CN108807808B - Preparation method of biomass carbon aerogel modified lithium-sulfur battery diaphragm - Google Patents
Preparation method of biomass carbon aerogel modified lithium-sulfur battery diaphragm Download PDFInfo
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- CN108807808B CN108807808B CN201810998056.9A CN201810998056A CN108807808B CN 108807808 B CN108807808 B CN 108807808B CN 201810998056 A CN201810998056 A CN 201810998056A CN 108807808 B CN108807808 B CN 108807808B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/431—Inorganic material
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention discloses a special diaphragm for a biomass charcoal aerogel modified lithium-sulfur battery, which comprises a diaphragm body and a modified coating coated on the surface of one side, close to a positive electrode, of the diaphragm body, wherein the modified coating comprises shaddock peel-based biomass charcoal aerogel, a conductive agent and a binder, and the modified coating has a porous structure. The modified coating pomelo peel-based biomass charcoal aerogel material of the special diaphragm and the porous barrier layer of the conductive agent can allow lithium ions to pass through, can also have certain blocking and adsorption effects on polysulfide generated in the process of the redox reaction of the anode, and has more advantages on the electrochemical performance and the cycle performance of the battery. The invention also discloses a preparation method of the special diaphragm for the biomass carbon aerogel modified lithium-sulfur battery, which is simple, does not need to develop a novel diaphragm, can be used only by coating a layer of modified material on the conventional commercial normal diaphragm, and greatly saves time and cost. The invention also discloses a lithium-sulfur battery assembled by adopting the special diaphragm.
Description
Technical Field
The invention belongs to the field of lithium ion batteries, and particularly relates to a biomass carbon aerogel modified special diaphragm for a lithium sulfur battery, a preparation method of the diaphragm and the lithium sulfur battery.
Background
The lithium-sulfur battery is a secondary battery with sulfur as a positive electrode material and a metal lithium sheet as a negative electrode material, and the theoretical specific capacity and the theoretical specific energy of the battery are 1675mAh/g and 2600Whk/g respectively. And the sulfur element has higher content in the crust of the earth, is an environment-friendly element, has low cost and has good application prospect in the fields of electric vehicles, consumer electronics and the like. However, the lithium-sulfur battery has certain problems in the application process, and the most important problem is that the intermediate discharge product of the lithium-sulfur battery can be dissolved in the organic electrolyte, so that the viscosity of the electrolyte is increased, and the ionic conductivity is reduced. Polysulfide ions can migrate between the positive electrode and the negative electrode to generate a shuttle effect, so that active substances are lost and electric energy is wasted, and dissolved polysulfide can spread to the negative electrode across the diaphragm to react with the negative electrode, so that an SEI (solid electrolyte interface) film of the negative electrode is damaged.
Therefore, blocking or inhibiting the shuttling effect of polysulfides has been one of the most effective methods for improving the performance of lithium-sulfur batteries. For example, chinese patent CN 105280867 a discloses a method for modifying a lithium sulfur battery separator, which is to coat a modified coating layer added with ketjen black coated metal oxide on a normal commercial separator of a lithium sulfur battery. The porous barrier layer compounded by the nano Ketjen black and the metal oxide can allow lithium ions to pass through, and in addition, the porous barrier layer can also have certain blocking and adsorption effects on polysulfide generated in the oxidation-reduction reaction process of the anode, so that the capacity and long-time cycle performance of the lithium-sulfur battery are greatly improved. However, the barrier layers formed by these materials have limited porosity, greatly limit the adsorption of polysulfide, and have high cost, so it is necessary to develop a material having strong adsorption capacity and low price as the barrier layer of the separator.
Disclosure of Invention
The invention aims to solve the technical problems, overcome the defects and shortcomings in the background technology, and provide a biomass charcoal aerogel modified special diaphragm for a lithium-sulfur battery, which has strong adsorption capacity and low price, a preparation method of the diaphragm and the lithium-sulfur battery formed by using the diaphragm.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
the utility model provides a special diaphragm of living beings charcoal aerogel modified lithium sulphur battery, includes diaphragm body and coating the diaphragm body is close to the modified coating of anodal side surface, the modified coating includes shaddock peel base living beings charcoal aerogel, conductive agent and binder, the modified coating has porous structure.
In the lithium sulfur battery, the loss of polysulfide generates a shuttle effect, thereby causing the loss of active substances and the waste of electric energy, so that the blocking of polysulfide becomes a key for improving the performance of the lithium sulfur battery. Due to the existence of the porous structure of the biomass charcoal-based material, the porous barrier layer formed by the shaddock peel-based biomass charcoal aerogel material and the conductive agent can allow lithium ions to pass through; meanwhile, the biomass carbon-based material has the characteristics of large specific surface area, excellent conductivity and adsorption performance, simple preparation method and the like, and the modified coating prepared from the biomass carbon-based material has certain blocking and adsorption effects on polysulfide generated in the redox reaction process of the lithium-sulfur battery, blocks shuttling of the polysulfide, and effectively inhibits the shuttling effect, so that the capacity and long-time cycle performance of the lithium-sulfur battery are greatly improved.
The biomass carbon aerogel is mainly made of carbon-containing materials, is black in appearance, developed in internal pore structure, large in specific surface area and excellent in adsorption capacity, so that the adsorption capacity of the modified diaphragm porous barrier layer is greatly enhanced, the capacity of the lithium-sulfur battery is improved, and the cycle life of the lithium-sulfur battery is prolonged. Compared with other biomass charcoal materials, the raw material shaddock peel adopted by the shaddock peel-based biomass charcoal aerogel material contains abundant plant fibers and a large number of functional groups such as hydroxyl, carboxyl, amino and the like, and is an adsorption material with good development prospect. The shaddock peel still has very strong adsorption capacity after being made into the biochar, and can effectively adsorb polysulfide in the lithium-sulfur battery. In addition, the shaddock peel is a renewable resource, is very cheap, has wide sources, is easy to obtain, has a relatively simple preparation process, is suitable for commercial production, is applied to a battery, realizes sustainable utilization of resources, and is green, environment-friendly and pollution-free.
The modified coating adopts the shaddock peel-based biomass charcoal aerogel material and the conductive agent, does not adopt expensive metal oxide materials, not only improves the electrochemical performance of the lithium-sulfur battery using the modified diaphragm, but also reduces the production cost of the battery to a certain extent, and is suitable for commercial production.
Preferably, the separator body is a commercial separator Celgard2400, and the thickness of the modified coating is 10-200 μm.
Preferably, the conductive agent is one or more of Ketjen black, acetylene black and Super-P, and the conductive agents can improve the conductivity of the modified coating to a certain extent; the binder is one or more of polyvinylidene fluoride, polyvinyl alcohol and polytetrafluoroethylene, and the modified coating material can be well fixed on the diaphragm body by selecting the binders, so that the modified coating material cannot fall off in long-time circulation of the battery; the mass ratio of the pomelo peel-based biomass charcoal aerogel to the conductive agent to the binder is (5-8) to (1-3) to (2-5).
Preferably, the shaddock peel-based biomass charcoal aerogel is obtained by carrying out hydrothermal reaction on shaddock peel, then carrying out freeze drying on the shaddock peel, and then carrying out pyrolysis in a nitrogen atmosphere.
Preferably, the shaddock peel-based biomass charcoal aerogel is doped with nitrogen elements and boron elements. The electronic structure in the carbon material can be changed by introducing different elements, so that the conductivity of the material is improved. Besides physical blocking and adsorption, chemical adsorption is considered as a means for effectively fixing polysulfide, and nitrogen and boron elements and carbon elements form a certain chemical bond to be introduced to a framework of the pomelo peel-based biomass charcoal aerogel charcoal material, so that the electronic structure of the surface and the interior of the charcoal material can be changed, and the electrical conductivity of the material can be improved. Therefore, the nitrogen and boron element doped carbon material can generate a strong chemical adsorption effect on polysulfide through the effect between charges to a certain extent, so that the polysulfide can be effectively fixed, and the performance of the lithium-sulfur battery is improved.
Based on a general technical concept, the invention also provides a preparation method of the special diaphragm for the biomass carbon aerogel modified lithium-sulfur battery, which comprises the following steps:
(1) performing hydrothermal reaction on the shaddock peel, performing freeze drying, and performing pyrolysis in a nitrogen atmosphere to obtain a shaddock peel-based biomass charcoal aerogel material;
(2) mixing a binder and a solvent to obtain a binder solution, mixing the binder solution with a conductive agent and the shaddock peel-based biomass charcoal aerogel material obtained in the step (1), and mechanically stirring uniformly to obtain coating slurry;
(3) and (3) uniformly coating the coating slurry obtained in the step (2) on one side, close to the positive electrode, of the diaphragm body on a coating machine, and drying to obtain the biomass charcoal aerogel modified special diaphragm for the lithium-sulfur battery.
In the above preparation method, preferably, in the step (1), the hydrothermal reaction specifically includes the following steps: removing hard skin of pomelo peel, cutting into blocks, cleaning, putting into a hydrothermal reaction kettle, carrying out hydrothermal reaction for 8-12 h at 130-200 ℃ in a blast drying oven, then soaking in a hot water bath at 50-80 ℃ for 1-3 days to remove soluble impurities, freezing in an environment at-30-10 ℃ for 12-36 h, and then freeze-drying in a vacuum freeze-drying oven for 12-48 h; the pyrolysis temperature is 600-1000 ℃. The pomelo peel is pyrolyzed within the temperature range of 600-1000 ℃ to obtain a graphitized structure with gap defects, which is important for the conductivity of the material; in addition, hydroxyl, carboxyl and the like groups are pyrolyzed and disappear at the temperature, and the material forms a maximized porous structure.
Preferably, in the step (2), the solvent is one or more of ethanol, acetone and N-methylpyrrolidone; the mass ratio of the binder to the solvent is (1-3) to (10-30); the mechanical stirring speed is 500-1000 r/min, and the stirring time is 2-5 min.
Preferably, in the step (3), the drying temperature is 20-40 ℃, and the drying time is 12-48 h.
Based on a general technical concept, the invention also provides a lithium-sulfur battery, which comprises a positive electrode, a negative electrode, electrolyte and a diaphragm, wherein the diaphragm is the special diaphragm for the biomass carbon aerogel modified lithium-sulfur battery, the positive electrode is a carbon-sulfur composite positive electrode, the negative electrode is a metal lithium sheet, and the electrolyte comprises a mixture of 1, 3-dioxolane and ethylene glycol dimethyl ether, lithium bistrifluoromethylenesulfonate imide and lithium nitrate. In the mixture of the 1, 3-dioxolane and the ethylene glycol dimethyl ether, the volume ratio of the 1, 3-dioxolane to the ethylene glycol dimethyl ether is 1:1, the concentration of lithium bistrifluoromethylenesulfonamide in the electrolyte is 1-3M, and the concentration of lithium nitrate is 0.1-0.3M.
The invention is mainly based on the following invention ideas: the method comprises the steps of selecting a commercial normal diaphragm commonly used for the lithium-sulfur battery as a modification object, using the commercial normal diaphragm as a substrate, coating a porous barrier layer (preferably adopting dual-element doped pomelo peel-based biomass carbon aerogel) containing a pomelo peel-based biomass carbon aerogel material and a conductive agent on the surface of the diaphragm close to the positive electrode side, using the modified diaphragm as a special diaphragm of the lithium-sulfur battery, and using a carbon-sulfur composite material as a positive electrode material to assemble the lithium-sulfur battery.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the special diaphragm for the biomass charcoal aerogel modified lithium sulfur battery, lithium ions can pass through the porous barrier layer of the shaddock peel-based biomass charcoal aerogel material and the conductive agent, and in addition, the diaphragm can have certain barrier and adsorption effects on polysulfide generated in the positive electrode redox reaction process, wherein the shaddock peel-based biomass charcoal aerogel material has a higher specific surface area, so that the shaddock peel-based biomass charcoal aerogel material is endowed with more excellent adsorption capacity, and the addition of the shaddock peel-based biomass charcoal aerogel material is more favorable for adsorbing the polysulfide, has a better effect than the porous barrier layer formed by metal oxide in blocking shuttling of the polysulfide, and has more advantages on the electrochemical performance and the cycle performance of the battery.
2. According to the special diaphragm for the biomass carbon aerogel modified lithium-sulfur battery, the carbon material doped with nitrogen and boron elements is adopted, and a strong chemical adsorption effect can be generated on polysulfide through the effect between charges to a certain extent, so that the polysulfide can be effectively fixed, and the performance of the lithium-sulfur battery is improved.
3. Compared with other porous carbon-based materials, the biomass carbon aerogel modified special diaphragm for the lithium-sulfur battery, disclosed by the invention, has the advantages that the raw material shaddock peel contains abundant plant fibers and a large number of functional groups, such as hydroxyl, carboxyl, amino and the like, so that the diaphragm is an adsorption material with a good development prospect, and the shaddock peel still has strong adsorption capacity after being prepared into biochar, so that polysulfide in the lithium-sulfur battery can be effectively adsorbed; in addition, the shaddock peel is a renewable resource, is very cheap, has wide sources, is easy to obtain, has a relatively simple preparation process, is suitable for commercial production, is applied to a battery, realizes sustainable utilization of resources, and is green, environment-friendly and pollution-free.
4. According to the preparation method, the prepared pomelo peel-based biomass charcoal aerogel material belongs to one biomass charcoal material, the conductivity of the biomass charcoal aerogel material is mainly that graphitized crystals appear in the biomass charcoal aerogel in the carbonization process, and the graphite crystals gradually gather to be orderly along with the increase of the carbonization temperature, so that the conductivity is gradually increased, the pomelo peel-based biomass charcoal aerogel material also has a certain excellent conductivity, and the modified special diaphragm for the lithium-sulfur battery has high conductivity and good chemical stability; the preparation method is simple, does not need to develop a novel diaphragm, can be used only by coating a layer of modified material on the conventional commercial normal diaphragm, and greatly saves time and cost.
5. According to the invention, the battery is assembled by using the biomass carbon aerogel modified special diaphragm for the lithium-sulfur battery, so that the shuttle effect of polysulfide in the lithium-sulfur battery is well inhibited, and the battery has good charge-discharge performance and rate capability.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a scanning electron microscope (a) and a transmission electron microscope (b, c) of the bi-element doped pomelo peel-based biomass charcoal aerogel material prepared in example 1 of the present invention.
Fig. 2 is a voltammogram of a lithium sulfur battery assembled by the bi-element doped biomass charcoal aerogel modified lithium sulfur battery special-purpose membrane prepared in example 1 of the present invention.
Fig. 3 is a cycle performance curve diagram of 500 cycles of the lithium sulfur battery assembled by the biomass charcoal aerogel modified lithium sulfur battery special-purpose diaphragm prepared in the embodiments 1 and 2 of the invention under the condition that the charge-discharge rate is 1C.
Fig. 4 is a cycle performance graph of a lithium sulfur battery assembled by a biomass charcoal aerogel modified lithium sulfur battery special-purpose diaphragm prepared in examples 2, 3 and 4 of the present invention and a lithium sulfur battery prepared in proportion and circulating 200 cycles at a charge-discharge rate of 1C.
Detailed Description
In order to facilitate understanding of the invention, the invention will be described more fully and in detail with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.
Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
Example 1:
the special diaphragm for the double-element doped biomass carbon aerogel modified lithium sulfur battery comprises a commercial diaphragm Celgard2400 body and a modified coating coated on the surface of one side, close to a positive electrode, of the diaphragm body, wherein the modified coating has a porous structure, the mass ratio of the double-element doped shaddock peel based biomass carbon aerogel, a conductive agent Super-P and a binder polyvinylidene fluoride (PVDF) in the modified coating is about 6:1:3, the doped double elements are nitrogen and boron, and the thickness of the modified coating is about 15 micrometers.
The preparation method of the special diaphragm for the lithium-sulfur battery by using the double-element doped shaddock peel-based biomass carbon aerogel modification comprises the following steps:
(1) preparing a double-element doped shaddock peel-based biomass charcoal aerogel material: removing hard skin from pericarpium Citri Grandis, cutting into pieces, washing, placing into a hydrothermal reaction kettle, performing hydrothermal reaction in a forced air drying oven at 180 deg.C for 10 hr, soaking in hot water bath at 70 deg.C for 2 days to remove soluble impurities, freezing at-20 deg.C for 24 hr, and freeze-drying in a vacuum freeze-drying oven for 48 hr; putting the obtained block material into an ammonium borate solution, magnetically stirring for 24 hours, taking out, and freeze-drying for 48 hours again; finally, pyrolyzing the material for 1h at 800 ℃ in a nitrogen atmosphere, and grinding to obtain a powdery double-element doped pomelo peel-based biomass charcoal aerogel material (shown in figure 1);
(2) preparation of binder solution: the adhesive adopted by the commercial normal diaphragm coated by the double-element-doped shaddock-peel-based biomass carbon aerogel is PVDF, the solvent is N-methylpyrrolidone (NMP), the PVDF and the NMP are mixed according to the mass ratio of 1:25, and the mixture is magnetically stirred for about 4 hours to obtain a mixed adhesive solution;
(3) double-element doped shaddock peel-based biomass charcoal aerogel coating commercial normal diaphragm: uniformly mixing 0.09g of the double-element doped pomelo peel-based biomass charcoal aerogel material, 0.015g of Super-P and 1.125g of binder solution (mixed solution of PVDF and NMP) in a beaker, and mechanically stirring in a stirrer for 3min to obtain coating slurry;
(4) and uniformly coating the prepared coating slurry on the surface of the Celgard2400 diaphragm close to the positive electrode side by using a scraper on an automatic coating machine, and drying the coated modified diaphragm at room temperature of 25 ℃ for 24 hours to obtain the special diaphragm for the double-element doped biomass carbon aerogel modified lithium-sulfur battery.
The Mapping scanning results are shown in (a) of FIG. 1, and the TEM results are shown in (b), (c) of FIG. 1. As can be seen from fig. 1, the surface of the bi-element doped pomelo peel-based biomass charcoal presents a regular strip-shaped network structure, and is distributed with non-uniform holes, and the nitrogen element and the boron element are also distributed on the charcoal material uniformly, which indicates that a certain effect is obtained by doping. These results indicate that the bi-element doped shaddock peel-based biomass charcoal generates a structure with holes of different sizes, and the holes have a certain adsorption effect on polysulfide generated in the redox process of the battery.
Example 2:
the invention relates to a special diaphragm for a pure pomelo peel-based biomass carbon aerogel modified lithium sulfur battery, which comprises a commercial diaphragm Celgard2400 body and a modified coating coated on the surface of one side, close to a positive electrode, of the diaphragm body, wherein the modified coating has a porous structure, the mass ratio of the pomelo peel-based biomass carbon aerogel, a conductive agent Super-P and a binder polyvinylidene fluoride (PVDF) in the modified coating is about 6:1:3, and the thickness of the modified coating is about 15 mu m.
The preparation method of the special diaphragm for the pure pomelo peel-based biomass carbon aerogel modified lithium-sulfur battery comprises the following steps:
(1) preparing a pure pomelo peel-based biomass charcoal aerogel material: removing hard skin from pericarpium Citri Grandis, cutting into pieces, washing, placing into a hydrothermal reaction kettle, performing hydrothermal reaction in a forced air drying oven at 180 deg.C for 10 hr, soaking in hot water bath at 70 deg.C for 2 days to remove soluble impurities, freezing at-20 deg.C for 24 hr, and freeze-drying in a vacuum freeze-drying oven for 48 hr; finally, pyrolyzing the material for 1h at 800 ℃ in a nitrogen atmosphere, and grinding to obtain a powdery pure pomelo peel-based biomass charcoal aerogel material;
(2) preparation of binder solution: the adhesive adopted by the commercial normal diaphragm coated by the pure pomelo peel-based biomass carbon aerogel is PVDF, the solvent is NMP, the PVDF and the NMP are mixed according to the mass ratio of 1:25, and the mixture is magnetically stirred for about 4 hours to obtain a mixed adhesive solution;
(3) pure shaddock peel-based biomass charcoal aerogel coated commercial normal membranes: taking 0.09g of the pure shaddock peel-based biomass charcoal aerogel material, 0.015g of Super-P and 1.125g of binder solution (mixed solution of PVDF and NMP) to be uniformly mixed in a beaker, and putting the beaker into a stirrer to be mechanically stirred for 3min to obtain coating slurry;
(4) and (3) uniformly coating the prepared coating slurry on the surface of the Celgard2400 diaphragm close to the positive electrode side by using a scraper on an automatic coating machine, and drying the coated modified diaphragm at room temperature of 25 ℃ for 24 hours to obtain the pure shaddock peel-based biomass carbon aerogel modified special diaphragm for the lithium-sulfur battery.
Data of specific surface area, total pore volume and average pore diameter of the pure pomelo peel-based biomass charcoal aerogel material of the example and the double-element doped pomelo peel-based biomass charcoal aerogel material of the example 1 were measured by BET method, as shown in table 1.
Table 1: data comparison of pure pomelo peel-based biomass charcoal aerogel and double-element doped pomelo peel-based biomass charcoal aerogel materials
Watch with watch1, the specific surface area of the double-element doped pomelo peel carbon aerogel material is formed by undoped 495.66m2g-1Increased to 674.53m2g-1Due to the improvement of the specific surface area of the doped material, the modified coating of the diaphragm plays a role in enhancing the adsorption of polysulfide generated in the oxidation-reduction reaction and plays a certain auxiliary role in the conduction of lithium ions.
Example 3:
the invention relates to a special diaphragm for a pure pomelo peel-based biomass carbon aerogel modified lithium sulfur battery, which comprises a commercial diaphragm Celgard2400 body and a modified coating coated on the surface of one side, close to a positive electrode, of the diaphragm body, wherein the modified coating has a porous structure, the mass ratio of the pomelo peel-based biomass carbon aerogel, a conductive agent Super-P and a binder polyvinylidene fluoride (PVDF) in the modified coating is about 7:1:2, and the thickness of the modified coating is about 15 mu m.
The preparation method of the special diaphragm for the pure pomelo peel-based biomass carbon aerogel modified lithium-sulfur battery comprises the following steps:
(1) preparing a pure pomelo peel-based biomass charcoal aerogel material: removing hard skin from pericarpium Citri Grandis, cutting into pieces, washing, placing into a hydrothermal reaction kettle, performing hydrothermal reaction in a forced air drying oven at 180 deg.C for 10 hr, soaking in hot water bath at 70 deg.C for 2 days to remove soluble impurities, freezing at-20 deg.C for 24 hr, and freeze-drying in a vacuum freeze-drying oven for 48 hr; finally, pyrolyzing the material for 1h at 700 ℃ in a nitrogen atmosphere, and grinding to obtain a powdery pure pomelo peel-based biomass charcoal aerogel material;
(2) preparation of binder solution: the adhesive adopted by the commercial normal diaphragm coated by the pure pomelo peel-based biomass carbon aerogel is PVDF, the solvent is NMP, the PVDF and the NMP are mixed according to the mass ratio of 1:25, and the mixture is magnetically stirred for about 4 hours to obtain a mixed adhesive solution;
(3) pure shaddock peel-based biomass charcoal aerogel coated commercial normal membranes: taking 0.07g of the pure pomelo peel-based biomass charcoal aerogel material, 0.01g of Super-P and 0.52g of binder solution (mixed solution of PVDF and NMP), uniformly mixing in a beaker, and mechanically stirring in a stirrer for 3min to obtain coating slurry;
(4) and (3) uniformly coating the prepared coating slurry on the surface of the Celgard2400 diaphragm close to the positive electrode side by using a scraper on an automatic coating machine, and drying the coated modified diaphragm at room temperature of 25 ℃ for 24 hours to obtain the pure shaddock peel-based biomass carbon aerogel modified special diaphragm for the lithium-sulfur battery.
Example 4:
the invention relates to a special diaphragm for a pure pomelo peel-based biomass carbon aerogel modified lithium sulfur battery, which comprises a commercial diaphragm Celgard2400 body and a modified coating coated on the surface of one side, close to a positive electrode, of the diaphragm body, wherein the modified coating has a porous structure, the mass ratio of the pomelo peel-based biomass carbon aerogel, a conductive agent Super-P and a binder polyvinylidene fluoride (PVDF) in the modified coating is about 5:2:3, and the thickness of the modified coating is about 15 mu m.
The preparation method of the special diaphragm for the pure pomelo peel-based biomass carbon aerogel modified lithium-sulfur battery comprises the following steps:
(1) preparing a pure pomelo peel-based biomass charcoal aerogel material: removing hard skin from pericarpium Citri Grandis, cutting into pieces, washing, placing into a hydrothermal reaction kettle, performing hydrothermal reaction in a forced air drying oven at 180 deg.C for 10 hr, soaking in hot water bath at 70 deg.C for 2 days to remove soluble impurities, freezing at-20 deg.C for 24 hr, and freeze-drying in a vacuum freeze-drying oven for 48 hr; finally, pyrolyzing the material for 1h at 600 ℃ in a nitrogen atmosphere, and grinding to obtain a powdery pure pomelo peel-based biomass charcoal aerogel material;
(2) preparation of binder solution: the adhesive adopted by the commercial normal diaphragm coated by the pure pomelo peel-based biomass carbon aerogel is PVDF, the solvent is NMP, the PVDF and the NMP are mixed according to the mass ratio of 1:25, and the mixture is magnetically stirred for about 4 hours to obtain a mixed adhesive solution;
(3) pure shaddock peel-based biomass charcoal aerogel coated commercial normal membranes: taking 0.075g of the pure shaddock peel-based biomass charcoal aerogel material, 0.03g of Super-P and 1.125g of a binder solution (a mixed solution of PVDF and NMP) to be uniformly mixed in a beaker, and putting the beaker into a stirrer to be mechanically stirred for 3min to obtain coating slurry;
(4) and (3) uniformly coating the prepared coating slurry on the surface of the Celgard2400 diaphragm close to the positive electrode side by using a scraper on an automatic coating machine, and drying the coated modified diaphragm at room temperature of 25 ℃ for 24 hours to obtain the pure shaddock peel-based biomass carbon aerogel modified special diaphragm for the lithium-sulfur battery.
Example 5:
the lithium-sulfur battery comprises a positive electrode, a negative electrode, electrolyte and a diaphragm, wherein the diaphragm is the special diaphragm for the biomass carbon aerogel modified lithium-sulfur battery prepared in the embodiment 1-4, the positive electrode is a carbon-sulfur composite positive electrode, the negative electrode is a metal lithium sheet, and the electrolyte is a mixture containing lithium bistrifluoromethylenesulfonate imide, 1, 3-dioxolane and ethylene glycol dimethyl ether. The preparation method of the lithium-sulfur battery comprises the following steps:
(1) preparing a positive electrode material: putting 1g of Ketjen black powder, 4g of sulfur and 10g of absolute ethyl alcohol into a ball milling tank, alternately rotating the ball milling tank for 4 hours in a positive and negative rotation mode at the rotating speed of 800r/min, taking out the spheroidal graphite tank, putting the spheroidal graphite tank into a 45 ℃ forced air drying oven for drying for 12 hours, then putting the mixture of the Ketjen black and the sulfur into a polytetrafluoroethylene reaction kettle inner container, and putting the mixture into a box-type furnace for heat treatment at 155 ℃ for 10 hours to obtain a Ketjen black-sulfur composite material;
(2) preparing a lithium-sulfur battery positive electrode: uniformly mixing 0.1g of PVDF and 4.9g of 4.9g N-methyl pyrrolidone (NMP), then carrying out magnetic stirring for 4 hours to obtain a binder, uniformly mixing 0.14g of the prepared carbon-sulfur composite anode material, 0.02g of Super-P and 0.5g of the prepared binder, mechanically stirring for 4 minutes at the rotating speed of 800r/min to obtain a mixed slurry, uniformly coating the mixed slurry on a carbon-coated aluminum foil on an automatic coating machine by using a scraper, and drying the coated anode aluminum foil in a blast drying box at 50 ℃ for 24 hours to obtain a carbon-sulfur composite anode;
(3) assembling the lithium-sulfur battery: assembling the carbon-sulfur composite positive electrode obtained in the step (2), the biomass carbon modified special diaphragm for the lithium-sulfur battery prepared in the above embodiments 1-4, the lithium negative electrode and the organic electrolyte into a button lithium-sulfur battery in a glove box with the water oxygen value lower than 1 ppm; wherein the organic electrolytic solution includes: 1M LiTFSI (lithium bistrifluoromethylsulfonimide) +0.1M LiNO3(lithium nitrate) + DOL (1, 3-dioxolane)/DME (ethylene glycol)Alcohol dimethyl ether), the volume ratio of the 1, 3-dioxolane to the glycol dimethyl ether is 1: 1.
The voltammogram of the lithium-sulfur battery assembled by using the membrane special for the bi-element doped biomass charcoal aerogel modified lithium-sulfur battery prepared in example 1 is shown in fig. 2. As can be seen from fig. 2, the reduction peak of the battery of the membrane modified by the bi-element doped pomelo peel carbon aerogel material is 2.02V, and a higher reduction voltage indicates that the kinetics of the chemical reaction inside the battery is improved to a certain extent, which also means that the bi-element doped pomelo peel carbon aerogel material coating has a catalytic effect on sulfur reduction. Meanwhile, the battery with the diaphragm modified by the double-element-doped pomelo peel carbon aerogel material can also be observed to show sharp and higher oxidation and reduction peaks, which shows that the double-element-doped pomelo peel carbon aerogel material coating has good conductivity and improves the internal reaction kinetics of the battery.
The lithium sulfur battery assembled by the biomass carbon aerogel modified lithium sulfur battery special-purpose diaphragm prepared in the above examples 1 to 4 was subjected to cycle performance test under the condition of 1C. The cycle test results of the lithium sulfur batteries assembled with the separators of examples 1 and 2 are shown in fig. 3, and the cycle test results of the lithium sulfur batteries assembled with the separators of examples 2, 3 and 4 are shown in fig. 4.
As can be seen from fig. 3, the first discharge specific capacity of 0.1C of the lithium-sulfur battery assembled by the dual-element-doped pomelo peel carbon aerogel material modified diaphragm in example 1 is 1463.6mAh/g, the discharge specific capacity after 500 cycles of 1C cycle is 586.6mAh/g, and the coulombic efficiency is higher than 98.9%.
As can be seen from FIG. 4, the 0.1C initial specific discharge capacity of the pure pomelo peel carbon aerogel modified diaphragm battery is 1152.6mAh/g, the specific discharge capacity can still reach 567.5mAh/g after 1C circulation for 200 circles, and the coulombic efficiency is higher than 99%.
Comparative example:
a lithium sulfur battery using a separator, which is a common commercial separator, Celgard 2400.
The method for manufacturing the lithium-sulfur battery of the present comparative example includes the steps of:
(1) preparing a positive electrode material: putting 1g of Ketjen black powder, 4g of sulfur and 10g of absolute ethyl alcohol into a ball milling tank, alternately rotating the ball milling tank for 4 hours in a positive and negative rotation mode at the rotating speed of 800r/min, taking out the spheroidal graphite tank, putting the spheroidal graphite tank into a 45 ℃ forced air drying oven for drying for 12 hours, then putting the mixture of the Ketjen black and the sulfur into a polytetrafluoroethylene reaction kettle inner container, and putting the mixture into a box type furnace for heat treatment at 155 ℃ for 10 hours to obtain a Ketjen black-sulfur composite material;
(2) preparing a lithium-sulfur battery positive electrode: 0.1g of PVDF and 4.9g N-methyl pyrrolidone (NMP) are taken and uniformly mixed, magnetic stirring is carried out for 4 hours to obtain a binder, 0.14g of the prepared carbon-sulfur composite anode material, 0.02g of Super-P and 0.5g of the prepared binder are uniformly mixed, mechanical stirring is carried out for 4 minutes at the rotating speed of 800r/min to obtain mixed slurry, a scraper is used for uniformly coating the mixed slurry on a carbon-coated aluminum foil on an automatic coating machine, and the coated anode aluminum foil is put into a blast drying box and dried for 24 hours at the temperature of 50 ℃ to obtain the carbon-sulfur composite anode.
(3) Assembling the lithium-sulfur battery: mixing the carbon-sulfur composite positive electrode obtained in the step (2), a common commercial diaphragm Celgard2400, a lithium negative electrode, an organic electrolyte 1M LiTFSI (lithium bis (trifluoromethyl) sulfenamide) +0.1M LiNO3(lithium nitrate) + DOL (1, 3-dioxolane)/DME (ethylene glycol dimethyl ether), a coin lithium sulfur battery was assembled in a glove box with a water oxygen value of less than 1 ppm.
The lithium sulfur battery prepared in this comparative example was subjected to a cycle performance test at 1C, and the cycle test results are shown in fig. 4. As can be seen from fig. 4, compared with the battery assembled by adding the pure pomelo peel carbon biomass charcoal material modified diaphragm, the cycle performance of the battery using the commercial diaphragm is worse and is reduced to 351.3mAh/g after 200 cycles, and the battery assembled by adopting the pure pomelo peel carbon biomass charcoal material modified diaphragm of the invention has more advantages in electrochemical performance and cycle performance.
By combining the analysis of fig. 3 and fig. 4, the cycle performance and the rate capability of the lithium sulfur battery assembled by the dual-element-doped pomelo peel carbon aerogel material modified diaphragm are greatly improved compared with the battery assembled by the pure pomelo peel-based biomass carbon material modified diaphragm; compared with the battery assembled by the common commercialized diaphragm, the battery assembled by the special diaphragm coated with the shaddock peel-based biomass charcoal modified lithium sulfur battery has greatly improved cycle performance and rate capability.
Claims (4)
1. A preparation method of a biomass charcoal aerogel modified lithium sulfur battery diaphragm comprises a diaphragm body and a modified coating coated on the surface of one side, close to a positive electrode, of the diaphragm body, wherein the modified coating comprises shaddock peel-based biomass charcoal aerogel, a conductive agent and a binder, and the modified coating has a porous structure;
the conductive agent is one or more of Ketjen black, acetylene black and Super-P; the binder is one or more of polyvinylidene fluoride, polyvinyl alcohol and polytetrafluoroethylene; the mass ratio of the pomelo peel-based biomass charcoal aerogel to the conductive agent to the binder is (5-8) to (1-3) to (2-5); the pomelo peel-based biomass carbon aerogel is doped with nitrogen elements and boron elements;
the preparation method comprises the following steps:
(1) removing hard skin from pericarpium Citri Grandis, cutting into pieces, washing, placing into a hydrothermal reaction kettle, performing hydrothermal reaction in a forced air drying oven at 180 deg.C for 10 hr, soaking in hot water bath at 70 deg.C for 2 days to remove soluble impurities, freezing at-20 deg.C for 24 hr, and freeze-drying in a vacuum freeze-drying oven for 48 hr; putting the obtained block material into an ammonium borate solution, magnetically stirring for 24 hours, taking out, and freeze-drying for 48 hours again; finally, pyrolyzing the material for 1h at 800 ℃ in a nitrogen atmosphere, and grinding to obtain a powdery double-element doped pomelo peel-based biomass charcoal aerogel material;
(2) mixing a binder and a solvent to obtain a binder solution, mixing the binder solution with a conductive agent and the double-element doped shaddock peel-based biomass charcoal aerogel material obtained in the step (1), and mechanically stirring uniformly to obtain coating slurry;
(3) and (3) uniformly coating the coating slurry obtained in the step (2) on one side, close to the positive electrode, of the diaphragm body on a coating machine, and drying to obtain the biomass charcoal aerogel modified lithium-sulfur battery diaphragm.
2. The preparation method according to claim 1, wherein the separator body is a commercial separator Celgard2400, and the thickness of the modified coating is 10-200 μm.
3. The preparation method according to claim 1, wherein in the step (2), the solvent is one or more of ethanol, acetone and N-methylpyrrolidone; the mass ratio of the binder to the solvent is (1-3) to (10-30); the mechanical stirring speed is 500-1000 r/min, and the stirring time is 2-5 min.
4. The method according to any one of claims 1 to 3, wherein in the step (3), the drying temperature is 20 to 40 ℃ and the drying time is 12 to 48 hours.
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| CN111785892B (en) * | 2019-04-03 | 2021-10-08 | 中南大学 | Preparation method of lithium-sulfur battery composite diaphragm |
| CN111403659A (en) * | 2020-03-18 | 2020-07-10 | 中国科学技术大学 | Ultrahigh-specific-surface-area carbon aerogel coating diaphragm intermediate layer for lithium-sulfur battery, preparation method of ultrahigh-specific-surface-area carbon aerogel coating diaphragm intermediate layer and lithium-sulfur battery |
| CN113782912A (en) * | 2021-09-15 | 2021-12-10 | 电子科技大学长三角研究院(湖州) | Composite diaphragm modified by rhizopus hypha carbon and preparation method and application thereof |
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