A kind of spherical micro-nano ferric phosphate/carbon composite and preparation method thereof
Technical field
The invention belongs to technical field of lithium ion, concrete a kind of spherical micro-nano ferric phosphate/carbon composite and preparation method thereof.
Background technology
Ferric phosphate (FePO
4) be a kind of outward appearance in white or the monoclinic crystal of pale powder, at first in field extensive uses such as agricultural, glass-ceramic, iron and steel and surface passivations, the FePO of research discovery subsequently
4also application is had in the fields such as oxidative dehydrogenation catalysis, ion-exchange and chemical property.In the application of electrochemical field, FePO
4can as preparing lithium ion battery LiFePO
4the framework material of positive electrode.Research shows, adopts FePO
4as precursor power LiFePO
4positive electrode has the following advantages: (1) FePO
4there is fixing Fe/P ratio, therefore more easily obtain pure LiFePO
4positive electrode; (2) FePO
4and LiFePO
4there is similar crystalline structure, Li
+embedding de-time crystalline structure decay less; (3) FePO
4compared with divalence source of iron, as raw material, not only price is low and there is not the oxidized puzzlement of raw material.To sum up analyze, by controlling synthesis FePO
4the structure of presoma, pattern and granularity can prepare the LiFePO of excellent electrochemical performance
4positive electrode.
Spherical ferric phosphate lithium micro-nanometer structural material meets the design requirement of high-energy-density, high rate capability lithium ion battery, but being direct mostly in prior art is that LiFePO4 prepared by raw material by molysite, phosphate, material with carbon element, the degree of mixing of such one side reaction raw materials is uncontrollable, the LiFePO of preparation on the other hand
4positive electrode is not spherical.Existing carbon coating technology is add carbon source when raw material mixes mostly, although technological operation is simple, can not ensure that the complete carbon of material is coated, and it is coated to be generally a carbon, to material modification DeGrain.At present, relevant FePO
4the report of production technology is relatively less and immature.
Summary of the invention
The object of this invention is to provide a kind of spherical micro-nano ferric phosphate/carbon composite and preparation method thereof, take macromolecular material as spherical micro-nano ferric phosphate/carbon composite prepared by binding agent.
To achieve these goals, the following technical scheme of the present invention's employing:
A preparation method for spherical micro-nano ferric phosphate/carbon composite, comprises the following steps:
(1) configure the aqueous solution of molysite and phosphorus-containing compound, the mol ratio of described ferro element and P elements is (0.9-1.2): 1, and described solution concentration is 0.2-5mol/L;
(2) be scattered in by macromolecular material binding agent in the solution of step (1), described macromolecular material consumption of binder is the 0.5-90wt% of molysite;
(3) by solution obtained for step (2) and alkaline solution and stream adds in reactor, the pH in reactor is kept to remain 2-4 (preferably: described alkaline solution concentration is 0.5-10mol/L), the temperature of described reaction system is 20-90 DEG C, (preferably: described stir speed (S.S.) is 0-1000r/s) obtains the spherical micro-nano ferric phosphate/polymer composite containing the crystallization water after reacting 1-60 hour;
(4) under an inert atmosphere, 300 ~ 800 DEG C of roastings cooled after 3 ~ 12 hours spherical micro-nano ferric phosphate/polymer composite step (3) prepared, and obtained the spherical micro-nano ferric phosphate/carbon composite removing the crystallization water.
Preferred: molysite is FeNO
3, FeCl
3, Fe
2(SO
4)
3, FeSO
4, FeC
2o
4in the mixture of one or more.
Preferred: described phosphorus-containing compound is H
3pO
4, NH
4h
2pO
4, (NH
4)
2hPO
4, LiH
2pO
4and Na
3pO
4in the mixture of one or more.
Preferred: described macromolecule has the mixture of one or more in polystyrene, polyphenylene oxide, formaldehyde-aniline resin, polyacrylamide, butadiene-styrene rubber, polyphenyl phenol, polyethylene glycol oxide, starch and phenolic resins.
Preferred: described alkali compounds has the mixture of one or more of ammoniacal liquor, NaOH, sodium carbonate and sodium acid carbonate.
Preferred: described inert gas is one in nitrogen, argon gas or gaseous mixture.
Preferred: the volume of reaction kettle for reaction system is 0.5-100L.
Spherical micro-nano ferric phosphate/carbon composite that said method prepares, this material is at preparation LiFePO
4application in positive electrode, glass-ceramic, iron and steel and surface passivation material thereof.
Beneficial effect of the present invention:
The present invention is binding agent with macromolecular material, by nanometer Fe PO
4particle bond is a granulated into a micron spheric granules, prepares the preparation method of spherical micro-nano ferric phosphate/carbon composite after calcining.Spherical micro-nano ferric phosphate/carbon composite prepared by this method has spherical structure, and it is coated to achieve material carbon, to follow-up preparation high density, high performance lithium ion battery LiFePO
4positive electrode serves vital effect.
Preparation nano material and carbon coated be the effective means of modified phosphate iron lithium anode material high rate capability, but nano material itself has lower tap density, reduce lithium iron phosphate positive material energy density, spherical micro-nano ferric phosphate/carbon composite prepared by this method, adopt high polymer binder that nano ferric phosphate particle bond is become micron particles, both ensure that the tap density of material, the carbon achieving again ferric phosphate forerunner is coated, serves vital effect to the modification of follow-up LiFePO 4 material.
This technique adopts the standby ferric phosphate/polymer composite of precognition, and the carbon achieving ferric phosphate persursor material after pre-burning is coated, and again adding carbon source when burning eventually, can to realize the secondary carbon of LiFePO 4 material coated, material modification successful.
Accompanying drawing explanation
Fig. 1 is with the SEM photo of the spherical micro-nano ferric phosphate/carbon composite of embodiment 2 preparation;
Fig. 2 is the LiFePO that is precursor power with the spherical micro-nano ferric phosphate/carbon composite prepared by embodiment 2,4,6,8
4the first charge-discharge curve of/C positive electrode material under 0.1C multiplying power.
Embodiment
Below in conjunction with accompanying drawing and embodiment, the invention will be further described.
Embodiment 1
Take equimolar Fe (NO
3)
39H
2o and H
3pO
4be made into 0.2mol/L mix acid liquor, measure certain ammoniacal liquor and be diluted to 0.5mol/L by both the parallel crystallization reaction of input continuously stills, reaction temperature is 50 DEG C, regulate and keep the pH of reaction system about 2, control stirring intensity is 200r/s, reactant liquor natural overflow after being full of reactor is discharged, and stirring reaction obtained FePO after 10 hours after centrifugal, washing and drying
4xH
2o powder.This precursor powder is obtained nanometer Fe PO after 500 DEG C of heat treatment 10h
4presoma, adopts carbothermic method to prepare nanometer LiFePO
4/ C positive electrode material.Take the FePO of 12g
4the Li of presoma, 2.982g
2cO
3add 5ml deionized water with the sucrose of 2.5g fully to mix, be placed in tube furnace, pass into High Purity Nitrogen at 700 DEG C of heat treatment 16h, obtain nanometer LiFePO through pyrocarbon thermal reduction reaction
4/ C material.As shown in Figure 1, the present embodiment gained FePO
4particle D50 is 3.6um, and carbon content is 3.9870%, the nanometer LiFePO of preparation
4under/C material 0.1C multiplying power, specific discharge capacity is that under 147mAh/g, 1C multiplying power, specific discharge capacity is that under 140mAh/g, 10C multiplying power, specific discharge capacity is 110mAh/g, and with the increase of discharge-rate, specific discharge capacity declines more obvious.
Embodiment 2
Take equimolar Fe (NO
3)
39H
2o and H
3pO
4be made into 0.2mol/L mix acid liquor, take FePO
4after the polyacrylamide of Theoretical Mass 0.5wt% is dissolved in acid solution, measure certain ammoniacal liquor and be diluted to 0.5mol/L by both parallel continuous input control crystallization reaction stills, reaction temperature is 50 DEG C, regulate and keep the pH of reaction system about 2, control stirring intensity is 200r/s, reactant liquor natural overflow after being full of reactor is discharged, and stirring reaction obtained 0.5wt%PAM-FePO after 10 hours after centrifugal, washing and drying
4xH
2o powder.This precursor powder is obtained PAM-FePO after 500 DEG C of heat treatment 10h
4presoma, adopts the nanometer LiFePO of PAM modification by the method preparation of embodiment 1
4/ C positive electrode material.As shown in Figure 1, the present embodiment gained PAM-FePO
4particle D50 is 4.3um, and carbon content is 4.4028%, the nanometer LiFePO of preparation
4/ C material 0.1C multiplying power discharge capacity is that under 150mAh/g, 1C multiplying power, specific discharge capacity is that under 146mAh/g, 10C multiplying power, specific discharge capacity is 115mAh/g, and high rate capability improves compared to embodiment 1.
Embodiment 3
Take equimolar Fe (NO
3)
39H
2o and H
3pO
4be made into 0.2mol/L mix acid liquor, take FePO
4after the soluble starch of Theoretical Mass 0.5wt% is dissolved in acid solution, measure certain ammoniacal liquor and be diluted to 0.5mol/L by both parallel continuous input control crystallization reaction stills, reaction temperature is 50 DEG C, regulate and keep the pH of reaction system about 2, control stirring intensity is 200r/s, reactant liquor natural overflow after being full of reactor is discharged, and stirring reaction obtained 0.5wt% soluble starch-FePO after 1 hour after centrifugal, washing and drying
4xH
2o powder.This precursor powder is obtained spherical micro-nano FePO after 600 DEG C of heat treatment 10h
4presoma, adopts the micro-nano LiFePO of soluble starch modification according to the method preparation of embodiment 1
4/ C positive electrode material.As shown in Figure 1, the present embodiment gained soluble starch-FePO
4in particle, D50 is 4.5um, and carbon content is 4.5497%, the micro-nano LiFePO of preparation
4under/C material 0.1C multiplying power, specific discharge capacity is 154mAh/g, 1C multiplying power discharge capacity is that under 147mAh/g, 10C multiplying power, specific discharge capacity is 120mAh/g, and high rate capability improves compared to embodiment 1.
Embodiment 4
Take equimolar Fe (NO
3)
39H
2o and H
3pO
4be made into 0.4mol/L mix acid liquor, take FePO
4after the soluble starch of Theoretical Mass 0.5wt% is dissolved in acid solution, measure certain ammoniacal liquor and be diluted to 1.0mol/L by both parallel continuous input control crystallization reaction stills, reaction temperature is 25 DEG C, regulate and keep the pH of reaction system about 3, control stirring intensity is 200r/s, reactant liquor natural overflow after being full of reactor is discharged, and stirring reaction obtained spherical micro-nano 0.5wt% starch-FePO after 5 hours after centrifugal, washing and drying
4xH
2o powder.This precursor powder is obtained after 500 DEG C of heat treatment 10h spherical micro-nano starch-FePO
4presoma, the method according to embodiment 1 prepares the micro-nano LiFePO of starch conversion
4/ C positive electrode material.As shown in Figure 1, the present embodiment gained PAM-FePO
4particle D50 is 5.0um, and carbon content is 4.5584%, the micro-nano LiFePO of preparation
4under/C material 0.1C multiplying power, specific discharge capacity is that under 159mAh/g, 1C multiplying power, specific discharge capacity is that under 160mAh/g, 10C multiplying power, specific discharge capacity is 123mAh/g, and high rate capability improves compared to embodiment 1.
Embodiment 5
Take equimolar FeSO
4with H
3pO
4be made into 0.4mol/L mix acid liquor, take FePO
4after the polyacrylamide of Theoretical Mass 1.0wt% is dissolved in acid solution, measure certain ammoniacal liquor and be diluted to 1.0mol/L by both parallel continuous input control crystallization reaction stills, reaction temperature is 50 DEG C, regulate and keep the pH of reaction system about 3, control stirring intensity is 200r/s, reactant liquor natural overflow after being full of reactor is discharged, and stirring reaction obtained spherical micro-nano 1.0wt%PAM-FePO after 5 hours after centrifugal, washing and drying
4xH
2o powder.This precursor powder is obtained spherical micro-nano PAM-FePO after 600 DEG C of heat treatment 10h
4presoma, the method according to embodiment 1 prepares the micro-nano LiFePO of PAM modification
4/ C positive electrode material.As shown in Figure 1, the present embodiment gained PAM-FePO
4particle D50 is 4.3um, and carbon content is 4.7093%, the micro-nano LiFePO of preparation
4under/C material 0.1C multiplying power, specific discharge capacity is that under 165mAh/g, 1C multiplying power, specific discharge capacity is that under 156mAh/g, 10C multiplying power, specific discharge capacity is 134mAh/g, and high rate capability improves compared to embodiment 1.
Embodiment 6
Take equimolar Fe (NO
3)
39H
2o and H
3pO
4be made into 0.4mol/L mix acid liquor, take FePO
4after the butadiene-styrene rubber of Theoretical Mass 1.0wt% is dissolved in acid solution, measure certain ammoniacal liquor and be diluted to 1.0mol/L by both parallel continuous input control crystallization reaction stills, reaction temperature is 50 DEG C, regulate and keep the PH of reaction system about 2, control stirring intensity is 200r/s, reactant liquor natural overflow after being full of reactor is discharged, and stirring reaction obtained spherical micro-nano 1.0wt%SBR-FePO after 1 hour after centrifugal, washing and drying
4xH
2o powder.This precursor powder is obtained spherical micro-nano SBR-FePO after 600 DEG C of heat treatment 10h
4presoma, the method according to embodiment 1 prepares the micro-nano LiFePO of SBR modification
4/ C positive electrode material.As shown in Figure 1, the present embodiment gained SBR-FePO
4particle D50 is 3.8um, and carbon content is 4.7284%, the micro-nano LiFePO of preparation
4under/C material 0.1 multiplying power, specific discharge capacity is that under 160mAh/g, 1C multiplying power, specific discharge capacity is that under 154mAh/g, 10C multiplying power, specific discharge capacity is 128mAh/g, and high rate capability improves compared to embodiment 1.
Embodiment 7
Take equimolar FeSO
4with H
3pO
4be made into 0.4mol/L mix acid liquor, take FePO
4after the butadiene-styrene rubber of Theoretical Mass 1.0wt% is dissolved in acid solution, measure certain ammoniacal liquor and be diluted to 1.0mol/L by both parallel continuous input control crystallization reaction stills, reaction temperature is 50 DEG C, regulate and keep the PH of reaction system about 2, control stirring intensity is 200r/s, reactant liquor natural overflow after being full of reactor is discharged, and stirring reaction obtained spherical micro-nano 1.0wt%SBR-FePO after 10 hours after centrifugal, washing and drying
4xH
2o powder.This precursor powder is obtained spherical micro-nano SBR-FePO after 600 DEG C of heat treatment 8h
4presoma, the method according to embodiment 1 prepares the micro-nano LiFePO of SBR modification
4/ C positive electrode material.As shown in Figure 1, the present embodiment gained SBR-FePO
4particle D50 is 8um, and carbon content is 4.7384%, the micro-nano LiFePO of preparation
4under/C material 0.1C multiplying power, specific discharge capacity is that under 160mAh/g, 1C multiplying power, specific discharge capacity is that under 152mAh/g, 10C multiplying power, specific discharge capacity is 130mAh/g, and high rate capability improves compared to embodiment 1.
Embodiment 8
Take equimolar Fe (NO
3)
39H
2o and NH4H
2pO
4be made into 0.4mol/L mix acid liquor, take FePO
4after the butadiene-styrene rubber of Theoretical Mass 5.0wt% is dissolved in acid solution, measure certain ammoniacal liquor and be diluted to 1.0mol/L by both parallel continuous input control crystallization reaction stills, reaction temperature is 50 DEG C, regulate and keep the PH of reaction system about 3, control stirring intensity is 200r/s, reactant liquor natural overflow after being full of reactor is discharged, and stirring reaction obtained spherical micro-nano 1.0wt%SBR-FePO after 20 hours after centrifugal, washing and drying
4xH
2o powder.This precursor powder is obtained spherical micro-nano SBR-FePO after 500 DEG C of heat treatment 10h
4presoma, the method according to embodiment 1 prepares the micro-nano LiFePO of SBR modification
4/ C positive electrode material.As shown in Figure 1, the present embodiment gained SBR-FePO
4particle D50 is 13um, and carbon content is 4.7584%, the micro-nano LiFePO of preparation
4under/C material 0.1C multiplying power, specific discharge capacity is that under 163mAh/g, 1C multiplying power, specific discharge capacity is that under 156mAh/g, 10C multiplying power, specific discharge capacity is 132mAh/g, and high rate capability improves compared to embodiment 1.
By reference to the accompanying drawings the specific embodiment of the present invention is described although above-mentioned; but not limiting the scope of the invention; one of ordinary skill in the art should be understood that; on the basis of technical scheme of the present invention, those skilled in the art do not need to pay various amendment or distortion that creative work can make still within protection scope of the present invention.