Preparation method of expanded graphite

Abstract

Provided are an expanded graphite and a preparation method therefor. The preparation method comprises the following steps: (1) in a protective atmosphere, mixing a graphite powder with a metal peroxid

Description

Tr^liIVTi^ A T 171171 TA ri 1 a 1 L / r IILLLf The present invention belongs to the technical field of carbon materials, and more particularly, 5 relates to a preparation method of an expanded graphite. 26 £3 25 BACKGROUND An expanded graphite (EG) is a novel functional carbon material, which has a characteristic of high thermal conductivity, and may be used as a heat conduction material and a conductive 10 material. The expanded graphite is resistant to high temperature, high pressure and corrosion, and may be used to prepare an advanced sealing material. The expanded graphite may easily adsorb oils, organic molecules and hydrophobic substances, and may be used as an adsorption material with excellent performance. At present, the expanded graphite is widely used in more than 20 fields, such as chemical industry, building materials and environmental protection, with huge demand, and is a research hotspot in the field of materials. A preparation method of an existing expanded graphite is that: a natural flake graphite is processed with an intercalator and then expanded at a high temperature to obtain the expanded graphite, wherein the intercalator is mostly selected from sulfuric acid, nitric acid, phosphoric acid and ammonium persulfate, which leads to that the prepared expanded graphite contains residual 20 harmful elements and substances such as sulfur and sulfide. SUMMARY The present invention aims to solve at least one of the technical problems in the prior art. Therefore, the present invention provides a preparation method of an expanded graphite, the 25 preparation method can effectively avoid harmful elements and substances such as sulfur and sulfide generated during preparation of the expanded graphite, thus reducing environmental pollution. The technical object of the present invention above is achieved by the following technical solutions. 26 03 25 A preparation method of an expanded graphite comprises the following steps of: (1) mixing a graphite powder with a metal peroxide or an alkali metal superoxide and standing under protective atmosphere to obtain a mixed graphite-metal peroxide or graphite-alkali metal superoxide composite material; (2) putting the composite material prepared in step (1) into a liquid medium and 5 reacting to obtain an intercalated graphite; and (3) heating the intercalated graphite prepared in step (2) to prepare the expanded graphite; wherein the metal peroxide is at least one of CaO2, K2O2, Na2O2 or Li2O2; the alkali metal superoxide is at least one of KO2 or NaO2; the liquid medium is at least one of water, formic acid, acetic acid, propionic acid, hydrochloric acid, carbonic acid, citric acid, hydrofluoric acid, malic 10 acid, gluconic acid, lactic acid, benzoic acid, acrylic acid, stearic acid, hydrosulphuric acid, hypochlorous acid or boric acid; and a mass ratio of the graphite powder to the metal peroxide or the alkali metal superoxide in step (1) is 1:1 to 20:1. Preferably, the standing in step (1) lasts for 12 hours to 24 hours. Preferably, the heating in step (3) is carried out at l,000°C to l,500°C, and lasts for 15 seconds to 30 seconds. Preferably, a particle size of the graphite powder ranges from 80 meshes to 100 meshes. Preferably, the graphite powder is obtained by washing, drying and sieving leached residues of a waste lithium ion battery. The leached residues of the waste lithium ion battery are remaining leached residues after dissolving and leaching a preprocessed electrode material to allow a valuable 20 metal in an active substance to enter a solution in a form of ion, and filtering the solution. Preferably, the washing refers to washing to be neutral. Preferably, the drying is carried out at 50°C to 60°C. The present invention has the beneficial effects as follows: (1) compared with an existing preparation method of an expanded graphite, the obtained 25 expanded graphite of the preparation method of the expanded graphite of the present invention has no residual harmful elements and substances such as sulfur and sulfide, thus reducing environmental pollution; (2) according to the preparation method of the expanded graphite of the present invention, the graphite is used as a raw material, other highly active metal peroxide and / or alkali metal superoxide 30 is used as an intercalation material, hydrogen peroxide is generated based on the reaction of the metal peroxide and / or the alkali metal superoxide with the liquid medium to oxidize the graphite, positive charges are generated between graphite sheets, and under repelling interaction of the positive charges, a spacing between the graphite sheets is gradually increased, and meanwhile, a large amount of oxygen is generated and released when the metal peroxide and / or the alkali metal superoxide reacts with the liquid medium to further increase expansion of the graphite sheets, so that the finally prepared expanded graphite has a large expanding volume; and (3) according to the preparation method of the expanded graphite of the present invention, the graphite in the leached residues of the waste lithium ion battery is used as a raw material, and recycled to prepare the expanded graphite, which is simple in process and easy for industrial production, and meanwhile, an anode graphite in a waste lithium ion battery material is recycled with high assignment, which can not only solve a pollution problem of the leached residues, but also extract the graphite from the leached residues as the raw material to prepare the expanded graphite, thus realizing resource reuse of the leached residues of the waste lithium ion battery. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a SEM graph of an expanded graphite prepared in Embodiment one of the present disclosure. DETAILED DESCRIPTION The present invention is further described hereinafter with reference to the specific embodiments. Embodiment one: A preparation method of an expanded graphite, comprised the following steps of: (1) washing leached residues of a waste lithium ion battery, drying the leached residues in an oven at 60°C, and sieving the leached residues with an 80-mesh sieve to obtain a graphite powder; (2) stirring and mixing the graphite powder with CaO2 according to a mass ratio of 10: 1, stirring and then repeatedly folding and rolling the mixture until the mixture was evenly mixed, and then placing the mixture in argon for 12 hours to obtain an evenly mixed graphite-CaO2 composite material; (3) taking the mixed material above out of the argon, and putting the mixed material into a propionic acid solution, wherein CaO2 and propionic acid reacted rapidly to generate gas, and the composite material expanded rapidly, dispersing in the propionic acid, ultrasonically processing the solution for 1 hour after finishing the reaction, then repeatedly washing the composite material, and subjecting the composite material to extract filtration and separation to obtain an intercalated graphite; and (4) transferring the intercalated graphite into a resistance furnace at l,200°C for heating for 20 seconds to prepare the expanded graphite. 5 An expanded graphite, prepared by the preparation method above. It was measured that an expansion volume of the expanded graphite was 250 ml / g. A SEM graph of the expanded graphite is shown in FIG 1, and it can be seen from FIG. 1 that the expanded graphite prepared by the preparation method of the expanded graphite of the present invention has a loose structure. 10 Embodiment two: A preparation method of an expanded graphite, comprised the following steps of: (1) washing leached residues of a waste lithium ion battery, drying the leached residues in an oven at 60°C, and sieving the leached residues with a 100-mesh sieve to obtain a graphite powder; (2) stirring and mixing the graphite powder with Na2O2 according to a mass ratio of 12: 1, stirring and then repeatedly folding and rolling the mixture until the mixture was evenly mixed, and then placing the mixture in argon for 15 hours to obtain an evenly mixed graphite-Na2O2 composite material; (3) taking the mixed material above out of the argon, and putting the mixed material into water, wherein Na2O2 and water reacted rapidly to generate gas, and the composite material expanded 20 rapidly, dispersing in the water, ultrasonically processing the solution for 1 hour after finishing the reaction, then repeatedly washing the composite material, and subjecting the composite material to extract filtration and separation to obtain an intercalated graphite; and (4) transferring the intercalated graphite into a resistance furnace at l,200°C for heating for 20 seconds to prepare the expanded graphite. 25 An expanded graphite, prepared by the preparation method above. It was measured that an expansion volume of the expanded graphite was 270 ml / g. Embodiment three: A preparation method of an expanded graphite, comprised the following steps of: (1) washing leached residues of a waste lithium ion battery, drying the leached residues in an 30 oven at 60°C, and sieving the leached residues with an 80-mesh sieve to obtain a graphite powder; (2) stirring and mixing the graphite powder with K2O2 according to a mass ratio of 15: 1, stirring and then repeatedly folding and rolling the mixture until the mixture was evenly mixed, and then placing the mixture in argon for 20 hours to obtain an evenly mixed graphite-K2O2 composite material; (3) taking the mixed material above out of the argon, and putting the mixed material into a 0.1 mol / L hydrochloric acid solution, wherein K2O2 and hydrochloric acid reacted rapidly to generate gas, and the composite material expanded rapidly, dispersing in the hydrochloric acid, ultrasonically processing the solution for 1 hour after finishing the reaction, then repeatedly washing the composite material, and subjecting the composite material to extract filtration and separation to obtain an intercalated graphite; and (4) transferring the intercalated graphite into a resistance furnace at 1,200°C for heating for 20 seconds to prepare the expanded graphite. An expanded graphite, prepared by the preparation method above. It was measured that an expansion volume of the expanded graphite was 260 ml / g. Embodiment four: A preparation method of an expanded graphite, comprised the following steps of: (1) washing leached residues of a waste lithium ion battery, drying the leached residues in an oven at 60°C, and sieving the leached residues with an 80-mesh sieve to obtain a graphite powder; (2) stirring and mixing the graphite powder with KO2 according to a mass ratio of 20: 1, stirring and then repeatedly folding and rolling the mixture until the mixture was evenly mixed, and then placing the mixture in argon for 24 hours to obtain an evenly mixed graphite-KO2 composite material; (3) taking the mixed material above out of the argon, and putting the mixed material into a saturated carbonic acid solution, wherein KO2 and carbonic acid reacted rapidly to generate gas, and the composite material expanded rapidly, dispersing in the carbonic acid solution, ultrasonically processing the solution for 1 hour after finishing the reaction, then repeatedly washing the composite material, and subjecting the composite material to extract filtration and separation to obtain an intercalated graphite; and (4) transferring the intercalated graphite into a resistance furnace at l,200°C for heating for 20 seconds to prepare the expanded graphite. An expanded graphite, prepared by the preparation method above. It was measured that an expansion volume of the expanded graphite was 320 ml / g. 26 03 25 Embodiment five: A preparation method of an expanded graphite, comprised the following steps of: (1) washing leached residues of a waste lithium ion battery, drying the leached residues in an oven at 60°C, and sieving the leached residues with an 80-mesh sieve to obtain a graphite powder; 5 (2) stirring and mixing the graphite powder with NaCh according to a mass ratio of 20: 1, stirring and then repeatedly folding and rolling the mixture until the mixture was evenly mixed, and then placing the mixture in argon for 24 hours to obtain an evenly mixed graphite-NaO2 composite material; (3) taking the mixed material above out of the argon, and putting the mixed material into water, 10 wherein NaO2 and water reacted rapidly to generate gas, and the composite material expanded rapidly, dispersing in the water, ultrasonically processing the solution for 1 hour after finishing the reaction, then repeatedly washing the composite material, and subjecting the composite material to extract filtration and separation to obtain an intercalated graphite; and (4) transferring the intercalated graphite into a resistance furnace at l,200°C for heating for 20 seconds to prepare the expanded graphite. An expanded graphite, prepared by the preparation method above. It was measured that an expansion volume of the expanded graphite was 335 ml / g. Embodiment six: A preparation method of an expanded graphite, comprised the following steps of: 20 (1) washing leached residues of a waste lithium ion battery, drying the leached residues in an oven at 60°C, and sieving the leached residues with an 80-mesh sieve to obtain a graphite powder; (2) stirring and mixing the graphite powder with Li2O2 according to a mass ratio of 20: 1, stirring and then repeatedly folding and rolling the mixture until the mixture was evenly mixed, and then placing the mixture in argon for 24 hours to obtain an evenly mixed graphite-Li2O2 composite 25 material, (3) taking the mixed material above out of the argon, and putting the mixed material into a 2% citric acid solution, wherein Li2O2 and citric acid reacted rapidly to generate gas, and the composite material expanded rapidly, dispersing in the citric acid solution, ultrasonically processing the solution for 1 hour after finishing the reaction, then repeatedly washing the composite material, and 30 subjecting the composite material to extract filtration and separation to obtain an intercalated graphite; and 26 03 25 (4) transferring the intercalated graphite into a resistance furnace at l,200°C for heating for 20 seconds to prepare the expanded graphite. An expanded graphite, prepared by the preparation method above. It was measured that an expansion volume of the expanded graphite was 320 ml / g. 5 Comparative Example one: A preparation method of an expanded graphite, comprised the following steps of: (1) washing leached residues of a waste lithium ion battery, drying the leached residues in an oven at 60°C, and sieving the leached residues with an 80-mesh sieve to obtain a graphite powder; (2) putting the graphite powder into a mixed solution of concentrated sulfuric acid and 10 concentrated nitric acid according to a solid-liquid ratio of 1 g: 150 ml, wherein a ratio of the concentrated sulfuric acid to the concentrated nitric acid in the mixed solution was 3: 1, adding ammonium persulfate as an intercalator for reacting for 10 hours under stirring, filtering the solution after finishing the reaction, and adjusting pH to be equal to 7 by water washing for several times to obtain an intercalated graphite; and (3) placing the intercalated graphite in argon, and roasting the intercalated graphite at 900°C for 0.5 hours to obtain the expanded graphite. An expanded graphite, prepared by the preparation method above. It was measured that an expansion volume of the expanded graphite was 220 ml / g. In Comparative Example one, the sulfuric acid is used as the intercalator and an oxidant, which 20 is subjected to oxidative intercalation with a mixed solution of the nitric acid as an oxidant, assisted by the ammonium persulfate as an intercalator, to obtain the expanded graphite. In Comparative Example one, the ammonium persulfate needs to be additionally added as the intercalator, and the expansion volume of the obtained expanded graphite is only 220 ml / g. In the present invention, an alkali product of the reaction of the metal peroxide and / or the alkali metal superoxide with the 25 liquid medium is used as the intercalator, without adding other intercalators. Compared with Comparative Example one, the expanded graphite prepared by the present invention is above 250 ml / g, so that a larger expansion volume is obtained, and addition amounts of other impurities or pollutants are reduced, thus having a simple process and a, industrialization prospect.

Claims

1. A preparation method of an expanded graphite, comprising the following steps of:(1) mixing a graphite powder with a metal peroxide or an alkali metal superoxide and standing under protective atmosphere to obtain a mixed graphite-metal peroxide or graphite-5 alkali metal superoxide composite material;(2) putting the composite material prepared in step (1) into a liquid medium and reacting to obtain an intercalated graphite; and(3) heating the intercalated graphite prepared in step (2) to prepare the expanded graphite;1020wherein the metal peroxide is at least one of CaO2, K2O2, Na2O2 or Li2O2; the alkali metal superoxide is at least one of KO2 or NaO2; the liquid medium is at least one of water, formic acid, acetic acid, propionic acid, hydrochloric acid, carbonic acid, citric acid, hydrofluoric acid, malic acid, gluconic acid, lactic acid, benzoic acid, acrylic acid, stearic acid, hydrosulphuric acid, hypochlorous acid or boric acid; and a mass ratio of the graphite powder to the metal peroxide or the alkali metal superoxide in step (1) is 1:1 to 20:1.

2. The preparation method of the expanded graphite according to claim 1, wherein the standing in step (1) lasts for 12 hours to 24 hours.

3. The preparation method of the expanded graphite according to claim 1, wherein the heating in step (3) is carried out at l,000°C to l,500°C, and lasts for 15 seconds to 30 seconds.

4. The preparation method of the expanded graphite according to claim 1, wherein a particle size of the graphite powder ranges from 80 meshes to 100 meshes.

5. The preparation method of the expanded graphite according to claim 1, wherein the graphite powder is obtained by washing, drying and sieving leached residues of a waste lithium ion battery.

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