CN116040627A - Porous carbon, composite material, diaphragm modification material and application - Google Patents

Porous carbon, composite material, diaphragm modification material and application Download PDF

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CN116040627A
CN116040627A CN202211656485.0A CN202211656485A CN116040627A CN 116040627 A CN116040627 A CN 116040627A CN 202211656485 A CN202211656485 A CN 202211656485A CN 116040627 A CN116040627 A CN 116040627A
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sulfide
porous carbon
diaphragm
drying
inert gas
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曹菲菲
蒋思捷
徐艳松
伍翠霞
陈恒
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Huazhong Agricultural University
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/30—Active carbon
    • C01B32/312—Preparation
    • C01B32/342—Preparation characterised by non-gaseous activating agents
    • C01B32/348—Metallic compounds
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/30—Active carbon
    • C01B32/312—Preparation
    • C01B32/318—Preparation characterised by the starting materials
    • C01B32/324—Preparation characterised by the starting materials from waste materials, e.g. tyres or spent sulfite pulp liquor
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/30—Active carbon
    • C01B32/312—Preparation
    • C01B32/336—Preparation characterised by gaseous activating agents
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • 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

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Abstract

The invention belongs to the field of energy storage materials, and in particular relates to porous carbon, a composite material, a diaphragm modification material and application thereof, wherein the porous carbon is prepared from agricultural wastes through a carbonization-activation method, and metal sulfide particles are compounded with the porous carbon through a load-annealing mode. The membrane modification layer prepared by coating the obtained material on the surface of a commercial membrane can inhibit the shuttle effect of polysulfide in a lithium sulfur and sodium sulfur battery through a capture-catalytic conversion mechanism, so that the service life of the battery is prolonged; in lithium ion batteries, lithium metal batteries and sodium ion batteries, the wettability of the electrolyte can be improved, the ion flux is uniform, and the generation of dendrites to pierce through a diaphragm is effectively prevented. The invention has simple operation, can realize the disposal and high-value utilization of agricultural wastes, and provides a new idea for the disposal of organic solid wastes and the research and development of high-performance secondary batteries.

Description

Porous carbon, composite material, diaphragm modification material and application
Technical Field
The invention belongs to the field of energy storage materials, and particularly relates to porous carbon, a composite material, a diaphragm modification material and application.
Background
Organic matter discarded in the agricultural production process is called agricultural waste. It is estimated that the amount of agricultural waste in China is increasing at a rate of 5-10% per year, outputting about 9 billion tons of straw-like agricultural waste per year, of which about 2 billion tons are not utilized; the nitrogen and phosphorus production amounts of the raw livestock and poultry wastes produced each year are 1.229 multiplied by 10 respectively 7 t and 2.046X10 6 t, the comprehensive utilization rate is lower than 60%, most of the materials are directly abandoned and burnt in situ, and the ecological environment is destroyed.
Alkali metal sulfur cells (lithium sulfur cells, sodium sulfur cells) are of great interest because of their high theoretical capacity and high energy density. However, the shuttle effect and poor redox reaction kinetics of long chain polysulfide ions during charge and discharge have hindered the commercial development of batteries. In addition, the aperture (50-500 nm) of the current commercial polypropylene diaphragm is far larger than the dynamic diameter (> 1.6 nm) of polysulfide ions, so that the shuttle effect cannot be effectively inhibited, and the long-cycle stability and the rate performance of the sulfur anode are further affected.
Disclosure of Invention
According to the defects of the prior art, the invention provides the porous carbon, the composite material, the diaphragm modification material and the application, a new way and a solution are effectively developed for the subsequent treatment of agricultural wastes, the expansion production can be realized, the prepared porous carbon has the characteristics of rich surface active functional groups and metal-heteroatom co-doping, and the performance of a plurality of types of secondary batteries can be generally improved by further loading metal sulfide and then using the porous carbon as the diaphragm modification material. In addition, the scheme for constructing the diaphragm modification layer is utilized to solve the problem of capacity rapid decay caused by the shuttle effect in lithium sulfur and sodium sulfur batteries and the problem of battery safety caused by dendrite growth in other secondary batteries, and has good ecological benefit and economic benefit.
Through extensive research, 1) the inventors have found that by selecting different activators toAnd optimizing technical parameters such as treatment atmosphere, treatment temperature, feeding ratio and the like, and can convert agricultural wastes into the agricultural wastes with specific surface area of 800-3500m by using a carbonization-activation strategy 2 The hierarchical porous structure of the porous carbon can promote the rapid transmission of electrolyte and ions, and the shuttle of polysulfide ions is blocked by utilizing physical interactions such as electrostatic adsorption and the like. In addition, the catalyst has larger specific surface area, is an ideal host for a catalyst with high catalytic activity, can effectively inhibit the catalyst from being deactivated due to agglomeration or adsorption of a large amount of polysulfide ions, provides a larger reaction interface for the conversion of the polysulfide ions, and effectively anchors the dissolved polysulfide ions to accelerate the catalytic conversion efficiency. And has wide application value in the fields of catalysis, energy storage and environmental remediation. 2) Furthermore, the inventor finds that after the obtained porous carbon material is subjected to heteroatom doping and transition metal sulfide loading, the high-value utilization of resources can be realized at the same time, the performance of the alkali metal sulfur battery is improved, the electrochemical performance of the alkali metal sulfur battery is further improved, the preparation method has great development advantages, and the preparation method can be used for preparing a diaphragm modified layer material with good electrochemical performance, accelerates the charge-discharge reaction kinetics, and improves the battery capacity. 3) The membrane modification layer formed by the membrane modification material after application has rich surface pores and functional groups, better wettability with electrolyte, good ionic conduction on an interface, and can effectively and uniformly flux ions and reduce dendrite formation. Meanwhile, compared with a polymer membrane, the membrane modification layer has certain rigidity, and can effectively avoid battery short circuit caused by the penetration of dendrites through the membrane, so that the membrane modification layer has great application potential in the field of other secondary batteries (such as lithium ion batteries, lithium metal batteries and sodium ion batteries).
The invention specifically provides porous carbon, which is prepared by mixing biomass material and activating agent with agricultural waste as biomass material, and then placing the mixture in a reaction vessel, and performing activation heat treatment under the protection of inert gas;
wherein the agricultural waste is at least one of silkworm excrement, basswood, fungus residues, orange peel, wheat straw, rice straw, corn straw, miscanthus and ramie, and is preferably silkworm excrement;
the activator is at least one of zinc chloride, phosphoric acid, potassium ferrate, potassium hydroxide, ferric chloride, ferric nitrate and water vapor, preferably potassium hydroxide.
As a preferable scheme, the mass ratio of the biomass material to the activating agent is 1:0.1 to 6, preferably 1:4, a step of; in addition, when the activator is potassium ferrate, the concentration of the potassium ferrate solution is 0.01-0.4M, preferably 0.3M; when zinc chloride is selected as the activator, the concentration of the zinc chloride solution is 1-10M, preferably 5M; when phosphoric acid is used as the activator, the concentration of phosphoric acid is 1 to 85wt%, preferably 50wt%.
The inert gas is nitrogen, argon or hydrogen-argon mixed gas, preferably argon, and the flow rate of the inert gas is 0.1-2L/min, preferably 1L/min; the temperature of the activation heat treatment is 200-1500 ℃, preferably 800 ℃, the heating rate is 1-20 ℃/min, preferably 3 ℃/min, and the time of the activation heat treatment is 0.5-10h, preferably 3h.
Preferably, the agricultural waste is subjected to pretreatment, and the pretreatment step is cleaning and drying;
the cleaning is at least one of water washing, hydrochloric acid washing, sulfuric acid washing, nitric acid washing, hydrofluoric acid washing, sodium hydroxide washing, potassium hydroxide alkaline washing and ethanol washing, preferably acid washing, more preferably hydrochloric acid washing;
the drying temperature is 40-150 ℃, preferably 80 ℃, and the drying time is 6-72h, preferably 48h.
As a preferred scheme, depending on the type of agricultural waste, some agricultural waste with larger particle size after drying needs further crushing and sieving, and the particle size of the crushed powder is 50-400 meshes, preferably 100 meshes. And for some agricultural wastes with smaller particle sizes, such as silkworm excrement, fungus residues and the like, crushing and sieving are not needed.
Preferably, depending on the type of activator, the activator is readily reactive with impurities (calcium magnesium silicon, etc.) present in the biomass material, such as potassium hydroxide, potassium ferrate, etc. The pretreated agricultural waste is subjected to pre-carbonization heat treatment under the protection of inert gas before being mixed with an activating agent; wherein the inert gas is nitrogen, argon or hydrogen-argon mixed gas, preferably argon; the flow rate of the inert gas is 0.1-1L/min, preferably 1L/min; the temperature of the pre-carbonization heat treatment is 200-1500 ℃, preferably 500 ℃, the heating rate is 1-20 ℃/min, preferably 5 ℃/min, and the pre-carbonization heat treatment time is 0.5-10h, preferably 1h.
The porous carbon provided by the invention has the advantages that the carbonization-activation process is further used for cooperatively controlling the heat treatment process (such as atmosphere, heating rate, treatment temperature and treatment time) and the type and proportion of the doped activating agent, so that the morphology of the prepared precursor and the specific surface area of the material can be regulated and the electrochemical performance of the precursor can be improved. Biomass porous carbon with different physicochemical characteristics can be obtained by changing the kind of biomass treated by utilizing its natural morphology and elemental composition. The present inventors have found that the specific surface area of the porous carbon obtained can be significantly increased by using an activator in the system of the present invention, and the specific surface area of the porous carbon obtained is distributed in the range of 800-3500m 2 Between/g, the biomass can be converted into carbon lattices which can be embedded with various endogenous non-carbon elements in the combined biomass in a directional manner in the heat treatment process by combining the reaction characteristics of different activators or modified on the surface of porous carbon in a form of functional groups, so that rich active sites can be provided for the catalytic and adsorption processes in subsequent application. By further loading sulfide on porous carbon, the application potential of the porous carbon in the lithium-sulfur battery catalytic material can be improved.
The invention also provides a composite material, which is prepared by mixing the porous carbon and sulfide in a solvent, vacuum-filtering the mixture, drying filter residues, and annealing under the protection of inert gas.
Preferably, the sulfide is cobalt disulfide, sodium sulfide, potassium sulfide, zinc sulfide, magnesium sulfide, ferrous sulfide, manganese sulfide, lead sulfide, cadmium sulfide, antimony sulfide, bismuth sulfide, molybdenum sulfide, stannous sulfide, silver sulfide, copper sulfide, nickel sulfide, calcium sulfide, strontium sulfide, barium sulfide, preferably cobalt disulfide; the solvent is ethanol, glycol, dimethylformamide, ethylene glycol monomethyl ether, butanol, octanol or octyl acetate; the inert gas is nitrogen, argon or hydrogen-argon mixed gas, preferably argon, and the gas flow rate is 0.1-1L/min, preferably 1L/min; the annealing treatment temperature is 200-1500 ℃, preferably 600 ℃, the heating rate is 1-20 ℃/min, preferably 5 ℃/min, and the annealing treatment time is 0.5-10h, preferably 2h.
The sulfide can be directly selected from the sulfides in the mixing process with the porous carbon, or can be prepared by mixing and heat treating a sulfur source and transition metal salt in a high-boiling-point solvent, wherein the sulfur source is sulfur powder, thiourea or cysteine, and thiourea is preferable; the transition metal salt is a cobalt source, and the cobalt source is cobalt chloride, cobalt nitrate or cobalt acetate, preferably cobalt chloride; the high boiling point solvent is ethylene glycol, dimethylformamide, ethylene glycol monomethyl ether, butanol, octanol or octyl acetate, preferably ethylene glycol; the heat treatment temperature is 80-300 ℃, preferably 150 ℃, the reaction time is 12-24 hours, preferably 12 hours, and the heating mode is hydrothermal, water bath or oil bath, preferably oil bath; the stirring mode is magnetic stirring, and the stirring speed is 0-1500rpm, preferably 300rpm.
The invention also provides a diaphragm decorative material, which is obtained by mixing the composite material with the conductive agent, the adhesive and the solvent and grinding the mixture into slurry.
Preferably, the conductive agent is at least one of Super-P, superconducting carbon black, acetylene black and ketjen black, and preferably Super-P; the binder is at least one of polyvinylidene fluoride (PVDF), sodium carboxymethylcellulose (CMC) and Styrene Butadiene Rubber (SBR), and preferably polyvinylidene fluoride; the solvent is at least one of ultrapure water, N-methyl pyrrolidone (NMP) and ethanol, and preferably N-methyl pyrrolidone; the mass ratio of the composite material to the conductive agent to the binder is 8:1:1, and the mass of the solvent is 1-10 times, preferably 5 times, of the total mass of the composite material, the conductive agent and the binder.
The invention also provides application of the diaphragm modification material, the diaphragm modification material is compounded on the surface of the diaphragm and dried to obtain a diaphragm modification layer, the diaphragm modification layer is applied to a secondary battery, and the secondary battery mainly comprises a lithium sulfur battery, a sodium sulfur battery, other types of lithium ion batteries, lithium metal batteries, sodium ion batteries and the like; the operating temperature of the secondary battery is-20 to 80 deg.c, preferably 25 deg.c.
Wherein the material of the diaphragm is polyethylene, polypropylene, glass fiber or cellulose, preferably polypropylene, the number of layers of the diaphragm is 1-3, preferably 1, the diameter of the diaphragm is 10-50mm, preferably 12-19mm, most preferably 19mm; the composite process of the diaphragm decorative material and the diaphragm is knife coating, spraying and spin coating, preferably knife coating; the drying mode is vacuum drying, freeze drying or air drying, preferably air drying, and the drying temperature is 25-200deg.C, preferably 50deg.C; the thickness of the separator-modifying material after drying is 1 to 100. Mu.m, preferably 15. Mu.m.
The invention has the following advantages:
(1) The invention can realize the high-value utilization of agricultural wastes, solve the problem of environmental pollution caused by improper disposal mode and generate considerable economic benefit. The existing agricultural waste converted products have the defects of low added value, poor quality and the like. The invention converts agricultural wastes into porous carbon with high specific surface area, and is applied as a catalyst carrier, so that the performance advantage of biomass is effectively utilized, and the invention has great economic benefit.
(2) Compared with the traditional catalyst carriers such as graphene, carbon nano tubes and the like, the porous carbon prepared by the method has obvious cost advantage, can be directly obtained by a carbonization-activation two-step method or a biomass one-step activation method, and has the potential of expanding production. After the sulfide is loaded, the catalytic performance is further improved.
(3) The porous carbon prepared by carbonization-activation two-step method or biomass direct activation is characterized by high specific surface area, and the original doping of non-carbon element improves the intrinsic adsorption capacity and catalytic activity. In the heat treatment process of the supported sulfide, the high specific surface area provides a good place for the growth of crystals, and the dispersibility and the catalytic activity of the supported sulfide are improved. Effectively inhibit the catalyst from being deactivated due to agglomeration or adsorption of a large amount of polysulfide ions, provide a larger reaction interface for the conversion of the polysulfide ions, and effectively anchor the dissolved polysulfide ions to accelerate the catalytic conversion efficiency.
(4) Compared with other types of carriers, the porous carbon also has a larger contribution in the anchoring and conversion processes of polysulfide, firstly, the graphitization degree of the porous carbon is increased in the pyrolysis process, and the defect that the conductivity of elemental sulfur and discharge products thereof is poor is overcome. Secondly, biomass itself has a large amount of non-carbon elements, can assist in construction of a porous carbon beneficial structure in carbonization-activation process, polar hetero atoms are mainly beneficial to improving catalytic performance of the porous carbon, and metal salts are mainly beneficial to improving graphitization degree of the material. Thirdly, in the activation process, a large number of micropores, mesopores and macropores are formed on the surface of the carbon material, which is favorable for fixing polysulfide by physical action and facilitating rapid transmission of ions. Fourth, the specific surface area of the membrane modification layer is large, active sites are rich, the weight is light, and the total mass of the battery is not increased remarkably.
(5) The porous carbon loaded with the metal sulfide, which is prepared by the invention, is mixed with the conductive agent, the adhesive and the solvent, and then the diaphragm modification layer can be obtained by simply grinding and coating the porous carbon on a commercial diaphragm, so that the porous carbon is suitable for mass production, combines the stabilizing effect of the porous carbon on the battery cathode, and can be further popularized to lithium ion batteries, sodium ion batteries, other types of lithium metal batteries and the like in the application field.
Drawings
FIG. 1 is a transmission electron microscope image of a bacterial dreg derived porous carbon prepared by a carbonization-potassium hydroxide activation method;
FIG. 2 is a transmission electron microscope image of silkworm excrement derived porous carbon prepared by a carbonization-potassium hydroxide activation method;
FIG. 3 is a scanning electron microscope image of silkworm excrement derived porous carbon loaded with cobalt sulfide;
FIG. 4 is a graph of charge and discharge curves for a lithium sulfur battery assembled using different separators at 0.2C;
FIG. 5 is a long cycle diagram of a lithium sulfur battery assembled using different separators at 0.2C;
FIG. 6 is 0.5mA/cm 2 Constant current charge and discharge curve graphs of lithium symmetric batteries assembled by using different diaphragms under current density.
FIG. 7 is a nitrogen adsorption-desorption isotherm plot of bacterial dreg carbon activated with 0.3M potassium ferrate.
Detailed Description
The invention is further described below with reference to examples and figures.
Example 1:
the agricultural and forestry waste in this embodiment is silkworm excrement, and the silkworm excrement is only one of the agricultural wastes, and if the requirements on the structure and the element composition of the biomass are met, the corresponding agricultural waste is selected. The cobalt dichloride described in this example is only one of the supported materials, and other types of catalysts may be supported on the porous carbon support depending on the nature of the reaction to be catalyzed. The method of the embodiment can also be applied to the treatment of other organic solid wastes, and the application field of the product can be expanded to the development of devices of other secondary batteries and the non-energy storage field with the requirement for carbon materials.
Construction of a membrane-modified interlayer is believed to be an effective way to inhibit the shuttle effect, whereas cobalt disulfide is a catalytic species widely used in interlayers, with a strong affinity for polysulfides. However, cobalt disulfide has poor conductivity (6.7X10 3 S/cm, 300K) so that the electron transfer process of the sulfur anode in the oxidation-reduction reaction cannot be effectively mediated, and cobalt disulfide is easy to generate agglomeration phenomenon in the charge-discharge process, so that the catalytic activity of the cobalt disulfide is obviously reduced along with the increase of the cycle number.
In order to improve the above problem, the present embodiment takes the following measures: and cleaning the silkworm excrement biomass raw material with ultrapure water to remove superfluous impurities on the surface, placing the dried biomass raw material in a tube furnace, heating to 500 ℃ at a heating rate of 5 ℃/min under argon atmosphere, and preserving heat for 1h. After the material is cooled to room temperature, the carbonized silkworm excrement and potassium hydroxide powder (mass ratio=1:4) are taken and ground uniformly in a mortar to be fully mixed, and then the mixture is placed in a tube furnace to be heated to 800 ℃ at 3 ℃/min under Ar atmosphere, and the temperature is kept for 3 hours. Transferring the cooled product into a beaker, slowly dropwise adding dilute hydrochloric acid while stirring until the solution becomes acidic, stirring at room temperature for 12h, filtering the activated material to neutrality by distilled water, and then placing in a blast oven at 80 ℃ for drying treatment, wherein the structural characteristics of the material are shown in figure 2.
242mg CoCl was taken 2 ·6H 2 O, 170mg of thiourea and 150mg of silkworm excrement carbon are added into 70mL of glycol solution, the temperature of the oil bath is 150 ℃, the magnetic stirring is kept at 300rpm, and after heating for 12 hours, the mixture is cooled, filtered and dried. And (3) annealing the dried sample for 2 hours at 600 ℃ under the argon atmosphere at the heating rate of 5 ℃/min to prepare the composite material, wherein the structural characteristics of the material are shown in figure 3.
Weighing the composite material, acetylene black and polyvinylidene fluoride according to the mass ratio of 8:1:1, adding a proper amount of N-methyl pyrrolidone, and grinding uniformly in a mortar. The slurry was then coated onto the surface of a commercial septum with a doctor blade, and the coated septum was dried in an oven at 50 ℃ and sliced into discs 19mm in diameter. And matching the sulfur anode and the lithium cathode loaded on the CMK-3 to assemble the button lithium sulfur battery. The battery performance is shown in fig. 4-6.
Example 2:
and cleaning the orange peel biomass raw material with ultrapure water to remove superfluous impurities on the surface, crushing, placing the dried biomass raw material into a tube furnace, heating to 500 ℃ at a heating rate of 5 ℃/min under an argon atmosphere, and preserving heat for 1h. After the material cooled to room temperature, the carbonized orange peel and potassium hydroxide powder (mass ratio=1:4) were taken and ground uniformly in a mortar to mix them thoroughly, then placed in a tube furnace at 5 ℃/min to 800 ℃ under Ar atmosphere, and kept for 2 hours. Transferring the cooled product into a beaker, slowly dropwise adding dilute hydrochloric acid while stirring until the solution becomes acidic, stirring at room temperature for 12 hours, filtering the activated material to be neutral by distilled water, and then placing the material in a blast oven at 80 ℃ for drying treatment.
The other steps are the same as in example 1.
Example 3:
washing a fungus dreg biomass raw material (solid waste after mushroom cultivation) with ultrapure water to remove superfluous impurities on the surface, soaking the fungus dreg biomass raw material in dilute hydrochloric acid with the mass concentration of 10wt% for 24 hours to remove the impurities, washing the fungus dreg biomass raw material with ultrapure water to be neutral, drying, placing the dried biomass raw material in a tube furnace, heating to 500 ℃ at a heating rate of 3 ℃/min under argon atmosphere, and preserving heat for 1 hour. After the material was cooled to room temperature, the carbonized bacterial residue and potassium hydroxide powder (mass ratio=1:4) were taken and thoroughly mixed in a container, then placed in a tube furnace, heated to 800 ℃ at 3 ℃/min under Ar atmosphere, and kept for 3 hours. Transferring the cooled product into a beaker, slowly dropwise adding dilute hydrochloric acid while stirring until the solution becomes acidic, stirring at room temperature for 12h, filtering the activated material to neutrality by distilled water, and then placing in a blast oven at 80 ℃ for drying treatment, wherein the structural characteristics of the material are shown in figure 1.
291mg of cobalt nitrate hexahydrate, 64mg of sulfur powder and 150mg of fungus dreg carbon are taken and added into 70mL of glycol solution, the temperature of the oil bath is 150 ℃, the magnetic stirring is kept at 300rpm, and after heating for 12 hours, the mixture is cooled, filtered and dried. And (3) annealing the dried sample for 2 hours at 600 ℃ at a heating rate of 5 ℃/min under the argon atmosphere to prepare the composite material.
The other steps are the same as in example 1.
Example 4:
the same as in example 1, except that the porous carbon-supported sulfide was manganese sulfide.
170mg of MnSO 4 ·5H 2 O was dissolved in a mixed solution of 8mL of ethanol and 12mL of water, followed by adding 170mg of porous carbon of silkworm excrement, magnetically stirring at 300rpm at room temperature for 10 hours, and drying. And (3) annealing the dried material for 2 hours at 600 ℃ under the argon atmosphere at the heating rate of 5 ℃/min to prepare the porous carbon composite material loaded with manganese sulfide. The other steps are the same as in example 1.
Example 5:
the same as in example 1, except that the separator modification layer obtained was applied to other lithium metal batteries, and the positive electrode material was elemental substances of elements of the sixth main group or the seventh main group of the periodic table, such as selenium, iodine, and the like. Taking lithium selenium battery and lithium iodine battery as examples, the method mainly solves the shuttle problem of the discharge intermediate product polyselenide and polyiodide, improves the overall conductivity of the anode material, prevents side reaction with the lithium metal cathode, and causes rapid capacity decay. Meanwhile, as the material has certain rigidity, dendrites can be prevented from penetrating through the diaphragm to cause short circuit of the battery. The membrane modification layer is positioned on one side or two sides of the membrane.
The other steps are the same as in example 1.
Example 6:
the same as in example 1, except that the separator modification layer obtained was applied to a lithium ion battery, and the positive electrode material was lithium iron phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganate (lithium aluminate) and ternary composite materials thereof. The main functions are as follows: the wettability of the diaphragm and the electrolyte is improved, the lithium ion flux is uniform, the phenomenon of lithium precipitation generated by the negative electrode is prevented, the growth of lithium dendrites is inhibited, and dendrites are prevented from penetrating through the diaphragm. The membrane modification layer is positioned on one side or two sides of the membrane.
The other steps are the same as in example 1.
Example 7:
the same as in example 1, except that the resulting separator modification layer was applied to a sodium ion battery. The positive electrode material is Na x MO 2 (M is transition metal element such as Fe, co, ni, mn, cr, ti, etc.), na x M[M’(CN) 6 ]y·zH 2 O, (M and M' are transition metals such as Fe, co, ni, mn, cu, zn), polyanion positive electrode (sodium iron sulfate, sodium vanadium fluorophosphate, and sodium vanadium phosphate), etc., and its main functions are: the wettability of the diaphragm and the electrolyte is improved, the flux of sodium ions is uniform, the phenomenon of sodium precipitation generated by the negative electrode is prevented, the reversible storage of sodium ions is promoted, the growth of sodium dendrites is inhibited, and the dendrites are prevented from penetrating through the diaphragm. The membrane modification layer is positioned on one side or two sides of the membrane.
The other steps are the same as in example 1.
Example 8:
the same as in example 1, except that the resulting separator modification layer was applied to a (room temperature) sodium sulfur battery, a sodium selenium battery or a sodium iodine battery. The method mainly solves the shuttle problem of discharge intermediate products polysulfide, polyselenide and polyiodide, and prevents side reaction with sodium metal cathode to cause rapid decay of capacity. When the carbon material is applied to a high-temperature sodium-sulfur battery, the heat resistance of the diaphragm material can be improved and the stable operation of the battery can be maintained due to the good heat stability of the carbon material. The membrane modification layer is positioned on one side or two sides of the membrane.
The other steps are the same as in example 1.
Example 9:
the same as in example 3, except that the resulting porous carbon was activated by potassium ferrate. The other steps are the same as in example 3.
The bacterial dreg biomass raw material is cleaned by ultrapure water to remove superfluous impurities on the surface, soaked in dilute hydrochloric acid with the mass concentration of 10wt% for 24 hours to remove the impurities, then washed to be neutral by ultrapure water and dried, the dried biomass raw material is placed in a tube furnace and heated to 500 ℃ at a heating rate of 5 ℃/min under argon atmosphere, and the temperature is kept for 1 hour. After the material is cooled to room temperature, the carbonized bacterial residues and potassium ferrate solution (0.3M) are taken and fully mixed in a container, a proper amount of distilled water is added for stirring for 12 hours, the mixture is dried at 80 ℃, then the dried mixture is placed in a tube furnace, the temperature is raised to 800 ℃ at 5 ℃/min under Ar atmosphere, and the heat is preserved for 2 hours. Transferring the cooled product into a beaker, slowly dropwise adding dilute hydrochloric acid while stirring until the solution becomes acidic, stirring at room temperature for 12 hours, alternately washing with hydrochloric acid and sodium hydroxide solution until filtrate is colorless, filtering the material to be neutral with distilled water, and then placing the material in a blast oven at 80 ℃ for drying treatment to obtain a nitrogen adsorption-desorption isotherm graph of the material, wherein the nitrogen adsorption-desorption isotherm graph is shown in figure 7. The specific surface area of the material is 1911.8m calculated by the instrument according to the BET formula after the test 2 /g。
Comparative example 1:
the same as in example 1, except that the biomass was not subjected to potassium hydroxide activation treatment. The other steps are the same as in example 1. The pore-forming effect of potassium hydroxide is realized mainly by converting carbonaceous substances (amorphous carbon, methyl, methine and the like) into carbon monoxide under the high-temperature condition, and the specific reaction is as follows:
6KOH+2C＝2K+3H 2 +2K 2 CO 3
K 2 CO 3 ＝K 2 O+CO 2
CO 2 +C＝2CO
K 2 CO 3 +2C＝2K+3CO
K 2 O+C＝2K+CO
therefore, the porosity and specific surface area of the carbon material obtained by direct pyrolysis without adding an activator are low, and a large adsorption reaction interface cannot be provided, so that the capacity of adsorbing other substances and supporting a metal catalyst is reduced.
Comparative example 2:
the procedure was as in example 1, except that the resulting porous carbon was directly applied to a separator modification layer of a lithium sulfur battery without cobalt sulfide loading, and the other procedures were the same as in example 1. The battery performance is shown in fig. 5.
In summary, the invention prepares the active carbon with high specific surface area by using a carbonization-activation method, is a good barrier for blocking polysulfide shuttle, and compared with other methods for preparing the active carbon, the active carbon produced by the method is partially graphitized amorphous carbon, and the specific surface area is more than 3000m at most 2 And/g. The method is a universal method for producing the porous carbon with high specific surface area by utilizing agricultural wastes, and has popularization significance. After loading about 10% of the sulphide, the specific surface area can be maintained at about 2000m 2 And/g, which ensures efficient transport of lithium ions in the electrolyte while effectively anchoring polysulfides (fig. 4). Meanwhile, the application of the catalyst in the field of supported catalysts can be expanded by supporting other types of transition metal salt nano particles.
According to the invention, the porous carbon is prepared from agricultural waste and is loaded with cobalt sulfide and then applied to the diaphragm modification layer of the lithium-sulfur battery, so that the shuttle effect in the charge-discharge process can be effectively inhibited, the redox kinetics of the charge-discharge reaction can be accelerated, and the specific capacity and the cycling stability of the lithium-sulfur battery can be improved; the initial capacity of the lithium sulfur battery using the common polypropylene diaphragm in the previous research is about 1200mAh/g, and the sulfur loading capacity is about 1.6mg/cm after the cobalt sulfide-loaded porous carbon is used 2 When the first-round capacity of 0.2C multiplying power can reach more than 1500mAh/g (figures 4-5). In addition, the membrane modification layer has the advantages of improving electrolyte wettability, promoting ion conduction, uniform ion flux and the like, and can improve goldBelongs to the dendrite growth problem in the battery, and has certain application value in lithium ion batteries, lithium metal batteries, sodium ion batteries and sodium metal batteries (figure 6).

Claims (10)

1. A porous carbon, characterized by: the agricultural waste is used as biomass material, the biomass material is mixed with an activating agent and then placed in a reaction vessel, and activated heat treatment is carried out under the protection of inert gas to obtain porous carbon;
wherein the agricultural waste is at least one of silkworm excrement, basswood, fungus residues, orange peel, wheat straw, rice straw, corn straw, miscanthus and ramie;
the activator is at least one of zinc chloride, phosphoric acid, potassium ferrate, potassium hydroxide, ferric chloride, ferric nitrate and water vapor.
2. A porous carbon according to claim 1, wherein: the mass ratio of the biomass material to the activating agent is 1:0.1-6; the inert gas is nitrogen, argon or hydrogen-argon mixed gas, and the flow rate of the inert gas is 0.1-2L/min; the temperature of the activation heat treatment is 200-1500 ℃, the heating rate is 1-20 ℃/min, and the time of the activation heat treatment is 0.5-10h.
3. A porous carbon according to claim 1, wherein: the agricultural waste is subjected to pretreatment, and the pretreatment step is cleaning and drying;
the cleaning is at least one of water washing, hydrochloric acid washing, sulfuric acid washing, nitric acid washing, hydrofluoric acid washing, sodium hydroxide washing, potassium hydroxide alkaline washing and ethanol washing;
the drying temperature is 40-150 ℃ and the drying time is 6-72h.
4. A porous carbon according to claim 4, wherein: the dried agricultural waste can be further crushed and sieved, and the granularity of the crushed powder is 50-400 meshes.
5. A porous carbon according to claim 3 or 4, characterized in that: the pretreated agricultural waste is subjected to pre-carbonization heat treatment under the protection of inert gas before being mixed with an activating agent;
wherein the inert gas is nitrogen, argon or hydrogen-argon mixed gas; the flow rate of the inert gas is 0.1-1L/min; the temperature of the pre-carbonization heat treatment is 200-1500 ℃, the heating rate is 1-20 ℃/min, and the pre-carbonization heat treatment time is 0.5-10h.
6. A composite material, characterized in that the porous carbon of claim 1 and sulfide are mixed in a solvent, then the mixture is filtered in vacuum, filter residues are taken and dried, and annealing treatment is carried out under the protection of inert gas, thus obtaining the porous carbon-sulfide composite material.
7. The composite material of claim 6, wherein the sulfide is cobalt disulfide, sodium sulfide, potassium sulfide, zinc sulfide, magnesium sulfide, ferrous sulfide, manganese sulfide, lead sulfide, cadmium sulfide, antimony sulfide, bismuth sulfide, molybdenum sulfide, stannous sulfide, silver sulfide, copper sulfide, nickel sulfide, calcium sulfide, strontium sulfide, barium sulfide; the solvent is ethanol, glycol, dimethylformamide, ethylene glycol monomethyl ether, butanol, octanol or octyl acetate; the inert gas is nitrogen, argon or hydrogen-argon mixed gas, and the gas flow rate is 0.1-1L/min; the annealing treatment temperature is 200-1500 ℃, the heating rate is 1-20 ℃/min, and the annealing treatment time is 0.5-10h.
8. A membrane modification material, characterized in that the membrane modification material is obtained by mixing the composite material according to claim 6 with a conductive agent, a binder and a solvent and grinding the mixture into slurry.
9. The separator-modifying material of claim 8, wherein the conductive agent is at least one of Super-P, superconducting carbon black, acetylene black, ketjen black; the binder is at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose and styrene-butadiene rubber; the solvent is at least one of ultrapure water, N-methyl pyrrolidone and ethanol; the mass ratio of the composite material to the conductive agent to the binder is 8:1:1, and the mass of the solvent is 1-10 times of the total mass of the composite material, the conductive agent and the binder.
10. The use of the membrane modification material of claim 8, wherein the membrane modification material is compounded on the surface of a membrane and dried to obtain a membrane modification layer, and the membrane modification layer is used in a secondary battery;
wherein the diaphragm is made of polyethylene, polypropylene, glass fiber or cellulose, the number of layers of the diaphragm is 1-3, and the diameter of the diaphragm is 10-50mm; the process of compounding the diaphragm decorative material and the diaphragm is knife coating, spraying and spin coating; the drying mode is vacuum drying, freeze drying or air drying, and the drying temperature is 25-200 ℃; the thickness of the membrane modification material after drying is 1-100 μm.
CN202211656485.0A 2022-12-22 2022-12-22 Porous carbon, composite material, diaphragm modification material and application Pending CN116040627A (en)

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