the present invention will be more clearly and completely described by the following specific examples. The commercial multi-walled carbon nanotubes of the following comparative examples were commercially available, and had a length of 10 to 30 μm and a diameter of 10 to 20 nm.
Example 1
Weighing 0.5g of cobalt nitrate hexahydrate particles, grinding the particles to obtain light red powder, weighing 5g of melamine, adding the melamine into a mortar, and mixing and grinding the two particles until the whole body becomes green; putting the mixed powder into a porcelain boat, and introducing Ar/H2Heating to 900 ℃ at the speed of 2 ℃/min in a tubular furnace in the atmosphere, and keeping the temperature for two hours to obtain black cobalt-doped carbon nanotube (CNT @ Co) powder; centrifuging and washing the obtained powder with distilled water and anhydrous ethanol twice respectively, and drying the collected product in an air-blast drying oven for later use to obtain carbon nanotubes with length of 5-100 μm and diameter of 30-90 nm;
dispersing a Graphene Oxide (GO) paste in distilled water to prepare a dispersion liquid with the concentration of 2.5mg/mL, adding the prepared CNT @ Co powder into the dispersion liquid with the addition amount of 1% of the weight of GO, and performing ultrasonic dispersion for two hours to obtain a uniform suspension liquid; adding the suspension into a watch glass, putting the watch glass into a freeze dryer for freeze drying, and after drying is finished, carrying out self-propagating combustion reduction on a product to obtain the cobalt-doped carbon nanotube enhanced graphene-based aerogel;
dissolving sublimed sulfur particles in a carbon disulfide solution, stirring the solution until sulfur is completely dissolved by using a magnetic stirrer, preparing the solution with the sulfur concentration of 10mg/ml, immersing the cobalt-doped carbon nanotube reinforced graphene-based aerogel in the sulfur-containing carbon disulfide solution, transferring the solution into a fume hood to completely volatilize the carbon disulfide solution to obtain aerogel containing active substance sulfur, transferring the aerogel into a tubular furnace under Ar gas protection, and heating and preserving the heat at 155 ℃ for 12 hours. And finally, pressing the thermally treated aerogel into a compact film through a tablet press, and cutting the compact film into small wafers with the diameter of 14mm to obtain the flexible self-supporting anode.
Example 2
The concentration of the graphene oxide dispersion in this example was 5mg/mL, and the other steps were the same as in example 1.
Example 3
The concentration of the graphene oxide dispersion in this example was 10mg/mL, and the other steps were the same as in example 1.
Example 4
The addition amount of CNT @ Co in this example is 2% of the GO mass, and the other steps are the same as those in example 1.
Example 5
The addition amount of CNT @ Co in this example is 2% of the GO mass, and the other steps are the same as those in example 2. The flexible self-supporting cathode material prepared in the embodiment is subjected to optical photo collection, as shown in fig. 1 and fig. 2, the electrode sheet has good flexibility, the structure of the electrode sheet cannot be damaged after being bent, and the electrode sheet can be rapidly restored to the previous appearance after external pressure is removed; meanwhile, scanning electron microscopy analysis is carried out, and as can be seen from fig. 3, the sulfur element is not obviously agglomerated and is uniformly filled in the holes in the aerogel, and meanwhile, the lamellar structure of the aerogel skeleton is not damaged after being loaded with sulfur, which indicates that the strength of the aerogel is high.
Example 6
The addition amount of CNT @ Co in this example is 2% of the GO mass, and the other steps are the same as those in example 3.
Example 7
The addition amount of CNT @ Co in this example is 5% of the GO mass, and the other steps are the same as those in example 1.
Example 8
The addition amount of CNT @ Co in this example is 5% of the GO mass, and the other steps are the same as those in example 2.
Example 9
The addition amount of CNT @ Co in this example is 5% of the GO mass, and the other steps are the same as those in example 3.
Example 10
In this example, the concentration of sulfur in the carbon disulfide solution was 20mg/mL, and the other steps were the same as in example 5, to obtain a highly loaded cathode material.
Example 11
In this example, CNT @ Fe was grown by replacing cobalt nitrate hexahydrate with iron nitrate hexahydrate, and the other steps were the same as in example 5.
Example 12
In this example, the cobalt nitrate hexahydrate was replaced by nickel nitrate hexahydrate to grow CNT @ Ni, and the other steps were the same as in example 5.
Example 13
In this example, the Co-doped carbon nanotubes in example 5 were replaced with Co-doped carbon nanofibers (with a diameter of 50-300nm and a length of 5-15 μm), the addition amount was 2% of the mass of GO, the active material was replaced with sodium sulfide, and sodium sulfide was very sensitive to water and oxygen and is susceptible to deliquescence reaction, so it was necessary to disperse the sodium sulfide in an ethanol solution in a glove box, immerse the prepared aerogel material in the ethanol solution, evaporate the ethanol solution by heating, and finally hot-pressed to obtain a flexible self-supporting anode using sodium sulfide as an active material.
Comparative example 1
Aerogel prepared by replacing the doped carbon nanotubes with commercial multiwall carbon nanotubes (MWCNTs) in this comparative example, having a length of 10-30 μm and a diameter of 10-20nm, was prepared by the same procedure as in example 1.
Comparative example 2
Aerogel was prepared by replacing the doped carbon nanotubes with commercial multiwall carbon nanotubes (MWCNTs) in this comparative example, and the other steps were the same as in example 2.
Comparative example 3
Aerogel was prepared by replacing the doped carbon nanotubes with commercial multiwall carbon nanotubes (MWCNTs) in this comparative example, and the other steps were the same as in example 5.
Comparative example 4
In this comparative example, the preparation of the cobalt-doped carbon nanotube-reinforced graphene-based aerogel is the same as that in example 5, except that in the preparation process of the cathode material, the cobalt-doped carbon nanotube-reinforced graphene-based aerogel is ground into powder and then mixed with sublimed sulfur powder according to the mass ratio of 2:8, after the cobalt-doped carbon nanotube-reinforced graphene-based aerogel is uniformly ground, heat preservation treatment is performed at 155 ℃ in a tubular furnace for 12 hours to fully diffuse sulfur into the aerogel material, so as to obtain a sulfur-aerogel composite material, and then the following steps are performed: conductive carbon black (SP): grinding the polyvinylidene fluoride (PVDF) in an agate mortar for half an hour according to the ratio of 8:1:1, fully mixing the PVDF, the PVDF and the NMP, adding a certain amount of N-methylpyrrolidone (NMP) to prepare slurry, uniformly coating the slurry on an aluminum foil by using a scraper with the thickness of 150 microns, drying the aluminum foil, and cutting the aluminum foil into round pieces with the diameter of 14 millimeters to prepare the non-self-supporting positive electrode.
Comparative example 5
This comparative example differs from comparative example 4 in that the cobalt-doped carbon nanotube reinforced graphene-based aerogel was replaced with a commercial multiwall carbon nanotube (MWCNT) reinforced graphene-based aerogel.
Comparative example 6
This comparative example is the same as example 10 except that the cobalt-doped carbon nanotube-reinforced graphene-based aerogel was changed to a commercial multiwall carbon nanotube (MWCNT) -reinforced graphene-based aerogel.
Test example
1. The cathode materials in examples 1-12 and comparative examples 1-6 were assembled into lithium sulfur batteries for electrochemical performance testing, and the specific steps were as follows:
and (3) positive electrode: the positive electrode materials in examples 1 to 12 and comparative examples 1 to 6 were used;
negative electrode: a lithium metal wafer with the diameter of 15.6mm and the thickness of 0.45mm is used as a negative electrode;
a diaphragm: punching a polypropylene (PP) diaphragm into a wafer with the diameter of 16mm for use as a diaphragm;
electrolyte solution: in an inert gas protected glove box (wherein the water content is less than 0.1ppm, and the oxygen content is less than 0.1ppm), a lithium-sulfur battery electrolyte is prepared, ethylene glycol dimethyl ether (DME) and 1, 3-Dioxolane (DOL) are mixed according to a volume ratio of 1:1, and then a certain amount of lithium bistrifluoromethylsulfonyl imide (LiTFSI) is added, so that the final concentration of the LiTFSI is 1 mol/L. Then adding lithium nitrate (LiNO) accounting for 2 percent of the total mass of the electrolyte3) Mixing thoroughly and uniformly for use.
2. The positive electrode material of example 13 was used as a positive electrode, and the electrolyte was changed to 1M NaCF3SO3Dissolving in DIGLYDME solution, using metal sodium sheet as cathode, selecting glass fiber as diaphragm,the other battery assembly steps were the same as in examples 1-12.
And (3) manufacturing a CR2032 type button full cell in a glove box filled with argon, assembling the button cell according to the sequence of a negative electrode shell, a lithium sheet, a PP diaphragm, electrolyte, a positive electrode, a steel sheet, a spring piece and a positive electrode shell, and packaging. The battery is tested by adopting a Xinwei test system, and the charging and discharging voltage range is 1.7-2.8V. The cycle performance test was performed at 0.1C rate. The rate performance tests were performed at 0.1C, 0.2C, 0.5C, 1C, 2C, and the test results are shown in table 1, fig. 4, and fig. 5.
Table 1 relevant parameters of positive electrode materials and electrochemical performance test results in examples and comparative examples
The test data in table 1 show that the electrochemical performance of the battery assembled by adding the CNT @ Co positive electrode is better than that of the battery assembled by adding the commercial multiwalled carbon nanotube positive electrode, and the capacity retention rate is higher after 100 times of charge-discharge cycles, which indicates that the introduction of Co has good catalytic and adsorption effects on soluble polysulfide generated in the charge-discharge process of the battery, so that the utilization rate of active substance sulfur can be improved, and the electrochemical performance of the battery can be improved. It can be seen from a comparison of examples 1-9 that the best electrochemical performance is exhibited by the cell when GO is present at a concentration of 5mg/mL and the CNT @ Co is added at 2%.
In addition, as can be seen from the cycle performance test results of example 5 and comparative example 3 in fig. 4, the lithium sulfur battery made of the flexible self-supporting cathode material of the present invention has good cycle performance.
As can be seen from the rate performance test results of example 5 and comparative example 3 in fig. 5, the lithium sulfur battery made of the flexible self-supporting cathode material of the present invention has better rate performance.
The comparison shows that the performance of the battery assembled by the flexible self-supporting anode prepared by using the cobalt-doped carbon nanotube as the graphene-based aerogel additive is obviously improved compared with that of the battery assembled by using the commercial multi-walled carbon nanotube as the additive, and the expected chemical anchoring and electrochemical catalysis effects of the doping of the cobalt element can be proved.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. The utility model provides a flexible self-supporting cathode material which characterized in that, it comprises active material and aerogel skeleton, active material attach in the internal pore structure of aerogel skeleton, active material is simple substance sulphur, lithium sulfide or sodium sulfide, the aerogel skeleton comprises reduced graphene oxide and transition metal doped carbon nanomaterial.
2. The flexible self-supporting cathode material according to claim 1, wherein the transition metal doped carbon nanomaterial is carbon nanotube or carbon nanofiber, and the transition metal comprises one of iron, cobalt, nickel, copper, and zinc.
3. The flexible self-supporting cathode material according to claim 2, wherein the carbon nanotubes have a length of between 5 μm and 100 μm and a diameter of between 30nm and 90 nm;
the carbon nanofiber has a length of 5-15 μm and a diameter of 50-300 nm.
4. A method for preparing a flexible self-supporting positive electrode material according to any one of claims 1 to 3, characterized in that it comprises the following steps:
adding a transition metal-doped carbon nanomaterial into the graphene oxide dispersion liquid for uniform dispersion to obtain a uniform suspension, and freeze-drying the suspension and then carrying out self-propagating combustion reduction to obtain a carbon nanomaterial-doped reinforced graphene-based aerogel;
immersing the carbon nanomaterial-doped reinforced graphene-based aerogel in a solution in which an active substance material is dissolved, completely volatilizing the solution to obtain an aerogel containing the active substance, and carrying out hot pressing and cutting on the aerogel to obtain the flexible self-supporting cathode material.
5. The method of claim 4, wherein the transition metal-doped carbon nanomaterial is a transition metal-doped carbon nanotube, and the transition metal-doped carbon nanotube is prepared by: the metal salt is prepared by mixing metal salt and a carbon source, fully grinding and calcining, wherein the metal salt is nitrate, sulfate or chloride of transition metal.
6. The method according to claim 5, wherein the mass ratio of the metal salt to the carbon source is 1: (5-10).
7. The preparation method according to claim 4, wherein the specific process of the calcination is as follows: heating to 700-900 ℃ at the heating rate of 2-5 ℃/min in the mixed atmosphere of inert gas and hydrogen, and then preserving the heat for at most 5 hours.
8. The preparation method according to claim 4, wherein the concentration of the graphene oxide dispersion is 2.5mg/mL to 10 mg/mL;
the addition amount of the transition metal doped carbon nanomaterial is 1-5% of the mass of the graphene oxide;
in the solution with the dissolved active substance material, the concentration of the active substance material is 10mg/mL-20 mg/mL.
9. The preparation method according to claim 4, wherein the hot pressing comprises the following specific processes: heating and insulating the aerogel for 10-24h, and pressing into a film.
10. Use of a flexible self-supporting positive electrode material according to any one of claims 1 to 3 for the preparation of a lithium-sulphur battery or a room temperature sodium-sulphur battery.
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| CN114614027A (en) * | 2022-02-18 | 2022-06-10 | 三峡大学 | Preparation method of CoFe-S @3D-S-NCNT electrode and quasi-solid zinc-air battery |
| CN114614027B (en) * | 2022-02-18 | 2024-03-15 | 三峡大学 | Preparation method of CoFe-S@3D-S-NCNT electrode and quasi-solid zinc-air battery |
| CN115520955A (en) * | 2022-09-23 | 2022-12-27 | 清华大学 | Biological filler, preparation method and application thereof, and method for removing nitrate in water |
| CN115520955B (en) * | 2022-09-23 | 2023-08-25 | 清华大学 | Biological filler, preparation method and application thereof, and method for removing nitrate in water |
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