CN102201576B - Porous carbon in situ composite lithium iron phosphate cathode material and preparation method thereof - Google Patents
Porous carbon in situ composite lithium iron phosphate cathode material and preparation method thereof Download PDFInfo
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Abstract
The invention, which belongs to the technical field of lithium ion battery cathode materials, discloses a porous carbon in situ composite lithium iron phosphate cathode material and a preparation method thereof. A synthetic process mainly comprises the following steps: dispersing porous carbon; compositing a precursor FePO4.2H2O/porous carbon, and synthesizing the product of the porous carbon in situ coating lithium iron phosphate cathode material. The porous carbon in situ composite lithium iron phosphate cathode material comprises 0.5 to 15 wt% of the porous carbon, 85 to 99.5 wt% of lithium iron phosphate, and 0 to 10 wt% of residual carbon obtained after organic carbon source pyrolysis. Most lithium iron phosphate particles are restricted in the inner of pores of carbon through in situ coating, so obtained composite cathode material particles have small diameters and a good uniformity. Carbon walls of porous carbon allow uniform coating of the lithium iron phosphate particles to be realized and simultaneously particle agglomeration to be largely reduced. The porous carbon in situ composite lithium iron phosphate cathode material has the advantages of good charge-discharge performance, stable circular property, rate capability, novelty, simple synthetic technology and easy large-scale production.
Description
Technical field
The invention belongs to the energy and material technical field, particularly a kind of porous carbon in situ composite lithium iron phosphate cathode material and preparation method thereof.
Background technology
The energy is All Around The World development and the most basic power of economic growth, is the basis that the mankind depend on for existence.Since the industrial revolution, the past, traditional fossil fuel (coal, oil, natural gas) can't satisfy the energy demand of human increase year after year.In order to realize the sustainable development of entire society, the regenerative resource of exploring and developing alternative fossil fuel and possess efficient, cleaning, safety, economic dispatch characteristics becomes the strategic objective of new century energy and material and energy technology development.As a kind of novel energy products, discharge voltage is high because having for lithium rechargeable battery, specific energy and specific power are high, have extended cycle life and outstanding feature that environmental pollution is little, be subject to scientific research and industrial dual favor, be widely used in the fields such as mobile communication equipment, notebook computer, instrument and meter, along with the these years fast development of lithium ion battery, future will be as power source constantly expansion on electric automobile and hybrid vehicle.
In the present lithium rechargeable battery system, the large young pathbreaker of the specific capacity of positive electrode determines the capacity of battery, also is simultaneously the key factor that restriction lithium battery chemical property improves, production cost descends.Early stage LiCoO
2, LiNiO
2Positive electrode is subject to the restriction of the problems such as cost, fail safe and environmental pollution, is difficult to become the Typical Representative of green energy resource material; Stratiform LiMnO
2With spinelle LiMn
2O
4Then cause the rapid decay of capacity because of the structural aberration meeting, the high temperature circulation poor stability of material is not suitable for being used in the electrokinetic cell field.And polyanion type Fe based compound LiFePO
4Have the advantages such as raw material resources is abundant, nontoxic, environment compatibility is good, theoretical specific capacity high (170mAh/g), and cycle performance is good, thermal stability is outstanding and be expected to become anode material for lithium-ion batteries of new generation.
The fault of construction of LiFePO4 itself causes that its electronic conductivity is low, the lithium ion diffusion rate is slow, thereby material specific capacity when large current density is low, and cyclical stability is poor.Research finds, by the high-rate discharge ability that carbon coats, particle nanometer and the technological means such as bulk phase-doped can be improved LiFePO 4 material.Wherein, using is the carbon coating technology the most widely, and the carbon majority during conventional carbon coats is amorphous carbon, and the pattern of itself and distribute all uncontrollablely is difficult to realize " evenly coating " to lithium iron phosphate particles, causes LiFePO
4The tap density of/C composite material and volume energy density descend, and chemical property is unstable.
The advantage of porous carbon is:
(1) compare with organic carbon (sucrose, glucose, starch etc.) with simple substance carbon (graphite, acetylene black, Super-p etc.), porous carbon is in the preparation through 1500 ~ 2000 ℃ high-temperature process, and degree of graphitization is high, and conductivity is better.
(2) pattern of porous carbon itself is fixed, coats and most of lithium iron phosphate particles can be limited in the carbon hole by original position, and the particle size of LiFePO4 will be determined by the aperture in carbon hole, so the composite positive pole particle size that obtains is little and good uniformity.
(3) the carbon wall of porous carbon has been guaranteed " evenly coat " of LiFePO4 and can also have been increased substantially the contact of active material and electrolyte.
The record that does not also have at present the porous carbon in situ covered iron lithium phosphate compound anode material in the publication of China.Commercial solid phase method the most commonly used is lithium source, source of iron, phosphorus source mixing and ball milling to be processed again sintering forms under protective atmosphere; owing to can't raw-material pattern, size be had requirements at the higher level; add solid/the solid phase reaction interface is little; thereby synthesis cycle is long, energy consumption is high; the LiFePO4 distribution of sizes that obtains is inhomogeneous; granular size is difficult to control, and purity is lower, is difficult to higher chemical property and (sees China Patent Publication No.: CN1767238).
The disclosed lithium iron phosphate/nano carbon composite material of patent CN101834288 A, lack the proof to nano-sized carbon pattern and distribution, the combination product that patent is described is growth in situ nano-sized carbon on lithium iron phosphate particles, nano-sized carbon is lower on the impact of particle size, only satisfy compound and do not reach the effect of " evenly coat ", in addition, mutually reunite between lithium iron phosphate particles.These insoluble shortcomings have all limited the further raising of material electrochemical performance.
Summary of the invention
The present invention is directed to the problem that synthetic lithium iron phosphate particles size is large, distribution is wide, reunion is serious, a kind of novel porous carbon in situ composite lithium iron phosphate cathode material and preparation method thereof is provided.Utilize the aperture size of porous carbon to limit the granular size of LiFePO4, guarantee lithium iron phosphate particles size homogeneous; The carbon wall is separated lithium iron phosphate particles mutually, reduces intergranular mutual reunion, improves thus charge-discharge performance and the cycle performance of LiFePO4.
Technical scheme of the present invention is: a kind of porous carbon in situ composite lithium iron phosphate cathode material, its component are in mass fraction: porous carbon accounts for 0.5 ~ 15%, and LiFePO4 accounts for 85 ~ 99.5%, and all the other are the residual carbon after the organic carbon source pyrolysis, account for 0 ~ 10%.
Another object of the present invention is the preparation method of above-mentioned porous carbon in situ composite lithium iron phosphate cathode material, and concrete preparation process is as follows:
(1) dispersion of porous carbon: take by weighing the porous carbon that a certain amount of aperture is 5 ~ 200nm, put it in the solvent of 1 ~ 10L, behind strong stirring 2 ~ 8h, ultrasonic dispersion 0.5 ~ 10h finally obtains the suspension of porous carbon, and is for subsequent use;
(2) precursor FePO
42H
2O/ porous carbon compound: with ferric iron source and phosphorus source with deionized water dissolving and be made into the solution of 0.01 ~ 5mol/L; Ferric iron source and the phosphorus source solution of same concentrations are mixed in 1:1 ~ 1.2 by volume, with peristaltic pump it being sent into the step 1 that continues to stir with the charging rate of 1 ~ 50ml/min prepares in the porous carbon suspension, sending into ammoniacal liquor adjusting pH scope with peristaltic pump simultaneously is 1.85 ~ 2.35, by the time iron, the titration of phosphorus mixed solution complete after, continue to stir again 2 ~ 5h, then with deionized water washing sediment to neutral and filter, at 80 ~ 120 ℃ of drying 12 ~ 24h;
(3) product porous carbon in situ coated LiFePO 4 for lithium ion batteries is synthetic: the precursor FePO that takes by weighing lithium source and step 2 preparation by Li:Fe=1 ~ 1.1:1
42H
2The O/ porous carbon grinds 1 ~ 5h raw material is mixed, and is the Ar/H of 95:5 in ratio
2Protective atmosphere under be warming up to 250 ~ 450 ℃ and be incubated 2 ~ 10h with the programming rate of 3 ~ 10 ℃/min; with again grinding 0.5 ~ 5h after the stove cooling; under same protective atmosphere and the heating rate sample is warming up to 550 ~ 750 ℃ and be incubated 5 ~ 15h, finally obtain the porous carbon in situ covered iron lithium phosphate compound anode material.
Further, also can add organic carbon source in the described step 3; The organic carbon source addition is 0 ~ 40 wt% of gross mass.
Further, described organic carbon source comprises: sucrose, glucose, fructose, citric acid, ascorbic acid, starch, cellulose, polypropylene, polyethylene glycol, phenolic resins and polyvinyl alcohol.
Further, described solvent is deionized water, supercritical water, industrial alcohol, absolute ethyl alcohol or acetone.
Further, described source of iron comprises ferric nitrate, ironic citrate, ferric trichloride, ferric sulfate; Described phosphorus source comprises phosphorus pentoxide, phosphoric acid, ammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, sodium phosphate, sodium dihydrogen phosphate, disodium-hydrogen, potassium phosphate, potassium dihydrogen phosphate and potassium phosphate,monobasic.
Further, described lithium source comprises: lithium carbonate, lithium nitrate, lithium hydroxide, lithium acetate, lithium fluoride, lithium phosphate, phosphoric acid one hydrogen lithium, lithium dihydrogen phosphate, lithium iodide.
The invention has the beneficial effects as follows: porous carbon in situ composite lithium iron phosphate cathode material of the present invention has good charge-discharge performance, cycle performance and high rate performance.The lithium iron phosphate particles size that coats by porous carbon in situ is little, particle diameter distribution homogeneous, reunion degree are low.Building-up process is simple to operate, equipment cost is low, be easy to control, environmental protection, is convenient to enterprise scale production.
Description of drawings
The FE-SEM shape appearance figure of Fig. 1 embodiment of the invention 1 raw material porous carbon.
The FePO that Fig. 2 embodiment of the invention 1 is prepared
42H
2O/C precursor SEM shape appearance figure.
The XRD figure of the porous carbon in situ composite lithium iron phosphate cathode material that Fig. 3 embodiment of the invention 1 is prepared.
The porous carbon in situ composite lithium iron phosphate cathode material 0.2C that Fig. 4 embodiment of the invention 2 is prepared and the first charge-discharge curve chart of 2C.
The cycle performance figure of the porous carbon in situ composite lithium iron phosphate cathode material that Fig. 5 embodiment of the invention 3 is prepared.
The multiplying power discharging figure of the porous carbon in situ composite lithium iron phosphate cathode material that Fig. 6 embodiment of the invention 4 is prepared.
Embodiment
The below is that the present invention will be further described in conjunction with example, but the protection range that the present invention requires is not limited only to the example express ranges.
Embodiment 1:
(1) select the porous carbon of carbon hole aperture 80nm, take by weighing 1g and put it in the deionized water of 1L, behind the strong stirring 4h, ultrasonic dispersion 1h finally obtains the suspension of porous carbon.
(2) with ferric nitrate and phosphoric acid with deionized water dissolving and be made into the solution of 0.05mol/L.
1:1 mixes ferric nitrate and the phosphoric acid solution of above-mentioned concentration by volume, it is sent in the porous carbon suspension that continues to stir with peristaltic pump with the 2ml/min charging rate, send into certain density ammoniacal liquor with peristaltic pump simultaneously and maintain 2.1 with the pH value of guaranteeing whole wriggling titration process reaction system, by the time after the mixed solution titration of iron, phosphorus is complete, continue to stir again 2h, then with deionized water washing sediment to neutral and filter, at 80 ℃ of dry 24h.
(3) take by weighing 9.5gCH by Li:Fe=1:1
3COOLi2H
2O and 18.4gFePO
42H
2The O/ porous carbon adds 25 wt% (lithium source amount+precursor FePO again
42H
2O/ porous carbon amount) sucrose 7g; Grind 1h raw material are mixed, at Ar/H
2Be warming up to 350 ℃ and be incubated 5h with the programming rate of 5 ℃/min under the protective atmosphere (95:5); with again grinding 1h after the stove cooling; under same protective atmosphere and the heating rate sample is warming up to 600 ℃ and be incubated 10h, finally obtain porous carbon in situ composite lithium iron phosphate cathode material.
The FE-SEM pattern of raw material porous carbon is seen Fig. 1, precursor FePO
42H
2The SEM pattern of O/ porous carbon is seen Fig. 2, and the XRD of porous carbon in situ composite lithium iron phosphate cathode material the results are shown in Figure 3.Analysis of carbon and sulfur is the result show: the LiFePO4 in the porous carbon in situ composite lithium iron phosphate cathode material accounts for 89.8%, and porous carbon accounts for 5.45%, and residue 4.75% is residual carbon.
Embodiment 2:
(1) select the porous carbon of carbon hole aperture 100nm, take by weighing 10g and put it in the deionized water of 5L, behind the strong stirring 4h, ultrasonic dispersion 5h finally obtains the suspension of porous carbon.
(2) with ferric trichloride and ammonium dihydrogen phosphate with deionized water dissolving and be made into the solution of 0.1mol/L.
1:1 mixes ferric trichloride and the ammonium dihydrogen phosphate of above-mentioned concentration by volume, it is sent in the porous carbon suspension that continues to stir with peristaltic pump with the 20ml/min charging rate, send into certain density ammoniacal liquor with peristaltic pump simultaneously and maintain 2.1 with the pH value of guaranteeing whole wriggling titration process reaction system, by the time after the mixed solution titration of iron, phosphorus is complete, continue to stir again 4h, then with deionized water washing sediment to neutral and filter, at 100 ℃ of dry 12h.
(3) take by weighing 18.3gLi by Li:Fe=1.02:1
2CO
3And 100gFePO
42H
2The O/ porous carbon does not add organic carbon source; Grind 2h raw material are mixed, at Ar/H
2Be warming up to 350 ℃ and be incubated 7h with the programming rate of 5 ℃/min under the protective atmosphere (95:5); with again grinding 3h after the stove cooling; under same protective atmosphere and the heating rate sample is warming up to 600 ℃ and be incubated 12h, finally obtain porous carbon in situ composite lithium iron phosphate cathode material.
The preparation of positive plate and the assembling of button cell and test
Take synthetic porous carbon in situ composite lithium iron phosphate as active material, Super-P is conductive electrode, and segregation PVF (PVDF) is binding agent, mix with 1-METHYLPYRROLIDONE (NMP) according to the ratio of 70:20:10 successively and grind after obtain slurry.Slurry is coated on the collector aluminium foil, and 120 ℃ of dry 12h of vacuum are in order to desolventizing and moisture.The aluminium foil that drying is good strikes out the anodal disk of diameter 14mm, puts into the glove box that is full of Ar gas and prepares the assembling battery.Test battery is selected the LIR2032 button cell, negative pole is selected the metal lithium sheet of diameter 14mm, and barrier film is selected the Celgard2325 film, and electrolyte is selected 1mol LiFP6 (EC:DMC:EMC=1:1:1, v/v), mounted battery need be placed on interior 25 ℃ of thermostatic drying chamber and leave standstill 10 ~ 12h.Testing equipment is selected LAND CT2001A, discharges and recharges cut-ff voltage scope 2.0-4.3V, 25 ℃ of probe temperatures.
Blue electrical test results shows: porous carbon in situ composite lithium iron phosphate cathode material has good charge-discharge performance and cycle performance, 0.2C, the specific discharge capacity of 1C, 2C, 5C is successively: 150.3mAh/g, 143.2mAh/g, 133.6mAh/g, 118.4mAh/g, wherein the curve that charges and discharge first of 0.2C and 2C is seen Fig. 4.
Embodiment 3:
(1) select the porous carbon of carbon hole aperture 80nm, take by weighing 5g and put it in the deionized water and absolute ethyl alcohol mixed solution that the 3L volume ratio is 1:1, behind the strong stirring 5h, ultrasonic dispersion 2h finally obtains the suspension of porous carbon.
(2) with ironic citrate and ammonium phosphate with deionized water dissolving and be made into the solution of 0.05mol/L.
1:1.05 mixes ferric iron source and the phosphorus source solution of above-mentioned concentration by volume, it is sent in the porous carbon suspension that continues to stir with peristaltic pump with the 10ml/min charging rate, send into certain density ammoniacal liquor with peristaltic pump simultaneously and maintain 2.05 with the pH value of guaranteeing whole wriggling titration process reaction system, by the time after the mixed solution titration of iron, phosphorus is complete, continue to stir again 5h, then with deionized water washing sediment to neutral and filter, at 80 ℃ of dry 24h.
(3) take by weighing 11.2gLiOHH by Li:Fe=1.05:1
2O and 50gFePO
42H
2The O/ porous carbon adds 15wt% (lithium source amount+precursor FePO again
42H
2O/ porous carbon amount) glucose 9.18g; Grind 2h raw material are mixed, at Ar/H
2Be warming up to 400 ℃ and be incubated 6h with the programming rate of 5 ℃/min under the protective atmosphere (95:5); with again grinding 2h after the stove cooling; under same protective atmosphere and the heating rate sample is warming up to 700 ℃ and be incubated 10h, finally obtain porous carbon in situ composite lithium iron phosphate cathode material.
Analysis of carbon and sulfur is the result show: the LiFePO4 in the porous carbon in situ composite lithium iron phosphate cathode material accounts for 92%, and porous carbon accounts for 5.01%, and residue 2.99% is residual carbon.Material at the specific discharge capacity of 0.2C, 1C, 2C, 5C is successively: 150.1mAh/g, 144.6mAh/g, 137.2mAh/g, 120mAh/g, the cycle performance of its 0.2C and 5C is seen Fig. 5.
Embodiment 4:
(1) select the porous carbon of carbon hole aperture 140nm, take by weighing 2.5g and put it in the supercritical water and absolute ethyl alcohol mixed solution that the 1L volume ratio is 1:1, behind the strong stirring 8h, ultrasonic dispersion 10h finally obtains the suspension of porous carbon.
(2) with ferric nitrate and phosphoric acid one hydrogen ammonia with deionized water dissolving and be made into the solution of 2.5mol/L.
1:1 mixes ferric iron source and the phosphorus source solution of above-mentioned concentration by volume, it is sent in the porous carbon suspension that continues to stir with peristaltic pump with the 5ml/min charging rate, send into certain density ammoniacal liquor with peristaltic pump simultaneously and maintain 1.95 with the pH value of guaranteeing whole wriggling titration process reaction system, by the time after the mixed solution titration of iron, phosphorus is complete, continue to stir again 5h, then with deionized water washing sediment to neutral and filter, at 110 ℃ of dry 10h.
(3) take by weighing 7.1gLiNO by Li:Fe=1.01:1
3And 20.0gFePO
42H
2The O/ porous carbon adds 5wt% (lithium source amount+precursor FePO again
42H
2O/ porous carbon amount) polyvinyl alcohol 1.355g; Grind 5h raw material are mixed, at Ar/H
2 (Be warming up to 400 ℃ and be incubated 10h with the programming rate of 10 ℃/min under protective atmosphere 95:5); with again grinding 2h after the stove cooling; under same protective atmosphere and the heating rate sample is warming up to 700 ℃ and be incubated 5h, finally obtain porous carbon in situ composite lithium iron phosphate cathode material.
Porous carbon in situ composite lithium iron phosphate cathode material at the specific discharge capacity of 0.2C, 1C, 2C, 5C is successively: 144.5mAh/g, 134.4mAh/g, 127.1mAh/g, 111.4mAh/g, the multiplying power test result is seen Fig. 6.
Embodiment 5:
(1) select the porous carbon of carbon hole aperture 100nm, take by weighing 1g and put it in the 1L acetone, behind the strong stirring 2h, ultrasonic dispersion 2h finally obtains the suspension of porous carbon.
(2) with ferric sulfate and sodium phosphate with deionized water dissolving and be made into the solution of 0.15mol/L.
1:1.15 mixes ferric iron source and the phosphorus source solution of above-mentioned concentration by volume, it is sent in the porous carbon suspension that continues to stir with peristaltic pump with the 1.5ml/min charging rate, send into certain density ammoniacal liquor with peristaltic pump simultaneously and maintain 2.0 with the pH value of guaranteeing whole wriggling titration process reaction system, by the time after the mixed solution titration of iron, phosphorus is complete, continue to stir again 1h, then with deionized water washing sediment to neutral and filter, at 90 ℃ of dry 15h.
(3) take by weighing 2.7gLiF and 20gFePO by Li:Fe=1.01:1
42H
2The O/ porous carbon adds 10wt% (lithium source amount+precursor FePO again
42H
2O/ porous carbon amount) ascorbic acid 2.27g; Grind 3h raw material are mixed, at Ar/H
2Be warming up to 350 ℃ and be incubated 7h with the programming rate of 10 ℃/min under the protective atmosphere (95:5); with again grinding 3h after the stove cooling; under same protective atmosphere and the heating rate sample is warming up to 650 ℃ and be incubated 10h, finally obtain porous carbon in situ composite lithium iron phosphate cathode material.
The first discharge specific capacity of porous carbon in situ composite lithium iron phosphate cathode material 0.2C, 1C, 2C, 5C is successively: 141.3mAh/g, 135.2mAh/g, 122.7mAh/g, 106.2mAh/g
Embodiment 6:
(1) select the porous carbon of carbon hole aperture 80nm, take by weighing 2g and put it in the deionized water and industrial alcohol mixed solution that the 4L volume ratio is 1:1, behind the strong stirring 2h, ultrasonic dispersion 5h finally obtains the suspension of porous carbon.
(2) with ferric trichloride and potassium phosphate,monobasic with deionized water dissolving and be made into the solution of 0.5mol/L.
1:1 mixes ferric iron source and the phosphorus source solution of above-mentioned concentration by volume, it is sent in the porous carbon suspension that continues to stir with peristaltic pump with the 6ml/min charging rate, send into certain density ammoniacal liquor with peristaltic pump simultaneously and maintain 2.25 with the pH value of guaranteeing whole wriggling titration process reaction system, by the time after the mixed solution titration of iron, phosphorus is complete, continue to stir again 4h, then with deionized water washing sediment to neutral and filter, at 80 ℃ of dry 24h.
(3) take by weighing 10.5gLiH by Li:Fe=1:1
2PO
4And 20gFePO
42H
2The O/ porous carbon adds the citric acid 9.15g of 30wt% (lithium source amount+precursor FePO42H2O/ porous carbon amount) again; Grind 3h raw material are mixed, at Ar/H
2Be warming up to 325 ℃ and be incubated 10h with the programming rate of 2 ℃/min under the protective atmosphere (95:5); with again grinding 5h after the stove cooling; under same protective atmosphere and the heating rate sample is warming up to 650 ℃ and be incubated 10h, finally obtain porous carbon in situ composite lithium iron phosphate cathode material.
The first discharge specific capacity of porous carbon in situ composite lithium iron phosphate cathode material 0.2C, 1C, 2C, 5C is successively: 144.3mAh/g, 135.4mAh/g, 128.2mAh/g, 110.6mAh/g.
Embodiment 7:
(1) select aperture, carbon hole 90nm porous carbon, take by weighing 1.5g and put it in the supercritical water and acetone mixed solution that the 2.5L volume ratio is 1:1, behind the strong stirring 2h, ultrasonic dispersion 5h finally obtains the suspension of porous carbon.
(2) with ferric iron source and phosphorus source with deionized water dissolving and be made into the solution of 0.05mol/L.
1:1.2 mixes ferric iron source and the phosphorus source solution of above-mentioned concentration by volume, it is sent in the porous carbon suspension that continues to stir with peristaltic pump with the 50ml/min charging rate, send into certain density ammoniacal liquor with peristaltic pump simultaneously and maintain 1.90 with the pH value of guaranteeing whole wriggling titration process reaction system, by the time after the mixed solution titration of iron, phosphorus is complete, continue to stir again 2h, then with deionized water washing sediment to neutral and filter, at 90 ℃ of dry 15h.
(3) take by weighing 8.54gLiI3H by Li:Fe=1:1
2O and 10gFePO
42H
2The O/ porous carbon does not add organic carbon source; Grind 5h raw material are mixed, at Ar/H
2Be warming up to 350 ℃ and be incubated 5h with the programming rate of 2 ℃/min under the protective atmosphere (95:5); with again grinding 5h after the stove cooling; under same protective atmosphere and the heating rate sample is warming up to 550 ℃ and be incubated 15h, finally obtain porous carbon in situ composite lithium iron phosphate cathode material.
The first discharge specific capacity of porous carbon in situ composite lithium iron phosphate cathode material 0.2C, 1C, 2C, 5C is successively: 140.4mAh/g, 132.4mAh/g, 117.6mAh/g, 97.8mAh/g.
Claims (5)
1. the preparation method of a porous carbon in situ composite lithium iron phosphate cathode material, the component of described material are in mass fraction: porous carbon accounts for 0.5 ~ 15%, and LiFePO4 accounts for 85 ~ 99.5%, and the residual carbon after the organic carbon source pyrolysis accounts for 0 ~ 10%; It is characterized in that: concrete preparation process is as follows:
(1) dispersion of porous carbon: take by weighing the porous carbon that a certain amount of aperture is 5 ~ 200nm, put it in the solvent of 1 ~ 10L, behind strong stirring 2 ~ 8h, ultrasonic dispersion 0.5 ~ 10h finally obtains the suspension of porous carbon, and is for subsequent use;
(2) precursor FePO
42H
2O/ porous carbon compound: with ferric iron source and phosphorus source with deionized water dissolving and be made into the solution of 0.01 ~ 5mol/L; Ferric iron source and the phosphorus source solution of same concentrations are mixed in 1:1 ~ 1.2 by volume, with peristaltic pump it being sent into the step 1 that continues to stir with the charging rate of 1 ~ 50ml/min prepares in the porous carbon suspension, sending into ammoniacal liquor adjusting pH scope with peristaltic pump simultaneously is 1.85 ~ 2.35, by the time iron, the titration of phosphorus mixed solution complete after, continue to stir again 2 ~ 5h, then with deionized water washing sediment to neutral and filter, at 80 ~ 120 ℃ of drying 12 ~ 24h; Obtain precursor FePO
42H
2The O/ porous carbon, for subsequent use;
(3) product porous carbon in situ coated LiFePO 4 for lithium ion batteries is synthetic: the precursor FePO that takes by weighing lithium source and step 2 preparation by Li:Fe=1 ~ 1.1:1
42H
2The O/ porous carbon adds organic carbon source again, and grind 1 ~ 5h raw material are mixed, be the Ar/H of 95:5 in ratio
2Protective atmosphere under be warming up to 250 ~ 450 ℃ and be incubated 2 ~ 10h with the programming rate of 3 ~ 10 ℃/min, with again grinding 0.5 ~ 5h after the stove cooling, under same protective atmosphere and the heating rate sample is warming up to 550 ~ 750 ℃ and be incubated 5 ~ 15h, finally obtain the porous carbon in situ covered iron lithium phosphate compound anode material; Wherein, described organic carbon source addition is lithium source and precursor FePO
42H
20 ~ 40 wt% of the quality sum of O/ porous carbon.
2. the preparation method of porous carbon in situ composite lithium iron phosphate cathode material according to claim 1, it is characterized in that: described organic carbon source is sucrose, glucose, fructose, citric acid, ascorbic acid, starch, cellulose, polypropylene, polyethylene glycol, phenolic resins or polyvinyl alcohol.
3. the preparation method of porous carbon in situ composite lithium iron phosphate cathode material according to claim 1, it is characterized in that: described solvent is deionized water, supercritical water, industrial alcohol, absolute ethyl alcohol or acetone.
4. the preparation method of porous carbon in situ composite lithium iron phosphate cathode material according to claim 1, it is characterized in that: described source of iron comprises ferric nitrate, ironic citrate, ferric trichloride or ferric sulfate; Described phosphorus source is phosphorus pentoxide, phosphoric acid, ammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, sodium phosphate, sodium dihydrogen phosphate, disodium-hydrogen, potassium phosphate, potassium dihydrogen phosphate or potassium phosphate,monobasic.
5. the preparation method of porous carbon in situ composite lithium iron phosphate cathode material according to claim 1, it is characterized in that: described lithium source is lithium carbonate, lithium nitrate, lithium hydroxide, lithium acetate, lithium fluoride, lithium phosphate, phosphoric acid one hydrogen lithium, lithium dihydrogen phosphate or lithium iodide.
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| CN102723484A (en) * | 2012-06-07 | 2012-10-10 | 浙江工业大学 | Carbon-coated lithium iron phosphate composite material and application thereof |
| CN102903913B (en) * | 2012-06-13 | 2015-10-28 | 浙江谷神能源科技股份有限公司 | The coated ferric phosphate of carbon, its carbon coated lithium ferrous phosphate composite material prepared and application thereof |
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