CN101656311A - Preparation method of LiFePO4/C composite material - Google Patents

Preparation method of LiFePO4/C composite material Download PDF

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Publication number
CN101656311A
CN101656311A CN200910195813A CN200910195813A CN101656311A CN 101656311 A CN101656311 A CN 101656311A CN 200910195813 A CN200910195813 A CN 200910195813A CN 200910195813 A CN200910195813 A CN 200910195813A CN 101656311 A CN101656311 A CN 101656311A
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composite material
preparation
lifepo
fepo
hour
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余爱水
刘佳丽
黄桃
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Fudan University
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Fudan University
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention relates to a preparation method of a lithium ion battery anode material, in particular to a preparation method of an LiFePO4/C composite material, which comprises the following steps: dissolving ferric salt in deionized water, adding a surface active agent to be used as a regulating agent, stirring and mixing uniformly, adding a precipitator NH4H2PO4, continuously stirring for 3-5h,performing suction filtration, washing, drying to obtain FePO4; and then mixing the obtained FePO4 with lithium salt and carbon source, pretreating for 3-5h at 450 DEG C, and calcining to prepare theLiFePO4/C composite material, wherein the volume ratio of the surface active agent to the ferric salt is 1:1-2:1. The LiFePO4 prepared by the method has the advantages of uniform particle distribution, excellent performance, low cost, simpler step, and the like; the thermal after-treatment is carried out according to the demand in the synthesis process.

Description

A kind of LiFePO 4The preparation method of/C composite material
Technical field
The present invention relates to a kind of preparation method of anode material for lithium-ion batteries, be specifically related to a kind of LiFePO 4The preparation method of/C composite material.
Background technology
1997, Padhi and Goodenough etc. found olivine-type LiFePO 4Have the embedding of taking off behavior, its space group is Pnmb, and oxygen atom is arranged with a kind of hexagonal closs packing form of dislocation slightly, and phosphorus atoms occupies tetrahedral 4c position, and iron atom and lithium atom occupy octahedral 4c and 4a position respectively.If set out FeO with the axial visual angle of b 6Octahedron couples together with certain angle on the bc plane, and LiO 6Octahedron then is total to the limit along the b direction of principal axis, forms chain.A FeO 6Octahedron respectively with a PO 4Tetrahedron and two LiO 6Octahedra limit altogether, a PO simultaneously 4Tetrahedron also with two LiO 6Octahedra limit altogether, this has just formed the hole that can supply the free embedding of lithium ion to take off.So LiFePO 4Have lithium ion and take off the embedding passage, good electrochemical, discharge platform is very steady, Stability Analysis of Structures in the charge and discharge process, theoretical capacity is 170mAh/g, with traditional positive electrode LiMn 2O 4And LiCoO 2Compare, it has the following advantages: fail safe is good, and cycle performance is more stable, and cycle life can reach more than 2000 times, and high-temperature behavior is better, and is pollution-free, and environmental friendliness is cheap.
At present, LiFePO 4Synthetic method mainly contain high temperature solid-state method, hydrothermal synthesis method, microwave process for synthesizing etc.High temperature solid-state method is the method for more generally taking at present, Yamada Li 2CO 3, Fe (CH 3COO) 22H 2O, (NH 4) 2H 2PO 4As starting material, under the nitrogen atmosphere protection, high-temperature calcination obtains LiFePO 4Hydrothermal synthesis method is that M.Stanley Whittingham seminar proposes first, adopts FeSO 4As starting material, hydro-thermal reaction prepares LiFePO under HTHP 4(S.F.Yang, P.Y.Zavalij, M.S.Whittingham, Electrochem.Commun., 3 (2001) 505).People such as M.Iguchi are with Li 2CO 3, NH 4H 2PO 4, Fe (CH 3COO) 2Or contain the Fe (CH of Fe powder 3CHOCOO) 22H 2O is dissolved in ethanol, and the argon gas atmosphere protection adds reaction for preparation LiFePO down in microwave oven 4(M.Higuchi, K.Katayama, Y.Azuma, M.Yukawa, M.Suhara, J.Power Sources, 119-121 (2003) 258-261).The common shortcoming of these methods is generally to take the comparatively expensive and easily oxidized Fe of price 2+As starting material, pyroreaction need be carried out, under inert atmosphere to prevent Fe 2+Be oxidized to Fe 3+, operate comparatively loaded down with trivial details.
For this reason, at present a lot of research groups begin to adopt Fe 3+As raw material, preparation LiFePO 4LiFePO 4Electronic conductivity own is lower, but carbon coats the conductance that can effectively improve material.Human FePO such as L.N.Wang 44H 2O is as starting material, and PEG prepares LiFePO as reducing agent and carbon source 4/ C (L.N.Wang, Z.G.Zhang, K.L.Zhang, J.PowerSources 167 (2007) 200).Human FePO such as Y.Q.Wang 4With (NH 4) 2SO 3Be the synthetic NH of starting material 4FePO 4, further synthetic again LiFePO 4(Y.Q.Wang, J.L.Wang, J.Yang, Y.Nuli, Adv.Funct.Mater, 16 (2006) 2135).With Fe 3+Prepare LiFePO as starting material 4Cost is lower, and is easy and simple to handle, and follow-up carbon source also can be used as reducing agent further with Fe 3+Be reduced to Fe 2+, have very extensive studies and application prospect.
Summary of the invention
The purpose of this invention is to provide a kind of LiFePO 4The preparation method of/C composite material.
The present invention solves in the existing in prior technology conventional solid-state method to adopt Fe 2+As starting material, and the difficult control of preparation LiFePO4 granular size, the agglomeration in the follow-up calcining.Prepare the FePO that particle is less and be evenly distributed by the precipitation method 4Precursor, and then preparation LiFePO 4/ C composite material.
The LiFePO that the present invention proposes 4The preparation method of/C composite material, concrete steps are as follows:
Trivalent iron salt is dissolved in the deionized water, adds surfactant, mix, add precipitation reagent NH as adjusting control agent 4H 2PO 4, continue to stir 3-5 hour, suction filtration, washing, oven dry obtains FePO 4Then with gained FePO 4Mix with lithium salts, carbon source, under 450 ℃ of temperature preliminary treatment 3-5 hour, calcining made LiFePO 4/ C composite material.Wherein: the volume ratio of surfactant and ferric salt solution is 1: 1-2: 1.
Among the present invention, described trivalent iron salt is Fe 2(SO 4) 3Or FeCl 3When adopting FeCl 3During for the starting material molysite, precipitation reagent NH 4H 2PO 4Addition and mole such as molysite; When adopting Fe 2(SO 4) 3Be the starting material molysite, precipitation reagent NH 4H 2PO 4Addition is two times of molysite mole.
Among the present invention, described surfactant be among PEG (polyethylene glycol), P123 (polyethylene polypropylene-polyethylene block polymer) or the CTAB (softex kw) any.
Among the present invention, it is 5-15 hour with the trivalent iron salt time of mixing behind the described surfactant.
Among the present invention, described lithium salts is LiOH, Li 2CO 3Or LiCOOCH 3Deng in any, wherein LiOH and LiCOOCH 3Addition and FePO 4Equimolar amounts, Li 2CO 3The mole that adds is FePO 4Half.
Among the present invention, described carbon source be in sucrose, glucose, citric acid or the oxalic acid etc. any, the addition of described carbon source is LiFePO 4The 1%-10wt% of theoretical yield.
Among the present invention, described preliminary treatment and calcination atmosphere are H 2, H 2/ Ar,, N 2Or in the gas such as Ar any.
Among the present invention, describedly it is characterized in that 450 ℃ of pretreatment times are 3-5 hour.
Among the present invention, described calcining heat is 600-650 ℃, and calcination time is 3-5 hour.
The present invention prepares FePO by the aqueous solution precipitation method 4, add surfactant and can better disperse Fe 3+Fe 3+Be easy to be adsorbed on the surfactant surface, the backbone of activating agent can effectively be regulated and control the pattern of precipitation.Fe 3+Can further allow Fe with the stirring of activating agent 3+Be dispersed on the long-chain of activating agent.The deposit seed that obtains is evenly distributed, and particle diameter is less.Choose the molysite of solubility, a certain amount of Fe of dissolving preparation 3+Solution adds surfactant, and the addition of activating agent is adjustable according to the iron salt solutions amount of configuration, because the activating agent kind difference of selecting for use, therefore proportioning also can regulate.
The introducing of carbon source among the present invention can be played the effect that RESEARCH OF PYROCARBON coats, and can prepare LiFePO in high-temperature calcination simultaneously 4In/C the process as Fe 3+Reducing agent.
For anode material for lithium-ion batteries, its pattern, granular size all are the decisive factors of its chemical property, and the adding of activating agent can reduce the internal resistance between the ion in the precipitation process, the microscopic appearance of control product.And the different surfaces activating agent, the solvation effect difference, also different with the mating reaction between the metal ion, so also different to the regulating and controlling effect of product microscopic appearance.Therefore, this method can prepare the chemical property better products by the regulation and control to microscopic appearance.
The present invention has the LiFePO for preparing 4Even particle distribution, function admirable, cheap, can carry out after-baking as required in the synthesis technique, characteristics such as step is comparatively simple.
Description of drawings
Fig. 1 is the x-ray diffraction pattern of product.Wherein, a is embodiment 1, and b is comparative example 1-1, and a is pure phase and degree of crystallinity LiFePO preferably 4Li appears in material among the b 3PO 4And Fe 2The trace impurity of P.
Fig. 2 is FePO 4Stereoscan photograph.Wherein, a is embodiment 1, and b is comparative example 1-2.
Fig. 3 is the transmission electron microscope photo of product.Wherein, a is embodiment 1, and b is comparative example 1-1.
Fig. 4 is the electrochemistry cycle performance of product.Wherein, a is embodiment 1, and b is comparative example 1-1.
Fig. 5 is the stereoscan photograph of embodiment 2 products.
Fig. 6 is the discharge curve first under the embodiment 2 product 0.1C multiplying powers.
Embodiment
Below by embodiment, technical scheme of the present invention is described in further detail.
Embodiment 1: a kind of LiFePO 4The preparation method, the steps include:
A. dissolve 5mmol Fe 2(SO 4) 3In the 15ml deionized water, add 15ml PEG-400 surfactant, magnetic agitation 15 hours.
B. with 1mmol NH 4H 2PO 4Be dissolved in the 15ml deionized water, add in the above-mentioned solution, produce FePO immediately 4Precipitation continues to stir 5 hours.
C. will precipitate suction filtration, with deionized water and acetone washing.
D. according to ICP test, FePO in the analytic sample 4Content, add the LiOH of equimolar amounts, sucrose (is about LiFePO 4The 10wt% of ultimate output) after mortar mixes, hydrogen/450 ℃ of preliminary treatment of argon gas mist 5 hours.
E. after being cooled to room temperature, hydrogen argon gas mixed atmosphere continues 650 ℃ to be handled 3 hours.
The X ray diffracting data of present embodiment product is seen Fig. 1 a.
Present embodiment FePO 4Sem photograph and product LiFePO 4The transmission electron microscope picture of/C is seen Fig. 2 a and Fig. 3 a respectively.
The electrochemistry cycle performance of present embodiment product is seen Fig. 4.
Embodiment 2: a kind of LiFePO 4The preparation method, the steps include:
A. dissolve 5mmol FeCl 3In the 15ml deionized water, add 20ml P123 surfactant, magnetic agitation 10 hours.
B. with 5mmol NH 4H 2PO 4Be dissolved in the 15ml deionized water, add in the above-mentioned solution, produce FePO 4Precipitation continues to stir 10 hours.
C. will precipitate suction filtration, with deionized water and acetone washing.
According to ICP test, FePO in the analytic sample 4Content, add the LiOH of equimolar amounts, sucrose (is about LiFePO 4The 5wt% of ultimate output) after mortar mixes, hydrogen/450 ℃ of preliminary treatment of argon gas mist 5 hours.
E. after being cooled to room temperature, hydrogen argon gas mixed atmosphere continues 650 ℃ to be handled 5 hours.
The X ray diffracting data of present embodiment product is free from admixture phase LiFePO with Fig. 1 a. 4
ESEM picture such as Fig. 5 of present embodiment product.
Present embodiment is discharge curve such as Fig. 6 first.
Comparative example 1-1
The calcining heat of removing among the step e is 700 ℃, and all the other steps are identical with embodiment 1 method.
This comparative example X ray diffracting data is seen Fig. 1 b.As can be seen from the figure, when calcining heat to 700 ℃, Fe is arranged in the product 2P (arrow logo among the figure), Li 3PO 4(asterisk sign among the figure).So LiFePO among the present invention 4The follow-up calcining heat of/C is selected 600-650 ℃.
This comparative example transmission electron microscope data are seen Fig. 3 b.From its transmission electron microscope picture as can be seen, 700 ℃ of products obtained therefrom carbon coating layers do not have 650 ℃ carbon coating layer to be evenly distributed, because calcining heat is too high, coating layer are destroyed to some extent.
The electrochemistry cycle performance of present embodiment product is seen Fig. 4.
Under the 0.1C discharge-rate, 650 ℃ of LiFePO that processing obtains 4/ C composite material shows good cycle performance, its first discharge capacity be 147.9mAh g -1, 40 ThDischarge capacity is 148.5mAh g -1And the sample that 700 ℃ of processing obtain can not effectively improve its lower electronic conductivity because the preceding coating layer of addressing is damaged, and causes its cycle performance relatively poor.
Comparative example 1-2
Except that not adding surfactant in step a, all the other steps are identical with embodiment 1 method.
This comparative example ESEM picture is seen Fig. 2 b
From its sem photograph as can be seen, there is surfactant to have gained FePO 4The about 100nm of precipitation particle diameter, and do not have surfactant gained FePO 4Particle diameter is about 700nm.Can prove that from figure the adding surfactant described in the present invention is to regulation and control FePO 4The pattern effect.By the long-chain of surfactant, allow Fe 3+Be uniformly dispersed, obtain the FePO about the about 100nm of particle 4, by regulation and control FePO 4Pattern further regulate and control LiFePO 4The pattern of/C composite material is in case the appearance of the distribution of material non-uniform phenomenon that causes owing to reuniting in follow-up calcination process.
Can see with P123 (polyethylene polypropylene-polyethylene block polymer) when being surfactant gained FePO among the embodiment 2 4Precursor is 100-200nm spheric granules (Fig. 5), its under the 0.1C multiplying power first discharge curve (Fig. 6) can see extraordinary LiFePO 4Discharge platform, its first discharge capacity be 149mAh/g.

Claims (9)

1, a kind of LiFePO 4The preparation method of/C composite material is characterized in that concrete steps are as follows:
Trivalent iron salt is dissolved in the deionized water, adds surfactant, mix, add precipitation reagent NH as adjusting control agent 4H 2PO 4, continue to stir 3-5 hour, suction filtration, washing, oven dry obtains FePO 4Then with gained FePO 4Mix with lithium salts, carbon source, under 450 ℃ of temperature preliminary treatment 3-5 hour, calcining made LiFePO 4/ C composite material, wherein: the volume ratio of surfactant and ferric salt solution is 1: 1-2: 1.
2, LiFePO according to claim 1 4The preparation method of/C composite material is characterized in that described trivalent iron salt is Fe 2(SO 4) 3Or FeCl 3, when adopting FeCl 3During for the starting material molysite, precipitation reagent NH 4H 2PO 4Addition and mole such as molysite; When adopting Fe 2(SO 4) 3Be the starting material molysite, precipitation reagent NH 4H 2PO 4Addition is two times of molysite mole.
3, LiFePO according to claim 1 4The preparation method of/C composite material, it is characterized in that described surfactant be in polyethylene glycol, polyethylene polypropylene-polyethylene block polymer or the softex kw any.
4, LiFePO according to claim 1 4The preparation method of/C composite material is characterized in that behind the described surfactant with the trivalent iron salt time of mixing being 5-10 hour.
5, LiFePO according to claim 1 4The preparation method of/C composite material is characterized in that described lithium salts is LiOH, Li 2CO 3Or LiCOOCH 3In any, wherein LiOH and LiCOOCH 3Addition and FePO 4Equimolar amounts, Li 2CO 3The mole that adds is FePO 4Half.
6, LiFePO according to claim 1 4The preparation method of/C composite material, it is characterized in that described carbon source be in sucrose, glucose, citric acid or the oxalic acid any, the addition of described carbon source is LiFePO 4The 1%-10wt% of theoretical yield.
7, LiFePO according to claim 1 4The preparation method of/C composite material, its feature is H in described preliminary treatment and calcination atmosphere 2, H 2/ Ar,, N 2Or in the Ar gas any.
8, LiFePO according to claim 1 4The preparation method of/C composite material, its feature is characterized in that described 450 ℃ of pretreatment times are 3-5 hour.
9, LiFePO according to claim 1 4The preparation method of/C composite material, its feature is 600-650 ℃ in described calcining heat, calcination time is 3-5 hour.
CN200910195813A 2009-09-17 2009-09-17 Preparation method of LiFePO4/C composite material Pending CN101656311A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102390824A (en) * 2011-08-10 2012-03-28 朱叙国 Preparation method of lithium ion phosphate
CN102593452A (en) * 2012-03-22 2012-07-18 华南师范大学 Method for preparing carbon-coated lithium iron phosphate material
CN106654219A (en) * 2017-01-12 2017-05-10 吉林大学 Ion exchange assisted preparation method of LiFePO4/C nano composite material
CN113991120A (en) * 2021-12-27 2022-01-28 湖南长远锂科股份有限公司 Lithium iron phosphate anode material and preparation method thereof

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102390824A (en) * 2011-08-10 2012-03-28 朱叙国 Preparation method of lithium ion phosphate
CN102390824B (en) * 2011-08-10 2013-02-20 朱叙国 Preparation method of lithium iron phosphate
CN102593452A (en) * 2012-03-22 2012-07-18 华南师范大学 Method for preparing carbon-coated lithium iron phosphate material
CN106654219A (en) * 2017-01-12 2017-05-10 吉林大学 Ion exchange assisted preparation method of LiFePO4/C nano composite material
CN113991120A (en) * 2021-12-27 2022-01-28 湖南长远锂科股份有限公司 Lithium iron phosphate anode material and preparation method thereof
CN113991120B (en) * 2021-12-27 2022-03-22 湖南长远锂科股份有限公司 Lithium iron phosphate anode material and preparation method thereof

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Application publication date: 20100224