CN106340635B - A kind of aniline functionalization nitrogen-doped graphene modified lithium titanate composite material, preparation method and its application - Google Patents

A kind of aniline functionalization nitrogen-doped graphene modified lithium titanate composite material, preparation method and its application Download PDF

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CN106340635B
CN106340635B CN201610977411.5A CN201610977411A CN106340635B CN 106340635 B CN106340635 B CN 106340635B CN 201610977411 A CN201610977411 A CN 201610977411A CN 106340635 B CN106340635 B CN 106340635B
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nitrogen
composite material
lithium titanate
graphene
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CN106340635A (en
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田静
钟宽
林炳辉
刘洪明
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Gree Electric Appliances Inc of Zhuhai
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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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • 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
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • 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
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
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    • 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 present invention provides a kind of preparation methods of modified lithium titanate composite material, the following steps are included: A) graphene oxide solution, lithium titanate, water are mixed with nitrogen source after hydro-thermal reaction, the modified lithium titanate composite material of nitrogen-doped graphene is obtained, the nitrogen source is that there are one of pyridine nitrogen, pyrroles's nitrogen and graphitization nitrogen or a variety of nitrogen sources in structure；B impregnation after) mixing in composite material that step A) is obtained, amine source with solvent, obtains modified lithium titanate composite material；The amine source is can be with step A) obtained composite material forms the aromatic amine of non-covalent bond effect.This application provides a kind of modified lithium titanate composite material and preparation methods, i.e., are combined using hydro-thermal-infusion process, realize N doping and non-covalent bond dual function graphite alkene, and better simply process can be used and realize to Li4Ti5O12Carry out amino-functionalization graphene coated.

Description

A kind of aniline functionalization nitrogen-doped graphene modified lithium titanate composite material, its preparation Method and its application
Technical field
The present invention relates to electrode material technical field more particularly to a kind of modified metatitanic acids of aniline functionalization nitrogen-doped graphene Lithium composite material, preparation method and its application.
Background technique
Graphite-like carbon negative pole material (theoretical capacity 372mAh/g) has at low cost, good conductivity, charging/discharging voltage curve The advantages that stable and cycle efficieny high (> 95%), it is widely used in lithium ion battery.However, graphite-like Carbon anode material Material irreversible capacity loss in charge and discharge process is larger, and there are safety issues, cause graphite material gradually new by other Replaced profile material.Silica-base material has biggish theoretical specific capacity (4200mAh/g), but the volume expansion in charge and discharge process Rate is big, cycle efficieny is poor, keeps its application limited.Spinelle Li4Ti5O12It is a kind of " zero strain " material, there is excellent safety Performance, cheap cost, simple preparation process and cycle performance, cause the extensive concern of people.However, Li4Ti5O12Material Expect (theoretical capacity 175mAh/g) due to conductivity lower (about 10-9S·cm-1), influence the electrochemistry under its high magnification Can, constrain its commercial applications.Therefore, how Li is improved4Ti5O12Electric conductivity and high rate capability, become Li4Ti5O12Make It is crucial for the research of lithium ion battery negative material.
Graphene is a kind of two-dimentional Novel Carbon Nanomaterials, has large specific surface area, electron transport ability fast, conductive/hot Property good and flexibility it is good the advantages that, can be applied in lithium ion battery electrode material.However, pure graphene (theoretical capacity 740~760mAh/g) a coulomb low efficiency, charge and discharge platform are higher and cyclical stability is poor due to recycling for the first time for material, and The carbon material that cannot replace current commercialization is used directly as lithium ion battery negative material.But graphene can be used as a kind of excellent Basis material bigger effect is played in lithium battery combination electrode material, i.e., using special between graphene and electrode material Face contact mode, efficient three-dimensional conductive network can be formed, for electronics it is quick transmission channel is provided, can significantly drop The internal resistance of low battery improves its multiplying power, circulation and security performance.
Li is coated using high-electroconductivity graphene4Ti5O12Material prepares combination electrode material with good conductivity, is mesh Preceding raising Li4Ti5O12The common method of electric conductivity.The Chinese patent of Publication No. CN104646068A disclose it is a kind of simple, Hydro-thermal-dipping of green, which combines, prepares amino-functionalization graphene/TiO2The method of composite photocatalyst material, prepared is compound There is material excellent PhotoelectrocatalytiPerformance Performance and azo dyes to show unique selective photocatalysis degradation property. CN103788646A discloses a kind of in-situ chemical polymerization and prepares nitrogen-doped graphene/cobalt ferrite/polyaniline nano composite wood The method (using urea as nitrogen source) of material, this electrode material is used for power density with higher in supercapacitor but its energy is close It spends low.
Summary of the invention
Present invention solves the technical problem that being to provide a kind of modified lithium titanate composite material, preparation method and its answering With the comprehensive performance of lithium ion battery can be improved in the modified lithium titanate composite material active electrode material of the application preparation.
In view of this, this application provides a kind of preparation methods of modified lithium titanate composite material, comprising the following steps:
A), heated after graphene oxide solution, lithium titanate, water being mixed with nitrogen source, react, obtain nitrogen-doped graphene and change Property lithium titanate composite material, the nitrogen source is that there are pyridine nitrogen, pyrroles's nitrogen and graphitization one of nitrogen or a variety of in structure Nitrogen source；
B), impregnation after composite material that step A) is obtained, amine source being mixed with solvent, it is compound to obtain modified lithium titanate Material；The amine source is can be with step A) obtained composite material forms the aromatic amine of non-covalent bond effect.
Preferably, step A) in, the nitrogen source is one or both of organic amine and inorganic ammonia, and the organic amine is selected from One of hydrazine hydrate, urea, biuret, cyanamide, cyanamid dimerization, ethylenediamine and thiocarbamide are a variety of, and the inorganic ammonia is ammonia Water.
Preferably, step B) in, the amine source be one of aniline, porphyrin, naphthalene, phthalocyanine, polyaniline and polypyrrole or It is a variety of.
Preferably, step A) in, the concentration of the graphene oxide solution is 0.2~1.5wt%, the graphene oxide The content of graphene oxide in solution is 0.5wt%~10wt% of the metatitanic acid lithium content, and the content of the nitrogen source is institute State 0.5wt%~10wt% of graphene oxide content in graphene oxide solution.
Preferably, step B) in, the mass ratio of graphene is in the composite material that the amine source is obtained with the step A) (1~100): 1.
Preferably, step A) in, the temperature of the heating is 160~200 DEG C, and the time of the reaction is 6~12h；Step Rapid B) in, the temperature of the reaction is 0~30 DEG C, and the time of the reaction is 4~8h.
Present invention also provides a kind of modified lithium titanate composite materials, including lithium titanate and the function for being coated on lithium titanate surface Energy graphite alkene, the functionalization graphene is the nitrogen-doped graphene to form non-covalent bond functionalization.
Preferably, the nitrogen-doped graphene is with one of pyridine nitrogen, pyrroles's nitrogen and graphitization nitrogen or a variety of nitrogen sources The graphene of doping.
Preferably, the mass ratio of the lithium titanate and functionalization graphene is 0.5wt%~10wt%, the N doping stone The doping of nitrogen is 0.5wt%~10wt% in black alkene, in the substance and the functionalization graphene for forming non-covalent bond The mass ratio of graphene is (1~100): 1.
Present invention also provides prepared by the preparation method described in above scheme or modification metatitanic acid described in above scheme Application of the lithium composite material as electrode material.
This application provides a kind of preparation methods of modified lithium titanate composite material, use hydro-thermal method that will aoxidize stone first Black alkene, lithium titanate are reacted with nitrogen source, so that graphene oxide is reduced to graphene, while by nitrogen in a manner of covalent bond It is doped into graphene, forms tentatively modified lithium titanate, then mix lithium titanate obtained above with nitrogen source again, react, With non-covalent bond effect, i.e. π-πconjugation is modified above-mentioned tentatively modified lithium titanate again, obtains modified lithium titanate Composite material.
The application hydro-thermal composite algorithm can improve the adhesive force between graphene and lithium titanate, and lithium titanate is made to be dispersed in nitrogen A conductive network is formed between the lamella of doped graphene, and lithium titanate can be prevented by the coating function of nitrogen-doped graphene Reunion, and lithium titanate is distributed in graphene sheet layer and empty structure the accumulation that can also prevent graphene film, nearly all Lithium titanate particle be all attached to the nitrogen-doped graphene on piece of high conductivity；In the electrolytic solution, these functional groups and lithium metal The effect of ion electrostatic attraction, effectively can be attached to graphene nano on piece for lithium titanate particle, in addition numerous on graphene film Hole, the electric conductivity of modified lithium titanate composite material can also be effectively increased with accommodating portion lithium titanate particle；It is non-total simultaneously The nitrogen-doped modified lithium titanate material of valence link functionalization, be remarkably improved graphene electron transport ability and embedding de- lithium Can, it can significantly improve the comprehensive performance of composite material, such as high rate performance, cycle performance, reversible specific capacity and safety Property.
Detailed description of the invention
Fig. 1 is the lithium ion deintercalation mechanism figure of modified lithium titanate composite material prepared by the present invention；
Fig. 2 is prepared by the embodiment of the present invention 1The XPS N1S power spectrum of composite material Figure；
Fig. 3 is prepared by the embodiment of the present invention 2The XPS N1S energy of composite material Spectrogram；
Fig. 4 is prepared by the embodiment of the present invention 3The XPS N1S energy of composite material Spectrogram；
Fig. 5 is GO and RGO/Li4Ti5O12The C1s energy spectrum diagram of composite material；
Fig. 6 is N-RGO/Li4Ti5O12The C1s energy spectrum diagram of composite material.
Specific embodiment
For a further understanding of the present invention, the preferred embodiment of the invention is described below with reference to embodiment, still It should be appreciated that these descriptions are only further explanation the features and advantages of the present invention, rather than to the claims in the present invention Limitation.
The embodiment of the invention discloses a kind of preparation methods of modified lithium titanate composite material, comprising the following steps:
A), hydro-thermal reaction after graphene oxide solution, lithium titanate, water being mixed with nitrogen source obtains nitrogen-doped graphene and changes Property lithium titanate composite material, the nitrogen source is that there are pyridine nitrogen, pyrroles's nitrogen and graphitization one of nitrogen or a variety of in structure Nitrogen source；
B), composite material that step A) is obtained, amine source are reacted with solvent impregnated, obtains modified carbonic acid lithium composite material； The amine source is can be with step A) obtained composite material forms the aromatic amine of non-covalent bond effect.
Lithium titanate is synthetically prepared the present invention provides a kind of method that simple hydro-thermal and infusion process combine to be modified again Condensation material realizes N doping and non-covalent bond dual function graphite alkene, uses better simply process pair to realize Li4Ti5O12Carry out functionalization graphene cladding.
The application is prepared for nonmetalloid nitrogen-doped graphene (N-RGO) first, the typical n-type semiconductor having Material properties shows excellent electric conductivity, then, by N-RGO with can formed non-covalent bond nitrogen source by π-π it is total The LBL self-assembly method of yoke effect, obtains the new carbon of " supermolecule " structure, which can further increase graphene Interlamellar spacing, prevent graphene nanometer sheet between stacking.That is, the graphene that N doping and non-covalent bond functionalization are modified jointly, It is remarkably improved the electrode conductivity of lithium ion battery；It can also be used as electric current collection substance, can inhibit Li4Ti5O12Reunion；It is multiple The specific capacity of condensation material improves a lot relative to pure graphene；Li4Ti5O12Nano particle can also protect graphene surface layer, prevent Only electrolyte insertion graphene sheet layer leads to electrode material peeling phenomenon.
According to the present invention, the preparation of nitrogen-doped graphene modified lithium titanate composite material has been carried out first, i.e., will aoxidize stone Hydro-thermal reaction after black alkene solution, lithium titanate, water are mixed with nitrogen source obtains the modified lithium titanate composite material of nitrogen-doped graphene, The nitrogen source is that there are one of pyridine nitrogen, pyrroles's nitrogen and graphitization nitrogen or a variety of nitrogen sources in structure.In the process, originally Application is not particularly limited the source of the graphite oxide weak solution, lithium titanate, water and nitrogen source；It is exemplary, the oxygen Graphite alkene solution is the graphene oxide (GO) prepared using improved Hummer ' s method, then passes through ultrasonic disperse, is obtained Graphene oxide (GO) solution；The concentration of herein described graphene oxide solution is preferably 0.5~4g/L, and more preferably 2 ~3g/L.The preparation process of the lithium titanate is preferred are as follows: respectively with Li2CO3And TiO2For lithium source and titanium source, after grinding uniformly in 800~1000 DEG C of 8~15h of high-temperature calcination, obtain spinel-type Li4Ti5O12Presoma is cooled to room temperature, and is ground uniform.This Shen Please the nitrogen source is not particularly limited, as long as being capable of forming in hydro-thermal reaction mainly with pyridine nitrogen, pyrroles's nitrogen or stone One or more nitrogen sources, exemplary present in inkization nitrogen, and the nitrogen source is preferably organic amine and inorganic ammonia, described organic Amine is selected from one of hydrazine hydrate, urea, biuret, cyanamide, cyanamid dimerization, ethylenediamine and thiocarbamide or a variety of, described inorganic Ammonia is ammonium hydroxide.
In above process, pass through suction-operated containing a large amount of oxygen-containing functional group in graphene oxide, it can fabricated in situ Graphene/lithium titanate (RGO/Li4Ti5O12) composite material.Wherein, nonmetalloid N have electronegativity similar with C atom and Atomic radius, often occurs doping reaction in the form of substitution with graphene, and the N doped graphene of generation has typical N-shaped half Conductor material properties shows electric conductivity more superior than pure graphene.Modified lithium titanate (the N-RGO/ of nitrogen-doped graphene Li4Ti5O12) composite material preparation depend primarily on load graphene content and doping nitrogen source content.Wherein institute The content for stating the graphene oxide in graphene oxide solution is preferably 0.5wt%~10wt% of the metatitanic acid lithium content, more Preferably 0.5wt%~6.0wt%, the content of the nitrogen source are preferably graphene oxide content in the graphene oxide solution 0.5wt%~10wt%, more preferably 2wt%~8wt%.Wherein, the content of graphene is very few, does not have conductive network The amount of connection function, graphene is added excessively, causes the bulk deposition of graphene, influences its dispersion, is unfavorable for Li in electrolyte+ Transmitting.Meanwhile the graphene of high nitrogen-containing (5%), due to the larger adsorbable a large amount of Li of electronegativity+, material can be dramatically increased The storage lithium performance of material, these features make the composite material all have excellent performance in terms of energy storage and conversion.
The nitrogen adulterated in the modified lithium titanate composite material of the nitrogen-doped graphene of the application preparation is mainly with pyridine nitrogen, pyrrole The form coughed up nitrogen and be graphitized nitrogen exists, and the nitrogen various forms proportion wherein adulterated in different nitrogen sources is different, most preferably to match Than existing；The nitrogen of doping is less, and performance boost is smaller；The too high levels of the nitrogen of doping cause graphene defect excessive, cause whole A conductive network collapses, and electric conductivity will be reduced seriously.
According to the present invention, in preparation N-RGO/Li4Ti5O12During composite material, it is completed at the same time using hydro-thermal method The reduction of graphene oxide and the process of N doping；The temperature of the heating is preferably 160~200 DEG C, the time of the reaction Preferably 6~12h.
After the preparation, the application then carries out the modification of non-covalent bond functionalization, then with non-covalent bond effect, i.e. π-π is total Yoke is acted on to N-rGO/Li4Ti5O12Composite material is modified.Detailed process are as follows: by N-RGO/Li4Ti5O12Composite material, amine After source is mixed with solvent, reaction obtains the graphene of N doping and non-covalent bond functional modification.Herein described amine source does not have Special limitation, as long as can be with N-RGO/Li4Ti5O12Composite material forms the material of non-covalent bond, exemplary, institute It states nitrogen source and is preferably selected from one of aniline, porphyrin, naphthalene, phthalocyanine, polyaniline and polypyrrole or a variety of；More preferably aniline.Institute State amine source and N-RGO/Li4Ti5O12The mass ratio of graphene is (1~100): 1, more preferably (20~80) in composite material: 1.The application is using the nitrogen source of non-covalent bond to N-RGO/Li4Ti5O12Composite material is modified, and makes the structure of N-rGO will not It is destroyed again, the special property of aniline molecule can be introduced modified N-RGO/LTO by taking aniline as an example by the nitrogen source In material, and then synthesize combination electrode material.The nitrogen source by taking aniline as an example, the addition of aniline, more conducively electronics from Li4Ti5O12It is transferred on N- graphene film, then migrates into aniline molecule, it, can be significant finally by electronics transfer to collector Improve the electric conductivity of such composite material.
Present invention also provides a kind of modified lithium titanate composite materials, including lithium titanate and the function for being coated on lithium titanate surface Energy graphite alkene, the functionalization graphene is the nitrogen-doped graphene to form non-covalent bond functionalization.
According to the present invention, the nitrogen-doped graphene preferably with pyridine nitrogen, pyrroles's nitrogen and graphitization one of nitrogen or The doped graphene that diversified forms carry out preferably carries out obtaining nitrogen-doped graphene with pyridine nitrogen, pyrroles's nitrogen and graphitization nitrogen, more The nitrogen-doped graphene preferably carried out with pyridine nitrogen.
In the application, the functionalization graphene is 0.5wt%~10wt% of lithium titanate quality, the N doping graphite The doping of nitrogen is 0.5wt%~10wt% in alkene, stone in the substance and the functionalization graphene for forming non-covalent bond The mass ratio of black alkene is (1~100): 1.
Present invention also provides prepared by the preparation method described in above scheme or modification metatitanic acid described in the above method Application of the lithium composite material as electrode material.
The electrode material can be the electrode material of capacitor well known to those skilled in the art, lithium ion battery etc., make For preferred embodiment, electrode material of the herein described modified lithium titanate composite material as lithium ion battery is remarkably improved lithium Specific capacity, high rate capability and the cyclical stability of ion battery.
For a further understanding of the present invention, below with reference to embodiment to modified lithium titanate composite material provided by the invention Preparation method is described in detail, and protection scope of the present invention is not limited by the following examples.
Embodiment 1
Step 1: the graphene oxide (GO) prepared by improved Hummer ' s method is configured to 2g/L, i.e. 0.2wt% GO solution (ultrasonic disperse 2h) (wherein the concentration of GO solution can be formulated as 0.5~4g/L)；
Step 2: respectively with Li2CO3And TiO2It is obtained for lithium source and titanium source in 800 DEG C of high-temperature calcination 12h after grinding uniformly To spinel-type Li4Ti5O12Presoma is cooled to room temperature, then 4h is handled in rotating ball mill, is ground uniform rear spare；
Step 3: it measures a certain amount of GO solution and is added to Li4Ti5O12In presoma, then plus certain density N2H4· H2The distilled water of O solution and respective volume is transferred in the stainless steel autoclave of polytetrafluoroethyllining lining after magnetic agitation 2h, in 200 DEG C of hydro-thermal 12h, are cooled to room temperature, then are dried in vacuo 8h at 60 DEG C after being washed, be centrifuged repeatedly with distilled water, and N- is made RGO/Li4Ti5O12Composite material (wherein mGO/mLTO=1.5wt%, mN/mGO=6wt%)；
Step 4: the N-RGO/Li prepared in a certain amount of step 3 is weighed4Ti5O12Composite material is added to aniline In ethanol solution, obtained product is used ethyl alcohol and distillation water washing 3 times, through 0.22 μ by the magnetic agitation 5h at 25 DEG C respectively again After m micropore filter paper filters, 8h is dried in vacuo at 60 DEG C to get PhNH is arrived2/N-RGO/Li4Ti5O12Nanocomposite is (wherein The mass ratio of aniline and graphene are as follows: 50:1)；
Step 5: with the mass ratio of best aniline and graphene in step 3, by a certain amount of Li4Ti5O12Presoma It is added in the ethanol solution of the aniline of respective volume, the product of synthesis is used ethyl alcohol by the magnetic agitation 5h at 25 DEG C respectively again 8h is dried in vacuo at 60 DEG C to get PhNH is arrived after 0.22 μm of micropore filter paper filters with distillation water washing 3 times2/Li4Ti5O12 Composite material is blank control sample.
Fig. 1 is PhNH2/N-RGO/Li4Ti5O12The embedding off line reason figure of the lithium ion of composite material；After nitrogen doped, Li+More Tend to the top for being adsorbed on pyridine nitrogen and pyrroles's nitrogen and the centrical surface of graphene defect, this is because defect is former nearby Valence electron of the lone pair electrons easily with combination Li atom in son, and pyridine nitrogen and pyrroles's N doping bring electronic defects, increase Electric charge transfer between Li atom and graphene；Aniline is connected to the surface N-RGO with π-πconjugation by infusion process, into one Step enhances the elecrtonegativity of graphene surface, more conducively absorption Li+；Meanwhile the graphene of dual function is remarkably improved lithium The conductivity of ion battery electrode can also be used as electric current collection substance.
Fig. 2 isThe XPS N1S energy spectrum diagram of composite material；The nitrogen of doping is with pyridine nitrogen (theoretical reversible capacity 1262mAh/g, account for 14.4%), pyrroles's nitrogen (reversible capacity 1198mAh/g, account for 69.3%) and graphitization nitrogen (reversible capacity 1087mAh/g, the form accounted for 16.3%) exist, and the nitrogen-doped graphene of synthesis has typical n-type semiconductor Material properties shows electric conductivity more superior than pure graphene.
As shown in Figure 5, after hydrothermal reduction, most of oxygen-containing functional group has been removed GO, predominantly C=C, C-C and C h bond is coated on lithium titanate completely after illustrating that GO and lithium titanate are compound, forms RGO/Li4Ti5O12Composite material；By Fig. 6 is it is found that with NH3、N2H4With CO (NH2)2It respectively can be by N element success through one step hydro thermal method with GO and lithium titanate material for nitrogen source It is inserted into graphene sheet layer, and is respectively formed the nitrogen-doped graphene based on pyridine nitrogen, graphitization nitrogen and pyrroles's nitrogen, wherein C- The bright N element of N key table is successfully compounded in N-RGO/Li4Ti5O12And PhNH2/N-RGO/Li4Ti5O12In composite material, and with NH3、 N2H4With CO (NH2)2Adulterating C-N key proportion in RGO for nitrogen source is respectively 0.149,0.138 and 0.151 (as shown in table 1). Since the content of aniline functionalized is less, the corresponding diffraction maximum of aniline molecule can not be seen in XRD spectrum, compared The electrical property of composite material is it is found that aniline molecule is successfully supported on N-RGO/Li4Ti5O12On nano particle, PhNH is formed2/N- RGO/Li4Ti5O12Combination electrode material.
The various functional group's proportion tables of data of table 1
Samples AC=C/A AC-N/A AC-O/A AC=O/A ACOOH/A
GO 0.498 0 0.376 0.110 0.016
rGO/Li4Ti5O12 0.873 0 0.087 0.006 0.034
N-rGO/Li4Ti5O12(NH3) 0.753 0.149 0.046 0.031 0.021
N-rGO/Li4Ti5O12(CO(NH2)2) 0.77 0.138 0.045 0.030 0.017
N-rGO/Li4Ti5O12(N2H4) 0.726 0.151 0.067 0.045 0.011
In 0.2C, Li4Ti5O12The charging capacity reversible for the first time of material is 165mAh/g, and coulombic efficiency is about 94%；And RGO/Li4Ti5O12Reversible capacity be 174mAh/g, coulombic efficiency is about 98.2%；'s Reversible capacity is 186mAh/g, and coulombic efficiency is about 99.3%；Reversible appearance Amount is about 194mAh/g, and coulombic efficiency is about 99.8%；AndCombination electrode material The discharge platform of material is about 1.56V, and corresponding charging platform is about 1.57V, they are compared to Li4Ti5O12Discharge platform 1.52V It is 0.01V with the polarizing voltage of charging platform voltage 1.58V, there is smaller polarizing voltage, is being total to due to graphene and nitrogen Valence link doping and the non-covalent bond effect collaboration of aniline improve Li4Ti5O12The electric conductivity of composite material.
AndComposite material has There are good chemical property, especially chemical property under the conditions of big multiplying power；Specific capacity of the composite material under 0.2C, 1C, 10C current density be respectively 194,185 and 167mAh/g has apparent charge and discharge platform.The specific capacity of electrode material subtracts with the increase of current density Small, the lithium ion in electrolyte cannot effectively enter inside combination electrode material, only carry out oxygen on the surface of electrode material Change reduction reaction, reduces the utilization rate of active material, and then specific capacity is caused to decline.Wherein, under 10C multiplying powerComposite material initial specific capacities are about 155mAh/g, the capacity retention ratio after circulation 100 times About 85%；Combination electrode material initial specific capacities are about 167mAh/g, are followed Capacity retention ratio after ring 100 times is about 90%；It is above Li4Ti5O1270%；ShowAndComposite material is under high magnification The raising of capacity retention ratio can be attributed to the fact that the stability of this body structure of electrode material and the graphene of superior electron conductivity and non- The synergistic effect of the non-covalent bond functionalization of the covalent bond doping and aniline of metallic element nitrogen, while Li4Ti5O12Nano particle can To be adsorbed on the graphene nano on piece of high electron conduction, the conductivity of bulk material also can be improved.
Embodiment 2
Step 1: graphene oxide (GO) the ultrasonic disperse 2h prepared by improved Hummer ' s method is configured to 2mg/ The GO solution of mL, i.e. 0.2wt%；
Step 2: respectively with Li2CO3And TiO2It is obtained for lithium source and titanium source in 800 DEG C of high-temperature calcination 12h after grinding uniformly To spinel-type Li4Ti5O12Presoma is cooled to room temperature, then 4h is handled in rotating ball mill, is ground uniform rear spare；
Step 3: it measures a certain amount of GO solution and is added to Li4Ti5O12In presoma, then plus certain density NH3·H2O The distilled water of solution and respective volume is transferred in the stainless steel autoclave of polytetrafluoroethyllining lining after magnetic agitation 2h, in 200 DEG C hydro-thermal 12h, is cooled to room temperature, then be dried in vacuo 8h at 60 DEG C after being washed, be centrifuged repeatedly with distilled water, and N-RGO/ is made Li4Ti5O12Composite material (wherein mGO/mLTO=1.5wt%, mN/mGO=6wt%)；
Step 4: the N-RGO/Li prepared in a certain amount of step 3 is weighed4Ti5O12Composite material is added to aniline In ethanol solution, obtained product is used ethyl alcohol and distillation water washing 3 times, through 0.22 μ by the magnetic agitation 8h at 25 DEG C respectively again After m micropore filter paper filters, 8h is dried in vacuo at 60 DEG C to get arrivingIt receives Nano composite material (the wherein mass ratio of aniline and graphene are as follows: 50:1).
Fig. 3 isThe XPS N1S energy spectrum diagram of composite material；The nitrogen of doping is with pyridine Nitrogen (theoretical reversible capacity 1262mAh/g, account for 83.7%), pyrroles's nitrogen (reversible capacity 1198mAh/g, account for 11.5%) and graphitization (reversible capacity 1087mAh/g, the form accounted for 4.8%) exists nitrogen, and shows than showing to compareThe superior electric conductivity of composite material.
Specific capacity of the composite material under 0.2C, 1C, 10C current density point Not Wei 209,198 and 180mAh/g, have apparent charge and discharge platform.The specific capacity of electrode material with current density increase And reduce, the lithium ion in electrolyte cannot effectively enter inside combination electrode material, only the surface of electrode material into Row redox reaction, reduces the utilization rate of active material, and then specific capacity is caused to decline.Wherein, under 10C multiplying powerComposite material initial specific capacities are about 168mAh/g, and the capacity after circulation 100 times is protected Holdup is about 89%；PCombination electrode material initial specific capacities are about 180mAh/g, the capacity retention ratio after recycling 100 times is about 95%；It is above Li4Ti5O1270%；ShowAndComposite material is in high magnification Under the raising of capacity retention ratio can be attributed to the fact that the stability of this body structure of electrode material and the graphene of superior electron conductivity And the synergistic effect of the non-covalent bond functionalization of the covalent bond doping and aniline of nonmetalloid nitrogen, while Li4Ti5O12Nanometer Grain can be adsorbed on the graphene nano on piece of high electron conduction, and the conductivity of bulk material also can be improved.
There are also very big rooms for promotion for the specific capacitance of current nitrogen-doped graphene, if can control doping nitrogen in experiment Type (table 2), introduce the N doping defect sturcture of some pyridine types, or reduce the defect sturcture of graphite mould nitrogen, so more The combination electrode material synthesized will further improve the chemical property and stability of lithium ion battery.Using ammonium hydroxide as nitrogen source The extreme value variation of the pyridine type nitrogen of doped graphene, insertion voltage is steady, illustrates Li during insertion, without result in titanium The big phase transformation of sour lithium material.
Doped forms proportion tables of data in the various nitrogen source doped graphenes of table 2 (on the basis of the gross area at the peak N1S)
Samples APyridine nitrogen/A APyrroles's nitrogen/A AIt is graphitized nitrogen/A
PhNH2/N-RGO/Li4Ti5O12(NH3.H2O) 0.837 0.115 0.048
PhNH2/N-RGO/Li4Ti5O12(CO(NH2)2) 0.329 0.591 0.081
PhNH2/N-RGO/Li4Ti5O12(N2H4) 0.144 0.693 0.163
Embodiment 3
Step 1: graphene oxide (GO) the ultrasonic disperse 2h prepared by improved Hummer ' s method is configured to 2mg/ The GO solution of mL, i.e. 0.2wt%；
Step 2: respectively with Li2CO3And TiO2It is obtained for lithium source and titanium source in 800 DEG C of high-temperature calcination 12h after grinding uniformly To spinel-type Li4Ti5O12Presoma is cooled to room temperature, then 4h is handled in rotating ball mill, is ground uniform rear spare；
Step 3: it measures a certain amount of GO solution and is added to Li4Ti5O12In presoma, then plus certain density urea (CO (NH2)2) solution and respective volume distilled water, the stainless steel autoclave of polytetrafluoroethyllining lining is transferred to after magnetic agitation 2h In, it in 200 DEG C of hydro-thermal 12h, is cooled to room temperature, then be dried in vacuo 8h at 60 DEG C after being washed, be centrifuged repeatedly with distilled water, is madeComposite material (wherein mGO/mLTO=1.5wt%, mN/mGO=6wt%)；
Step 4: it weighs and prepares in a certain amount of step 3Composite material, It is added in the ethanol solution of aniline, the magnetic agitation 8h at 25 DEG C, by obtained product again respectively with ethyl alcohol and distillation washing It washs 3 times, after 0.22 μm of micropore filter paper filters, is dried in vacuo 8h at 60 DEG C to get arrivingNanocomposite (the wherein mass ratio of aniline and graphene are as follows: 50: 1)。
Fig. 4 isThe XPS N1S energy spectrum diagram of composite material；The nitrogen of doping is with pyridine Nitrogen (theoretical reversible capacity 1262mAh/g, account for 32.9%), pyrroles's nitrogen (reversible capacity 1198mAh/g, account for 59.1%) and graphitization (reversible capacity 1087mAh/g, the form accounted for 8.1%) exist nitrogen.
AndComposite wood Material all has apparent charge and discharge platform.Wherein,Composite material exists Specific capacity under 0.2C, 1C, 10C current density is respectively 200,191 and 173mAh/g, and the specific capacity of electrode material is with electric current The increase of density and reduce, the lithium ion in electrolyte cannot effectively enter inside combination electrode material, only in electrode material The surface of material carries out redox reaction, reduces the utilization rate of active material, and then specific capacity is caused to decline.Wherein, in 10C Under multiplying powerComposite material initial specific capacities are about 161mAh/g, after circulation 100 times Capacity retention ratio is about 87%；PhNH2/N(CO(NH2)2)-RGO/Li4Ti5O12Combination electrode material initial specific capacities are about 173mAh/g, the capacity retention ratio after recycling 100 times is about 93%；It is above Li4Ti5O1270%；ShowAnd Composite material is in high power The raising of capacity retention ratio under rate can be attributed to the fact that the stability of this body structure of electrode material and the graphite of superior electron conductivity The synergistic effect of the non-covalent bond functionalization of the doping of the covalent bond of alkene and nonmetalloid nitrogen and aniline, while Li4Ti5O12Nanometer Particle can be adsorbed on the graphene nano on piece of high electron conduction, and the conductivity of bulk material also can be improved.
The above description of the embodiment is only used to help understand the method for the present invention and its core ideas.It should be pointed out that pair For those skilled in the art, without departing from the principle of the present invention, the present invention can also be carried out Some improvements and modifications, these improvements and modifications also fall within the scope of protection of the claims of the present invention.
The foregoing description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, as defined herein General Principle can be realized in other embodiments without departing from the spirit or scope of the present invention.Therefore, of the invention It is not intended to be limited to the embodiments shown herein, and is to fit to and the principles and novel features disclosed herein phase one The widest scope of cause.

Claims (5)

1. a kind of preparation method of modified lithium titanate composite material, comprising the following steps:
A), heat, react after graphene oxide solution, lithium titanate, water being mixed with nitrogen source, obtain what nitrogen-doped graphene was modified Lithium titanate composite material；
B), impregnation after composite material that step A) is obtained, amine source being mixed with solvent, obtains modified lithium titanate composite wood Material；The amine source is that the composite material obtained with step A) forms the amine of non-covalent bond effect；
Step A) in, the nitrogen source is one or both of organic amine and inorganic ammonia, and the organic amine is selected from hydrazine hydrate, urine One of element, biuret, cyanamide, cyanamid dimerization, ethylenediamine and thiocarbamide are a variety of, and the inorganic ammonia is ammonium hydroxide；
Step B) in, the amine source is one of aniline, porphyrin, naphthalene, phthalocyanine, polyaniline and polypyrrole or a variety of；
Nitrogen-doped graphene is the doped graphite carried out with one of pyridine nitrogen, pyrroles's nitrogen and graphitization nitrogen or diversified forms Alkene.
2. preparation method according to claim 1, which is characterized in that step A) in, the graphene oxide solution it is dense Degree is 0.2 ~ 1.5wt%, and the content of the graphene oxide in the graphene oxide solution is the 0.5wt% of the metatitanic acid lithium content ~ 10wt%, the content of the nitrogen source are 0.5wt% ~ 10wt% of graphene oxide content in the graphene oxide solution.
3. preparation method according to claim 1, which is characterized in that step B) in, the amine source and the step A) To composite material in graphene mass ratio be (1 ~ 100): 1.
4. preparation method according to claim 1, which is characterized in that step A) in, the temperature of the heating is 160 ~ 200 DEG C, the time of the reaction is 6 ~ 12h；Step B) in, the temperature of the reaction is 0 ~ 30 DEG C, the time of the reaction is 4 ~ 8h。
5. modified lithium titanate composite material prepared by the described in any item preparation methods of claim 1 ~ 4 is as electrode material Using.
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