CN101847712B - Method for depositing TiO2 on surface of multiwall carbon nano-tube for improving memory property of lithium ion - Google Patents

Abstract

The invention relates to a method for depositing TiO2 on the surface of a multiwall carbon nano-tube for improving the memory property of a lithium ion, which belongs to the technical field of the preparation technology of anode materials for lithium ion batteries. The method is characterized by comprising the following steps of: preparing a precursor by mixing oleic acid and tetrabutyl titanate in the weight ratio of 4 to 1, and then adding proper catalyst triethylamine into the precursor; weighting a certain amount of multiwall carbon nano-tubes (MWCNTs), adding the multiwall carbon nano-tubes into a mixed solvent of ethanol and toluene, then carrying out ultrasonic mixing on the obtained mixture and adding the mixture into the precursor; stirring and mixing the mixture, and moving the mixture to a Teflon high pressure reactor, and then putting the high pressure reactor in a baking oven at the temperature of 150 DEG C so as to make the mixture in the high pressure reactor react completely; washing reaction products by using the ethanol and the toluene, and then carrying out centrifugal separation on the reaction products so as to obtain an MWCNTs-TiO2 composite. The composite is easy to be dispersed in the toluene, and can be coated on a copper foil by the spin coating process so as to prepare the anode materials for thin film type lithium ion batteries.

Description

At multi-walled carbon nano-tubes surface deposition nano-TiO 2Improve the method for lithium ion memory property

Technical field

The present invention relates to a kind of at multi-walled carbon nano-tubes surface deposition nano-TiO ₂Improve the method for lithium ion memory property, belong to lithium ion battery negative material fabricating technology field.

Background technology

In exploring new type lithium ion battery negative material process, it is found that the charge/discharge capacity of CNT can surpass more than a times of graphite lithium intercalation compound, make the research of CNT lithium cell cathode material become focus.Yet; Be prone in the CNT first charge-discharge process form irreversible SEI film (solid electrolyte interface film) at electrode and electrolyte interface; Thereby cause CNT problem such as enclosed pasture efficient very low (＜40%) and cyclical stability extreme difference first, hindered its industrialized development.

MWCNT-TiO ₂Compound is that people study more carbon back heterojunction composite in recent years, and its research is inquired on the one hand is to utilize the right separation in the light induced electron hole of CNT aided nano titanium dioxide to improve the efficient of optically catalytic TiO 2; Then be to utilize the carbon nano tube modified nano titanium oxide of tool satisfactory electrical conductivity on the other hand to improve titanium dioxide lithium ion memory property.Yet, the influence of the lithium ion memory property of CNT is never studied at the nano titanium oxide of this composite surface deposition.

Summary of the invention

The object of the present invention is to provide a kind of multi-walled carbon nano-tubes surface deposition nano-TiO ₂Improve the method for lithium ion memory property.

The present invention is a kind of at multi-walled carbon nano-tubes surface deposition nano-TiO ₂Improve the method for lithium ion memory property, it is characterized in that having following technical process and step:

A. measure the butyl titanate and the oleic acid of certain volume, the preparing titanium dioxide predecessor; The volume ratio of butyl titanate and oleic acid is 1: 4; Oleic acid is heated to 55～65 ℃, in stirring, adds butyl titanate, get bright brown precursor liquid; It is subsequent use to be cooled to room temperature;

B. get a certain amount of above-mentioned predecessor liquid, in stirring, add proper catalyst triethylamine; The addition of triethylamine is 6～7% of a said predecessor liquid volume amount;

C. taking by weighing a certain amount of multi-walled carbon nano-tubes (MWCNTs) joins in the mixed solvent of a certain amount of ethanol and toluene; The volume ratio of ethanol and toluene is 1: 1.5～1: 3 in the mixed solvent; Multi-walled carbon nano-tubes (MWCNTs) is 2.5～4.0mg/ml with the ratio that cooperates of said mixed solvent by the mass volume ratio suffering, the multi-walled carbon nano-tubes (MWCNTs) that promptly per 1 milliliter of mixed solvent configuration is 2.5～4.0 milligrams; Ultrasonic mixing 15～20 minutes;

D. join then in the above-mentioned precursor fluid that is added with triethylamine, continue to stir 2～3 hours, make to mix; Then this mixture is moved in the Teflon autoclave, and be positioned in 120～150 ℃ of baking ovens, reacted 12～15 hours; Obtain the black mixed liquor;

E. be 10000 rev/mins centrifugal separator centrifugation sedimentation with above-mentioned black mixed liquor use rotating speed, obtain black precipitate; Then with washing with alcohol once to remove excessive oleic acid, again with toluene wash 1～2 time to remove free titanium dioxide nano-particle; Through centrifugation, promptly obtain MWCNTs-TiO again ₂Compound.

The characteristics of the inventive method are: through TiO ₂Self assembly and the growth in situ of nano particle on CNT makes MWCNTs-TiO ₂Compound.TiO ₂Deposition at the multi-wall carbon nano-tube tube-surface can be used as protective layer, can suppress electrode surface effectively and produce irreversible solid electrolyte interface film (SEI film), thereby improve the lithium ion memory property.

Adopted the catalysis triethylamine among the present invention, but catalysis predecessor aminolysis forms nano titanium oxide.

The MWCNTs-TiO that the inventive method makes ₂Compound very easily is dispersed in the toluene, can directly be coated on making film lithium ion battery negative material on the Copper Foil through the method such as the spin coating proceeding of solution-operated.

Description of drawings

Fig. 1 is the prepared MWCNTs-TiO of the inventive method ₂The transmission electron microscope of compound (TEM) photo figure.

Fig. 2 is (a) original MWCNTs, (b) TiO among the present invention ₂Nano particle, (c) MWCNTs-TiO ₂The X-ray diffraction analysis of compound (XRD) collection of illustrative plates.

Fig. 3 is (a) former CNT, (b) MWCNTs-TiO ₂Specific capacity-the voltage curve of compound.

Fig. 4 is the MWCNTs-TiO of the inventive method gained ₂Compound enclosed pasture efficiency curve diagram.

Embodiment

After specific embodiment of the present invention being described at present.

Embodiment 1

The step of present embodiment is described below:

(1), get oleic acid and be heated to about 60 ℃, add butyl titanate in the stirring and obtain bright brown predecessor (oleic acid and butyl titanate volume ratio are 4: 1), it is subsequent use to be cooled to room temperature.

(2), get adding 0.2ml triethylamine in the stirring of 3mL predecessor.

(3), take by weighing 20mg MWCNTS and add in the mixed liquor of 2ml ethanol and 5ml toluene, add behind the ultrasonic 15min and mix with predecessor; Move to teflon autoclave (the agitated reactor volume is 30mL) after continuing to stir 2h, and be positioned in 150 ℃ of electric dry ovens, keep constant temperature 15h, make abundant reaction.

(4), the product that obtains removes unnecessary oleic acid one time with washing with alcohol, again with toluene wash 1-2 all over removing the titanium dioxide nano-particle that dissociates, obtain the MWCNTs-TiO2 compound after the centrifugation.This sample ability stable dispersion is in toluene.

Detection and test to the present embodiment products therefrom

(1), transmission electron microscope (TEM) detects

MWCNTs-TiO ₂The testing result of compound is seen Fig. 1.

(2), X-ray diffractometer (XRD) analyzing and testing

Referring to Fig. 2, among Fig. 2, a is original CNT XRD diffracting spectrum, and b is pure anatase-type nanometer titanium dioxide diffracting spectrum, and c is MWCNTs-TiO ₂The compound diffracting spectrum, the diffraction maximum of CNT is penetrated but also comprised to the diffraction that it had not only comprised titanium dioxide.Though (101 peaks of titanium dioxide overlap with CNT (002) peak among the figure, and (101) peak of CNT shows in compound explains existing CNT in the compound.)

(3), the measurement of lithium ion memory property (cyclic voltammetry)

The making of negative pole:

The ion cathode material lithium preparation method is in this experiment: with MWCNTs-TiO ₂It is to get rid of film on the 14mm copper sheet that toluene solution drops in diameter, and 200 ℃ of annealing 1min repeat twice, and it is of poor quality that the active material quality is the copper sheet that gets rid of the film front and back, is 0.0006g in this example, tests as negative pole;

As relatively, the storage characteristics of original CNT is done the contrast test, specific practice is: with CNT and 4: 1 mixed pressuring plates of PTFE (20%) mass ratio as GND.

Referring to Fig. 3 and Fig. 4.

Among Fig. 3, (a) and (b) are respectively the specific capacity-voltage curve of original CNT and preceding 20 circulations of instance gained composite sample, in 0.005～2.5 potential range, compare their lithium ion memory property.Can know from (a): the discharge capacity first of original CNT is for～750 MAH/grams, and charging capacity is～175 MAH/grams, first coulomb efficient be merely～23%; Can know from (b): and the discharge first of the composite sample that makes is sung～320 MAH/grams, charging capacity still is～298 MAH/grams, enclosed pasture efficient reaches 93% first.The compound of this explanation CNT and titanium dioxide is compared the carbon nano-tube reversible capacity and is significantly increased, and promptly enclosed pasture efficient is improved significantly.

Among Fig. 4, the enclosed pasture efficiency curve of the 20th～100 circulation of composite sample is stabilized between 95～97%, explains that the composite sample charge-discharge performance is superior.

Claims (1)

1. one kind at multi-walled carbon nano-tubes surface deposition nano-TiO ₂Improve the method for lithium ion memory property, it is characterized in that having following technical process and step:

A. measure the butyl titanate and the oleic acid of certain volume, the preparing titanium dioxide predecessor; The volume ratio of butyl titanate and oleic acid is 1: 4; Oleic acid is heated to 55～65 ℃, in stirring, adds butyl titanate, get bright brown precursor liquid; It is subsequent use to be cooled to room temperature;

B. get a certain amount of above-mentioned predecessor liquid, in stirring, add proper catalyst triethylamine; The addition of triethylamine is 6～7% of a said predecessor liquid volume amount;

C. take by weighing a certain amount of multi-walled carbon nano-tubes, promptly MWCNTs joins in the mixed solvent of a certain amount of ethanol and toluene; The volume ratio of ethanol and toluene is 1: 1.5～1: 3 in the mixed solvent; Multi-walled carbon nano-tubes is 2.5～4.0mg/ml with the ratio that cooperates of said mixed solvent in the mass and size ratio, the multi-walled carbon nano-tubes that promptly per 1 milliliter of mixed solvent configuration is 2.5～4.0 milligrams; Ultrasonic mixing 15～20 minutes;

D. join then in the above-mentioned precursor fluid that is added with triethylamine, continue to stir 2～3 hours, make to mix; Then this mixture is moved in the Teflon autoclave, and be positioned in 120～150 ℃ of baking ovens, reacted 12～15 hours; Obtain the black mixed liquor;

E. be 10000 rev/mins centrifugal separator centrifugation sedimentation with above-mentioned black mixed liquor use rotating speed, obtain black precipitate; Then with washing with alcohol once to remove excessive oleic acid, again with toluene wash 1～2 time to remove free titanium dioxide nano-particle; Through centrifugation, promptly obtain MWCNTs-TiO again ₂Compound.

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