CN101734927B - Method for preparing lithium iron phosphate/carbon nano tube compound material - Google Patents

Abstract

The invention relates to a method for preparing a material for an anode of a lithium ion power battery, in particular to a method for preparing a lithium iron phosphate/carbon nano tube compound material. The method comprises the following steps of: using simple soluble acid, alkali, salt and a reducible protectant of organic micromolecules as initial reaction raw materials, and putting the raw materials in a low-temperature refluxing reaction device with an opening system to perform a refluxing reaction at the temperature of between 100 and 200 DEG C for 30 to 300 minutes to obtain hydrous lithium iron phosphate; and combining the hydrous lithium iron phosphate with carbon nano tubes and the reducible protectant of organic micromolecules, and further performing dehydration and thermal crystallization for 1 to 12 hours at temperature of between 300 and 800 DEG C to obtain the lithium iron phosphate/carbon nano tube compound material. The lithium iron phosphate/carbon nano tube compound anode material with a sheet layer superstructure prepared by the method of the invention is an ideal anode material used for preparing a new-generation lithium ion power battery, and the method is suitable for mass industrial production.

Description

A kind of method for preparing lithium iron phosphate/carbon nano tube compound material

" technical field "

The present invention relates to a kind of preparation method of lithium ion power battery cathode material, particularly a kind of method for preparing lithium iron phosphate/carbon nano tube compound material.

" background technology "

Lithium ion battery is state-of-the-art secondary cell up to now, also is state-of-the-art novel green power supply, has become global people's focal point and study hotspot about research, exploitation and the Commercialization application of lithium ion battery.Wherein, improve the key of performance of lithium ion battery, be to select suitable electrode materials, especially positive electrode material.

At present, the positive electrode material of lithium-ion secondary cell mainly adopts cobalt acid lithium material, but it is being faced with the situation that is eliminated owing to the deficiency of cobalt acid lithium self: cost is high, in short supply, the cobalt of cobalt resource is to the severe contamination of environment, the relatively relatively poor low-security that causes of thermostability of cobalt acid lithium etc.

People are by research, and the lithium-ion secondary cell take iron lithium phosphate as positive electrode material will have excellent thermostability and stable charge-discharge performance, are the ideal materials of making all kinds of great-capacity power batteries.The advantages such as raw material sources are abundant, price is low because LiFePO 4 material possesses again, environmental friendliness, safety performance are good it is believed that iron lithium phosphate will replace the sour lithium of cobalt gradually as the first-selection of the positive electrode material of lithium-ion secondary cell.

At present, the study hotspot of industry mainly concentrates on the new synthetic method of development iron lithium phosphate and material is carried out the actual application ability that modification improves iron lithium phosphate: be the breakthrough (comprising high temperature solid-state synthetic system, liquid phase synthetic system) of synthetic method on the one hand, on the one hand be the breakthrough that forms (take iron lithium phosphate as the basis, then carry out ion doping, carbon coat, metal-doped etc.).In actual mechanical process, the two mutually merges again with intersecting and carries out:

The synthetic method aspect, what adopt at first is traditional high temperature solid-state synthetic method (relevant report has: US005910382A, CN1280185C), the high temperature solid-state method (CN1821064A, CN101555004A), High Temperature High Pressure solid-phase synthesis (CN100374366C) of pyrocarbon hot reducing method (CN100398435C, CN1830765A), high-temperature molten salt method (CN100390052C), microwave heating etc. have occurred again subsequently.

The liquid-phase synthesis process that occurs subsequently mainly contains the precipitator method (CN101393982A, CN1208241C), the hot method of hydrothermal/solvent (CN100454615C, CN100522803C, CN100480178C), sol-gel method (CN100395907C, CN101546830A), microwave heating auxiliary law (CN1986396A) etc.

All there are some geneogenous defectives in aforesaid method:

The high temperature solid state reaction system is no doubt simple and convenient; processing ease; but it generally comprises twice thermal treatment process (thermolysis of 300～500 ℃/3～5h; the high temperature crystallization of 800～1000 ℃/6～12h) with twice mechanical disintegration process (raw material pulverizing and product are pulverized), thereby cause its synthesis cycle long; energy consumption is high; pollute large; noise is large; the control of batch products difficult quality; strict omnidistance atmosphere protection (preventing that ferrous iron is oxidized); product cut size large (D50 〉=10 μ m) and distribution range are wide; the technical bottleneck that hard aggregation etc. are intrinsic.

And in the liquid phase synthetic system, although can realize the molecular level combination of lithium ion, ferrous ion or iron ion, phosphate anion by the chemical reaction of solution system, the presoma that namely " from bottom to top " prepares iron lithium phosphate, but these liquid-phase synthesis process come with some shortcomings equally, for example: what hydrothermal/solvent Re Fayin adopted is high temperature high pressure enclosed reaction system, and it only limits to the preparation of a small amount of powder in the fundamental research.Just be subject to many restrictions if enlarge output, particularly for large-scale high temperature high voltage resistant reactor, its design is large with manufacture difficulty, and cost is high, the more important thing is to be absolutely unsafe.The sol-gel rule exists that the presoma dry shrinkage is large, water content is high, the suitability for industrialized production difficulty is large, synthesis cycle is long, be difficult for purifying.Be exactly that the metal alkoxide cost is high in addition, and pure salt solvent is volatile, poisonous, contaminate environment.Microwave heating no doubt is a kind of good body heat phase mode, and still, reactor high-power, large volume but is difficult to make.At present, the Microwave-assisted firing method still rests on the laboratory study stage (preparation of a small amount of powder).

Therefore, if can develop a kind ofly can obtain simultaneously high purity, high conductivity, particle is tiny and uniform LiFePO 4 material, can be suitable for again the preparation method that large-scale industrial is produced, and will have very important realistic meaning.With the develop actively that directly advances iron lithium phosphate as anode material of lithium battery and related industries thereof, and realize that really iron lithium phosphate is as anode material of lithium battery or commercial applications in other respects.

" summary of the invention "

Purpose of the present invention; just provide and a kind ofly can obtain high purity, high conductivity, particle is tiny and uniform LiFePO 4 material; can be suitable for again the preparation method that large-scale industrial is produced; detect through experiment; the lithium iron phosphate/carbon nanotube composite positive pole capacity 〉=155mAh/g of the lamella superstructure with nanoscale that makes; after 2000 charge and discharge cycles, capability retention 〉=85%.Has good chemical property.

For achieving the above object, technical scheme provided by the present invention is:

A kind of method for preparing lithium iron phosphate/carbon nano tube compound material, step comprises: the composite granule of the synthetic hydration iron lithium phosphate → Separation ﹠ Purification of preparation precursor reagent → low temperature reflux → preparation hypophosphite monohydrate iron lithium/carbon nanotube/restitutive protection's agent → dehydration is processed with thermal crystallisation.

Concrete steps are as follows:

(1) preparation precursor reagent

A. reaction mass: comprise the water-soluble cpds that lithium ion, ferrous ion, phosphate anion can be provided; Also be included as the not oxidized needed restitutive protection's agent of protection ferrous ion; PH value conditioning agent; Aqueous solvent;

B. blending process: the dissolving and reducing protective material gets solution A in aqueous solvent; It is divided equally into 3 equal portions; The ferrous ion water-soluble cpds matches with the phosphate anion water-soluble cpds, is dissolved in 2 parts of solution A, gets solution B; The lithium ion water-soluble cpds is dissolved in 1 part of solution A, gets solution C; With solution C by part add in the solution B and vigorous stirring to evenly, add at last an amount of pH value conditioning agent with regulation system pH value, thereby make precursor reagent D;

(2) the synthetic hydration iron lithium phosphate of low temperature reflux

Take above-mentioned precursor reagent D as reaction mass, adopt the low temperature reflux reaction unit of the system of opening wide, the nitrogen insulation blocking, at 100～200 ℃ of lower back flow reaction 30～300min, through cooling off and naturally leaving standstill the obvious layering of system behind 15～30min, take off layer precipitation, make hypophosphite monohydrate iron lithium;

(3) Separation ﹠ Purification

The hypophosphite monohydrate iron lithium that makes is carried out centrifugation and washing removal of impurities, until exist without free zwitterion in the hypophosphite monohydrate iron lithium;

(4) preparation hypophosphite monohydrate iron lithium/carbon nano-tube composite powder

A. reaction mass: the hypophosphite monohydrate iron lithium that makes, carbon nanotube, restitutive protection's agent, dispersion agent, aqueous solvent;

B. blending process: at first be that dispersion agent is dissolved in the water, then add carbon nanotube, carry out high speed shear with colloidal mill or clarifixator and be dispersed to evenly; Then add restitutive protection's agent and fully dissolving, add again prepared hypophosphite monohydrate iron lithium, behind the high-shear homogenizer homogeneous, thereby make the composite mortar of homodisperse hypophosphite monohydrate iron lithium/carbon nanotube/restitutive protection's agent; Then with gained composite mortar spraying drying under 100～150 ℃ of temperature, namely make hypophosphite monohydrate iron lithium/carbon nano-tube composite powder;

(5) dehydration is processed with thermal crystallisation

Hypophosphite monohydrate iron lithium/carbon nano-tube composite powder that above-mentioned steps is made dewaters further and processes with thermal crystallisation; the nitrogen insulation blocking; thermal treatment temp is 300～800 ℃, and heat treatment time is 1～12h, thereby makes finished product lithium iron phosphate/carbon nano tube compound material.

Further,

In step (1), the lithium ion water-soluble cpds can be lithium hydroxide, lithium nitrate.

The ferrous ion water-soluble cpds can be ferrous sulfate, iron protochloride, ferrous ammonium sulphate.

The phosphate anion water-soluble cpds can be phosphoric acid, primary ammonium phosphate, SODIUM PHOSPHATE, MONOBASIC, potassium primary phosphate, ammonium hydrogen phosphate, sodium hydrogen phosphate, potassium hydrogen phosphate.

Restitutive protection's agent can be the micromolecular water soluble organisms such as glucose, citric acid, vitamins C, rosmarinic acid, and this water soluble organic substance can self at first oxidizedly fall, and the protection ferrous ion is not oxidized.

PH value conditioning agent is ammoniacal liquor, is commercially available analytical pure or chemical pure ammoniacal liquor, and concentration is 25～28%, and main application is the conditioned reaction system pH, and ammoniacal liquor is easy to remove in the treating processes of back simultaneously.

Aqueous solvent is deionized water or distilled water, makes solvent and uses, and the reactant aqueous solution system is provided.

In the step (1), the molar ratio of each component of reaction mass is: $n_{{\mathrm{Li}}^{+}}:n_{{\mathrm{Fe}}^{2+}}:n_{{{\mathrm{PO}}_4}^{3-}}:n_P:n_A:H_{2}O=(1.5~$ $2.5):1.0:1.0:(0.05~0.10):(0.5~1.5):(50.0~350.0)$ 。

Wherein

Represent the amount of substance of lithium ion,

n _P, n _A,

Then represent respectively the amount of substance of ferrous ion, phosphate anion, restitutive protection's agent, ammoniacal liquor, aqueous solvent.

According to the prepared precursor reagent system of said ratio, its pH value is 9.0～11.0.After back flow reaction was finished, system pH still was weakly alkaline, and the pH value is 7.5～8.5.Because phosphate anion belongs to the polyprotonic acid radical ion of three valence states, under alkaline condition, will be conducive to the formation of the phosphate anion of three valence states, and then be conducive to the formation of hypophosphite monohydrate iron lithium.

In step (2), type of heating can heat for oil bath, also can be the resistance wire direct heating, and high-power jumbo microwave reaction kettle also can adopt.For anaerobic atmosphere is provided, need namely adopt the nitrogen insulation blocking with the nitrogen isolation in the uncovered position of reflux condensing tube of the low temperature reflux reaction unit of the system of opening wide.

In step (3), centrifugation and washing removal of impurities process for routine can be cloth bag type centrifugation or suction filtration separate mode, and washing is until exist without free zwitterion in the hypophosphite monohydrate iron lithium product.

In step (4), carbon nanotube can be that homemade or commercially available purity is 〉=95% single wall, double-walled or multi-walled carbon nano-tubes, and caliber is 0.5～100nm, and pipe range is 50nm～50 μ m.

Using the purpose of dispersion agent, is that carbon nanotube can be dispersed in the middle of the compound system of whole hypophosphite monohydrate iron lithium/carbon nanotube/restitutive protection's agent uniformly.Dispersion agent should be hyper-dispersant, comprises a kind of or combination among CH-3, CH-6, CH-8, CH-12B, CH-13, CH-18, the CH-34A.

Wherein the quality proportioning of each component of reaction mass is:

$W_{{\mathrm{LiFePO}}_4\·{\mathrm{nH}}_{2}O}:W_H:W_{\mathrm{CNTs}}:W_P:W_{H_{2}O}=(20.0~200.0):(0.01~0.50):1.0:(1.0~100.0):(50.0~$ $500.0)$ 。Wherein W _H, E _CNTs, W _P,

Represent respectively the quality of hypophosphite monohydrate iron lithium, hyper-dispersant, carbon nanotube, restitutive protection's agent, aqueous solvent.

During spraying drying, adopt general industrial spray drying device to get final product, temperature range is 100～150 ℃.

In step (5), the equipment that adopts is the high-temperature atmosphere tubular react furnace, and this tube furnace is equipped with program temperature control unit and atmosphere protection device, and combustion chamber material wherein can be quartzy material, also can be stainless steel, also can be ceramic material.

In one word, the present invention combines liquid phase method and solid phase method dexterously, tries hard to avoid the deficiency of the two, but has taken full advantage of the advantage of the two.

Usefulness of the present invention is:

(1) starting raw material adopts restitutive protection's agent of simple solubility acid, alkali, salt, organic molecule, and is with low cost, and the low temperature liquid phase back flow reaction system of opening wide system is fit to large-scale industrial production; The hypophosphite monohydrate iron lithium presoma that makes is crystalline state, rather than unbodied gelinite or reunion powder.

(2) adopted restitutive protection's agent of organic molecule, so that ferrous ion is not oxidized, this has effectively guaranteed the purity of hypophosphite monohydrate iron lithium.

(3) the hypophosphite monohydrate iron lithium with crystal form dewaters, its thermal treatment temp is relatively low, but but be enough to make the crystalline structure of iron lithium phosphate to become perfect and stable, the carbon of having strengthened simultaneously iron lithium phosphate coats, has effectively promoted the composite effect of iron lithium phosphate and carbon nanotube.Adopt above-mentioned simple method for preparing, the lithium iron phosphate/carbon nano tube compound material of the lamella superstructure with nanoscale that makes, lamella superstructure thickness is 10～50nm approximately, width is 50～200nm approximately, this matrix material has good chemical property, gram volume 〉=155mAh/g, after 2000 charge and discharge cycles, capability retention 〉=85%.

" embodiment "

The below will set forth a plurality of specific embodiment of the present invention from amount of substance proportioning, reflux temperature and the time of each component of forerunner's precursor reactant material, quality proportioning, thermal crystallisation treatment temp and time 4 significant parameters of each component of hypophosphite monohydrate iron lithium/carbon nano-tube composite powder.

Among each embodiment, carry out the compound experiment of hypophosphite monohydrate iron lithium presoma selected be the 5000ml reactor, the tube furnace that thermal crystallisation is processed adopts the combustion chamber of quartzy material, is of a size of Φ * L=20cm * 150cm.All embodiment have all carried out XRD, SEM and chemical property and have detected and characterize.

Embodiment 1

1, selects material: LiOHH ₂O, FeSO ₄7H ₂O, H ₃PO ₄(85%), C ₆H ₁₂O ₆(glucose), NH ₃H ₂O (25%), multi-walled carbon nano-tubes (caliber 〉=20nm, length≤10 μ m, 95%), CH-12B hyper-dispersant, H ₂O.

2, experiment parameter

The amount of substance proportioning of each component of precursor reagent material:

$n_{{\mathrm{Li}}^{+}}:n_{{\mathrm{Fe}}^{2+}}:n_{{{\mathrm{PO}}_4}^{3-}}:n_P:n_A:H_{2}O=1.5:1.0:1.0:0.05:0.5:50.0,$ Reaction system pH=9.0;

Reflux temperature and time: 100 ℃/300min;

The quality proportioning of each component of hypophosphite monohydrate iron lithium/carbon nano-tube composite powder:

$W_{{\mathrm{LiFePO}}_4\·{\mathrm{nH}}_{2}O}:W_H:W_{\mathrm{CNTs}}:W_P:W_{H_{2}O}=20.0:0.01:1.0:1.0:50.0,$ 120 ℃ of spraying drying temperature;

Dehydration and thermal crystallisation treatment temp and time: 300 ℃/12h.

3, operating process

(1) at first be to calculate the consumption of each reaction mass-252.0g LiOHH according to the amount of substance proportioning of reactor volume (5000ml) and each component of precursor reagent material ₂O, 1112.0g FeSO ₄7H ₂O, 461.0g H ₃PO ₄(85%), 36.0g C ₆H ₁₂O ₆(glucose), 280.0g NH ₃H ₂O (25%), 3600.0g H ₂Then O accurately takes by weighing each reaction mass consumption.

(2) low temperature reflux of hypophosphite monohydrate iron lithium is synthetic: load weighted glucose is soluble in water, get solution A, and it is divided into 3 equal portions; FeSO ₄7H ₂O and H ₃PO ₄Match, add 2 parts of A solution, be stirred to fully dissolving, get solution B; LiOHH ₂O then is dissolved in 1 part of A solution, gets solution C; Then solution C is added in the solution B by part, and vigorous stirring, after adding fully, add again NH ₃H ₂O is with the conditioned reaction system pH, and vigorous stirring then makes precursor reagent D this moment to evenly simultaneously.

(3) precursor reagent D is shifted in the low temperature reflux reaction unit of the system of opening wide, pass into nitrogen, behind 100 ℃ of lower constant temperature back flow reaction 300min, just can make hypophosphite monohydrate iron lithium, through cooling, centrifugation, washing removal of impurities, until exist without free zwitterion in the hypophosphite monohydrate iron lithium product, make altogether hypophosphite monohydrate iron lithium 775.2g.

(4) preparation of hypophosphite monohydrate iron lithium/carbon nano-tube composite powder: at first be to calculate the consumption of other reaction mass according to the weight (775.2g) of the hypophosphite monohydrate iron lithium that has made with the quality proportioning of each component of composite granule reaction mass (a), and accurately take by weighing: 775.2g LiFePO ₄NH ₂O (hypophosphite monohydrate iron lithium), 0.4g CH-12B, 38.8g multi-walled carbon nano-tubes, 38.8g C ₆H ₁₂O ₆(glucose), 1938.0g H ₂O (water).(b) hyper-dispersant CH-12B is dissolved in the water, then adds multi-walled carbon nano-tubes, carry out high speed shear with colloidal mill or clarifixator and be dispersed to evenly, then add restitutive protection's agent C ₆H ₁₂O ₆(glucose) and fully dissolving; add again hypophosphite monohydrate iron lithium; behind the high-shear homogenizer homogeneous; thereby make the composite mortar of homodisperse hypophosphite monohydrate iron lithium/carbon nanotube/restitutive protection's agent; then with gained composite mortar spraying drying under 120 ℃ of temperature, obtain hypophosphite monohydrate iron lithium/carbon nano-tube composite powder.

(5) with further dehydration and thermal crystallisation processing of composite granule: the hypophosphite monohydrate iron lithium/carbon nano-tube composite powder that makes is placed porcelain crucible, and put into the flat-temperature zone of tube furnace, pass into nitrogen, process 12h at 300 ℃ of lower constant temp. heatings and get final product.After thermal treatment was finished, cooling was taken out, and obtains powder product---the lithium iron phosphate/carbon nano tube compound material of grey black.

4, experimental result

Make altogether lithium iron phosphate/carbon nano tube compound material 670.0g.

XRD result shows that it belongs to typical olivine-type crystalline structure.

SEM figure shows that it is lamella superstructure pattern, and the thickness of superstructure is 20nm approximately, and width is 100nm approximately.

On chemical property, gram volume is 155mAh/g, and after 2000 charge and discharge cycles, capability retention is 86%.

Embodiment 2

1, selects material: LiOHH ₂O, FeSO ₄7H ₂O, H ₃PO ₄(85%), C ₆H ₈O ₇H ₂O (citric acid), NH ₃H ₂O (25%), Single Walled Carbon Nanotube (caliber≤2nm, length≤50 μ m, 95%), CH-6 hyper-dispersant, H ₂O.

2, experiment parameter

The amount of substance proportioning of each component of precursor reagent material:

$n_{{\mathrm{Li}}^{+}}:n_{{\mathrm{Fe}}^{2+}}:n_{{{\mathrm{PO}}_4}^{3-}}:n_P:n_A:H_{2}O=2.0:1.0:1.0:0.10:1.0:150.0,$ Reaction system pH=10.0;

Reflux temperature and time: 150 ℃/150min;

The quality proportioning of each component of hypophosphite monohydrate iron lithium/carbon nano-tube composite powder:

$W_{{\mathrm{LiFePO}}_4\·{\mathrm{nH}}_{2}O}:W_H:W_{\mathrm{CNTs}}:W_P:W_{H_{2}O}=50.0:0.2:1.0:10.0:200.0,$ 100 ℃ of spraying drying temperature;

Dehydration and thermal crystallisation treatment temp and time: 400 ℃/10h.

3, operating process

(1) at first is consumption---the 126.0g LiOHH that calculates each reaction mass according to the amount of substance proportioning of reactor volume and each component of precursor reagent material ₂O, 417.0g FeSO ₄7H ₂O, 173.0g H ₃PO ₄(85%), 31.5.0gC ₆H ₈O ₇H ₂O (citric acid), 210.0g NH ₃H ₂O (25%), 4050.0g H ₂Then O accurately takes by weighing each material consumption.

(b) with embodiment 1.

(3) precursor reagent D is shifted in the low temperature reflux reaction unit of the system of opening wide, pass into nitrogen, behind 150 ℃ of lower constant temperature back flow reaction 150min, just can make hypophosphite monohydrate iron lithium, with it cooling, centrifugation, washing removal of impurities, until exist without free zwitterion in the hypophosphite monohydrate iron lithium product, make altogether hypophosphite monohydrate iron lithium 290.7g.

(4) preparation of composite granule: at first be to calculate the consumption of other each material with the quality proportioning of each component of composite granule and accurately take by weighing-290.7g LiFePO according to the quality (290.7g) of the hypophosphite monohydrate iron lithium that made (a) ₄NH ₂O, 1.2g CH-6 hyper-dispersant, 5.8g Single Walled Carbon Nanotube, 58.1g C ₆H ₈O ₇H ₂O (citric acid), 1162.8g H ₂O.(b) next be that hyper-dispersant is dissolved in the water; then add carbon nanotube; carrying out high speed shear with colloidal mill or clarifixator is dispersed to evenly; then add restitutive protection's agent and fully dissolving; add again hypophosphite monohydrate iron lithium, behind the high-shear homogenizer homogeneous, thereby make the composite mortar of homodisperse hypophosphite monohydrate iron lithium/carbon nanotube/restitutive protection's agent; then with gained composite mortar spraying drying under 100 ℃ of temperature, obtain composite granule.

(5) further dehydration is processed with thermal crystallisation: the composite granule of the above-mentioned drying that makes is placed in the porcelain crucible, and puts into the flat-temperature zone of tube furnace, pass into nitrogen, process 10h at 400 ℃ of lower constant temp. heatings and get final product.After thermal treatment was finished, cooling was taken out, and obtains powder product---the lithium iron phosphate/carbon nano tube compound material of grey black.

4, experimental result

Make altogether lithium iron phosphate/carbon nano tube compound material 245.5g.

XRD result shows that it belongs to typical olivine-type crystalline structure.

SEM figure shows that it is lamella superstructure pattern, and the thickness of lamella superstructure is 30nm approximately, and width is 120nm approximately.

On chemical property, gram volume is 162mAh/g, and after 2000 charge and discharge cycles, capability retention is 87%.

Embodiment 3

1, reaction mass: LiOHH ₂O, FeSO ₄(NH ₄) ₂SO ₄6H ₂O, H ₃PO ₄(85%), C ₆H ₈O ₆(vitamins C), NH ₃H ₂O (25%), double-walled carbon nano-tube (caliber≤3nm, length≤50 μ m, 95%), CH-13 hyper-dispersant, H ₂O.

2, experiment parameter

The amount of substance proportioning of each component of precursor reagent material:

$n_{{\mathrm{Li}}^{+}}:n_{{\mathrm{Fe}}^{2+}}:n_{{{\mathrm{PO}}_4}^{3-}}:n_P:n_A:H_{2}O=2.5:1.0:1.0:0.10:1.5:350.0,$ Reaction system pH=11.0;

Reflux temperature and time: 170 ℃/60min;

Each constituent mass proportioning of composite granule:

$W_{{\mathrm{LiFePO}}_4\·{\mathrm{nH}}_{2}O}:W_H:W_{\mathrm{CNTs}}:W_P:W_{H_{2}O}=100.0:0.5:1.0:50.0:400,$ 150 ℃ of spraying drying temperature;

Dehydration and thermal crystallisation treatment temp and time: 800 ℃/1h.

3, operating process

(1) at first be to ask the quality of calculating each material according to the amount of substance proportioning of reactor volume (5000ml) and each component of precursor reagent material---68.3g LiOHH ₂O, 254.8g FeSO ₄(NH ₄) ₂SO ₄6H ₂O, 75.0g H ₃PO ₄(85%), 11.4g C ₆H ₈O ₆(vitamins C), 136.5g NH ₃H ₂O (25%), 4095.0g H ₂Then O accurately takes by weighing each material consumption.

(2) with embodiment 1.

(3) precursor reagent D is added in the low temperature reflux reaction unit of the system of opening wide, pass into nitrogen, behind 170 ℃ of lower constant temperature back flow reaction 60min, just can make hypophosphite monohydrate iron lithium, with it cooling, centrifugation, washing removal of impurities, until exist without free zwitterion in the hypophosphite monohydrate iron lithium product, make altogether hypophosphite monohydrate iron lithium 126.0g.

(4) preparation of composite granule: at first be to ask the quality of calculating other material also accurately to take by weighing according to the quality (126.0g) of the hypophosphite monohydrate iron lithium that has made with the extra fine quality proportioning of above-mentioned composite granule (a)---126.0g LiFePO ₄NH ₂O, 0.6g CH-13 hyper-dispersant, 1.3g multi-walled carbon nano-tubes, 63.0g C ₆H ₈O ₆(vitamins C), 503.9g H ₂O.(b) at first be that hyper-dispersant is dissolved in the water; then add carbon nanotube; carrying out high speed shear with colloidal mill or clarifixator is dispersed to evenly; then add restitutive protection's agent and fully dissolving; add again hypophosphite monohydrate iron lithium, behind the high-shear homogenizer homogeneous, thereby make the composite mortar of homodisperse hypophosphite monohydrate iron lithium/carbon nanotube/restitutive protection's agent; then with gained composite mortar spraying drying under 150 ℃ of temperature, obtain composite granule.

(5) further dehydration is processed with thermal crystallisation: the composite granule of the above-mentioned drying that makes is placed in the porcelain crucible, and then the flat-temperature zone of transfer and tube furnace passes into nitrogen, processes 1h at 800 ℃ of lower constant temp. heatings and gets final product.After thermal treatment was finished, cooling was taken out, and obtains powder product---the lithium iron phosphate/carbon nano tube compound material of grey black.

4, experimental result

Make altogether lithium iron phosphate/carbon nano tube compound material 103.8g.

XRD result shows that it belongs to typical olivine-type crystalline structure.

SEM figure shows that it is lamella superstructure pattern, and the thickness of lamella superstructure is 50nm approximately, and width is 100nm approximately.

On chemical property, gram volume is 158mAh/g, and after 2000 charge and discharge cycles, capability retention is 88%.

Embodiment 4

1, selects material: LiOHH ₂O, FeCl ₂4H ₂O, H ₃PO ₄(85%), C ₁₈H ₁₆O ₈(rosmarinic acid), NH ₃H ₂O (25%), multi-walled carbon nano-tubes (caliber≤50nm, length≤20 μ m, 95%), CH-18 hyper-dispersant, H ₂O.

2, experiment parameter

The amount of substance proportioning of each component of precursor reagent material:

$n_{{\mathrm{Li}}^{+}}:n_{{\mathrm{Fe}}^{2+}}:n_{{{\mathrm{PO}}_4}^{3-}}:n_P:n_A:H_{2}O=2.2:1.0:1.0:0.08:1.0:200.0,$ Reaction system pH=10.5;

Reflux temperature and time: 200 ℃/30min;

Each constituent mass proportioning of composite granule:

$W_{{\mathrm{LiFePO}}_4\·{\mathrm{nH}}_{2}O}:W_H:W_{\mathrm{CNTs}}:W_P:W_{H_{2}O}=200.0:0.5:1.0:80.0:500,$ 140 ℃ of spraying drying temperature;

Dehydration and thermal crystallisation treatment temp and time: 500 ℃/8h.

3, operating process

(1) at first be to ask the quality of calculating each material-60.1g LiOHH according to the amount of substance proportioning of reactor volume (5000ml) and each component of precursor reagent material ₂O, 129.4g FeCl ₂4H ₂O, 75.0g H ₃PO ₄(85%), 18.8gC ₁₈H ₁₆O ₈(rosmarinic acid), 91.0g NH ₃H ₂O (25%), 4320.0g H ₂Then O accurately takes by weighing the consumption of each material by these data.

(2) with embodiment 1.

(3) precursor reagent D is added in the low temperature reflux reaction unit of the system of opening wide, pass into nitrogen, behind 200 ℃ of lower constant temperature back flow reaction 30min, just can make hypophosphite monohydrate iron lithium, with it cooling, centrifugation, washing removal of impurities, until exist without free zwitterion in the hypophosphite monohydrate iron lithium product, make altogether hypophosphite monohydrate iron lithium 126.0g.

(4) preparation of composite granule: at first be to ask the quality of calculating other material also accurately to take by weighing according to the quality (126.0g) of the hypophosphite monohydrate iron lithium that has made with the extra fine quality proportioning of above-mentioned composite granule (a)---126.0g LiFePO ₄NH ₂O, 0.3g CH-18 hyper-dispersant, 0.6g multi-walled carbon nano-tubes, 50.4g C ₁₈H ₁₆O ₈(rosmarinic acid), 314.9g H ₂O.(b) at first be that hyper-dispersant is dissolved in the water; then add carbon nanotube; carrying out high speed shear with colloidal mill or clarifixator is dispersed to evenly; then add restitutive protection's agent and fully dissolving; add again hypophosphite monohydrate iron lithium, behind the high-shear homogenizer homogeneous, thereby make the composite mortar of homodisperse hypophosphite monohydrate iron lithium/carbon nanotube/restitutive protection's agent; then with gained composite mortar spraying drying under 140 ℃ of temperature, obtain composite granule.

(5) further dehydration is processed with thermal crystallisation: the composite granule of the above-mentioned drying that makes is placed in the porcelain crucible, and then the flat-temperature zone of transfer and tube furnace passes into nitrogen, processes 8h at 500 ℃ of lower constant temp. heatings and gets final product.After thermal treatment was finished, cooling was taken out, and obtains powder product---the lithium iron phosphate/carbon nano tube compound material of grey black.

4, experimental result

Make altogether lithium iron phosphate/carbon nano tube compound material 103.2g.

XRD result shows that it belongs to typical olivine-type crystalline structure.

SEM figure shows that it is lamella superstructure pattern, and the thickness of lamella superstructure is 10nm approximately, and width is 60nm approximately.

On chemical property, gram volume is 161mAh/g, and after 2000 charge and discharge cycles, capability retention is 85%.

Embodiment 5

1, selects material: LiOHH ₂O, FeSO ₄7H ₂O, (NH ₄) H ₂PO ₄, C ₆H ₈O ₆(vitamins C), NH ₃H ₂O (25%), multi-walled carbon nano-tubes (caliber≤100nm, length≤50 μ m, 95%), CH-34A hyper-dispersant, H ₂O.

2, experiment parameter

The amount of substance proportioning of each component of precursor reagent material:

$n_{{\mathrm{Li}}^{+}}:n_{{\mathrm{Fe}}^{2+}}:n_{{{\mathrm{PO}}_4}^{3-}}:n_P:n_A:H_{2}O=1.8:1.0:1.0:0.05:0.8:150.0,$ Reaction system pH=10.0;

Reflux temperature and time: 160 ℃/120min;

Each constituent mass proportioning of composite granule:

$W_{{\mathrm{LiFePO}}_4\·{\mathrm{nH}}_{2}O}:W_H:W_{\mathrm{CNTs}}:W_P:W_{H_{2}O}=80.0:0.5:1.0:40.0:270.0,$ 135 ℃ of spraying drying temperature;

Dehydration and thermal crystallisation treatment temp and time: 600 ℃/8h.

3, operating process

(1) at first be to ask the quality of calculating each material-113.4g LiOHH according to the amount of substance proportioning of reactor volume (5000ml) and each component of precursor reagent material ₂O, 417.0g FeSO ₄7H ₂O, 172.5g (NH ₄) H ₂PO ₄, 13.2gC ₆H ₈O ₆(vitamins C), 168.0g NH ₃H ₂O (25%), 4050.0g H ₂Then O accurately takes by weighing the consumption of each material by these data.

(2) with embodiment 1.

(3) precursor reagent D is added in the low temperature reflux reaction unit, pass into nitrogen, behind 160 ℃ of lower constant temperature back flow reaction 120min, just can make hypophosphite monohydrate iron lithium, with it cooling, centrifugation, washing removal of impurities, until exist without free zwitterion in the hypophosphite monohydrate iron lithium product, make altogether hypophosphite monohydrate iron lithium 290.7g.

(4) preparation of composite granule: at first be to ask the quality of calculating other material also accurately to take by weighing-290.7g LiFePO according to the quality (290.7g) of the hypophosphite monohydrate iron lithium that has made with the extra fine quality proportioning of above-mentioned composite granule (a) ₄NH ₂O, 1.8g CH-34A hyper-dispersant, 3.6g multi-walled carbon nano-tubes, 145.4g C ₁₈H ₁₆O ₈(rosmarinic acid), 981.1g H ₂O.(b) at first be that hyper-dispersant is dissolved in the water; then add carbon nanotube; carrying out high speed shear with colloidal mill or clarifixator is dispersed to evenly; then add restitutive protection's agent and fully dissolving; add again hypophosphite monohydrate iron lithium, behind the high-shear homogenizer homogeneous, thereby make the composite mortar of homodisperse hypophosphite monohydrate iron lithium/carbon nanotube/restitutive protection's agent; then with gained composite mortar spraying drying under 135 ℃ of temperature, obtain composite granule.

(5) further dehydration is processed with thermal crystallisation: the composite granule of the above-mentioned drying that makes is placed in the porcelain crucible, and then the flat-temperature zone of transfer and tube furnace passes into nitrogen, processes 8h at 600 ℃ of lower constant temp. heatings and gets final product.After thermal treatment was finished, cooling was taken out, and obtains powder product---the lithium iron phosphate/carbon nano tube compound material of grey black.

4, experimental result

Make altogether lithium iron phosphate/carbon nano tube compound material 240.3g.

XRD result shows that it belongs to typical olivine-type crystalline structure.

SEM figure shows that it is lamella superstructure pattern, and the thickness of lamella superstructure is 30nm approximately, and width is 150nm approximately.

On chemical property, gram volume is 157mAh/g, and after 2000 charge and discharge cycles, capability retention is 87%.

Embodiment 6

1, selects material: LiNO ₃, FeSO ₄7H ₂O, (NH ₄) H ₂PO ₄, C ₆H ₁₂O ₆(glucose), NH ₃H ₂O (25%), double-walled carbon nano-tube (caliber≤40nm, length≤10 μ m, 95%), CH-12B hyper-dispersant, H ₂O.

2, experiment parameter

The amount of substance proportioning of each component of precursor reagent material:

$n_{{\mathrm{Li}}^{+}}:n_{{\mathrm{Fe}}^{2+}}:n_{{{\mathrm{PO}}_4}^{3-}}:n_P:n_A:H_{2}O=2.0:1.0:1.0:0.05:1.0:100.0,$ Reaction system pH=10.5;

Reflux temperature and time: 180 ℃/60min;

Each constituent mass proportioning of composite granule:

$W_{{\mathrm{LiFePO}}_4\·{\mathrm{nH}}_{2}O}:W_H:W_{\mathrm{CNTs}}:W_P:W_{H_{2}O}=100.0:0.5:1.0:25.0:200,$ 125 ℃ of spraying drying temperature;

Dehydration and thermal crystallisation treatment temp and time: 700 ℃/5h.

3, operating process

(1) at first be to ask the quality of calculating each material according to the amount of substance proportioning of reactor volume (5000ml) and each component of precursor reagent material---317.4g LiNO ₃, 639.4g FeSO ₄7H ₂O, 264.5g (NH ₄) H ₂PO ₄, 20.7gC ₆H ₁₂O ₆(glucose), 322.0g NH ₃H ₂O (25%), 4140.0g H ₂Then O accurately takes by weighing the consumption of each material by these data.

(2) low temperature reflux of hypophosphite monohydrate iron lithium is synthetic: with embodiment 1.

(3) precursor reagent D is added in the low temperature reflux reaction unit of the system of opening wide, pass into nitrogen, behind 180 ℃ of lower constant temperature back flow reaction 60min, just can make hypophosphite monohydrate iron lithium, with it cooling, centrifugation, washing removal of impurities, until exist without free zwitterion in the hypophosphite monohydrate iron lithium product, make altogether hypophosphite monohydrate iron lithium 445.7g.

(4) preparation of composite granule: at first be to ask the quality of calculating other material also accurately to take by weighing according to the quality (445.7g) of the hypophosphite monohydrate iron lithium that has made with the extra fine quality proportioning of above-mentioned composite granule (a)---445.7g LiFePO ₄NH ₂O, 2.2g CH-12B hyper-dispersant, 4.5g double-walled carbon nano-tube, 111.4g C ₆H ₁₂O ₆(glucose), 891.5g H ₂O.(b) at first be that hyper-dispersant is dissolved in the water, then add carbon nanotube, carry out high speed shear with colloidal mill or clarifixator and be dispersed to evenly, then add restitutive protection's agent C ₆H ₁₂O ₆(glucose) and fully dissolving; add again hypophosphite monohydrate iron lithium, behind the high-shear homogenizer homogeneous, thereby make the composite mortar of homodisperse hypophosphite monohydrate iron lithium/carbon nanotube/restitutive protection's agent; then with gained composite mortar spraying drying under 125 ℃ of temperature, obtain composite granule.

(5) further dehydration is processed with thermal crystallisation: the composite granule of the above-mentioned drying that makes is placed in the porcelain crucible, and then the flat-temperature zone of transfer and tube furnace passes into nitrogen, processes 5h at 700 ℃ of lower constant temp. heatings and gets final product.After thermal treatment was finished, cooling was taken out, and obtains powder product---the lithium iron phosphate/carbon nanotube compound material of grey black.

4, experimental result

Make altogether lithium iron phosphate/carbon nano tube compound material 367.4g.

XRD result shows that it belongs to typical olivine-type crystalline structure.

SEM figure shows that it is lamella superstructure pattern, and the thickness of lamella superstructure is 20nm approximately, and width is 80nm approximately.

On chemical property, gram volume is 165mAh/g, and after 2000 charge and discharge cycles, capability retention is 86%.

Below only be preferred forms of the present invention, not in order to limit the present invention.All foundations content disclosed by the invention, some identical, replacement schemes that those of ordinary skill in the art can expect apparently all should fall into protection scope of the present invention.

Claims (8)

1. method for preparing lithium iron phosphate/carbon nano tube compound material, step comprises: the synthetic hydration iron lithium phosphate → Separation ﹠ Purification of preparation precursor reagent → low temperature reflux → preparation hypophosphite monohydrate iron lithium/carbon nano-tube composite powder → dehydration is processed with thermal crystallisation, it is characterized in that, concrete steps are as follows:

(1) preparation precursor reagent:

A. reaction mass: comprise the water-soluble cpds that lithium ion, ferrous ion, phosphate anion can be provided, also be included as the not oxidized needed restitutive protection's agent of protection ferrous ion, pH value conditioning agent, aqueous solvent;

The molar ratio of each reaction mass is:

Wherein

Represent the amount of substance of lithium ion,

n _P, n _A, Then represent respectively the amount of substance of ferrous ion, phosphate anion, restitutive protection's agent, pH value conditioning agent, aqueous solvent; PH value conditioning agent is ammoniacal liquor, and concentration is 25～28%;

B. blending process: the dissolving and reducing protective material gets solution A in aqueous solvent; It is divided equally into 3 equal portions; The ferrous ion water-soluble cpds matches with the phosphate anion water-soluble cpds, is dissolved in 2 parts of solution A, gets solution B; The lithium ion water-soluble cpds is dissolved in 1 part of solution A, gets solution C; With solution C by part add in the solution B and vigorous stirring to evenly, add at last an amount of pH value conditioning agent with regulation system pH value, thereby make precursor reagent D;

(2) the synthetic hydration iron lithium phosphate of low temperature reflux

Take precursor reagent D as reaction mass, adopt the low temperature reflux reaction unit of the system of opening wide, the nitrogen insulation blocking at 100～200 ℃ of lower back flow reaction 30～300min, is taken off layer precipitation through cooling and after naturally leaving standstill, and makes hypophosphite monohydrate iron lithium;

(3) Separation ﹠ Purification

The hypophosphite monohydrate iron lithium that makes is carried out centrifugation and washing removal of impurities, until exist without free zwitterion in the hypophosphite monohydrate iron lithium;

(4) preparation hypophosphite monohydrate iron lithium/carbon nano-tube composite powder

A. reaction mass: the hypophosphite monohydrate iron lithium that makes, carbon nanotube, restitutive protection's agent, dispersion agent, aqueous solvent; Wherein the quality proportioning of each component is:

Wherein

W _H, W _CNTs, W _P,

Represent respectively the quality of hypophosphite monohydrate iron lithium, dispersion agent, carbon nanotube, restitutive protection's agent, aqueous solvent;

B. blending process: at first be that dispersion agent is dissolved in the water, then add carbon nanotube, carrying out high speed shear with colloidal mill or clarifixator is dispersed to evenly, then add restitutive protection's agent and fully dissolving, add again prepared hypophosphite monohydrate iron lithium, behind the high-shear homogenizer homogeneous, thereby make the composite mortar of homodisperse hypophosphite monohydrate iron lithium/carbon nanotube/restitutive protection's agent, then with gained composite mortar spraying drying under 100～150 ℃ of temperature, namely make hypophosphite monohydrate iron lithium/carbon nano-tube composite powder;

(5) dehydration is processed with thermal crystallisation

Hypophosphite monohydrate iron lithium/carbon nano-tube composite powder that above-mentioned steps is made dewaters further and processes with thermal crystallisation; the nitrogen insulation blocking; thereby make finished product lithium iron phosphate/carbon nano tube compound material, thermal treatment temp is 300～800 ℃, and heat treatment time is 1～12h.

2. the method for preparing lithium iron phosphate/carbon nano tube compound material according to claim 1 is characterized in that, in the step (1), the lithium ion water-soluble cpds is a kind of or combination in lithium hydroxide, the lithium nitrate;

The ferrous ion water-soluble cpds is a kind of or combination in ferrous sulfate, iron protochloride, the ferrous ammonium sulphate;

The phosphate anion water-soluble cpds is a kind of or combination in phosphoric acid, primary ammonium phosphate, SODIUM PHOSPHATE, MONOBASIC, the potassium primary phosphate;

Restitutive protection's agent is a kind of or combination in glucose, citric acid, vitamins C, the rosmarinic acid;

Aqueous solvent is deionized water or distilled water.

3. the method for preparing lithium iron phosphate/carbon nano tube compound material according to claim 1 is characterized in that, in step (4), described carbon nanotube is that purity is 〉=95% single wall, or multi-walled carbon nano-tubes; Caliber is 0.5～100nm, and pipe range is 50nm～50 μ m.

4. the method for preparing lithium iron phosphate/carbon nano tube compound material according to claim 1, it is characterized in that, in the step (4), described dispersion agent is hyper-dispersant, is a kind of or combination among CH-3, CH-6, CH-8, CH-12B, CH-13, CH-18, the CH-34A; The mass ratio of dispersion agent and carbon nanotube is W _H: W _CNTs=(0.01～0.50): 1.0; W wherein _H, W _CNTsRepresent respectively the quality of dispersion agent and carbon nanotube.

5. the method for preparing lithium iron phosphate/carbon nano tube compound material according to claim 1 is characterized in that, in step (2), type of heating is the oil bath heating, or Resistant heating, or microwave heating; The uncovered position of reflux condensing tube at the low temperature reflux reaction unit that opens wide system isolates with nitrogen.

6. the method for preparing lithium iron phosphate/carbon nano tube compound material according to claim 1 is characterized in that, in step (3), adopts cloth bag type centrifugation mode.

7. the method for preparing lithium iron phosphate/carbon nano tube compound material according to claim 1 is characterized in that, in step (4), what select is conventional industrial spray drying device.

8. the method for preparing lithium iron phosphate/carbon nano tube compound material according to claim 1; it is characterized in that; in step (5); the equipment that adopts is the high-temperature atmosphere tubular react furnace; be equipped with program temperature control unit and atmosphere protection device, combustion chamber material wherein is stainless steel or pottery.