Composite negative pole material of titanium-containing oxide/carbon nano-tube and preparation method thereof
Technical field
The present invention relates to the technical field of ion cathode material lithium, relate in particular to compound negative material of titanium-containing oxide/carbon nano-tube and preparation method thereof.
Background technology
The fast development of electric automobile, hybrid vehicle and energy-storage battery, to provide the lithium ion battery of energy to propose harsher requirement for it, its power-performance particularly.Negative material is the critical material of bearing lithium memory function in lithium ion battery.At present, business-like lithium ion battery negative material adopts embedding lithium material with carbon element mostly, as graphite, soft charcoal, hard charcoal etc.Material with carbon element has that wide material sources, charging/discharging voltage platform are low, theoretical capacity advantages of higher, but exist first charge-discharge efficiency low, have an effect with electrolyte, the poor safety performance of battery, the defect such as high rate during charging-discharging is poor, cycle life is short.Therefore, searching fail safe negative material better, that high rate charge-discharge performance is more excellent is imperative.
The eighties in last century, Canadian Studies person Michael Thackeray seminar just starts to carry out Li
4/3ti
5/3o
4as the research of lithium cell cathode material, within 1994, obtain the preparation of lithium cell negative pole material spinel structure Li-Ti oxide; Nineteen ninety-five, Japanology person Tsutamu Ohzuku (Zero-Strain Insertion Material of Li[Li1/3Ti5/3] O4for Rechargeable Lithium Cells, J.Electrochem.Soc., Vol.142, No.5) openly study first Li[Li
1/3ti
5/3] O
4in the crystal structure of material and charge and discharge process, Li+ inserts and takes off embedding to the almost not impact (" zero strain " material) of its structure, and the current potential of lithium electrode is 1.55V (vsLi/Li+) relatively, and theoretical capacity is 175mAh/g; P.Frangnaud also published paper and related to Li the same year
4/3ti
5/3o
4the preparation method of material (J.Sensors and Actuators A51 (1995) 21-23); 1996, Canadian Studies person K.zaghib proposed first, adopted lithium titanium oxide material to make negative pole and high-voltage anode material composition lithium ion battery, formed electrochemical capacitor with carbon resistance rod.Afterwards, lot of domestic and international researcher (Hydro-Quebec US2004202934A1, Aaltair Nanomaterials US20030017104A1, Bei Terui CN100530780C etc.) using it as lithium ion battery negative material, carried out the research of preparation method aspect.2007, Toshiba Corp announced the lithium ion battery " SCiB " of exploitation based on lithium titanium oxide material, is intended to be applied to hybrid power field.U.S. Enerdel company has shown hybrid vehicle lithium titanate electrokinetic cell in AABC-07 meeting.
Lithium titanate be a kind of have the long-life, can high current charge-discharge, the high performance lithium ionic cell cathode material of safety, environmental protection, cycle performance that equilibrium potential is high, good, very smooth characteristics such as voltage platform, and its platform capacity surpasses the more than 85% of total capacity, but, the conductivity of lithium titanate is low, when high power charging-discharging, capacitance can not be brought into play well, therefore, need to improve its conductivity to its modification.
The main path that improves at present the high-rate charge-discharge capability of lithium titanate has: nanometer particle size distributes; Porous or hollow structure meso-hole structure; Element doping or carbon are coated, because the contact area of clad material is limited, have limited the further raising of its performance.Patent (publication number: CN101630732A) after disclosing employing sol-gel process a certain proportion of carbon nano tube dispersion liquid being mixed with titanium, lithium compound and doped chemical solution, heat drying makes gel precursor, and under inert atmosphere, sintering obtains the preparation method that the coated particle diameter of a kind of carbon nano-tube is nano level lithium titanate compound.Same patent (publication number: CN102074681B) also disclose a kind of in lithium titanate directly doped carbon nanometer pipe prepare anode material, thereby improve the method for battery high rate performance.Chinese patent (publication number: the preparation method who CN101969112A) discloses a kind of negative material, by positive and negative electrode material and catalyst, be 100:(0.1~5 in mass ratio) after mechanical mixture, add in thermal reaction apparatus, pass to carbon-source gas, and pass to protective gas as carrying source gas, cooling after being incubated 1~72 hour after being warmed up to 400~900 ℃, the mixture of formation positive and negative electrode material, catalyst and carbon nano-tube; Again mixture and oxidant are added in reactor according to mass ratio, add water and stir into pastel; Pastel is heated at 50~400 ℃ and reacts 1~20 hour again, make the composite negative pole material that is coated with carbon nano-tube.Yet the method course of reaction is complicated, the positive and negative electrode stability of material making is poor, affects the cycle performance of battery.
Summary of the invention
In view of this, the invention provides a kind of preparation method of composite negative pole material of titanium-containing oxide/carbon nano-tube, this preparation method can obtain the composite negative pole material of high rate capability.
A method of preparing the composite negative pole material of titanium-containing oxide/carbon nano-tube, comprises the following steps:
(1) in the aqueous solution of the water soluble salt of doped chemical, add weak base, stir and obtain doped chemical dispersion liquid, it is a kind of or at least two kinds and be selected from a kind of in II A, III A, IV A family element or at least two kinds that described doped chemical is selected from VIII family element;
(2) inorganic lithium salt, titanium dioxide and dispersant are scattered in water, obtain lithium titanium dispersion liquid;
(3) mix described lithium titanium dispersion liquid and doped chemical dispersion liquid, then dry, obtain composite precursor;
(4) described composite precursor is carried out, after the pre-heat treatment, insert in reactor, in protective atmosphere, to passing into carbon-source gas in this reactor, carry out CVD, then cooling through heat treatment, obtain composite negative pole material.
In above-mentioned preparation method, described in step (1), water soluble salt is chloride or nitrate;
Preferably, weak base described in step (1) is a kind of in ammonia, ammoniacal liquor, carbon ammonium, carbonic hydroammonium and urea or at least two kinds;
Preferably, described in step (1), the pH of doped chemical dispersion liquid is 4.0~11.4.
Wherein, described in step (2), the mol ratio of inorganic lithium salt and titanium dioxide is 0.7~0.9:1;
Preferably, described in step (2), dispersant accounts for below the 3wt% of titanium dioxide quality;
Preferably, inorganic lithium compound described in step (2) is a kind of in lithium hydroxide, lithium carbonate, lithia, lithium acetate, lithium oxalate, lithium chloride, lithium nitrate and lithium fluoride or at least two kinds;
Preferably, described in step (2), dispersant is ethanol, polyvinyl alcohol, glucose, citric acid, polyvinylpyrrolidone, polyethylene glycol, a kind of in tween dispersant, BYK dispersant or at least two kinds;
The mode of preferably, disperseing described in step (2) is ball milling 1~40h, more preferably 10min~6h under 100~1500rpm.
The charging sequence that the middle inorganic lithium salt of step (3), titanium dioxide and dispersant are scattered in water can be, first inorganic lithium salt, titanium dioxide are mixed, then in the mixture of inorganic lithium salt, titanium dioxide, add the dispersant being dissolved in the water, insert in ball mill.The mol ratio of doped chemical dispersion liquid described in step (3) and lithium titanium dispersion liquid is not more than 0.5;
Preferably, described in step (3), dry temperature is 100~350 ℃;
Preferably, described in step (3), dry feed rate is 1~10kg/h;
Preferably, described in step (3), dry mode is dried for spraying.
Wherein, in step (4) reactor be well known to those skilled in the art in CVD legal system conventional in for carbon nano-tube, such as quartz boat etc.Described in step (4), the pre-heat treatment is specially: with 1~15 ℃/min speed, be warming up to 450~700 ℃ of heating 1~8h;
Preferably, described in step (4), heat treated temperature is 660~900 ℃;
Preferably, described in step (4), the heat treated time is 6~15h;
Preferably, described in step (4), the temperature of CVD is 550~900 ℃
Preferably, described in step (4), the time of CVD is 0.5~4h;
Preferably, described in step (4), cooling temperature is 95~105 ℃;
Preferably, described in step (4), carbon-source gas is methane, ethene, acetylene, propylene, ethanol, benzene, a kind of in natural gas and liquefied petroleum gas or at least two kinds;
Preferably, described in step (4), protective atmosphere is nitrogen or inert gas.Inert gas can be helium.What deserves to be explained is, carbon-source gas of the present invention and protective gas not only limit to and above-mentioned cited example, within described those skilled in the art should understand that easily realizing other carbon-source gas of the present invention and protective gas should be included in the present invention.
Further aspect of the present invention provides a kind of composite negative pole material of titanium-containing oxide/carbon nano-tube.This composite negative pole material has high rate capability.
Preferably, in composite material, carbon nano-tube average length is 0.01~50 μ m, and average caliber is 1~100nm.
Preferably, its average grain diameter of composite material is 0.05~30 μ m, and average tap density is 0.5~2.5g/cm
3, its powder conductivity is not less than 1.00E-07S/cm.
Thereby first the present invention uses doped chemical to adulterate and obtain doping vario-property titanium-containing oxide the titanium oxide being obtained by inorganic lithium salt, titanium dioxide reaction, then on this doping vario-property titanium-containing oxide surface, carry out CVD, make its surface in situ growth form one deck mesh carbon nanotube.With directly in lithium titanate doped carbon nanometer pipe compare, one aspect of the present invention is compared with directly in lithium titanate, the dispersion of the mode carbon nano-tube of doped carbon nanometer pipe is more even, adhesion is stronger, not only improved conductivity, and the Stability Analysis of Structures of improving battery material under large multiplying power discharging condition plays an important role; On the other hand, doped chemical can enter titanium oxide lattice dot matrix or compound with it, comprehensively promotes thus high rate performance, thereby can be used for the fields such as ultracapacitor, lithium ion battery.
Accompanying drawing explanation
Fig. 1 is the SEM figure of the composite negative pole material of one embodiment of the invention.
Fig. 2 is the XRD figure of the composite negative pole material of one embodiment of the invention.
Embodiment
Below in conjunction with embodiment, further illustrate technical scheme of the present invention.
Embodiment 1
Get the pure water of 100 parts of quality, the cobalt nitrate that contains 1 part of quality cobalt element, the aluminum nitrate that contains 1 part of quality aluminium element, stirring and dissolving is transparent to solution, then adding mass fraction is 30% ammonia spirit, fully stir and form cream, the pH that controls solution is stabilized in 9.2 left and right, obtains emulsus suspension emulsion A;
By LiOHH
2o and TiO
2weigh for the ratio of 0.7:1 in molar ratio; Raw material after above-mentioned weighing is added to titania weight 3wt% water soluble dispersing agent polyvinylpyrrolidone and appropriate amount of deionized water to be joined and in high-energy ball milling mixing apparatus, carries out nanometer and process 10h, stir speed (S.S.) 1500r/min; Then by stoichiometry mol ratio, be 0.3 to add cream A, after mix and blend refinement 1h, by said mixture slurry spray-drying process feed rate 10kg/h, baking temperature arranges 350 ℃, obtains titanium-containing oxide composite precursor;
Heating rate by powder presoma with 15 ℃/min, heat treatment 8h in the temperature range of 700 ℃ then passes into N always
2protective gas, passes into methane carbon-source gas 4h again when temperature is controlled at 900 ℃, stop passing into methane carbon-source gas, and temperature is controlled at 900 ℃ of heat treatment 15h, at N
2under protective gas condition, being cooled to 100 ℃, to obtain carbon nano-tube composite titanium be oxide cathode active material.
Embodiment 2
Get the pure water of 100 parts of quality, the cobalt nitrate that contains 2 parts of quality cobalt elements, the aluminum nitrate that contains 2 parts of quality aluminium elements, stirring and dissolving is transparent to solution, then add saturated ammonium bicarbonate soln, fully stir and form cream, the pH that controls solution is stabilized in 9.4 left and right, obtains emulsus suspension emulsion A;
By LiOHH
2o and TiO
2weigh for the ratio of 0.776:1 in molar ratio; Raw material after above-mentioned weighing is added to titania weight 2wt% water soluble dispersing agent polyvinylpyrrolidone and polyethylene glycol and appropriate amount of deionized water to be joined and in high-energy ball milling mixing apparatus, carries out nanometer and process 8h, stir speed (S.S.) 1200r/min; Then by stoichiometry mol ratio, be 0.5 to add cream A, after mix and blend refinement 1h, by said mixture slurry spray-drying process feed rate 8kg/h, baking temperature arranges 300 ℃, obtains titanium-containing oxide composite precursor;
Heating rate by powder presoma with 10 ℃/min, heat treatment 7h in the temperature range of 600 ℃ then passes into N always
2protective gas; when being controlled at 800 ℃, temperature passes into again methane carbon-source gas 3h; stop passing into methane carbon-source gas, temperature is controlled at 800 ℃ of heat treatment 12h, and under N2 protective gas condition, being cooled to 100 ℃, to obtain carbon nano-tube composite titanium be oxide cathode active material.
Embodiment 3
Get the pure water of 100 parts of quality, the nickel nitrate that contains 1 part of quality nickel element, the aluminum nitrate that contains 1 part of quality aluminium element, the magnesium nitrate that contains 1 part of quality magnesium elements, stirring and dissolving is transparent to solution, then adding mass fraction is 30% ammonia spirit, fully stir and form cream, the pH that controls solution is stabilized in 11.4 left and right, obtains emulsus suspension emulsion A;
By LiOHH
2o and TiO
2weigh for the ratio of 0.824:1 in molar ratio; Raw material after above-mentioned weighing is added to titania weight 2.5wt% water soluble dispersing agent polyethylene glycol and appropriate amount of deionized water to be joined and in high-energy ball milling mixing apparatus, carries out nanometer and process 5h, stir speed (S.S.) 900r/min; Then by stoichiometry mol ratio, be 0.1 to add cream A, after mix and blend refinement 3h, by said mixture slurry spray-drying process feed rate 5kg/h, baking temperature arranges 260 ℃, obtains titanium-containing oxide composite precursor;
Heating rate by powder presoma with 5 ℃/min, heat treatment 8h in the temperature range of 550 ℃ then passes into N always
2protective gas; when being controlled at 750 ℃, temperature passes into again acetylene carbon-source gas 2h; stop passing into acetylene carbon-source gas, temperature is controlled at 750 ℃ of heat treatment 10h, and under N2 protective gas condition, being cooled to 100 ℃, to obtain carbon nano-tube composite titanium be oxide cathode active material.
Embodiment 4
Get the pure water of 100 parts of quality, the cobalt nitrate that contains 1 part of quality cobalt element, the aluminum nitrate that contains 1 part of quality aluminium element, stirring and dissolving is transparent to solution, then adding mass fraction is 30% ammonia spirit, fully stir and form cream, the pH that controls solution is stabilized in 9.2 left and right, obtains emulsus suspension emulsion A;
By Li
2cO
3with TiO
2weigh for the ratio of 0.85:1 in molar ratio; Raw material after above-mentioned weighing is added to titania weight 0.5wt% water soluble dispersing agent BYK-2015 and appropriate amount of deionized water to be joined and in high-energy ball milling mixing apparatus, carries out nanometer and process 6h, stir speed (S.S.) 800r/min; Then by stoichiometry mol ratio, be 0.25 to add cream A, after mix and blend refinement 3h, by said mixture slurry spray-drying process feed rate 3kg/h, baking temperature arranges 250 ℃, obtains titanium-containing oxide composite precursor;
Heating rate by powder presoma with 5 ℃/min, heat treatment 6h in the temperature range of 500 ℃ then passes into N always
2protective gas, passes into ethene carbon-source gas 4h again when temperature is controlled at 720 ℃, stop passing into ethene carbon-source gas, and temperature is controlled at 720 ℃ of heat treatment 8h, at N
2under protective gas condition, being cooled to 100 ℃, to obtain carbon nano-tube composite titanium be oxide cathode active material.
Embodiment 5
Get the pure water of 100 parts of quality, the ferric nitrate that contains 1 part of quality ferro element, the nickel nitrate that contains 1 part of quality nickel element, the magnesium nitrate that contains 1 part of quality magnesium elements, stirring and dissolving is transparent to solution, then add saturated carbon ammonium and carbonic hydroammonium mixed solution, fully stir and form cream, the pH that controls solution is stabilized in 10.4 left and right, obtains emulsus suspension emulsion A;
By Li
2cO
3with TiO
2weigh for the ratio of 0.824:1 in molar ratio; Raw material after above-mentioned weighing is added to titania weight 1.0wt% water soluble dispersing agent polyethylene glycol and glucose and appropriate amount of deionized water to be joined and in high-energy ball milling mixing apparatus, carries out nanometer and process 3h, stir speed (S.S.) 900r/min; Then by stoichiometry mol ratio, be 0.15 to add cream A, after mix and blend refinement 3h, by said mixture slurry spray-drying process feed rate 2kg/h, baking temperature arranges 260 ℃, obtains titanium-containing oxide composite precursor;
Heating rate by powder presoma with 5 ℃/min, heat treatment 8h in the temperature range of 550 ℃ then passes into N always
2protective gas, passes into acetylene carbon-source gas 2h again when temperature is controlled at 750 ℃, stop passing into acetylene carbon-source gas, and temperature is controlled at 750 ℃ of heat treatment 10h, at N
2under protective gas condition, being cooled to 100 ℃, to obtain carbon nano-tube composite titanium be oxide cathode active material.
Comparative example
By Li
2cO
3with TiO
2weigh for the ratio of 0.9:1 in molar ratio; Raw material after above-mentioned weighing is added to appropriate amount of deionized water to be joined and in high-energy ball milling mixing apparatus, carries out nanometer and process 6h, stir speed (S.S.) 1000r/min; By said mixture slurry spray-drying process feed rate 6kg/h, baking temperature arranges 280 ℃, obtains titanium-containing oxide composite precursor;
Heating rate by powder presoma with 10 ℃/min, heat treatment 6h in the temperature range of 620 ℃ then passes into N always
2protective gas, temperature is controlled at 780 ℃ of heat treatment 10h, at N
2under protective gas condition, be cooled to 100 ℃ and obtain titanium-containing oxide negative electrode active material.
Embodiment 1~5 and comparative example are averaged to the test of particle diameter, tap density and powder conductivity aspect, according to method of testing can adopt the means that those skilled in the art are habitual, at this, do not repeating.
Embodiment 1~5 and comparative example are carried out to electrochemical property test: by the carbon nano-tube composite titanium preparing in above-described embodiment, be respectively that oxide cathode active material, conductive black and Kynoar (PVDF) mix by 80:10:10 weight ratio, be applied on Copper Foil collector, through vacuumize dry for standby; Simulation half-cell is assemblied in the glove box of applying argon gas and carries out, electrolyte is 1mol/L LiPF6/EC+DMC+EMC solution, wherein EC, DMC, EMC volume ratio are 1:1:1, metal lithium sheet is to electrode, electrochemical property test carries out on land battery performance test instrument, and charging/discharging voltage scope is 1.0V to 2.5V.
The above-mentioned test result of embodiment 1~5 and comparative example contrasts table specific as follows:
Table 1
As shown in Figure 1, for composite negative pole material in the embodiment of the present invention SEM figure.From this figure, can find out, titanium-containing oxide material surface in-situ growing carbon nano tube, being dispersed in of the even carbon nanotube of growth forms between spheroid primary particle, and adhesion is stronger, more easily on lithium titanate surface, form network structure, improve the electron conduction of material, the Stability Analysis of Structures of material under large multiplying power discharging condition is played an important role; Promoting under the prerequisite of conductivity, the closely knit secondary ball body structure of preparation has promoted tap density and the mobility of material, is easy to processed and applied simultaneously.
As shown in Figure 2, be the XRD figure of the composite negative pole material of one embodiment of the invention.From figure, can find out, the diffraction maximum correspondence of embodiment 1~5 and comparative example angle of diffraction is everywhere roughly the same, illustrates that these composite negative pole materials have identical crystal formation.
Applicant's statement, the present invention illustrates detailed process equipment and process flow process of the present invention by above-described embodiment, but the present invention is not limited to above-mentioned detailed process equipment and process flow process, do not mean that the present invention must rely on above-mentioned detailed process equipment and process flow process and could implement.Person of ordinary skill in the field should understand, any improvement in the present invention, to the selection of the interpolation of the equivalence replacement of each raw material of product of the present invention and auxiliary element, concrete mode etc., within all dropping on protection scope of the present invention and open scope.