CN1278929C - Preparation method of counter opal structure liFePO4 powder - Google Patents

Abstract

The present invention discloses a method for preparing a LiFePO4 powder with a reverse opal structure, which belongs to the preparing field of electrochemical material. The LiFePO4 powder is often used in positive electrode material for energy source batteries. The method for preparing a LiFePO4 powder comprises the steps: first, a poly-emulsion particle suspension solution A using styrene, methyl methacrylate and acrylic acid as raw material and a clear solution B using iron oxalate dihydrate, lithium carbonate and ammonium dihydrogen phosphate as raw materials are respectively prepared; the solution B is dropped into the suspension solution A in drops under the condition of intense stir to be ultrasonically dispersed, and the mixed solution is baked and refined at the temperature of 70 DEG C to be pretreated and sintered into LiFePO4 material with a reverse opal structure. The method for preparing a LiFePO4 powder has the advantages of short time of a preparing process, low sintering temperature, low energy consumption, narrow distribution of the particle size of the prepared polycrystalline LiFePO4 powder and large specific surface area of synthetic material. The LiFePO4 powder can be directly sintered in inert atmosphere or reducing atmosphere without the coating treatment in the later period. The migration rate of the lithium ions of the material in the electrochemical process can be greatly improved.

Description

Counter opal structure LiFePO 4Powder preparation method

Technical field

The invention belongs to the electrochemical material preparation field, particularly a kind of LiFePO that is usually used in a kind of counter opal structure of secondary lithium battery or power source usefulness cell positive material ₄Powder preparation method.

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 big positive electrode material equivalent material of tool potentiality.Be with a wide range of applications and the very big market requirement.Existing several synthetic methods are arranged at present:

1) solid phase method: in Japanese Patent JP2000294238, as raw material, under inert atmosphere, calcine and obtain with Ferrox, Secondary ammonium phosphate and Quilonum Retard.In European patent EP 1193784, with Fe ₃(PO ₄) ₂And Li ₃PO ₄As raw material and add hydrocarbon polymer and carry out solid phase synthesis; The synthetic powder particle is thick, and material electrochemical performance is low.

2) sol-gel method: in the CN1410349 patent, with Fe (Ac) ₂, FeSO ₄7H ₂O, Ba (Ac) ₂And organic acid is a raw material; Technology is comparatively complicated, if process control is improper, introduces Ba easily ²⁺, Fe ³⁺Deng impurity.

3) reversed phase lithium inserting process: in the CN1469499 patent, normal heptane-ST80 system, the microreactor synthesis of nano FePO that utilizes micro emulsion to form ₄, utilize LiI to insert lithium then.This method technical process complexity, the flow process time is longer.

4) spray-drying process: S.L.Bewlay, K.Konstantinov, G.X.Wang waits the people in document " Materials Letters, 58 (11), 2004,1788." in can obtain the material of controllable grain size, technology is simple, but is unfavorable for the improvement of material property.

5) coprecipitation method: G.Arnold, J.Garche, R.Hemmer, et al. is at " Journal ofPower Sources 2003,119-121:247." middle report, this method is introduced impurity easily, is unfavorable for the improvement of material electrochemical performance.

6) emulsion desiccating method: S.T.Myung, S.Komaba, R.Takagai, et al exists., report in " ChemistryLetters, 32 (7), 2003,566 ", this method complicated process of preparation, the flow process time is longer.

7) hydrothermal method: Yang S.F, Zavalij P.Y et al is report in " electrochemistrycommunications.3,2001,505 ", and this method is unfavorable for the improvement of material electrochemical performance.

Summary of the invention

The LiFePO that the purpose of this invention is to provide a kind of counter opal structure ₄Powder preparation method.It is characterized in that: the LiFePO of counter opal structure ₄The processing step of powder preparation method is as follows:

(1) preparation of poly-emulsion particle: with vinylbenzene, methyl methacrylate and vinylformic acid are starting material, according to the quality proportioning is vinylbenzene: methyl methacrylate: vinylformic acid=(15～20): (2～10): (1～5) is evenly mixed, gets 20 grams then and adds 12 milliliters of distilled water, 0.5 gram NH ₄HCO ₃, 0.3 gram ammonium persulphate with 75 ℃ of down reactions 7.5 hours, react letex polymerization in 0.5 hour again after being warming up to 90 ℃ after, form the suspension liquid A of the poly-emulsion particle that has good stability, at 70 ℃ of dry suspension liquids down, and calculate its solid content.

(2) it is ferrous to take by weighing 2 oxalic acid hydrates according to mol ratio: Quilonum Retard: primary ammonium phosphate=1: 0.5: 1 is that violent stirring is to dissolving fully in 10～60% the nitric acid with being dissolved in the quality percentage composition after three kinds of material mixing; Thereby can obtain the xanchromatic settled solution B of 0.1Mol/L and 0.2Mol/L concentration.

(3) according to LiFePO in poly-emulsion particle solid load and the B solution among the suspension liquid A ₄Effective solid load be (1～30): measure suspension liquid A and solution B in 1 scope, dropwise solution B is splashed among the suspension liquid A under brute force stirs, ultra-sonic dispersion is 30～200 minutes afterwards, will mix also refinement of system oven dry 70 ℃ under.

(4) powder after the refinement is packed in the porcelain boat, 400 ℃ of following pre-treatment are burnt till under 550～850 ℃ then under reducing atmosphere or inert atmosphere, and are incubated 8～36 hours under firing temperature, thereby obtain the LiFePO of counter opal structure ₄Material.

The invention has the beneficial effects as follows that preparation process time is short, firing temperature is low, and energy consumption is low; The polycrystalline LiFePO of preparation ₄The diameter of particle narrowly distributing directly burns till at inert atmosphere or under reducing atmosphere, can obtain the LiFePO of the counter opal structure of rigid carbon coating ₄Powder is handled the electronic conductivity that can improve material so need not carry out the coating in later stage; The synthetic materials counter opal structure has very big specific surface area, so can improve material lithium ion rate of migration in electrochemical process to a great extent, and the material diameter of particle is adjustable.

Description of drawings

Fig. 1 is the XRD figure spectrum of present method synthetic materials under the differing temps.

Fig. 2 is the SEM figure of poly-emulsion particle.

Fig. 3 is the SEM figure of present method synthetic materials.

Fig. 4 is the SEM figure of present method synthetic materials.

Fig. 5 is the SEM figure of present method synthetic materials.

Embodiment

The invention provides a kind of LiFePO of counter opal structure ₄Powder preparation method.The processing step of its preparation method is as follows:

(1) preparation of poly-emulsion particle: with vinylbenzene, methyl methacrylate and vinylformic acid are starting material, according to the quality proportioning is vinylbenzene: methyl methacrylate: vinylformic acid=(15～20): (2～10): (1～5) is evenly mixed, gets 20 grams then and adds 12 milliliters of distilled water, 0.5 gram NH ₄HCO ₃, 0.3 gram ammonium persulphate with 75 ℃ of down reactions 7.5 hours, react letex polymerization in 0.5 hour again after being warming up to 90 ℃ after, form the suspension liquid A of the poly-newborn microballoon that has good stability.Dry suspension liquid under 70 ℃, and calculate its solid content.

(2) it is ferrous to take by weighing 2 oxalic acid hydrates according to mol ratio: Quilonum Retard: primary ammonium phosphate=1: 0.5: 1 is in 10～60% the nitric acid with being dissolved in the quality percentage composition after three kinds of material mixing, and violent stirring to dissolving fully gets final product.Thereby can obtain the xanchromatic settled solution B of 0.1Mol/L and 0.2Mol/L concentration.

(3) according to LiFePO in poly-emulsion particle solid load and the B solution among the suspension liquid A ₄Effective solid load be (1～30): measure suspension liquid A and solution B in 1 scope, dropwise solution B is splashed among the suspension liquid A under brute force stirs, ultra-sonic dispersion is 30～200 minutes afterwards, will mix also refinement of system oven dry 70 ℃ under.

(4) powder after the refinement is packed in the porcelain boat, 400 ℃ of following pre-treatment are burnt till under 550～850 ℃ then under reducing atmosphere or inert atmosphere, and are incubated 8～36 hours under firing temperature, thereby obtain the LiFePO of counter opal structure ₄Material.

Below by embodiment, further illustrate outstanding feature of the present invention and marked improvement, only be the present invention is described and never limit the present invention.

Prefabricated poly-emulsion particle suspension liquid:

According to the quality proportioning is vinylbenzene: methyl methacrylate: vinylformic acid=(15～20): (2～10): (1～5) is evenly mixed.Get 20 grams then and add 12 milliliters of distilled water, 0.5 gram NH ₄HCO ₃, 0.3 gram ammonium persulphate with 75 ℃ of down reactions 7.5 hours, be warming up to the suspension liquid A that reacts the poly-emulsion particle that can obtain having good stability in 0.5 hour after 90 ℃ again.Dry suspension liquid under 70 ℃, and calculate its solid content.Figure 2 shows that the SEM image of poly-emulsion particle.

Embodiment 1: it is ferrous to take by weighing 0.05 mole of 2 oxalic acid hydrate respectively, 0.05 mole of phosphoric acid ammonium dihydrogen and 0.025 mole of Quilonum Retard are inserted in the beaker of 100mL, add the 20mL deionized water and stir, dropwise add concentration and be in the nitric acid of 20% (quality percentage composition) till muddy system becomes clarification.Add deionized water then, solution is made into the solution of 0.1Mol/L.Get 50 milliliters of this solution, dropwise add among 50 milliliters of poly-emulsion particle suspension liquid A, and powerful the stirring 10 minutes.Flaxen mixed system is dried down at 70 ℃ after 40 minutes with ultrasonic dispersing.Mixture porphyrize after the oven dry is also crossed 120 mesh sieves.Powder after sieving is inserted in the stove, and 400 ℃ of pre-treatment are 8 hours under nitrogen atmosphere, obtain black porosity and looseness block in 16 hours 600 ℃ of insulations then, and porphyrize obtains LiFePO ₄Powder.Figure 1 shows that the XRD figure spectrum of material, 3 is the SEM figure of this material shown in the figure.

Embodiment 2: it is ferrous to take by weighing 0.05 mole of 2 oxalic acid hydrate respectively, 0.05 mole of phosphoric acid ammonium dihydrogen and 0.025 mole of Quilonum Retard are inserted in the beaker of 100mL, add the 20mL deionized water and stir, dropwise add in the nitric acid of 30% (quality percentage composition) till muddy system becomes clarification.Add deionized water then, solution is made into the solution of 0.2Mol/L.Get 50 milliliters of this solution, dropwise add among 200 milliliters of poly-emulsion particle suspension liquid A, and powerful the stirring 10 minutes.Flaxen mixed system is dried down at 70 ℃ after 40 minutes with ultrasonic dispersing.Mixture porphyrize after the oven dry is also crossed 120 mesh sieves.Powder after sieving is inserted in the atmosphere furnace under nitrogen atmosphere 400 ℃ of pre-treatment 8 hours, obtained black porosity and looseness block in 24 hours 700 ℃ of insulations then, porphyrize obtains LiFePO ₄Powder.Figure 1 shows that the XRD figure spectrum of material, Figure 4 shows that the SEM figure of this material.

Embodiment 3: it is ferrous to take by weighing 0.05 mole of 2 oxalic acid hydrate respectively, 0.05 mole of phosphoric acid ammonium dihydrogen and 0.025 mole of Quilonum Retard are inserted in the beaker of 100mL, add the 20mL deionization and stir, dropwise add in the nitric acid of 60% (quality percentage composition) till muddy system becomes clarification.Add deionized water then, solution is made into the solution of 0.1Mol/L.Get 50 milliliters of this solution, dropwise add among 150 milliliters of poly-emulsion particle suspension liquid A, and powerful the stirring 10 minutes.Flaxen mixed system is dried down at 70 ℃ after 40 minutes with ultrasonic dispersing.Mixture porphyrize after the oven dry is also crossed 120 mesh sieves.Powder after sieving is inserted in the atmosphere furnace under nitrogen atmosphere 400 ℃ of pre-treatment 8 hours, obtained black porosity and looseness block in 16 hours 800 ℃ of insulations then, porphyrize obtains LiFePO ₄Powder.Figure 1 shows that the XRD figure spectrum of material, Figure 5 shows that the SEM figure of this material.

In the XRD figure spectrum of above-mentioned synthetic materials shown in Figure 1, (200), (101), (210), (011), (111), (211), (301), (311), (121), (410), (401), diffraction peaks such as (022) is LiFePO ₄The characteristic peak of material.

Can find out that by above-described embodiment characteristics of the present invention are:

1) with Li⁺，Fe ²⁺And PO₄ ^3-Precursor insert sky between the poly-emulsion particle particle with opal structural In the crack.

2). utilize pretreating process will gather the emulsion particle cracking and form with the counter opal of original inverted configuration and tie Structure.

That 3) utilizes that counter opal structure forms has rationally solved lithium ion migration speed in the material than bigger serface The problem that rate is little.

4) utilize the poly-emulsion particle carbon black that cracking forms in inertia or reducing atmosphere effectively to solve LiFePO₄The problem that the material electronics electrical conductivity is low.

5)Li ⁺，Fe ²⁺And PO₄ ^3-Precursor be in the space that poly-emulsion particle piles up and can effectively stop Fe in the material²⁺Oxidation.

6) the material preparation process is simple, and flow time is of short duration, and the material productive rate is higher.

Claims (1)

1. the LiFePO of a counter opal structure ₄Powder preparation method is characterized in that: the LiFePO of counter opal structure ₄The powder preparing processing step is as follows:

(1) preparation of poly-emulsion particle: with vinylbenzene, methyl methacrylate and vinylformic acid are starting material, according to the quality proportioning is vinylbenzene: methyl methacrylate: vinylformic acid=(15～20): (2～10): (1～5) is evenly mixed, gets 20 grams then and adds 12 milliliters of distilled water, 0.5 gram NH ₄HCO ₃, 0.3 gram ammonium persulphate with 75 ℃ of down reactions 7.5 hours, react letex polymerization in 0.5 hour again after being warming up to 90 ℃ after, the suspension liquid A of the poly-emulsion particle that obtains having good stability at 70 ℃ of dry suspension liquids down, and calculates its solid content;

(2) it is ferrous to take by weighing 2 oxalic acid hydrates according to mol ratio: Quilonum Retard: primary ammonium phosphate=1: 0.5: 1, with being dissolved in the quality percentage composition after three kinds of material mixing is in 10～60% the nitric acid, violent stirring is extremely dissolved fully, thereby can obtain the xanchromatic settled solution B of 0.1Mol/L and 0.2Mol/L concentration;

(3) according to LiFePO in poly-emulsion particle solid load and the B solution among the suspension liquid A ₄Effective solid load be (1～30): measure suspension liquid A and solution B in 1 scope, dropwise solution B is splashed among the suspension liquid A under brute force stirs, ultra-sonic dispersion is 30～200 minutes afterwards, will mix also refinement of system oven dry 70 ℃ under;

(4) powder after the refinement is packed in the porcelain boat, 400 ℃ of following pre-treatment are burnt till under 550～850 ℃ then under reducing atmosphere or inert atmosphere, and are incubated 8～36 hours under firing temperature, thereby obtain the LiFePO of counter opal structure ₄Material.

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