CN105609770A - Preparation method of N-doped graphene - Google Patents
Preparation method of N-doped graphene Download PDFInfo
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- CN105609770A CN105609770A CN201510990999.3A CN201510990999A CN105609770A CN 105609770 A CN105609770 A CN 105609770A CN 201510990999 A CN201510990999 A CN 201510990999A CN 105609770 A CN105609770 A CN 105609770A
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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
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
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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
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- 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
Abstract
The invention provides a preparation method of N-doped graphene, and relates to a preparation method of a battery anode material, and aims at solving the technical problem that with the graphene as a negative electrode of a lithium battery, the discharge capacity is greatly decreased. The method comprises the following steps: (1) preparing a graphene oxide dispersion liquid; (2) preparing a dicyandiamide solution; (3) dropwise adding the dicyandiamide solution to the graphene oxide dispersion liquid and then obtaining a mixed solution; and (4) transferring the mixed solution into a hydrothermal reaction kettle for reaction, carrying out natural cooling to a room temperature, and carrying out centrifuging, washing, dialysis and drying to obtain the N-doped graphene. With the N-doped graphene prepared by the method as the battery anode material, the discharge capacity is kept at 450-1720mAh/g under the current density of 1A/g after 600 cycles; the rate discharge property is stable under the current density of 8A/g; and the specific discharge capacity is 385-580mAh/g. The preparation method of the N-doped graphene belongs to the field of preparation of the battery material.
Description
Technical field
The present invention relates to a kind of preparation method of cell negative electrode material.
Background technology
The development of the development of space technology and the demand of defence equipment and electric automobile and exploitation are to electrochmical power source, and particularly the needs of high-performance secondary cell increase rapidly. The advantages such as open-circuit voltage is high owing to having for lithium ion battery, energy density is large, long service life, memory-less effect, environmental pollution are little and self-discharge rate is low, apply increasingly extensive. But the electrode material of current lithium ion battery can't meet the demand for development of high-power electric tool and electric motor car etc., in the urgent need to exploitation high power capacity, large multiplying power, long-life lithium ion battery electrode material of future generation.
Graphene is that its electron motion speed can reach 1/300 of the light velocity by the tightly packed two dimensional crystal forming of monolayer carbon atom, considerably beyond the movement rate of electronics in general conductor. This make the character of " charge carrier " in Graphene and relativistic " neutrino " closely similar. Meanwhile, due to its special two dimensional crystal structure, high aspect ratio and theoretical specific area (2620m2/ g), and good pliability, chemistry and heat endurance, wide potential window, and excellent mechanical performance, make it have broad prospect of application in energy storage field. As lithium ion battery negative, its theoretical capacity is 2 times of conventional graphite negative pole, can reach 744mAh/g. But it also exists the side reaction of surface functional group and defective bit and electrolyte serious as cathode of lithium battery, negative pole irreversible capacity large (20 circulations, reach～75%[Z.S.Wu of irreversible capacity, W.C.Ren, L.Wen, etal., ACSNano, 2010,4:3187-3193]), coulombic efficiency is low, and discharge capacity significantly decays, and graphene oxide (GO) and graphite-phase after reduction have limited its practical application than the electrical conductivity still problem such as very low.
Summary of the invention
The object of the invention is the technical problem significantly decaying as cathode of lithium battery discharge capacity in order to solve Graphene, a kind of preparation method of N-doped graphene is provided.
A kind of preparation method of N-doped graphene carries out according to following steps:
One, under the condition that is 30kHz～80kHz in frequency, disperse 10min～100min, graphene oxide is distributed in deionized water, obtaining concentration is the graphene oxide dispersion liquid of 0.1mg/mL～10mg/mL;
Two, dicyandiamide is dissolved in water, obtaining concentration is the dicyandiamide solution of 0.2～1.0mol/L;
Three, according to the ratio of the mass ratio of graphene oxide and dicyandiamide 0.5～2 ﹕ 1, dicyandiamide solution is added drop-wise in graphene oxide dispersion liquid, under the condition that is then 10kHz～30kHz in frequency, disperse 10～60min, obtain mixed solution;
Four, mixed solution is proceeded in hydrothermal reaction kettle, be to keep 0.5h～8h under 100 DEG C～250 DEG C conditions in temperature, naturally cool to room temperature, centrifugal, washing, dialysis, dry, obtain N-doped graphene, in N-doped graphene, the doping molar percentage of N is 8～20%.
The atom doped electronegativity of N high (3.5V, carbon is 3.0V), foreign atom diameter is little, between material with carbon element after doping and Li, active force is strong, is conducive to embed Li, forms N-shaped semi-conducting material, alms giver's energy state approaches fermi level, can effectively improve the electronic structure of Graphene, reduces Li+Stopping through the energy of defective bit, and improve the surface chemistry of negative pole/electrolyte interface, increase the coulombic efficiency of circulating battery, reduce the side reaction of circulation first, is more satisfactory material with carbon element foreign atom.
Dicyandiamide, as the dimer of cyanamide, has the chain structure of prolongation, has water-solublely preferably in hot water, and 80 DEG C just can be decomposed and emit lentamente ammonia and cyano group, realizes stable, the Uniform Doped of N in graphite olefinic carbon hexatomic ring. It is as nitrogenous source, and the doping of N is high, and has following advantage:
(1) the N-doped graphene generating can be introduced many topology defects on graphene film, has increased the degree of disorder of graphene sheet layer, thereby has improved the lithium storage content of graphene film;
(2) not only the atom doped level of N is high, and is mainly wherein that pyridine type N is atom doped, can greatly improve the reversible specific capacity of electrode. Therefore, the N-doped graphene that adopts dicyandiamide to prepare as N source has higher electrical conductivity and defect sturcture, not only can improve its reversible specific capacity and high rate performance as electrode material of lithium battery, but also can be widely used in photocatalysis, ultracapacitor, Li-air-fuel battery etc., there is the performance more excellent than Graphene.
The present invention adopts the Hummers legal system of modification for graphene oxide, is reacted and obtains N-doped graphene with dicyandiamide by graphene oxide under hydrothermal condition, is a kind of desirable lithium ion battery negative material. N-doped graphene prepared by employing the present invention is as cell negative electrode material, under 1A/g current density, 600 times cyclic discharge capacity remains on 450mAh/g～1720mAh/g, under 8A/g current density, multiplying power discharging property is stable, and specific discharge capacity is 385mAh/g～580mAh/g.
The N-doped graphene material of adopting preparation in this way has the following advantages as lithium ion battery negative material:
1, selected raw material economics environmental protection;
2, this material has higher specific capacity, high rate performance and cyclical stability;
Preparation equipment and process are simple, easy operating, and cost is low, and suitability for industrialized is produced.
Detailed description of the invention
Technical solution of the present invention is not limited to following cited detailed description of the invention, also comprises any combination between each detailed description of the invention.
Detailed description of the invention one: the preparation method of a kind of N-doped graphene of present embodiment carries out according to following steps:
One, under the condition that is 30kHz～80kHz in frequency, disperse 10min～100min, graphene oxide is distributed in deionized water, obtaining concentration is the graphene oxide dispersion liquid of 0.1mg/mL～10mg/mL;
Two, dicyandiamide is dissolved in water, obtaining concentration is the dicyandiamide solution of 0.2～1.0mol/L;
Three, according to the ratio of the mass ratio of graphene oxide and dicyandiamide 0.5～2 ﹕ 1, dicyandiamide solution is added drop-wise in graphene oxide dispersion liquid, under the condition that is then 10kHz～30kHz in frequency, disperse 10～60min, obtain mixed solution;
Four, mixed solution is proceeded in hydrothermal reaction kettle, be to keep 0.5h～8h under 100 DEG C～250 DEG C conditions in temperature, naturally cool to room temperature, centrifugal, washing, dialysis, dry, obtain N-doped graphene, in N-doped graphene, the doping molar percentage of N is 8～20%.
The preparation method of the graphene oxide described in present embodiment step 1 is as follows:
The first step: the sodium nitrate of 0.5g is put into the 46mL concentrated sulfuric acid (98wt.%), and reaction is controlled in 0 DEG C of ice bath, the about 30min of magnetic agitation;
Second step: 1g natural flake graphite is slowly joined in the concentrated sulfuric acid solution of sodium nitrate to magnetic agitation 2h;
The 3rd step: slowly add the potassium permanganate of 2～8g, the joining day is controlled at 0.5g/10min again, controls bath temperature below 10 DEG C, and potassium permanganate all adds rear continuation to stir 90min;
The 4th step: subsequently 50 DEG C of hot water of 46mL are poured in the solution of step 3 gained, in this process, bath temperature is controlled at 98 DEG C, and is incubated 1h;
The 5th step: beaker is taken out from water-bath, cooling after, add 20mLH2O2(30wt.%), continue to stir 30min;
The 6th step: wash 1 time with 5wt.% watery hydrochloric acid, then washed several times with water, dialysis is until pH value of solution=6-7 obtains graphene oxide colloidal sol;
The 7th step: get above-mentioned graphene oxide colloidal sol, freeze drying or dry in 60 DEG C of drying boxes, obtains graphene oxide.
Detailed description of the invention two: what present embodiment was different from detailed description of the invention one is that in step 4, baking temperature is 50 DEG C～90 DEG C. Other is identical with detailed description of the invention one.
Detailed description of the invention three: what present embodiment was different from one of detailed description of the invention one or two is that the frequency described in step 1 is 40kHz～70kHz. Other is identical with one of detailed description of the invention one or two.
Detailed description of the invention four: what present embodiment was different from one of detailed description of the invention one to three is that the frequency described in step 1 is 50kHz～60kHz. Other is identical with one of detailed description of the invention one to three.
Detailed description of the invention five: the concentration of what present embodiment was different from one of detailed description of the invention one to four the is dispersion liquid of graphene oxide described in step 1 is 0.5mg/mL～8mg/mL. Other is identical with one of detailed description of the invention one to four.
Detailed description of the invention six: the concentration of what present embodiment was different from one of detailed description of the invention one to five the is dispersion liquid of graphene oxide described in step 1 is 2mg/mL～6mg/mL. Other is identical with one of detailed description of the invention one to five.
Detailed description of the invention seven: mass ratio 0.8～1.5 ﹕ 1 of what present embodiment was different from one of detailed description of the invention one to six is in step 3 graphene oxide and dicyandiamide. Other is identical with one of detailed description of the invention one to six.
Detailed description of the invention eight: mass ratio 1.5 ﹕ 1 of what present embodiment was different from one of detailed description of the invention one to seven is in step 3 graphene oxide and dicyandiamide. Other is identical with one of detailed description of the invention one to seven.
Detailed description of the invention nine: what present embodiment was different from one of detailed description of the invention one to eight is in step 4 is to keep 1h～6h under 110 DEG C～230 DEG C conditions in temperature. Other is identical with one of detailed description of the invention one to eight.
Detailed description of the invention ten: what present embodiment was different from one of detailed description of the invention one to nine is in step 4 is to keep 2h～5h under 100 DEG C～250 DEG C conditions in temperature. Other is identical with one of detailed description of the invention one to nine.
Adopt following experimental verification effect of the present invention:
Experiment one:
The preparation method of N-doped graphene carries out according to following steps:
One, under the condition that is 50kHz in frequency, disperse 30min, 5mg graphene oxide is distributed in deionized water, obtaining concentration is the graphene oxide dispersion liquid of 0.2mg/mL;
Two, 2mol dicyandiamide is dissolved in water, obtaining concentration is the dicyandiamide solution of 0.5mol/L;
Three, according to the ratio of the mass ratio of graphene oxide and dicyandiamide 0.5 ﹕ 1, dicyandiamide solution is added drop-wise in graphene oxide dispersion liquid, under the condition that is then 10kHz in frequency, disperse 20min, obtain mixed solution;
Four, mixed solution being proceeded in hydrothermal reaction kettle, is to keep 4h under 150 DEG C of conditions in temperature, naturally cools to room temperature, and centrifugal, washing, dialysis, dry, obtain N-doped graphene, and in N-doped graphene, the doping molar percentage of N is 15.92%.
The preparation method of the graphene oxide described in this experimental procedure one is as follows:
The first step: the sodium nitrate of 0.5g is put into the 46mL concentrated sulfuric acid (98wt.%), and reaction is controlled in 0 DEG C of ice bath, the about 30min of magnetic agitation;
Second step: 1g natural flake graphite is slowly joined in the concentrated sulfuric acid solution of sodium nitrate to magnetic agitation 2h;
The 3rd step: slowly add the potassium permanganate of 5g, the joining day is controlled at 0.5g/10min again, controls bath temperature below 10 DEG C, and potassium permanganate all adds rear continuation to stir 90min;
The 4th step: subsequently 50 DEG C of hot water of 46mL are poured in the solution of step 3 gained, in this process, bath temperature is controlled at 98 DEG C, and is incubated 1h;
The 5th step: beaker is taken out from water-bath, cooling after, add 20mLH2O2(30wt.%), continue to stir 30min;
The 6th step: wash 1 time with 5wt.% watery hydrochloric acid, then washed several times with water, dialysis is until pH value of solution=6-7 obtains graphene oxide colloidal sol;
The 7th step: get above-mentioned graphene oxide colloidal sol, freeze drying or dry in 60 DEG C of drying boxes, obtains graphene oxide.
The transmission electron microscope photo of the N-doped graphene material of this experiment preparation, can see thinly as silk, and there is a large amount of folds on surface; The XPS spectrum analysis of this material, the doping of its N element is 15.92at.%; N-doped graphene material prepared by this experiment and binding agent polyvinylidene fluoride (PVdF) in mass ratio 90 ﹕ 10 are dispersed in NMP, form cathode slurry, be coated on Cu paper tinsel as working electrode, lithium sheet is auxiliary and reference electrode, electrolyte is general lithium-ion battery electrolytes, as 1MLiPF6/ DMC:EC:DEC=1:1:1, prepare 2025 type button cells, under the current density of 1A/g, the cycle performance curve of this battery, the discharge capacity first that can find out this battery can reach 1300mAh/g, along with the increase specific discharge capacity of cycle-index reduces gradually, but after 600 circulations, specific discharge capacity still remains on 450mAh/g. The multiplying power discharging property curve of battery, at 0.5A/g, 1A/g, 2A/g, under the current density of 4A/g and 8A/g, its specific discharge capacity is stabilized in respectively 864mAh/g, 737mAh/g, 594mAh/g, 563mAh/g and 440mAh/g.
Experiment two:
The preparation method of N-doped graphene carries out according to following steps:
One, under the condition that is 30kHz in frequency, disperse 10min, 4mg graphene oxide is distributed in deionized water, obtaining concentration is the graphene oxide dispersion liquid of 0.4mg/mL;
Two, 1mol dicyandiamide is dissolved in water, obtaining concentration is the dicyandiamide solution of 0.2mol/L;
Three, according to the ratio of the mass ratio of graphene oxide and dicyandiamide 0.6 ﹕ 1, dicyandiamide solution is added drop-wise in graphene oxide dispersion liquid, under the condition that is then 20kHz in frequency, disperse 10min, obtain mixed solution;
Four, mixed solution being proceeded in hydrothermal reaction kettle, is to keep 2h under 120 DEG C of conditions in temperature, naturally cools to room temperature, and centrifugal, washing, dialysis, dry, obtain N-doped graphene, and in N-doped graphene, the doping molar percentage of N is 11.6%.
The preparation method of the graphene oxide described in this experimental procedure one is as follows:
The first step: the sodium nitrate of 0.5g is put into the 46mL concentrated sulfuric acid (98wt.%), and reaction is controlled in 0 DEG C of ice bath, the about 30min of magnetic agitation;
Second step: 1g natural flake graphite is slowly joined in the concentrated sulfuric acid solution of sodium nitrate to magnetic agitation 2h;
The 3rd step: slowly add the potassium permanganate of 5g, the joining day is controlled at 0.5g/10min again, controls bath temperature below 10 DEG C, and potassium permanganate all adds rear continuation to stir 90min;
The 4th step: subsequently 50 DEG C of hot water of 46mL are poured in the solution of step 3 gained, in this process, bath temperature is controlled at 98 DEG C, and is incubated 1h;
The 5th step: beaker is taken out from water-bath, cooling after, add 20mLH2O2(30wt.%), continue to stir 30min;
The 6th step: wash 1 time with 5wt.% watery hydrochloric acid, then washed several times with water, dialysis is until pH value of solution=6-7 obtains graphene oxide colloidal sol;
The 7th step: get above-mentioned graphene oxide colloidal sol, freeze drying or dry in 60 DEG C of drying boxes, obtains graphene oxide.
N-doped graphene prepared by this experiment and binding agent polyvinylidene fluoride (PVdF) in mass ratio 90 ﹕ 10 are dispersed in NMP, form cathode slurry, be coated on Cu paper tinsel as working electrode, lithium sheet is auxiliary and reference electrode, electrolyte is general lithium-ion battery electrolytes, as 1MLiPF6/ DMC:EC:DEC=1:1:1, preparation 2025 type button cells, discharge and recharge with the electric current of 1A/g, and discharge capacity is 1200mAh/g first. With the high current charge-discharge of 8A/g, after repeatedly circulating, its Capacitance reserve is at 385mAh/g.
Experiment three:
The preparation method of N-doped graphene carries out according to following steps:
One, under the condition that is 80kHz in frequency, disperse 90min, 8mg graphene oxide is distributed in deionized water, obtaining concentration is the graphene oxide dispersion liquid of 1mg/mL;
Two, 3mol dicyandiamide is dissolved in water, obtaining concentration is the dicyandiamide solution of 1.0mol/L;
Three, according to the ratio of the mass ratio of graphene oxide and dicyandiamide 0.4 ﹕ 1, dicyandiamide solution is added drop-wise in graphene oxide dispersion liquid, under the condition that is then 30kHz in frequency, disperse 60min, obtain mixed solution;
Four, mixed solution is proceeded in hydrothermal reaction kettle, be to keep 0.5h～8h under 100 DEG C～250 DEG C conditions in temperature, naturally cool to room temperature, centrifugal, washing, dialysis, 80 DEG C are dry, obtain N-doped graphene, in N-doped graphene, the doping molar percentage of N is 18.5%.
The preparation method of the graphene oxide described in this experimental procedure one is as follows:
The first step: the sodium nitrate of 0.5g is put into the 46mL concentrated sulfuric acid (98wt.%), and reaction is controlled in 0 DEG C of ice bath, the about 30min of magnetic agitation;
Second step: 1g natural flake graphite is slowly joined in the concentrated sulfuric acid solution of sodium nitrate to magnetic agitation 2h;
The 3rd step: slowly add the potassium permanganate of 5g, the joining day is controlled at 0.5g/10min again, controls bath temperature below 10 DEG C, and potassium permanganate all adds rear continuation to stir 90min;
The 4th step: subsequently 50 DEG C of hot water of 46mL are poured in the solution of step 3 gained, in this process, bath temperature is controlled at 98 DEG C, and is incubated 1h;
The 5th step: beaker is taken out from water-bath, cooling after, add 20mLH2O2(30wt.%), continue to stir 30min;
The 6th step: wash 1 time with 5wt.% watery hydrochloric acid, then washed several times with water, dialysis is until pH value of solution=6-7 obtains graphene oxide colloidal sol;
The 7th step: get above-mentioned graphene oxide colloidal sol, freeze drying or dry in 60 DEG C of drying boxes, obtains graphene oxide.
N-doped graphene prepared by this experiment and binding agent polyvinylidene fluoride (PVdF) in mass ratio 90 ﹕ 10 are dispersed in NMP, form cathode slurry, be coated on Cu paper tinsel as working electrode, lithium sheet is auxiliary and reference electrode, electrolyte is general lithium-ion battery electrolytes, as 1MLiPF6/ DMC:EC:DEC=1:1:1, preparation 2025 type button cells, discharge and recharge with the electric current of 1A/g, and discharge capacity is 1650mAh/g first. With the high current charge-discharge of 8A/g, after repeatedly circulating, its Capacitance reserve is at 540mAh/g.
Experiment four:
The preparation method of N-doped graphene carries out according to following steps:
One, under the condition that is 80kHz in frequency, disperse 90min, 8mg graphene oxide is distributed in deionized water, obtaining concentration is the graphene oxide dispersion liquid of 1mg/mL;
Two, 3mol dicyandiamide is dissolved in water, obtaining concentration is the dicyandiamide solution of 1.0mol/L;
Three, according to the ratio of the mass ratio of graphene oxide and dicyandiamide 0.3 ﹕ 1, dicyandiamide solution is added drop-wise in graphene oxide dispersion liquid, under the condition that is then 30kHz in frequency, disperse 60min, obtain mixed solution;
Four, mixed solution being proceeded in hydrothermal reaction kettle, is to keep 8h under 200 DEG C of conditions in temperature, naturally cools to room temperature, and centrifugal, washing, dialysis, 80 DEG C are dry, obtain N-doped graphene, and in N-doped graphene, the doping molar percentage of N is 19.8%.
The preparation method of the graphene oxide described in this experimental procedure one is as follows:
The first step: the sodium nitrate of 0.5g is put into the 46mL concentrated sulfuric acid (98wt.%), and reaction is controlled in 0 DEG C of ice bath, the about 30min of magnetic agitation;
Second step: 1g natural flake graphite is slowly joined in the concentrated sulfuric acid solution of sodium nitrate to magnetic agitation 2h;
The 3rd step: slowly add the potassium permanganate of 7g, the joining day is controlled at 0.5g/10min again, controls bath temperature below 10 DEG C, and potassium permanganate all adds rear continuation to stir 90min;
The 4th step: subsequently 50 DEG C of hot water of 46mL are poured in the solution of step 3 gained, in this process, bath temperature is controlled at 98 DEG C, and is incubated 1h;
The 5th step: beaker is taken out from water-bath, cooling after, add 20mLH2O2(30wt.%), continue to stir 30min;
The 6th step: wash 1 time with 5wt.% watery hydrochloric acid, then washed several times with water, dialysis is until pH value of solution=6-7 obtains graphene oxide colloidal sol;
The 7th step: get above-mentioned graphene oxide colloidal sol, freeze drying or dry in 60 DEG C of drying boxes, obtains graphene oxide.
N-doped graphene prepared by this experiment and binding agent polyvinylidene fluoride (PVdF) in mass ratio 90 ﹕ 10 are dispersed in NMP, form cathode slurry, be coated on Cu paper tinsel as working electrode, lithium sheet is auxiliary and reference electrode, electrolyte is general lithium-ion battery electrolytes, as 1MLiPF6/ DMC:EC:DEC=1:1:1, preparation 2025 type button cells, discharge and recharge with the electric current of 1A/g, and discharge capacity is 1720mAh/g first. With the high current charge-discharge of 8A/g, after repeatedly circulating, its Capacitance reserve is at 580mAh/g.
Experiment five:
The preparation method of N-doped graphene carries out according to following steps:
One, under the condition that is 80kHz in frequency, disperse 90min, 8mg graphene oxide is distributed in deionized water, obtaining concentration is the graphene oxide dispersion liquid of 1mg/mL;
Two, 8mL ammoniacal liquor is joined in graphene oxide dispersion liquid, the mass percent concentration of ammoniacal liquor is 28%, obtains mixed solution;
Three, mixed solution being proceeded in hydrothermal reaction kettle, is to keep 8h under 200 DEG C of conditions in temperature, naturally cools to room temperature, and centrifugal, washing, dialysis, 80 DEG C are dry, obtain N-doped graphene, and in N-doped graphene, the doping molar percentage of N is 6.75%.
The preparation method of the graphene oxide described in this experimental procedure one is as follows:
The first step: the sodium nitrate of 0.5g is put into the 46mL concentrated sulfuric acid (98wt.%), and reaction is controlled in 0 DEG C of ice bath, the about 30min of magnetic agitation;
Second step: 1g natural flake graphite is slowly joined in the concentrated sulfuric acid solution of sodium nitrate to magnetic agitation 2h;
The 3rd step: slowly add the potassium permanganate of 5g, the joining day is controlled at 0.5g/10min again, controls bath temperature below 10 DEG C, and potassium permanganate all adds rear continuation to stir 90min;
The 4th step: subsequently 50 DEG C of hot water of 46mL are poured in the solution of step 3 gained, in this process, bath temperature is controlled at 98 DEG C, and is incubated 1h;
The 5th step: beaker is taken out from water-bath, cooling after, add 20mLH2O2(30wt.%), continue to stir 30min;
The 6th step: wash 1 time with 5wt.% watery hydrochloric acid, then washed several times with water, dialysis is until pH value of solution=6-7 obtains graphene oxide colloidal sol;
The 7th step: get above-mentioned graphene oxide colloidal sol, freeze drying or dry in 60 DEG C of drying boxes, obtains graphene oxide.
N-doped graphene prepared by this experiment and binding agent polyvinylidene fluoride (PVdF) in mass ratio 90 ﹕ 10 are dispersed in NMP, form cathode slurry, be coated on Cu paper tinsel as working electrode, lithium sheet is auxiliary and reference electrode, electrolyte is general lithium-ion battery electrolytes, as 1MLiPF6/ DMC:EC:DEC=1:1:1, preparation 2025 type button cells, discharge and recharge with the electric current of 1A/g, and discharge capacity is 1350mAh/g first. With the high current charge-discharge of 8A/g, after repeatedly circulating, its Capacitance reserve is at 295mAh/g.
Experiment six:
The preparation method of Graphene carries out according to following steps:
The first step: the sodium nitrate of 0.5g is put into the 46mL concentrated sulfuric acid (98wt.%), and reaction is controlled in 0 DEG C of ice bath, the about 30min of magnetic agitation;
Second step: 1g natural flake graphite is slowly joined in the concentrated sulfuric acid solution of sodium nitrate to magnetic agitation 2h;
The 3rd step: slowly add the potassium permanganate of 5g, the joining day is controlled at 0.5g/10min again, controls bath temperature below 10 DEG C, and potassium permanganate all adds rear continuation to stir 90min;
The 4th step: subsequently 50 DEG C of hot water of 46mL are poured in the solution of step 3 gained, in this process, bath temperature is controlled at 98 DEG C, and is incubated 1h;
The 5th step: beaker is taken out from water-bath, cooling after, add 20mLH2O2(30wt.%), continue to stir 30min; The 6th step: wash 1 time with 5wt.% watery hydrochloric acid, then washed several times with water, dialysis is until pH value of solution=6-7 obtains graphene oxide colloidal sol;
The 7th step: graphene oxide is moved in hydrothermal reaction kettle, is to keep 2h under 180 DEG C of conditions in temperature, naturally cools to room temperature, centrifugal, washing, freeze drying, obtain the graphene oxide of reduction.
The graphene oxide of reduction prepared by this experiment and binding agent polyvinylidene fluoride (PVdF) in mass ratio 90 ﹕ 10 are dispersed in NMP, form cathode slurry, be coated on Cu paper tinsel as working electrode, lithium sheet is auxiliary and reference electrode, electrolyte is general lithium-ion battery electrolytes, as 1MLiPF6/ DMC:EC:DEC=1:1:1, preparation 2025 type button cells, discharge and recharge with the electric current of 1A/g, and discharge capacity is 700mAh/g first, circulates 30 times, and discharge capacity is reduced to 156mAh/g. With the high current charge-discharge of 8A/g, after repeatedly circulating, its Capacitance reserve is at 95mAh/g.
Claims (10)
1. a preparation method for N-doped graphene, the preparation method who it is characterized in that a kind of N-doped graphene according toLower step is carried out:
One, under the condition that is 30kHz～80kHz in frequency, disperse 10min～100min, by graphene oxide be distributed to fromIn sub-water, obtaining concentration is the graphene oxide dispersion liquid of 0.1mg/mL～10mg/mL;
Two, dicyandiamide is dissolved in water, obtaining concentration is the dicyandiamide solution of 0.2～1.0mol/L;
Three,, according to the ratio of the mass ratio of graphene oxide and dicyandiamide 0.5～2 ﹕ 1, dicyandiamide solution is added drop-wise to oxidation stoneIn China ink alkene dispersion liquid, under the condition that is then 10kHz～30kHz in frequency, disperse 10～60min, obtain mixed solution;
Four, mixed solution being proceeded in hydrothermal reaction kettle, is to keep 0.5h～8h under 100 DEG C～250 DEG C conditions in temperature, natureBe cooled to room temperature, centrifugal, washing, dialysis, dry, obtain N-doped graphene, and in N-doped graphene, the doping of N rubsYour percentage is 8～20%.
2. a kind of preparation method of N-doped graphene according to claim 1, is characterized in that dry temperature in step 4Degree is 50 DEG C～90 DEG C.
3. according to the preparation method of a kind of N-doped graphene described in claim 1 or 2, it is characterized in that institute in step 1The frequency of stating is 40kHz～70kHz.
4. according to the preparation method of a kind of N-doped graphene described in claim 1 or 2, it is characterized in that institute in step 1The frequency of stating is 50kHz～60kHz.
5. according to the preparation method of a kind of N-doped graphene described in claim 1 or 2, it is characterized in that institute in step 1The concentration of stating graphene oxide dispersion liquid is 0.5mg/mL～8mg/mL.
6. according to the preparation method of a kind of N-doped graphene described in claim 1 or 2, it is characterized in that institute in step 1The concentration of stating graphene oxide dispersion liquid is 2mg/mL～6mg/mL.
7. according to the preparation method of a kind of N-doped graphene described in claim 1 or 2, it is characterized in that oxygen in step 3Mass ratio 0.8～1.5 ﹕ 1 of functionalized graphene and dicyandiamide.
8. according to the preparation method of a kind of N-doped graphene described in claim 1 or 2, it is characterized in that oxygen in step 3Mass ratio 1.5 ﹕ 1 of functionalized graphene and dicyandiamide.
9. according to the preparation method of a kind of N-doped graphene described in claim 1 or 2, it is characterized in that in step 4Temperature is to keep 1h～6h under 110 DEG C～230 DEG C conditions.
10. according to the preparation method of a kind of N-doped graphene described in claim 1 or 2, it is characterized in that in step 4Temperature is to keep 2h～5h under 100 DEG C～250 DEG C conditions.
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