CN102593457A - Preparation method of lithium iron phosphate-carbon material composite - Google Patents
Preparation method of lithium iron phosphate-carbon material composite Download PDFInfo
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Abstract
The invention belongs to the technical field of energy material preparation and relates to a preparation method of a lithium iron phosphate-carbon material composite. The preparation method provided by the invention comprises the step of adding a phosphate-source compound, an iron-source compound and a lithium-source compound into a dispersed liquid containing a carbon material. With the adoption of the preparation method provided by the invention, the lithium iron phosphate-carbon material composite with a mean particle size of 0.02-10mum, a tap density of 1.8-2.2g/cm<3> and a discharge specific capacity of 140-164mAh/g under 0.2C (2.4A of current) at room temperature can be prepared. The composite can be used as a cathode material of a lithium battery, which requires a high specific capacity and high cycling stability.
Description
Technical field
The present invention relates to the energy and material technology, particularly, the present invention relates to the preparation method's of LiFePO4-carbon material compound, particularly lithium ion battery anode material lithium iron phosphate preparation method and the LiFePO4-carbon material compound for preparing by this method.
Background technology
LiFePO4 (LiFePO with regular olivine-type
4), its theoretical specific capacity higher relatively (170mAh/g) can produce 3.4V (vs.Li/Li
+) voltage, simultaneously, it has nontoxic, characteristics such as raw material sources are extensive, cost is low, Heat stability is good again, thereby LiFePO4 is considered to the desirable positive electrode of lithium-ion-power cell development.
In research process, it is found that LiFePO
4When little electric current discharges and recharges, can reach higher specific capacity, capacity is but decayed comparatively fast during big electric current; And circulation back capacity can decay about 20% first.The Pdaihi model is thought; General capacity attenuation be since electrode material granules in charge and discharge process, variation has taken place in volume and structure, has caused particle and particle; Electrically contacting between particle and the conductive agent is damaged, thereby caused that specific capacity irreversibly reduces.LiFePO
4Capacity attenuation then be because ion and electronic conductivity are lower, Li
+Less the causing of diffusion coefficient, be reversible, if reduce current density, capacity can recover again.The radius model of Andesrosn AS and mosaic model all propose in the first charge-discharge, and a spot of sluggish LiFePO is arranged in the active particle
4And FePO
4Conversion each other not taking place, thereby fail to participate in electrochemical reaction in afterwards the circulation, has caused the capacity attenuation after the circulation first.This influence is at big particle diameter LiFePO
4Bigger in the material.Therefore, the control grain growth improves LiFePO
4Electrical conductance become the emphasis of preparation research.
Though LiFePO
4Aboundresources, cheap, environmentally friendly is the anode material for lithium-ion batteries that has application potential, but LiFePO
4Electronic conductivity is low, and the electrochemical process under the high-multiplying power discharge condition receives Li again
+Diffusion control causes heavy-current discharge performance relatively poor.For overcoming above-mentioned defective, to LiFePO
4The research work of preparation mainly comprises two key points: a) control grain growth, prepare the LiFePO of uniform particle diameter, tiny, good sphericity
4Material, thus reduce because the accumulate capacity that the granule interior resistance to mass tranfer causes descends the ionic conduction performance of strengthening material; B) come to improve simultaneously electronics, the ionic conductivity of material through means such as compound or doping, for example prepare LiFePO
4Methods such as element doping such as-C composite material, employing Mg, Mn.
But because liquid phase method preparation technology is comparatively complicated, especially granularity control is difficult in product drying, the calcination process; Nanometer is gathered a fluid bed and is used for the preparation of nanoparticles process and has remarkable advantage, and distribution of particles is controlled, is convenient to gas phase easily and coats and reprocessing, but up to now, nanometer is gathered the bolus flow bed process be applied to the LiFePO4 preparation and do not see bibliographical information as yet.
Summary of the invention
For addressing the above problem; The present invention combines liquid phase method to prepare the advantage of LiFePO4 technology; Add material with carbon element in the LiFePO4 crystallization nucleation stage, make LiFePO4 degree of crystallinity and granular size obtain better controlling, strengthened the electric conductivity of LiFePO4 particle simultaneously; Adopt fluidized-bed process to carry out particle calcining, surface treatment; Can effectively reduce sintering, the coalescence of control product, thereby obtain the control of good granular size, gained LiFePO4-carbon material compound has higher charge/discharge capacity, good structural stability and good cycle performance.
Therefore, the present invention mainly comprises following aspect.
1. the preparation method of a LiFePO4-carbon material compound, this method may further comprise the steps:
1) in containing the dispersion liquid of material with carbon element, adds P source compound, Fe source compound and Li source compound, obtain the slurry product;
2) will in closed container, carry out solvent heat treatment by the slurry product that step 1) obtains; With
3) will be by step 2) product that obtains carries out powder calcination and handles.
2. as the preparation method of above-mentioned 1 described LiFePO4-carbon material compound, wherein, said material with carbon element is to be selected from carbon black, active carbon, CNT, Graphene and composition thereof one or more.
3. like the preparation method of above-mentioned 2 described LiFePO4-carbon material compound, wherein, the solvent in the dispersion liquid of said carbonaceous material is the mixture of water, alcohol or water and alcohol, and the concentration of material with carbon element is 0.001 grams per milliliter to 1 grams per milliliter in the said dispersion liquid.
4. like the preparation method of above-mentioned 3 described LiFePO4-carbon material compound, wherein, said alcohol is selected from one or more in methyl alcohol, ethanol, ethylene glycol and composition thereof.
5. the preparation method of a LiFePO4-carbon material compound, this method may further comprise the steps:
1) P source compound, Fe source compound and Li source compound are mixed in water, obtain the slurry product;
2) will in closed container, carry out solvent heat treatment by the slurry product that step 1) obtains; With
3) will be by step 2) product that obtains carries out powder calcination and handles, and this calcination processing is carried out under fluidized state, and introduces the air-flow that comprises ethene and/or acetylene.
6. like the preparation method of above-mentioned 1 to 5 any described LiFePO4-carbon material compound, this method also comprises with next, two or 3 characteristics:
In the powder calcination processing procedure of step 3), introduce the air-flow that comprises ethene and/or acetylene and carry out the gas-phase carbon coating;
Also comprise before the step 3), will be by step 2) product that the obtains step of mixing with one or more carbon-source cpd among being selected from sucrose, glucose, citric acid, starch, pitch, wax oil;
In step 1), also comprise and add the step that is selected from one or more additives in ammoniacal liquor, citric acid, ascorbic acid, glucose, urea, neopelex, softex kw and composition thereof.
7. like the preparation method of above-mentioned 1 to 5 any described LiFePO4-carbon material compound, wherein, said P source compound is phosphorous organic substance or inorganic matter, preferably phosphoric acid or phosphate; For example, said P source compound is to be selected from phosphoric acid, ferric phosphate, ferrous phosphate, ammonium hydrogen phosphate, ammonium dihydrogen phosphate and composition thereof one or more; Said Fe source compound is to be selected from ferric sulfate, ferrous sulfate, ferrocene, iron chloride, ferrous oxalate and composition thereof one or more; Said Li source compound is to be selected from lithium hydroxide, lithium carbonate, lithium acetate and composition thereof one or more.
8. like the preparation method of above-mentioned 6 described LiFePO4-carbon material compound, wherein, the said air-flow that comprises ethene and/or acetylene comprises inert gas, and like nitrogen and/or argon gas, the dividing potential drop of this inert gas is not less than 30% of air-flow total pressure.
9. as the preparation method of above-mentioned 7 described LiFePO4-carbon material compound; Wherein, In said step 1), said P source compound, Fe source compound and Li source compound are respectively the aqueous solution form adding of 0.02 mol to 1 mol independently with molar concentration.
10. as the preparation method of above-mentioned 1 to 5 any described LiFePO4-carbon material compound, wherein, in step 3), under fluidized state, carry out said powder calcination and handle, this calcination processing possesses in the following characteristic one or multinomial:
E) adopt gas-solid fluidized pattern, air speed is 1-5000 hour
-1, the void tower flow velocity of gas is the 0.005-1 meter per second, the bed density in the reactor remains on the 5-800 kilograms per cubic meter;
F) bed temperature is 200-900 ℃, preferred 300-800 ℃, and more preferably 500-800 ℃, 2-36 hour calcination processing time, preferred 4-24 hour;
G) the number average granular size of used LiFePO4 or LiFePO4-carbon material compound is the 0.02-10 micron, preferred 0.05-5 micron, more preferably 0.05-2 micron; And/or
H) mixture that adopts inert gas or inert gas and reducibility gas is as fluidizing gas; Wherein, Said inert gas is to be selected from argon gas, nitrogen, helium and composition thereof one or more, and said reducibility gas is to be selected from hydrogen, methane, ethene, acetylene, propylene, butylene, butane and composition thereof one or more.
11. as the preparation method of above-mentioned 1 to 5 any described LiFePO4-carbon material compound; Wherein, In said step 2) solvent heat treatment in, with said slurry product in closed container at 80-200 ℃, preferred 120-200 ℃ is carried out solvent heat treatment; Processing time 1-36 hour, preferred 2-24 hour; And/or
Before said step 3), will be through step 2) product after the solvent heat treatment is at 60-120 ℃, and preferred 80-120 ℃ of drying also pulverized.
12. the LiFePO4-carbon material compound of above-mentioned 1 to 11 any described method preparation.
Can prepare average grain diameter through preparation method of the present invention is 0.02-10 μ m (micron), tap density 1.8-2.2g/cm
3, the 0.2C specific discharge capacity can reach LiFePO4-carbon material compound of 140-165mAh/g under the room temperature, and this compound can be used as the anode material for lithium-ion batteries of high-volume and capacity ratio, high cyclical stability.
Description of drawings
The present invention combines accompanying drawing and following embodiment and embodiment to be understood better:
Fig. 1 shows the ESEM picture of LiFePO4-graphene complex of embodiment 1.
Fig. 2 shows X-ray diffraction (XRD) spectrogram of LiFePO4-graphene complex of embodiment 1.
LiFePO4-graphene complex that Fig. 3 shows embodiment 1 relation curve of specific capacity and voltage in the charge and discharge process under the 0.2C current condition.
Fig. 4 shows and selects the specific discharge capacity that gathers LiFePO4-carbon composite that a multi-walled carbon nano-tubes prepares as material with carbon element among the embodiment 4 for use.
Fig. 5 shows the ESEM picture of embodiment 5 LiFePO4 samples.
Embodiment
The object of the invention comprises for example provides LiFePO4 or the preparation method of LiFePO4-carbon material compound and the LiFePO4-carbon material compound that is prepared by this method that technology is simple, with low cost, be suitable for suitability for industrialized production.
In said method of the present invention; Solvent heat treatment through under 80-200 ℃ obtains the slurry product; After in 60-120 ℃ of following inert atmosphere, drying behind the vacuum filtration, pulverizing; Utilize nanometer to gather a fluid bed and under inertia or reducing atmosphere, carrying out a step or calcining of two steps and reprocessing, thereby obtain to have the LiFePO4-carbon material compound of homogeneous particle size distribution.
Specifically, the invention provides the preparation method of LiFePO4-carbon material compound, it comprises following steps:
A) material with carbon element is scattered in water and/or the alcohol, obtains dispersion liquid;
B) phosphorus source, source of iron, Li source compound (and additive) are distinguished in the mixed liquor of water-soluble, pure or water and alcohol, obtained corresponding solution respectively;
C) dispersion liquid that step a) is obtained mixes with the various solution that obtain in the step b), obtains the slurry product; With
D) said slurry product is carried out solvent heat treatment in the temperature that raises in closed container;
Randomly:
E) with perhaps being immersed in the solution of carbon-source cpd with the carbon-source cpd solid phase mixing after products therefrom suction filtration, oven dry, the pulverizing in the step d); Filter then and oven dry obtains powder; Wherein carbon-source cpd comprises one or more the mixture among sucrose, glucose, citric acid, starch, pitch, the wax oil; The employed solvent of solution that is immersed in carbon-source cpd comprises one or more the mixture among water, ethanol, acetone, the benzene,toluene,xylene, and this solution comprises about 0.01 weight % or more said carbon-source cpd in carbon;
With
F) to step d) or e) product that obtains carries out powder calcination in the temperature that raises and handles; Wherein the optional air-flow that comprises ethene and/or acetylene of introducing carries out the gas-phase carbon coating in this calcination processing process, and this air-flow comprises about 0.01 weight % or more said ethene and/or acetylene in carbon.
In the said method,, earlier the P source compound drips of solution that obtains in the step b) is added in the material with carbon element dispersion liquid that obtains in the step a) according to the preferred version one of step c); Stirred about 10-60 minute, and dripped the Fe source compound solution that obtains in the step b) then, stirred about 10-60 minute; Drip the Li source compound solution that obtains in the step b) again; Stirred about 10-60 minute, and dripped the additive solution that obtains in the step b) at last, obtain the slurry product;
In the said method,, earlier the additive solution that obtains in the step b) is added drop-wise in the material with carbon element dispersion liquid that obtains in the step a) according to the preferred version two of step c); Stirred about 10-60 minute; Drip the Fe source compound solution that obtains in the step b) then, stirred about 10-60 minute, drip the Li source compound solution that obtains in the step b) again; Drip the P source compound solution that obtains in the step b) at last, obtain the slurry product;
In the said method; According to the preferred version three of step c), respectively, the drips of solution of the additive that obtains in the step b) 1 is added in the material with carbon element dispersion liquid that obtains in the step a); The Fe source compound drips of solution that obtains in the step b) is added in the P source compound solution; Stirred about 10-60 minute, the solution or the dispersion liquid that obtain above inciting somebody to action then mix, stirred about 10-60 minute, drip the Li source compound solution that obtains in the step b) again; Drip the solution of the additive 2 that obtains in the step b) at last, obtain the slurry product; Additive 1 and additive 2 are one or more in ammoniacal liquor, citric acid, ascorbic acid, glucose, urea, neopelex, softex kw and composition thereof independently of one another.
In the said method, preferred, in step d), with said slurry product in closed container about 200 ℃ of about 80-, preferably approximately 120-carries out solvent heat treatment for about 200 ℃, about 36 hours of about 1-of processing time, preferably approximately 2-is about 24 hours;
In the said method, preferred, in step e); About 120 ℃ of about 60-, about 120 ℃ of dry down, pulverizing of 80-preferably approximately are then about 900 ℃ of about 200-to the product after the solvent heat treatment; Preferably approximately 300-is about 800 ℃; More preferably approximately 500-carries out the powder calcination processing for about 800 ℃, about 36 hours of the about 2-of calcination time, and preferably approximately 4-is about 24 hours.
In the said method, preferred, in step a), the content of material with carbon element is the about 1g/ml of about 0.001-in the dispersion liquid.
In the said method, preferred, in step b), the molar concentration of solute is the about 1mol/L of about 0.02-in the solution.
In the said method, each set of dispense ratio is for being approximately in the slurry product: material with carbon element: P source compound: Fe source compound: Li source compound (: additive)=and 0.05-3: 1: 1: 1-3 (: 0.01-1) (mol ratio).
Said alcohol is to be selected from methyl alcohol, ethanol, ethylene glycol and composition thereof one or more, and the mixture that forms of methyl alcohol, ethanol, ethylene glycol or its mixture and water.
Said P source compound can be this area any P source compound commonly used, comprises phosphorous organic substance or inorganic matter, preferably phosphoric acid or phosphate that any this area is suitable for.For example, said P source compound is to be selected from phosphoric acid, ferric phosphate, ferrous phosphate, ammonium hydrogen phosphate, ammonium dihydrogen phosphate and composition thereof one or more.
Said Fe source compound can be this area any Fe source compound commonly used, but it preferably is selected from ferric sulfate, ferrous sulfate, ferrocene, iron chloride, ferrous oxalate and composition thereof one or more.
Said Li source compound can be this area any Li source compound commonly used, but it preferably is selected from lithium hydroxide, lithium carbonate, lithium acetate and composition thereof one or more.
Said additive can be this area any additives commonly used, but it preferably is selected from citric acid, ascorbic acid, glucose, urea, neopelex, softex kw and composition thereof one or more.
Said material with carbon element can be this area any material with carbon element commonly used, but it preferably is selected from carbon black, active carbon, CNT, Graphene and composition thereof one or more.
In said method, the preferred said air-flow that comprises ethene and/or acetylene comprises inert gas, like nitrogen and/or argon gas.In one embodiment, make the dividing potential drop of inert gas be not less than 30% of air-flow total pressure.
The invention provides the preparation method of a kind of LiFePO4 or LiFePO4-carbon material compound, it is characterized in that comprising following steps: adopt fluidized-bed reactor, under fluidized state, carry out powder calcination and particle surface and handle.
In one embodiment, in the preparation method of said LiFePO4 or LiFePO4-carbon material compound, under fluidized state, carry out said powder calcination and particle surface and handle, and possess in the following characteristic one or multinomial:
A) adopt gas-solid fluidized pattern, air speed is about 5000 hours of about 1-
-1, the void tower flow velocity of gas is about 1 meter per second of about 0.005-, the bed density in the reactor remains on about 800 kilograms per cubic meter of about 5-;
B) bed temperature is about 900 ℃ of about 200-, and preferably approximately 300-is about 800 ℃, about 800 ℃ of more preferably about 500-, and about 36 hours of calcining and about 2-of surface treatment time, preferably approximately 4-is about 24 hours;
C) mean particle size of used LiFePO4 or LiFePO4-carbon material compound is about 10 microns of about 0.02-, and preferably approximately 0.05-is about 5 microns, about 2 microns of more preferably about 0.05-;
D) mixture that adopts inert gas or inert gas and reducibility gas is as fluidizing gas; Wherein, Inert gas is to be selected from argon gas, nitrogen, helium and composition thereof one or more, and reducibility gas is to be selected from hydrogen, methane, ethene, acetylene, propylene, butylene, butane and composition thereof one or more.
Be described in detail through the specific embodiment specific embodiments of the invention below, following embodiment only is used to explain the present invention, but and is not used in and limits practical range of the present invention.
Embodiment 1
(this kind preparation method of graphene is seen Ning to weighing 1.2g Graphene, G.; Fan, Z.; Wang, G.; Gao, J.; Qian, W.; Wei, F.Chemical Communications 2011,47; 5976), add in the mixed solution (ethanol: water=1: 3, volume ratio) of 100mL second alcohol and water; 5 minutes (Ultrasound Instrument model KH-2200 of ultrasonic dispersion; Power 600W, Kechuang supermarket, Kunshan Instr Ltd.), the dispersion liquid of formation homogeneous.Weighing 9.8g phosphoric acid, 27.8g ferrous sulfate hydrate, 4.2g lithium hydroxide and 5g citric acid add the solution that obtains in the 500mL deionized water separately respectively respectively.Under agitation; Earlier be added drop-wise to phosphate aqueous solution in the dispersion liquid of Graphene and continue to stir 10 minutes; Drip ferrous sulfate aqueous solution then and continue and stirred 10 minutes; Drip lithium hydroxide aqueous solution again and continue and stirred 10 minutes, drip aqueous citric acid solution at last and continue and stirred 10 minutes, obtain the slurry product.The gained slurry is transferred in the seal-off pressure container, and 110 ℃ of following heat treatment 12 hours is taken out slurry after reducing to room temperature, suction filtration, oven dry in inert atmosphere, grinds and is powder.At last said powder is put in the horizontal pipe furnace reactor (quartz ampoule, long 1000mm, diameter 50mm); Under 0.2L/min Ar entraining air stream, be warming up to 600 ℃; Calcination processing 6 hours is reduced to room temperature powder sample is taken out, and products obtained therefrom is LiFePO4-graphene complex.
Fig. 1 shows the ESEM picture of LiFePO4-graphene complex of embodiment 1.As shown in Figure 1, the sample of said process preparation contains uniform nano particle, the about 50nm of average grain diameter.Adopt LiFePO4-graphene complex of above-prepared to make the anode of lithium ion battery, obtained higher charge/discharge capacity, good multiplying power property and cycle performance.Fig. 2 shows X-ray diffraction (XRD) spectrogram of LiFePO4-graphene complex of embodiment 1.LiFePO4-graphene complex that Fig. 3 shows embodiment 1 relation curve of specific capacity and voltage in the charge and discharge process under the 0.2C current condition.From Fig. 3, can see charge and discharge platform voltage very close (being respectively 3.45V and 3.39V); Explain that electrode material pattern in the charge and discharge process, structure are more stable; Not along with the remarkable deformation of producing of electrode reaction, this is very important for stability that increases electrode and useful life.0.2C specific discharge capacity can reach 155mAh/g under the charging and discharging currents condition, specific discharge capacity can reach 135mAh/g under the 5C charging and discharging currents condition.Under the 1C charging and discharging currents condition, charge and discharge cycles 100 times, capability retention can reach 85%.
Embodiment 2
Adopt same proportioning and slurry solvent heat treatment process with embodiment 1; The powder that obtains after the solvent heat treatment is added in the vertical fluid bed, at first feed the 1L/min argon gas, be warming up to 600 ℃; Feed 1L/min ethene then; Close ethene after 30 minutes, feed 0.03L/min hydrogen, calcined 6 hours.Taking-up gained powder sample is final products after being cooled to room temperature.
Gained LiFePO4-carbon material compound tap density 2.2g/cm
3, specific discharge capacity can reach 163mAh/g under 0.2C charging and discharging currents condition, and specific discharge capacity can reach 145mAh/g under the 5C charging and discharging currents condition.Under the 1C charging and discharging currents condition, charge and discharge cycles 100 times, capability retention can reach 89%.
Embodiment 3
Adopt same proportioning and slurry solvent heat treatment process with embodiment 1, the powder that obtains after the solvent heat treatment is mixed with 3g sucrose, in high speed disintegrator, stir; Putting into diameter then is the horizontal tube reactor of 30mm; Under 0.2L/min Ar air-flow protection, carry out 200 ℃ of calcining 2h, the gained pressed powder is added in the vertical fluid bed calcine and reprocessing again: at first feed the 1L/min argon gas, be warming up to 600 ℃; Feed 1L/min ethene then; Close ethene after 30 minutes, feed 0.03L/min hydrogen, calcined 6 hours.Taking-up gained powder sample is final products after being cooled to room temperature.
Gained LiFePO4-carbon material compound tap density 2.1g/cm
3, specific discharge capacity can reach 160mAh/g under 0.2C charging and discharging currents condition, and specific discharge capacity can reach 145mAh/g under the 5C charging and discharging currents condition.Under the 1C charging and discharging currents condition, charge and discharge cycles 100 times, capability retention can reach 91%.
Embodiment 4
Identical with embodiment 1, just material with carbon element is selected CNT, carbon black or activated carbon for use, directly prepares LiFePO4-carbon mano-tube composite, LiFePO4-carbon black compound or LiFePO4-active carbon compound.
Select for use and gather a multi-walled carbon nano-tubes (preparation method sees Y.Wang, F.Wei, G.Luo; H.YuandG.Gu, Chem.Phys.Lett., 2002; 364,568.) LiFePO4-carbon composite for preparing as material with carbon element has higher charging and discharging capacity and good cycle life.As shown in Figure 4, specific discharge capacity can reach 161mAh/g under 0.2C charging and discharging currents condition, and specific discharge capacity can reach 147mAh/g under the 1C charging and discharging currents condition, and specific discharge capacity can reach 121mAh/g under the 5C charging and discharging currents condition.
Embodiment 5
Weighing 11.5g ammonium dihydrogen phosphate, 40.4g ferric nitrate, 6.6g lithium acetate, 1.76g ascorbic acid and 1.8g softex kw are dissolved in respectively in the 100mL water, obtain the aqueous solution of each compound.Under agitation; Be added in the ammonium dihydrogen phosphate softex kw drips of solution and lasting the stirring 30 minutes; Dripping iron nitrate solution then is added drop-wise in the said mixture and lasting the stirring 30 minutes; Drip lithium acetate solution again and continue and stirred 30 minutes, drip ascorbic acid solution at last and continue and stirred 30 minutes, obtain the slurry product.Products therefrom is transferred in the seal-off pressure container, and 200 ℃ of following solvent heat treatment 8 hours are taken out slurry after reducing to room temperature, and 80 ℃ of oven dry are 12 hours in inert atmosphere, grind then to be powder.At last said powder is added in the fluidized-bed reactor, fluidisation 20min in the mixed airflow of 500 ℃ of following 0.5L/min argon gas and 0.9L/min acetylene closes acetylene then, is warming up to 700 ℃ of calcinings 2 hours.After reducing to room temperature the taking-up of gained powder is final products.
LiFePO4-the carbon composite of said process preparation contains spindle particle shown in Figure 5, and specific discharge capacity can reach 150mAh/g under 0.2C charging and discharging currents condition, and specific discharge capacity can reach 135mAh/g under the 5C charging and discharging currents condition.Under the 1C charging and discharging currents condition, charge and discharge cycles 100 times, capability retention can reach 88%.
Embodiment 6
(this kind preparation method of graphene is seen Ning to weighing 1.5g Graphene sample, G.; Fan, Z.; Wang, G.; Gao, J.; Qian, W.; Wei, F.Chemical Communications 2011,47,5976), under agitation being dispersed in the 100mL ethylene glycol, weighing 9.8g phosphoric acid, 27.8g green vitriol, 11.3g hydronium(ion) oxidation lithium are dissolved in respectively in the 100mL ethylene glycol respectively.Under agitation, earlier copperas solution is added drop-wise in the Graphene dispersion liquid and continues and stirred 30 minutes, drip lithium hydroxide solution then and continue and stirred 30 minutes, drip phosphoric acid solution at last and continue and stirred 60 minutes.The gained slurry is transferred in the seal-off pressure container, and 180 ℃ of following solvent heat treatment 10 hours are taken out slurry after reducing to room temperature, in inert atmosphere, dry after suction filtration, the rinsing, grind to be powder.Said powder is added in the fluidized-bed reactor, in the mixed airflow of 5L/min nitrogen and 0.05L/min hydrogen, calcining 2 hours under 550 ℃, be cooled to room temperature then, the gained powder is has LiFePO4-graphene complex.
This LiFePO4-graphene complex has the particle size less than 100nm, and 0.1C discharges and recharges specific discharge capacity 165mAh/g under the condition.
Claims (12)
1. the preparation method of LiFePO4-carbon material compound, this method may further comprise the steps:
1) in containing the dispersion liquid of material with carbon element, adds P source compound, Fe source compound and Li source compound, obtain the slurry product;
2) will in closed container, carry out solvent heat treatment by the slurry product that step 1) obtains; With
3) will be by step 2) the product suction filtration or the oven dry of centrifugal back that obtain, carry out powder calcination then and handle.
2. the preparation method of LiFePO4-carbon material compound as claimed in claim 1, wherein, said material with carbon element is to be selected from carbon black, active carbon, CNT, Graphene and composition thereof one or more.
3. the preparation method of LiFePO4-carbon material compound as claimed in claim 2; Wherein, Solvent in the dispersion liquid of said carbonaceous material is the mixture of water, alcohol or water and alcohol, and the concentration of material with carbon element is 0.001 grams per milliliter to 1 grams per milliliter in the said dispersion liquid.
4. the preparation method of LiFePO4-carbon material compound as claimed in claim 3, wherein, said alcohol is selected from one or more in methyl alcohol, ethanol, ethylene glycol and composition thereof.
5. the preparation method of a LiFePO4-carbon material compound, this method may further comprise the steps:
1) P source compound, Fe source compound and Li source compound are mixed in water, obtain the slurry product;
2) will in closed container, carry out solvent heat treatment by the slurry product that step 1) obtains; With
3) will be by step 2) the product suction filtration or the oven dry of centrifugal back that obtain, to carry out powder calcination then and handle, this calcination processing is carried out under fluidized state, and introduces the air-flow that comprises ethene and/or acetylene.
6. like the preparation method of any described LiFePO4-carbon material compound of claim 1 to 5, this method also comprises with next, two or 3 characteristics:
In the powder calcination processing procedure of step 3), introduce the air-flow that comprises ethene and/or acetylene and carry out the gas-phase carbon coating;
Also comprise before the step 3), will be by step 2) product that the obtains step of mixing with one or more carbon-source cpd among being selected from sucrose, glucose, citric acid, starch, pitch, wax oil;
In step 1), also comprise and add the step that is selected from one or more additives in ammoniacal liquor, citric acid, ascorbic acid, glucose, urea, neopelex, softex kw and composition thereof.
7. like the preparation method of any described LiFePO4-carbon material compound of claim 1 to 5, wherein, said P source compound is phosphorous organic substance or inorganic matter, preferably phosphoric acid or phosphate; For example, said P source compound is to be selected from phosphoric acid, ferric phosphate, ferrous phosphate, ammonium hydrogen phosphate, ammonium dihydrogen phosphate and composition thereof one or more; Said Fe source compound is to be selected from ferric sulfate, ferrous sulfate, ferrocene, iron chloride, ferrous oxalate and composition thereof one or more; Said Li source compound is to be selected from lithium hydroxide, lithium carbonate, lithium acetate and composition thereof one or more.
8. the preparation method of LiFePO4-carbon material compound as claimed in claim 6, wherein, the said air-flow that comprises ethene and/or acetylene comprises inert gas, and like nitrogen and/or argon gas, the dividing potential drop of this inert gas is not less than 30% of air-flow total pressure.
9. the preparation method of LiFePO4-carbon material compound as claimed in claim 7; Wherein, In said step 1), said P source compound, Fe source compound and Li source compound are respectively the aqueous solution form adding of 0.02 mol to 1 mol independently with molar concentration.
10. like the preparation method of any described LiFePO4-carbon material compound of claim 1 to 5, wherein, in step 3), under fluidized state, carry out said powder calcination and handle, this calcination processing possesses in the following characteristic one or multinomial:
A) adopt gas-solid fluidized pattern, air speed is 1-5000 hour
-1, the void tower flow velocity of gas is the 0.005-1 meter per second, the bed density in the reactor remains on the 5-800 kilograms per cubic meter;
B) bed temperature is 200-900 ℃, preferred 300-800 ℃, and more preferably 500-800 ℃, 2-36 hour calcination processing time, preferred 4-24 hour;
C) the number average granular size of used LiFePO4 or LiFePO4-carbon material compound is the 0.02-10 micron, preferred 0.05-5 micron, more preferably 0.05-2 micron; And/or
D) mixture that adopts inert gas or inert gas and reducibility gas is as fluidizing gas; Wherein, Said inert gas is to be selected from argon gas, nitrogen, helium and composition thereof one or more, and said reducibility gas is to be selected from hydrogen, methane, ethene, acetylene, propylene, butylene, butane and composition thereof one or more.
11. preparation method like any described LiFePO4-carbon material compound of claim 1 to 5; Wherein, In said step 2) solvent heat treatment in, with said slurry product in closed container at 80-200 ℃, preferred 120-200 ℃ is carried out solvent heat treatment; Processing time 1-36 hour, preferred 2-24 hour; And/or
In said step 3), bake out temperature is 60-120 ℃, preferred 80-120 ℃.
12. the LiFePO4-carbon material compound of any described method preparation of claim 1 to 11.
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| CN110165203A (en) * | 2019-07-11 | 2019-08-23 | 兰州理工大学 | A method of improving lithium iron phosphate positive material cryogenic property |
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