CN104852028A - Lithium titanate/graphene composite cathode material for lithium ion battery - Google Patents
Lithium titanate/graphene composite cathode material for lithium ion battery Download PDFInfo
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Abstract
The invention discloses a lithium titanate/graphene composite cathode material for a lithium ion battery. The composite cathode material is obtained by mixing lithium titanate and graphene oxide and then performing reduction by a reducing agent. A preparation method of the composite cathode material comprises the steps of preparing pure-phase lithium titanate by a hydrothermal method, sufficiently mixing pure-phase lithium titanate and graphene oxide, adding an appropriate amount of reducing agent, and shifting pure-phase lithium titanate, graphene oxide and the reducing agent to a reaction kettle to react for a certain time at a certain temperature to obtain the lithium titanate/graphene composite cathode material. The method synthesizes the lithium titanate/graphene composite material by an industrially extensively used hydrothermal reaction, so that the method is simple to operate and low in equipment requirement, and is suitable for industrial production; and the prepared lithium titanate/graphene composite material has higher specific capacity, good high rate performance and excellent cycle performance, and is applicable to the fields of portable electronic equipment, electromobiles, energy storage equipment and the like.
Description
Technical field
The invention belongs to electrochemistry and new energy materials field, particularly relate to a kind of lithium ion battery lithium titanate/graphene composite negative pole.
Background technology
The fast development of modern society result in the sharply increase of the mankind to energy demand, and development and utilization cleaning new energy is the only way which must be passed of human social development.Lithium ion battery, as " the green secondary cell of 21 century ", has that voltage is high, specific energy is high, discharge and recharge life-span length, memory-less effect, environmental pollution are little, an advantage such as quick charge, self-discharge rate are low.As the chemical power source that a class is important, lithium ion battery progressively moves towards electric powered motor field by mobile phone, notebook computer, digital camera and portable small-sized electrical equipment battery used and submarine, aerospace field battery used.When global energy and environmental problem are more and more severeer, energy-storage battery used one after another instead by the vehicles is main power source, and lithium ion battery is considered to the choosing of ideal of high power capacity, high power battery.
Negative material, as one of the core of lithium ion battery, is always the key object that people research and develop, and the performance improving negative material improves the key of performance of lithium ion battery; Simultaneously the quality of negative material directly can affect the performance of lithium ion battery, price and use.Early stage lithium battery uses lithium metal as negative pole, but lithium easily forms dendrite in charging process, pierces through barrier film and causes internal short-circuit of battery; Be developed the negative material of the intercalation compound based on graphite as lithium ion battery for overcoming above-mentioned shortcoming, commercial lithium ion battery mainly uses this negative material at present.But graphite material also exists obvious shortcoming, as coulombic efficiency is low first, greatly, graphite linings is easily peeled off, efflorescence in material volume change; And the interlamellar spacing of graphite is excessive, easily make lithium ion and organic solvent jointly embed graphite linings, cause matrix to expand and organic solvent decomposition, affect cycle performance of battery and life-span.Spinel type lithium titanate Li
4ti
5o
12, as lithium ion battery negative material, its Stability Analysis of Structures, there is any change hardly in volume in charge and discharge process, therefore has extraordinary cycle performance; And discharge curve is smooth, simultaneously abundant, the clean environment firendly of titanium resource.
Graphene is as a kind of new carbon, since 2004 are found, due to the hexagon cellular shape void structure of its two-dimentional monolayer and the physico-chemical property of excellence, as high specific area, high electronic conductivity, superior mechanical property and good chemical stability etc., and be widely used in lithium ion battery.Many researchs in recent years show that Graphene not only increases the ability of negative material storage lithium in composite negative pole material, conductive network can also be formed and promote its conductivity, contribute to the evolving path shortening lithium ion simultaneously, the high rate charge-discharge performance of negative material is had greatly improved, and these are quite important for lithium titanate.Current lithium titanate and Graphene complex method great majority are directly mixed with Graphene by magnetic agitation with lithium titanate, it is even not that this simple mechanical mixture makes lithium titanate mix with Graphene, and adhesive force is more weak, the advantages such as Graphene high conductivity can not be given full play to, thus make the large high rate performance of lithium titanate/graphene composite material still not good, still can not meet the commercialization requirement of lithium titanate/graphene composite material.
Summary of the invention
The present invention aims to provide the preparation method of a kind of lithium ion battery lithium titanate/graphene composite negative pole, problem to be solved is the shortcomings such as the low specific capacity of lithium titanate anode material, low conductivity and high rate charge-discharge poor performance, provides that a kind of technical process is simple, the preparation method of low, with short production cycle, the eco-friendly lithium titanate/graphene composite negative pole that consumes energy simultaneously.
Technical solution problem of the present invention adopts following technical scheme:
The feature of lithium ion battery lithium titanate/graphene composite negative pole of the present invention is: described composite negative pole material obtains through reducing agent reduction after lithium titanate mixes with graphene oxide, and the chemical formula of described composite negative pole material is Li
4ti
5o
12/ Graphene, referred to as LTO/G.
The feature of lithium ion battery lithium titanate/graphene composite negative pole of the present invention is: first prepare pure phase lithium titanate by hydro thermal method, then fully mix with the graphene oxide obtained by the Hummers method improved, move to reaction kettle for reaction certain hour after adding appropriate reducing agent and obtain lithium titanate/graphene composite negative pole.
A kind of lithium ion battery lithium titanate/graphene composite negative pole, is characterized in that: described composite negative pole material prepares through reducing agent reduction after lithium titanate mixes with graphene oxide, comprises the steps:
(1) graphite oxide is joined ultrasonic disperse 0.5-5h in solvent, obtain graphene oxide solution;
(2) the pure phase lithium titanate prepared by hydro thermal method is dissolved in absolute ethyl alcohol, forms white suspension by magnetic agitation, more dropwise add above-mentioned graphene oxide solution and appropriate reducing agent wherein, continue to stir 0.5-3h energetically;
(3) the above-mentioned suspension containing lithium titanate and graphene oxide is moved to containing in teflon-lined stainless steel autoclave, successive reaction 2-24h at 60 DEG C-150 DEG C, after cool to room temperature wash, centrifugal, dry, lithium titanate/graphene composite negative pole can be obtained.
The preparation method of described lithium ion battery lithium titanate/graphene composite negative pole, is characterized in that, the solvent of described graphite oxide is the one in the mixed solvent of deionized water, absolute ethyl alcohol, water and ethanol.
The preparation method of described lithium ion battery lithium titanate/graphene composite negative pole, is characterized in that, the concentration of lithium titanate white suspension is 0.01-0.1g/ml, and the mass fraction of the graphene oxide solution obtained after ultrasonic is 0.5%-2wt%.
The preparation method of described lithium ion battery lithium titanate/graphene composite negative pole, is characterized in that, the compound consumption of described Graphene accounts for the 0.5%-15% of described lithium titanate quality.
The preparation method of described lithium ion battery lithium titanate/graphene composite negative pole, it is characterized in that, reducing agent used is one or more in hydrazine hydrate, sodium borohydride, aluminum hydride, sodium hydrogensulfite, HI, HBr, absolute ethyl alcohol, iron powder, and the mass ratio of its consumption and graphene oxide is (1-20): 1.
The preparation method of described lithium ion battery lithium titanate/graphene composite negative pole, it is characterized in that, the preparation method of described graphite oxide comprises the following steps:
(1) in the flask of about 3g graphite powder and the mixing of about 18g potassium permanganate, to add volume ratio be the concentrated sulfuric acid of about 9:1 and the mixture of phosphoric acid;
(2) said mixture is heated to about 50-70 DEG C and stirs 8-24h;
(3) again by said mixture cool to room temperature, slowly pour on the ice cube that frozen in advance, the hydrogenperoxide steam generator that this ice cube is 30% by the mass fraction of 400ml water and about 8-10ml forms, and leaves standstill a period of time until ice cube melts completely;
(4) clean rear drying respectively with water, watery hydrochloric acid, ethanol again and obtain graphite oxide.
The preparation method of described lithium ion battery lithium titanate/graphene composite negative pole, is characterized in that, hydro thermal method is prepared pure phase lithium titanate and comprised the following steps:
(1) be dissolved in absolute ethyl alcohol by titanium source compound, both volume ratios are that 1:1 forms solution A; Li source compound is dissolved in deionized water, is mixed with certain density containing Li
+solution;
(2) in solution A, dropwise add the certain density containing Li of above-mentioned preparation under magnetic stirring
+solution, formed white suspension B, continue stir 1 h energetically;
(3) be transferred in stainless steel autoclave by described white suspension B, put into air blast electrically heated drying cabinet and naturally cool to room temperature after successive reaction 12-24h at 120-200 DEG C, gains are centrifugal, washing, drying obtains precursor powder;
(4) by described presoma in Muffle furnace, under air atmosphere, calcine 2-12h at 500-800 DEG C after the white powder that obtains be obtained pure phase lithium titanate.
The preparation method of described lithium ion battery lithium titanate/graphene composite negative pole, is characterized in that,
Described titanium source compound is one or more in butyl titanate, tetraisopropyl titanate, titanium tetrachloride, Nano titanium dioxide;
Described Li source compound is one or more in lithium hydroxide, lithium acetate, lithium carbonate, lithia;
Mol ratio between Li in described lithium source and the Ti in titanium source is 0.8-1;
What described Li source compound was mixed with contains Li
+solution concentration be 1-5mol/L;
The heating rate heated up during described calcining is 4 DEG C/min.
The feature of lithium ion battery lithium titanate/graphene composite negative pole of the present invention is to operate according to the following steps:
A, preparation pure phase lithium titanate: titanium source compound is dissolved in absolute ethyl alcohol, both volume ratios are that 1:1 forms solution A; Li source compound is dissolved in deionized water, is mixed with certain density Li
+solution, dropwise adds the above-mentioned certain density Li be made under magnetic stirring in solution A
+solution, forms white suspension B; Be transferred to by described white suspension B in stainless steel autoclave, naturally cool to room temperature at 120-200 DEG C after successive reaction 12-24h, gains are centrifugal, washing, drying obtains precursor powder; By described presoma in Muffle furnace, under air atmosphere, calcine 2-12h at 500-800 DEG C after the white powder that obtains be obtained pure phase lithium titanate.
B, prepare graphite oxide: in the flask of 3g graphite powder and the mixing of 18g potassium permanganate, add volume ratio is the concentrated sulfuric acid of 9:1 and the mixture of phosphoric acid; Said mixture is heated to 50-70 DEG C and stirs 8-24h; Again by said mixture cool to room temperature, slowly pour on the ice cube that frozen in advance, the hydrogenperoxide steam generator that this ice cube is 30% by 400ml water and about 8-10ml mass fraction forms, and leaves standstill a period of time until ice cube melts completely; Clean rear drying respectively with water, watery hydrochloric acid, ethanol and obtain graphite oxide.
C, prepare lithium titanate/graphene composite material: be dissolved in absolute ethyl alcohol by the lithium titanate that hydro thermal method is obtained and form white suspension, fully mix with the graphene oxide solution after ultrasonic disperse, add appropriate reducing agent again, be transferred in stainless steel water heating kettle together, react certain hour at a certain temperature and obtain lithium titanate/graphene composite negative pole.
Described titanium source compound is one or more in butyl titanate, tetraisopropyl titanate, titanium tetrachloride, Nano titanium dioxide.
Described Li source compound is one or more in lithium hydroxide, lithium acetate, lithium carbonate, lithia.
Mol ratio between Li in described lithium source and the Ti in titanium source is 0.8-1.
What described Li source compound was mixed with contains Li
+solution concentration be 1-5mol/L.
The concentration of described lithium titanate white suspension is 0.01-0.1g/ml, and the mass fraction of the graphene oxide solution after ultrasonic is 0.5%-2wt%.
The compound consumption of described Graphene accounts for the 0.5%-15% of described lithium titanate quality.
The feature of lithium ion battery lithium titanate/graphene composite negative pole of the present invention is: it is that normal temperature lower magnetic force stirs 0.5-3h that lithium titanate described in step c mixes with graphene oxide; Described reducing agent is one or more in hydrazine hydrate, sodium borohydride, lithium aluminium hydride reduction, sodium hydrogensulfite, HI, HBr, absolute ethyl alcohol, iron powder, and the mass ratio of its consumption and graphene oxide is (1-20): 1; Described mixed liquor moves to reactor successive reaction 2-24h at 60-150 DEG C.
The heating rate heated up during described Muffle furnace calcining is 4 DEG C/min.
Compared with prior art, beneficial effect of the present invention is embodied in:
1. composite negative pole material of the present invention is the lithium ion battery lithium titanate/graphene composite negative pole of a kind of more height ratio capacity, better high rate performance.
2. present invention employs successive reaction 2-24h at the mixed liquor of lithium titanate and graphene oxide and reducing agent is placed in reactor 60-150 DEG C, fully graphene oxide can not only be reduced to Graphene by this condition, and recombination energy improves the adhesive force between lithium titanate and Graphene under this condition, lithium titanate is dispersed between graphene sheet layer and forms a conductive network, thus specific capacity and the high rate performance of lithium ion battery can be improved.
3. the present invention adopts hydro thermal method to prepare lithium titanate, can not only be more evenly distributed, target product that particle is more tiny, and can reduce the temperature and time of subsequent heat treatment, greatly reduces energy consumption.
4. present invention process simplicity of design, not high to equipment requirement, be easy to realize suitability for industrialized production.
Accompanying drawing explanation
Fig. 1. the X-ray diffraction spectrogram of lithium titanate (a) prepared by embodiment 1 and lithium titanate/Graphene (b).
Fig. 2. the X-ray diffraction spectrogram of lithium titanate prepared by embodiment 2.
Fig. 3. first charge-discharge curve under lithium titanate/Graphene 0.1C prepared by embodiment 3.
Fig. 4. Li prepared by embodiment 4
4ti
5o
12the cycle performance figure of/Gpaphene.
Fig. 5. the SEM figure of lithium titanate/Graphene prepared by embodiment 4.
Fig. 6. the X-ray diffraction spectrogram (interior graphene-containing XRD schemes) of lithium titanate prepared by embodiment 4 and lithium titanate/Graphene.
Embodiment
In order to understand content characteristic of the present invention and beneficial effect further, below by concrete example with reference, elaboration detailed further being done to the present invention, but not limiting protection scope of the present invention.
Embodiment 1:
In this example, lithium ion battery lithium titanate/graphene composite negative pole prepares according to the following steps:
A, take the lithium hydroxide (LiOHH of 0.04mol
2o) 1.680g, is dissolved in the deionized water of 20ml, is mixed with the lithium hydroxide solution of 2mol/L; The butyl titanate solution 17ml of 0.05mol is measured with graduated cylinder, mix with isopyknic absolute ethyl alcohol, dropwise add the lithium hydroxide solution prepared under magnetic stirring wherein, continue stirring after obtaining white suspension within 1 hour, to transfer in reactor and react 24h at 180 DEG C, cool to room temperature, be placed in Muffle furnace and calcined 10h by centrifugal, washing, drying at 500 DEG C, the white powder obtained is lithium titanate, for subsequent use after grinding.
B, by the above-mentioned lithium titanate Li prepared
4ti
5o
12take 2g, be dissolved in magnetic agitation in the absolute ethyl alcohol of 20ml; And add the graphite oxide 0.2g of this quality 10%, ultrasonic disperse obtains graphene oxide solution in deionized water, be added drop-wise to subsequently in the suspension of lithium titanate, add appropriate absolute ethyl alcohol again and make reducing agent, move to after abundant mixing in reactor and react 16h at 120 DEG C, gains drying can be obtained lithium titanate/graphene composite negative pole by cool to room temperature.
The lithium titanate Li that the present embodiment prepares
4ti
5o
12with lithium titanate/Graphene Li
4ti
5o
12the X-ray diffraction spectrogram of/Graphene is shown in Fig. 1.As can be seen from Figure 1, cause occurring obvious Detitanium-ore-type TiO because loss under lithium high temperature causes lithium source not enough
2diffraction maximum (101); Graphene due to become unformed shape so diffraction maximum is not obvious, and Graphene add the crystalline structure not affecting lithium titanate.
Lithium titanate/the Graphene obtained by the present embodiment mixes by the mass ratio of 80:10:10 with acetylene black and Kynoar PVDF, is rolled into the film of thick 120um, at 120 DEG C after dry 10h as experiment half-cell positive pole; Adopt the LiPF of 1mol/L
6/ vinyl carbonate (EC)-diethyl carbonate (DEC) (the volume ratio 1:1 of EC and DEC) electrolyte, is full of in the glove box of argon gas in drying, using metal lithium sheet as negative pole, is assembled into battery.Adopt battery test system, carry out volume test in 1.0-2.5V voltage range.Using the lithium titanate/Graphene prepared by the present embodiment as the positive pole of half-cell, the button cell being negative pole with lithium sheet first discharge specific capacity under 0.2C reaches 174.268mAh/g, but after 20 circulations, capacity is only 147.564mAh/g, and capability retention is only 84.7%, this and dephasign TiO
2existence and too much Graphene be compounded with relation.
Embodiment 2:
In this example, lithium ion battery lithium titanate/graphene composite negative pole prepares according to the following steps:
A, take the lithium hydroxide (LiOHH of 0.043mol
2o) 1.815g, wherein in order to make up the loss of lithium under high temperature, making lithium hydroxide excessive 8%, being dissolved in the deionized water of 10ml, being mixed with the lithium hydroxide solution of 4mol/L; Measure the butyl titanate solution 17ml of 0.05mol with graduated cylinder, mix with isopyknic absolute ethyl alcohol; Dropwise add the lithium hydroxide solution prepared under magnetic stirring wherein, continue stirring after obtaining white suspension and within 1 hour, transfer in reactor and react 24h at 180 DEG C; Cool to room temperature, be placed in Muffle furnace and calcined 10h by centrifugal, washing, drying at 700 DEG C, the white powder obtained is lithium titanate, for subsequent use after grinding.
B, by the above-mentioned lithium titanate Li prepared
4ti
5o
12take 2g, be dissolved in magnetic agitation in absolute ethyl alcohol; And adding the graphite oxide 0.1g of this quality 5%, ultrasonic disperse obtains graphene oxide solution in deionized water; Be added drop-wise in the suspension of lithium titanate subsequently, then add 1.0ml hydrazine hydrate, fully move in reactor after mixing and react 12h at 90 DEG C, gains drying can be obtained lithium titanate/graphene composite negative pole by cool to room temperature.
The lithium titanate Li that the present embodiment prepares
4ti
5o
12x-ray diffraction spectrogram see Fig. 2.As can be seen from 2, due to lithium excessive 8%, compensate for the loss of lithium under high temperature, the enough formation contributing to pure phase spinel type lithium titanate in lithium source.
The composite negative pole material prepared by the present embodiment is assembled into battery, concrete grammar is with embodiment 1, record its first discharge specific capacity under 0.1C and reach 180.035mAh/g, and capacity remains on 159.003mAh/g after 20 circulations, capability retention is 88.3%.
Embodiment 3:
In this example, lithium ion battery lithium titanate/graphene composite negative pole prepares according to the following steps:
A, take the lithium hydroxide (LiOHH of 0.043mol
2o) 1.815g, wherein in order to make up the loss of lithium under high temperature, making lithium hydroxide excessive 8%, being dissolved in the deionized water of 20ml, being mixed with the lithium hydroxide solution of 2mol/L; The butyl titanate solution 17ml of 0.05mol is measured with graduated cylinder, mix with isopyknic absolute ethyl alcohol, dropwise add the lithium hydroxide solution prepared under magnetic stirring wherein, continue stirring after obtaining white suspension and within 1 hour, transfer in reactor and react 24h at 180 DEG C; Cool to room temperature, be placed in Muffle furnace and calcined 10h by centrifugal, washing, drying at 700 DEG C, the white powder obtained is lithium titanate, for subsequent use after grinding.
B, by the above-mentioned lithium titanate Li prepared
4ti
5o
12take 2g, be dissolved in magnetic agitation in the absolute ethyl alcohol of 50ml, and add the graphite oxide 0.04g of this quality 2%, in absolute ethyl alcohol, ultrasonic disperse obtains graphene oxide solution, be added drop-wise to subsequently in the suspension of lithium titanate, add 0.5ml hydrazine hydrate again, fully move in reactor after mixing and react 6h at 100 DEG C, gains drying can be obtained lithium titanate/graphene composite negative pole by cool to room temperature.
The composite negative pole material prepared by the present embodiment is assembled into battery, and concrete grammar is with embodiment 1, and record its first discharge specific capacity under 0.1C and reach 183.614mAh/g, and capacity remains on 167.558mAh/g after 20 circulations, capability retention is 92%; And discharge platform is stablized, platform capacity reaches can about 90%, specifically sees in Fig. 3 first charge-discharge curve under the lithium titanate/Graphene 0.1C implementing 3 preparations.
Embodiment 4:
In this example, lithium ion battery lithium titanate/graphene composite negative pole prepares according to the following steps:
A, take the lithium hydroxide (LiOHH of 0.043mol
2o) 1.815g, wherein in order to make up the loss of lithium under high temperature, making lithium hydroxide excessive 8%, being dissolved in the deionized water of 10ml, being mixed with the lithium hydroxide solution of 4mol/L; Measure the butyl titanate solution 17ml of 0.05mol with graduated cylinder, mix with isopyknic absolute ethyl alcohol; Dropwise add the lithium hydroxide solution prepared under magnetic stirring wherein, continue stirring after obtaining white suspension and within 1 hour, transfer in reactor and react 24h at 180 DEG C; Cool to room temperature, be placed in Muffle furnace and calcined 10h by centrifugal, washing, drying at 700 DEG C, the white powder obtained is lithium titanate, for subsequent use after grinding.
B, by the above-mentioned lithium titanate Li prepared
4ti
5o
12take 2g, be dissolved in magnetic agitation in absolute ethyl alcohol, and add the graphite oxide 0.06g of this quality 3%, ultrasonic disperse obtains graphene oxide solution in deionized water; Be added drop-wise in the suspension of lithium titanate subsequently, then add 0.8ml hydrazine hydrate, fully move in reactor after mixing and react 2h at 100 DEG C, gains drying can be obtained lithium titanate/graphene composite negative pole by cool to room temperature.
The composite negative pole material prepared by the present embodiment is assembled into battery, and concrete grammar is with embodiment 1, and record its first discharge specific capacity under 0.1C and reach 197.457mAh/g, reversible capacity reaches 193.441mAh/g first, and coulombic efficiency reaches 98%.The cycle performance figure of lithium titanate/Graphene that the present embodiment prepares is shown in Fig. 4, and after 30 circulations, capacity also remains on 174.903mAh/g as can be seen from Figure 4, illustrates that it has good cyclical stability.Fig. 5 is the SEM figure of lithium titanate/Graphene prepared by embodiment 4, and the flaky texture in figure is Graphene.Fig. 6 is the lithium titanate of embodiment 4 preparation and the X-ray diffraction spectrogram (attached: the upper right corner is that Graphene XRD schemes) of lithium titanate/Graphene.
The Li that the present embodiment prepares
4ti
5o
12/ Graphene not only has higher specific capacity and good cyclical stability, and its high rate performance is also better.Discharge capacity first wherein under 0.1C is 197.457mAh/g, discharge capacity first under 0.2C is 194.584mAh/g, discharge capacity first under 0.5C is 159.680mAh/g, discharge capacity first under 1C is 145.867mAh/g, discharge capacity first under 2C is 138.856mAh/g, discharge capacity first under 5C is 121.197mAh/g, respectively higher than the discharge capacity of pure phase lithium titanate 170.560 mAh/g, 166.987 mAh/g, 152.895 mAh/g, 141.290 mAh/g, 130.441mAh/g, 108.427mAh/g under respective corresponding multiplying power.
Embodiment 5:
In this example, lithium ion battery lithium titanate/graphene composite negative pole prepares according to the following steps:
A, take the lithium hydroxide (LiOHH of 0.043mol
2o) 1.815g, wherein in order to make up the loss of lithium under high temperature, making lithium hydroxide excessive 8%, being dissolved in the deionized water of 10ml, being mixed with the lithium hydroxide solution of 4mol/L; Take the titanium dioxide (TiO of 0.05mol equally
2) 4g, be dissolved in the absolute ethyl alcohol of 17ml, dropwise add the lithium hydroxide solution prepared under magnetic stirring wherein, continue stirring after obtaining white suspension and within 1 hour, transfer in reactor and react 24h at 180 DEG C; Cool to room temperature, be placed in Muffle furnace and calcined 10h by centrifugal, washing, drying at 700 DEG C, the white powder obtained is lithium titanate, for subsequent use after grinding.
B, by the above-mentioned lithium titanate Li prepared
4ti
5o
12take 2g, be dissolved in magnetic agitation in absolute ethyl alcohol, and add the graphite oxide 0.06g of this quality 3%, ultrasonic disperse obtains graphene oxide solution in deionized water; Be added drop-wise to subsequently in the suspension of lithium titanate, add 1g iron powder (particle diameter 10um) and 20ml watery hydrochloric acid (mass fraction 35wt%) again, move to after abundant mixing in reactor and react 6h at 90 DEG C, gains drying can be obtained lithium titanate/graphene composite negative pole by cool to room temperature.
The composite negative pole material prepared by the present embodiment is assembled into battery, and concrete grammar is with embodiment 1, and record its first discharge specific capacity under 0.1C and reach 159.747mAh/g, and capacity remains on 137.504mAh/g after 10 circulations, capability retention is 86%.
Claims (8)
1. lithium ion battery lithium titanate/graphene composite negative pole, is characterized in that: described composite negative pole material prepares through reducing agent reduction after lithium titanate mixes with graphene oxide, comprises the steps:
(1) graphite oxide is joined ultrasonic disperse 0.5-5h in solvent, obtain graphene oxide solution;
(2) the pure phase lithium titanate prepared by hydro thermal method is dissolved in absolute ethyl alcohol, forms white suspension by magnetic agitation, more dropwise add above-mentioned graphene oxide solution and appropriate reducing agent wherein, continue to stir 0.5-3h energetically;
(3) the above-mentioned suspension containing lithium titanate and graphene oxide is moved to containing in teflon-lined stainless steel autoclave, successive reaction 2-24h at 60 DEG C-150 DEG C, after cool to room temperature wash, centrifugal, dry, lithium titanate/graphene composite negative pole can be obtained.
2. the preparation method of lithium ion battery lithium titanate/graphene composite negative pole according to claim 1, is characterized in that, the solvent of described graphite oxide is the one in the mixed solvent of deionized water, absolute ethyl alcohol, water and ethanol.
3. the preparation method of lithium ion battery lithium titanate/graphene composite negative pole according to claim 1, it is characterized in that, the concentration of lithium titanate white suspension is 0.01-0.1g/ml, and the mass fraction of the graphene oxide solution obtained after ultrasonic is 0.5%-2wt%.
4. the preparation method of lithium ion battery lithium titanate/graphene composite negative pole according to claim 1, is characterized in that, the compound consumption of described Graphene accounts for the 0.5%-15% of described lithium titanate quality.
5. the preparation method of lithium ion battery lithium titanate/graphene composite negative pole according to claim 1, it is characterized in that, reducing agent used is one or more in hydrazine hydrate, sodium borohydride, aluminum hydride, sodium hydrogensulfite, HI, HBr, absolute ethyl alcohol, iron powder, and the mass ratio of its consumption and graphene oxide is (1-20): 1.
6. the preparation method of lithium ion battery lithium titanate/graphene composite negative pole according to claim 1, it is characterized in that, the preparation method of described graphite oxide comprises the following steps:
(1) in the flask of about 3g graphite powder and the mixing of about 18g potassium permanganate, to add volume ratio be the concentrated sulfuric acid of about 9:1 and the mixture of phosphoric acid;
(2) said mixture is heated to about 50-70 DEG C and stirs 8-24h;
(3) again by said mixture cool to room temperature, slowly pour on the ice cube that frozen in advance, the hydrogenperoxide steam generator that this ice cube is 30% by the mass fraction of 400ml water and about 8-10ml forms, and leaves standstill a period of time until ice cube melts completely;
(4) clean rear drying respectively with water, watery hydrochloric acid, ethanol again and obtain graphite oxide.
7. the preparation method of lithium ion battery lithium titanate/graphene composite negative pole according to claim 1, is characterized in that, hydro thermal method is prepared pure phase lithium titanate and comprised the following steps:
(1) be dissolved in absolute ethyl alcohol by titanium source compound, both volume ratios are that 1:1 forms solution A; Li source compound is dissolved in deionized water, is mixed with certain density containing Li
+solution;
(2) in solution A, dropwise add the certain density containing Li of above-mentioned preparation under magnetic stirring
+solution, formed white suspension B, continue stir 1 h energetically;
(3) be transferred in stainless steel autoclave by described white suspension B, put into air blast electrically heated drying cabinet and naturally cool to room temperature after successive reaction 12-24h at 120-200 DEG C, gains are centrifugal, washing, drying obtains precursor powder;
(4) by described presoma in Muffle furnace, under air atmosphere, calcine 2-12h at 500-800 DEG C after the white powder that obtains be obtained pure phase lithium titanate.
8. the preparation method of lithium ion battery lithium titanate/graphene composite negative pole according to claim 7, is characterized in that,
Described titanium source compound is one or more in butyl titanate, tetraisopropyl titanate, titanium tetrachloride, Nano titanium dioxide;
Described Li source compound is one or more in lithium hydroxide, lithium acetate, lithium carbonate, lithia;
Mol ratio between Li in described lithium source and the Ti in titanium source is 0.8-1;
What described Li source compound was mixed with contains Li
+solution concentration be 1-5mol/L;
The heating rate heated up during described calcining is 4 DEG C/min.
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