CN1224124C - Reversed phase lithium inserting process of preparing polycrystal LiFePO4 nano powder material - Google Patents

Abstract

The present invention discloses a reversed phase lithium insertion method for a preparing polycrystalline LiFePO4 nanometer powder material. Span80 and Tween 80 are mixed into a composite surface active agent ST which is slowly added to normal heptane; the mixed water solution of FeCl3 and glacial acetic acid, and normal butanol are added to prepare reversed phase microemulsion of FeCl3; then, the mixed solution of LiFePO4 and acetic anhydride salt is added; FePO4 particles in nanometer scales are precipitated out by a microreactor of microemulsion; finally, through Lil to insert lithium, the nanometer LiFePO4 powder is obtained. The present invention has the advantages of low synthesis temperature, small particle diameter of composite materials, large specific surface area and high activity, and overcomes the defects of the prior art of large particles, large particle distribution, etc. which are caused by high temperature calcination. The LiFePO4 powder materials are nanometer level particles, and have the advantages of narrow particle distribution, high purity and uniform distribution; the LiFePO4 nanometer powder material can effectively solve the problem that the diffusion rate of lithium ions in the positive material of lithium cells, and is suitable for manufacturing lithium ion cells.

Description

A kind of employing reversed phase lithium inserting process prepares polycrystalline LiFePO 4The method of nano-powder material

Technical field

The invention belongs to field of nano material preparation, particularly a kind of employing reversed phase lithium inserting process prepares polycrystalline LiFePO ₄The method of nano-powder material.

Background technology

LiFePO ₄That material has is cheap, nontoxic, nonhygroscopic, Environmental compatibility is fine, rich in mineral resources, characteristics such as capacity is higher (theoretical capacity is 170mAh/g, and energy density is 550Wh/Kg), stability is fine.It is a kind of anode material of lithium battery substitution material of tool potentiality.Be with a wide range of applications and the very big market demand.At present existing several synthetic methods:

Solid-phase synthesis: JP2000294238 is with ferrous oxalate, and lithium carbonate and diammonium hydrogen phosphate mix the long-time high-temperature calcination in back as parent material.EP1193786 is with lithium phosphate, and ferrous phosphate is the parent material mixed calcining.That the material particle size of this solid phase synthesis distributes is big, electric conductivity is low, needs reserve to handle, and shortcoming such as this method cycle is long, and energy consumption is big.

Hydrothermal synthesis method: Y. Suo Fei human ferrous sulfate, phosphoric acid and lithium hydroxides such as (Shoufeng Yang) are 6.91,120 ℃ at the control pH value and synthesize down as parent material.The powder body material complex procedures that this method is synthetic, and synthetic material contains water-solubility impurity and moisture is more, is unfavorable for the making of lithium ion battery, and the material conductance that this method is synthesized is very little, needs post-processed.

Solution evaporation:, obtain powder body material 500 ℃ of high-temperature process then by evaporating the mixture of water miscible lithium salts, trivalent iron salt and phosphate anion.Shortcomings such as this method synthetic material purity is not high, and temperature is higher, and particle diameter is bigger.Be unfavorable for the modification of the chemical property of material.

Sol-gel process: in water-soluble ferric, the generation that phosphate and lithium salts are avoided precipitating by suitable selection organic complexing agent adds thermosetting colloidal sol and gel, burns till the pretty good powder body material of structural behaviour at last.But the material of this method preparation has the too high shortcoming of phosphorus content.

Employing iron ammonium sulfate such as Prosini and ammonium dihydrogen phosphate and hydrogen peroxide directly generate precipitation, insert lithium then, and be bigger but this synthetic material has purity not high (easily producing an iron oxide) particle, shortcomings such as skewness.

Summary of the invention

The purpose of this invention is to provide a kind of employing reversed phase lithium inserting process and prepare polycrystalline LiFePO ₄The method of nano-powder material is characterized in that: Span80 and Tween80 are made into complexed surfactant ST, slowly add in the normal heptane, then with FeCl ₃Add with the aqueous solution and the n-butanol of glacial acetic acid, be mixed with the reverse microemulsion liquid system.Add NH at last ₄H ₂PO ₄Mixed solution with acetate; Be settled out the FePO of nanoscale by the microreactor of microemulsion ₄Particle; Insert lithium by LiI and obtain nanometer LiFePO at last ₄Powder; Concrete implementation step is:

1). prefabricated required solution and surfactant

With FeCl ₃6H ₂O, NH ₄H ₂PO ₄Add in the deionized water with acetic anhydride salt, be made into 0.01～1.5M solution respectively with standby; 5～10: regulate the ratio of Span80 and Tween80 in 1 the volume ratio scope, the HLB of mixed system is equated with the HLB of normal heptane, then the mixed system of gained is needed complexed surfactant ST;

2). at FeCl ₃Add volume ratio (10-30) in the solution: 1 glacial acetic acid is as bulking agent;

3). get normal heptane and place beaker in right amount, stir down slowly adding surfactant ST, then with FeCl ₃The aqueous solution dropwise add, measure an amount of n-butanol, dropwise add solution system, clarify until solution system;

4). with NH ₄H ₂PO ₄With acetic anhydride salt volume ratio (10～40): 1 mixed solution slowly splashes into FeCl ₃Reverse micro emulsion in, the powerful stirring, solution system occurs till the white emulsion.With the solution system heating, isolate water and oil phase, with the water acetone that obtains, soaked in absolute ethyl alcohol is filtered then, then with washed with de-ionized water for several times;

5). 200～400 ℃ of following preliminary treatment precipitations.Material after handling is soaked in the LiI solution of 1M, takes out then with washed with de-ionized water for several times, vacuum degree is vacuumize under 1～5Pa afterwards.

6). final material places black-fead crucible, 100～800 ℃ of down calcinings and obtain structural behaviour LiFePO preferably under the inert atmosphere ₄Nano-powder material.

Described acetic anhydride salt is: lithium acetate, sodium acetate, potassium acetate.

Beneficial effect of the present invention is:

(1) be that surfactant, glacial acetic acid are that bulking agent has prepared FeCl with ST ₃The reverse microemulsion system.It is tiny that the sediment that generates in the nanoscale reaction compartment that the reverse microemulsion system provides has a particle, big, the active advantages of higher of specific surface, so the system firing temperature is low, having solved high temperature, to burn till the particle that brings thick, shortcoming such as it is bigger to distribute.

(2) because bulking agent brings more H ⁺Ion causes FeCl ₃With NH ₄H ₂PO ₄Precipitation reaction does not take place.The present invention has suppressed generation H by introducing acetic anhydride salt ⁺The ionization of ion makes FePO ₄Precipitation can be stablized, and generates rapidly.

(3) LiFePO ₄Nano-powder material is a nano-scale particle, is evenly distributed, and is to solve the very little committed step of lithium ion diffusion rate in the anode material of lithium battery effectively.

Description of drawings:

Fig. 1 is the FePO of reversed phase lithium inserting process preparation ₄XRD figure spectrum.

Fig. 2 is LiFePO ₄The XRD figure spectrum of material.

Fig. 3, Fig. 4, Fig. 5 are the TEM figure of reversed phase lithium inserting process synthetic material.

Embodiment

The present invention prepares polycrystalline LiFePO for a kind of employing reversed phase lithium inserting process ₄The method of nano-powder material.Span80 and Tween80 are made into complexed surfactant ST slowly add in the normal heptane, add FeCl ₃Prepare FeCl with the mixed water solution and the n-butanol of glacial acetic acid ₃Reverse microemulsion liquid; Add NH then ₄H ₂PO ₄With the mixed solution of acetic anhydride salt, utilize the microreactor of microemulsion to be settled out FePO with nanoscale ₄Particle (as shown in Figure 1); Insert lithium by LiI and obtain nanometer LiFePO at last ₄Powder (as Fig. 3, Fig. 4, shown in Figure 5); Concrete implementation step is:

1). prefabricated required solution and surfactant

With FeCl ₃6H ₂O, NH ₄H ₂PO ₄Add in the deionized water with acetic anhydride salt, be made into 0.01～1.5M solution respectively with standby.With Span80 and Tween80 5～10: mix in 1 the volume ratio scope, by regulating the ratio of Span80 and Tween80, make the HLB (hydrophilic lipophilic balance) of mixed system equate with the HLB of normal heptane, then the mixed system of gained is needed complexed surfactant ST.

2). at FeCl ₃Add volume ratio (10-30) in the solution: 1 glacial acetic acid is as bulking agent.

3). get the some beakers that place of normal heptane, stir down slowly adding surfactant ST, then with FeCl ₃The aqueous solution dropwise add.Measure an amount of n-butanol, dropwise add solution system, clarify until solution system.

4). with NH ₄H ₂PO ₄Volume ratio (10～40) with acetic anhydride salt: 1 mixed solution slowly splashes into FeCl ₃Reverse micro emulsion in, the powerful stirring, white emulsion appears in solution system.With solution system heating, isolate water and oil phase, the water that obtains is filtered after with solvent acetone or soaked in absolute ethyl alcohol, then for several times with washed with de-ionized water.

5). 200～400 ℃ of following preliminary treatment precipitations.Material after handling being soaked in the LiI solution of 1M, taking out then with after the washed with de-ionized water several, is vacuumize under 1～5Pa in vacuum degree.

6). final material places black-fead crucible, 100～800 ℃ of down calcinings and obtain LiFePO under the inert atmosphere ₄Nano-powder material.

Below by embodiment, further specify the present invention.

Embodiment 1:

Measure normal heptane 500ml and place beaker, adopt electromagnetic agitation, slowly add 120 gram surfactant ST.Measure the FeCl of 1.5M ₃Aqueous solution 40ml drips glacial acetic acid 1.5mL, will mix then in the oil phase liquid that liquid dropwise adds normal heptane, and evenly the solution after is orange red turbid liquid.Measure n-butanol 13ml, dropwise add turbid liquid, then liquid is Clear ﹠ Transparent gradually, finally forms W/O micro emulsion liquid.NH with 60ml, 1.5M ₄H ₂PO ₄Evenly mixed with the SAS of 15ml, 0.5M, evenly slowly add with buret, solution system becomes white emulsus dispersion soln system at last by the orange red transparent orange red muddiness that becomes gradually.Heated solution system to 70 ℃ also is incubated 10min, and the solution system profit separately.With the acetone washing, soak water, collecting precipitation then.300 ℃ drying precipitated 12 hours, Figure 1 shows that FePO ₄The XRD figure spectrum of precipitation.Wherein (100), (101), (003), (012), (110), (104), (112), (200), (114), (024) and diffraction maximums such as (212) are FePO ₄The characteristic peak of material.Then material is immersed among the LiI of 1M after 24 hours, filters washing and collecting precipitation.To finally precipitate 100 ℃ of vacuum dryings.Figure 2 shows that the XRD figure spectrum of material, wherein (121), (131), (211), (022), (011) and (020) are the TEM picture of characteristic peak Fig. 3 of LiFePO4 for material.

Embodiment 2:

Measure normal heptane 500ml and place beaker, adopt electromagnetic agitation, slowly add 120 gram surfactant ST.Measure the FeCl of 0.1M ₃Aqueous solution 40ml drips glacial acetic acid 2.5mL, in the oil phase liquid that the system that will mix then dropwise adds normal heptane, treats that evenly back solution is orange red turbid liquid.Measure n-butanol 5ml, dropwise add turbid liquid, then system is Clear ﹠ Transparent gradually, finally forms W/O micro emulsion liquid.NH with 80ml 0.8M ₄H ₂PO ₄Evenly mixed with 20ml 0.8M lithium acetate solution, evenly slowly add with buret, solution becomes the solution system that white emulsus is disperseed at last by the orange red transparent orange red muddiness that becomes gradually.Heating systems to 70 ℃ also is incubated 10min, and the solution system profit separately.With acetone washing, soak water, collecting precipitation then, 300 ℃ are drying precipitated 12 hours.Then material is immersed among the LiI of 1M after 24 hours, filters washing and collecting precipitation.To finally precipitate vacuum drying and change in the atmosphere furnace, 550 ℃ of insulations obtained LiFePO in 1 hour ₄Nano-powder.The TEM picture of material as shown in Figure 4.

Embodiment 3:

Measure normal heptane 500ml and place beaker, adopt electromagnetic agitation, slowly add 120 gram surfactant ST.Measure the FeCl of 0.05M ₃Aqueous solution 40ml drips glacial acetic acid 4mL, will mix then in the oil phase liquid that liquid dropwise adds normal heptane, and then liquid is Clear ﹠ Transparent gradually, final directly formation W/O micro emulsion liquid.With 60ml 1M NH ₄H ₂PO ₄Mixed evenly with 30ml 1M liquor kalii acetici, evenly slowly add with buret, solution is by the orange red transparent orange red muddiness that becomes gradually, becomes white milky dispersion system at last.Heating liquid to 70 ℃ also is incubated 10min, and the system profit separately.Use absolute ethanol washing, soak water, collecting precipitation then, 300 ℃ are drying precipitated 12 hours.Then material is immersed among the LiI of 1M after 24 hours, filters washing and collecting precipitation.To finally precipitate vacuum drying and change in the atmosphere furnace, 600 ℃ of insulations obtained LiFePO in 1 hour ₄Nano-powder.The TEM picture of material as shown in Figure 5.

Preparation process time of the present invention is short, and firing temperature is low, and energy consumption is low, and is pollution-free; Oil phase material can utilize by secondary again; The polycrystalline LiFePO of preparation ₄It is tiny that powder has a particle, evenly, directly burns till under inert atmosphere, can obtain the powder body material of particle diameter tens nanometers.Adjustable between 100 ℃～800 ℃ of the synthesis temperatures.The present invention has that synthesis temperature is low, the synthetic material particle diameter is little, distribution of particles is narrow, purity is high, the material specific area is big, is fit to make lithium ion battery.

Claims (2)

1. one kind is adopted reversed phase lithium inserting process to prepare polycrystalline LiFePO ₄The method of nano-powder material is characterized in that: Span80 and Tween80 are made into complexed surfactant ST, slowly add in the normal heptane, then with FeCl ₃Add with the aqueous solution and the n-butanol of glacial acetic acid, be mixed with the reverse microemulsion liquid system, add NH at last ₄H ₂PO ₄Mixed solution with acetate; Be settled out the FePO of nanoscale by the microreactor of microemulsion ₄Particle; Insert lithium by LiI and obtain nanometer LiFePO at last ₄Powder; Concrete implementation step is:

1). prefabricated required solution and surfactant

With FeCl ₃6H ₂O, NH ₄H ₂PO ₄Add in the deionized water with acetic anhydride salt, be made into 0.01～1.5M solution respectively with standby; 5～10: regulate the ratio of Span80 and Tween80 in 1 the volume ratio scope, the HLB of mixed system is equated with the HLB of normal heptane, then the mixed system of gained is needed complexed surfactant ST;

2). at FeCl ₃Add volume ratio (10-30) in the solution: 1 glacial acetic acid is as bulking agent;

3). get normal heptane and place beaker in right amount, stir down slowly adding surfactant ST, then with FeCl ₃The aqueous solution dropwise add, measure an amount of n-butanol, dropwise add solution system, clarify until solution system;

4). with NH ₄H ₂PO ₄With acetic anhydride salt volume ratio (10～40): 1 mixed solution slowly splashes into FeCl ₃Reverse micro emulsion in, the powerful stirring, solution system occurs till the white emulsion, with the solution system heating, isolates water and oil phase, the water that obtains is filtered then with acetone or soaked in absolute ethyl alcohol, then with washed with de-ionized water for several times;

5). 200～400 ℃ of following preliminary treatment precipitations, the material after handling is soaked in the LiI solution of 1M, takes out then with washed with de-ionized water for several times, vacuum degree is vacuumize under 1～5Pa afterwards;

6). final material places black-fead crucible, 100～800 ℃ of down calcinings and obtain LiFePO under the inert atmosphere ₄Nano-powder material.

2. prepare polycrystalline LiFePO according to the described employing reversed phase lithium inserting process of claim 1 ₄The method of nano-powder material is characterized in that: described acetic anhydride salt is lithium acetate, sodium acetate or potassium acetate.

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