CN102790214B - Method for preparing lithium iron phosphate - Google Patents
Method for preparing lithium iron phosphate Download PDFInfo
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- CN102790214B CN102790214B CN201210290313.6A CN201210290313A CN102790214B CN 102790214 B CN102790214 B CN 102790214B CN 201210290313 A CN201210290313 A CN 201210290313A CN 102790214 B CN102790214 B CN 102790214B
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Abstract
The invention relates to a method for preparing lithium iron phosphate and belongs to the technical field of preparation for an anode material of a lithium ion battery. The invention solves the technical problem of providing the low-cost method for preparing the lithium iron phosphate. The method for preparing the lithium iron phosphate provided by the invention comprises the following steps: a) taking 0.8-1.2 parts of lithium carbonate and 1.6-2.4 parts of ammonium phosphate by molar fractions, adding water for dissolving and uniformly mixing; taking 0.16-0.24 parts of reducing agent, adding water for dissolving, adding ferrous salt with the same molar fractions with the ammonium phosphate in the solution, and uniformly mixing; mixing the solutions, adjusting pH value of the mixed solutions to 6.5-7.5, stirring, and fully reacting at 90-100 DEG C, thereby obtaining a packaged precipitate precursor, wherein the reducing agent is at least one of ascorbic acid, glucose, cane sugar and hydrazine hydrate; b) causing the packaged precipitate precursor to react for 4-16h at 120-180 DEG C under a sealing condition; and c) cooling, filtering, washing till no SO4<2-> is detected, thereby obtaining a filter cake, and then drying the filter cake, thereby obtaining the lithium iron phosphate.
Description
Technical field
The present invention relates to prepare the method for LiFePO4, belong to anode material for lithium-ion batteries preparing technical field.
Background technology
Lithium ion battery is as a kind of high-performance secondary cell of environmental protection, there is the advantages such as energy density is high, average output voltage is high, power output is large, self discharge is little, efficiency for charge-discharge is high, memory-less effect, in various portable type electronic products, communication tool, electric automobile and hybrid vehicle, more and more applied.Lithium ion battery is since commercialization, and the research of positive electrode is the focus of this area research all the time.At present, commercial anode material for lithium-ion batteries has LiCoO
2, LiNiO
2and LiMn
2o
4deng, LiCoO
2the capacity of positive electrode is higher, have extended cycle life, but cobalt resource is deficient, expensive; LiNiO
2there is safety issue and synthetic very difficult; LiMn
2o
4cycle performance and high-temperature stability await strengthening, therefore, the positive electrode of development of new high energy cheapness is most important to the development of lithium battery.
Since U.S. Goodenough group in 1997 finds that LiFePO 4 material can be used as anode material for lithium-ion batteries, because it has cheap, security performance and the plurality of advantages such as thermal stability is good, pollution-free and specific energy is high, launched research widely both at home and abroad.Synthesis technique is the key of preparing material, and the optimization of process route and process conditions has decisive influence to the performance of material.At present, large-scale industrial is produced LiFePO
4technique be mainly solid reaction process and wet chemistry method.Application number US 2003007514, CN1581537A, CN1767258A have all reported the solid reaction process of preparing LiFePO 4 material, but the powder granule that solid reaction process makes is large and distribution is wide, impurity content is high and fluctuation large, affected to a certain extent the performance of material, these deficiencies are restricting the application of solid-phase synthesis in synthesizing iron lithium phosphate material.In order to address the above problem, Many researchers has been carried out the research of wet chemistry method synthesizing iron lithium phosphate, wherein hydro thermal method is because having reaction condition gentleness, raw material can be realized molecular level and mix in liquid phase, avoided forming hard aggregation because of high temperature sintering, the plurality of advantages such as prepared material granule good dispersion, granule size is controlled, be the method that wet chemistry method synthesizing iron lithium phosphate generally adopts, the Chinese invention patent application of application number 200710058353.7,200910019318.3 has been announced the hydro-thermal reaction method of preparing LiFePO 4 material.But, hydro thermal method is prepared the waste that stubborn problem of LiFePO 4 material is exactly lithium salts at present, in order to obtain pure iron phosphate powder, the lithium salts that must add excessive two times, although have and report and can reclaim lithium salts residual in filtrate, have the shortcoming that the lithium salts purity reclaiming is not high and technique is too complicated.
Summary of the invention
Technical problem to be solved by this invention is to provide a kind of method of preparing LiFePO4 that cost is lower.
The method that the present invention prepares LiFePO4 comprises the steps:
A, by molar part, get 1.6～2.4 parts of the ammonium salts of 0.8～1.2 part of lithium carbonate, phosphoric acid, be dissolved in water, mix; Separately get 0.16～0.24 part of reducing agent, be dissolved in water, and in solution, add the ferrous salt with the identical molar part of ammonium salt of phosphoric acid, mix; Then above-mentioned solution is mixed, and regulate mixed pH to 6.5～7.5, stir, make it in 90～100 ℃ of fully reactions, obtain coprecipitation coating presoma; Wherein, wherein, described reducing agent is at least one (reducing agent is preferably ascorbic acid) in ascorbic acid, glucose, sucrose, hydrazine hydrate;
B, by coprecipitation coating presoma under airtight condition, 120～180 ℃ reaction 4～16h;
C, cooling, filters, washs extremely without SO
4 2-till being detected, obtain filter cake, filtration cakes torrefaction, obtains LiFePO4.
Wherein, for the cost that economizes in raw materials, in a step of said method, by molar part, lithium carbonate is preferably 1 part, the ammonium salt of phosphoric acid and is preferably 2 parts, and reducing agent is preferably 0.2 part.
The inventive method is usingd the lithium source of insoluble lithium salts lithium carbonate as synthesizing iron lithium phosphate, ferrous salt is source of iron, the ammonium salt of phosphoric acid is as phosphorus source, first adopt the synthetic precipitation of coating precipitation method presoma, then precipitate presoma through hydro-thermal reaction synthesizing iron lithium phosphate powder, this is than current employing soluble lithium compounds (lithium sulfate, lithium hydroxide etc.) during as the lithium source of hydro-thermal reaction, adopt the consumption that can save 2/3 lithium salts over the lithium (normally Li:Fe:P mol ratio is 3:1:1) of theoretical consumption, can significantly reduce the production cost of LiFePO4.
Wherein, the ammonium salt of the phosphoric acid described in the inventive method can in ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate at least one; Described ferrous salt can be conventional ferrous salt, is preferably at least one in ferrous sulfate, iron ammonium sulfate, six ferrous sulfate hydrate ammoniums.
Wherein, in order to improve the quality of products, in above-mentioned a step, the average grain diameter of the lithium carbonate adding is preferably 0.8～1.2 μ m; The average grain diameter of the lithium carbonate adding most preferably is 1 μ m.The particle diameter of the lithium iron phosphate particles making is like this distributed as 100～1000nm, has realized material sub-micron, has improved specific area, has increased diffuse interface area, has shortened Li simultaneously
+at the evolving path of granule interior, thereby improved the utilance of LiFePO4 active material.
Wherein, in a step of said method, the ammonium salt concentration of the phosphoric acid after the ammonium salt of lithium carbonate, phosphoric acid is dissolved in water in gained solution is preferably 0.4～3.2mol/L; The be dissolved in water ferrous ion concentration of gained solution of ferrous salt is preferably 0.2～1.6mol/L.
Wherein, in a step of said method, preferably adopt ammoniacal liquor to regulate mixed pH.
Wherein, in the c step of the inventive method, can adopt usual manner washing, in order to save washing cost and to improve clean result, mode of washing is preferably first uses deionized water pulp washing 2～3 times, then uses absolute ethyl alcohol pulp washing 1 time.
Wherein, in the c step of said method, filter cake is preferable over 110～130 ℃ of vacuumize 1.5～2.5h, obtains LiFePO4.
The inventive method has following beneficial effect:
1, the inventive method is usingd the lithium source of insoluble lithium salts lithium carbonate as synthesizing iron lithium phosphate, ferrous salt is as source of iron, the ammonium salt of phosphoric acid is as phosphorus source, first adopt the synthetic precipitation of coating precipitation method presoma, then precipitate presoma through hydro-thermal reaction synthesizing iron lithium phosphate powder, this adopts during as the lithium source of hydro-thermal reaction the lithium (normally Li:Fe:P mol ratio is 3:1:1) that surpasses theoretical consumption can save the consumption of 2/3 lithium salts than take at present solubility lithium compound (lithium sulfate, lithium hydroxide etc.), can significantly reduce the cost of LiFePO4.
The particle diameter of the lithium iron phosphate particles that 2, prepared by the inventive method is distributed as 100nm～1000nm, has realized material sub-micron, has improved specific area, has increased diffuse interface area, has shortened Li simultaneously
+at the evolving path of granule interior, thereby improved the utilance of LiFePO4 active material.
3, the inventive method has solved the not high problem of lithium salts utilance in current Hydrothermal Synthesis LiFePO4 solution effectively, has reduced waste and the discharge of lithium salts, meets the requirement of environmental protection, this process route is simple simultaneously, easy to operate, and with low cost, be applicable to suitability for industrialized production.
Accompanying drawing explanation
The X-ray diffracting spectrum of Fig. 1 product, wherein, A is embodiment 2, and B is embodiment 5, and C is embodiment 6.
The stereoscan photograph of Fig. 2 product (embodiment 1).
The stereoscan photograph of Fig. 3 product (embodiment 2).
Embodiment
The method that the present invention prepares LiFePO4 comprises the steps:
A, by molar part, get 1.6～2.4 parts of the ammonium salts of 0.8～1.2 part of lithium carbonate, phosphoric acid, be dissolved in water, mix; Separately get 0.16～0.24 part of reducing agent, be dissolved in water, and in solution, add the ferrous salt with the identical molar part of ammonium salt of phosphoric acid, mix; Then above-mentioned solution is mixed, and regulate mixed pH to 6.5～7.5, stir, make it in 90～100 ℃ of fully reactions, obtain coprecipitation coating presoma; Wherein, wherein, described reducing agent is at least one (reducing agent is preferably ascorbic acid) in ascorbic acid, glucose, sucrose, hydrazine hydrate;
B, by coprecipitation coating presoma under airtight condition, 120～180 ℃ reaction 4～16h;
C, cooling, filters, washs extremely without SO
4 2-till being detected, obtain filter cake, filtration cakes torrefaction, obtains LiFePO4.
Wherein, for the cost that economizes in raw materials, in a step of said method, by molar part, lithium carbonate is preferably 1 part, the ammonium salt of phosphoric acid and is preferably 2 parts, and reducing agent is preferably 0.2 part.
The inventive method is usingd the lithium source of insoluble lithium salts lithium carbonate as synthesizing iron lithium phosphate, ferrous salt is source of iron, the ammonium salt of phosphoric acid is as phosphorus source, first adopt the synthetic precipitation of coating precipitation method presoma, then precipitate presoma through hydro-thermal reaction synthesizing iron lithium phosphate powder, this is than current employing soluble lithium compounds (lithium sulfate, lithium hydroxide etc.) during as the lithium source of hydro-thermal reaction, adopt the consumption that can save 2/3 lithium salts over the lithium (normally Li:Fe:P mol ratio is 3:1:1) of theoretical consumption, can significantly reduce the production cost of LiFePO4.
Wherein, the ammonium salt of the phosphoric acid described in the inventive method can in ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate at least one; Described ferrous salt can be conventional ferrous salt, is preferably at least one in ferrous sulfate, iron ammonium sulfate, six ferrous sulfate hydrate ammoniums.
Wherein, in order to improve the quality of products, in above-mentioned a step, the average grain diameter of the lithium carbonate adding is preferably 0.8～1.2 μ m; The average grain diameter of the lithium carbonate adding most preferably is 1 μ m.The particle diameter of the lithium iron phosphate particles making is like this distributed as 100～1000nm, has realized material sub-micron, has improved specific area, has increased diffuse interface area, has shortened Li simultaneously
+at the evolving path of granule interior, thereby improved the utilance of LiFePO4 active material.
Wherein, in a step of said method, the ammonium salt concentration of the phosphoric acid after the ammonium salt of lithium carbonate, phosphoric acid is dissolved in water in gained solution is preferably 0.4～3.2mol/L; The be dissolved in water ferrous ion concentration of gained solution of ferrous salt is preferably 0.2～1.6mol/L.
Wherein, in a step of said method, preferably adopt ammoniacal liquor to regulate mixed pH.
Wherein, in the c step of the inventive method, can adopt usual manner washing, in order to save washing cost and to improve clean result, mode of washing is preferably first uses deionized water pulp washing 2～3 times, then uses absolute ethyl alcohol pulp washing 1 time.
Wherein, in the c step of said method, filter cake is preferable over 110～130 ℃ of vacuumize 1.5～2.5h, obtains LiFePO4.
Below in conjunction with embodiment, the specific embodiment of the present invention is further described, does not therefore limit the present invention among described scope of embodiments.
Embodiment 1
(1) coprecipitation coating presoma is synthetic
Accurately take and analyze pure level Li
2cO
3, (NH
4)
2fe (SO
4)
26H
2o, (NH
4)
2hPO
4with each 0.369g(0.005mol of Vc), 3.921g (0.01mol), 1.320g (0.01mol), 0.176g (0.001mol).The reactor of synthetic presoma is placed in to heated at constant temperature magnetic agitation water-bath, when the temperature stabilization of water-bath is during at 100 ℃, in reactor, adds reactant carbonic acid lithium solid, then add ammonium dibasic phosphate solution (by (NH taking
4)
2hPO
4be dissolved in 20mL deionized water), under magnetic agitation effect, make two kinds of reactants be uniformly mixed into slurry, then add the solution ((NH taking of six ferrous sulfate hydrate ammoniums
4)
2fe (SO
4)
26H
2o is dissolved in 40mL deionized water, adds the Vc taking simultaneously), the pH value of adjusting suspension-turbid liquid, makes it be stabilized in pH=7, and stir 3 minutes under magnetic stirring apparatus effect, obtains uniform coprecipitation coating presoma.
(2) hydrothermal synthesis reaction
The coprecipitation coating presoma that (1) step is obtained is transferred to hydrothermal reaction kettle, and sealing hydrothermal reaction kettle, is placed in baking oven, in 180 ℃ of reaction 16h.
(3) the washing of product, filtration and dry
After (2) step completes, hydrothermal reaction kettle is shifted out to baking oven, be cooled to room temperature, open hydrothermal reaction kettle, product is filtered, twice of deionized water pulp washing of the filter cake obtaining, absolute ethyl alcohol pulp washing one time, again filter and obtain pure filter cake, last filter cake, in 120 ℃ of vacuumize 2h, obtains 1.460g canescence LiFePO4 product.
X-ray diffraction spectrogram and the LiFePO of this example product
4standard spectrogram (JCPDS card 40-1499) contrast, in the XRD spectra of product, there is no the diffraction maximum of impurity, simultaneously from the half-peak breadth at spectrum peak compared with I to find out that obtaining LiFePO4 product has higher degree of crystallinity.
Embodiment 2
(1) coprecipitation coating presoma is synthetic
Accurately take and analyze pure level Li
2cO
3, (NH
4)
2fe (SO
4)
26H
2o, (NH
4)
2hPO
4with each 1.478g of Vc (0.02mol), 15.686g (0.04mol), 5.282g (0.04mol), 0.704g (0.004mol).The reactor of synthetic presoma is placed in to heated at constant temperature magnetic agitation water-bath, when the temperature stabilization of water-bath is during at 100 ℃, in reactor, adds reactant carbonic acid lithium solid, then add the ammonium dibasic phosphate solution ((NH taking
4)
2hPO
4be dissolved in 20mL deionized water), under magnetic agitation effect, make two kinds of reactants be uniformly mixed into slurry, finally add the solution ((NH taking of six ferrous sulfate hydrate ammoniums
4)
2fe (SO
4)
26H
2o is dissolved in 40mL deionized water, adds the Vc taking simultaneously), the pH value of adjusting suspension-turbid liquid, makes it be stabilized in pH=7, and it is stirred 3 minutes under magnetic stirring apparatus effect, obtains uniform coprecipitation coating presoma.
(2) hydrothermal synthesis reaction
The coprecipitation coating presoma that (1) step is obtained is transferred to hydrothermal reaction kettle, and sealing hydrothermal reaction kettle, is placed in baking oven, in 180 ℃ of reaction 16h.
(3) the washing of product, filtration and dry
After (2) step completes, hydrothermal reaction kettle is shifted out to baking oven, be cooled to room temperature, open hydrothermal reaction kettle, product is filtered, twice of deionized water pulp washing of the filter cake obtaining, absolute ethyl alcohol pulp washing one time, again filter and obtain pure filter cake, last filter cake, in 120 ℃ of vacuumize 2h, obtains 5.782g canescence iron phosphate powder.
X-ray diffraction spectrogram and the LiFePO of this example product
4standard spectrogram (JCPDS card 40-1499) contrast, in the XRD spectra of product, there is no the diffraction maximum of impurity, simultaneously from the half-peak breadth at spectrum peak compared with I to find out that obtaining LiFePO4 product has higher degree of crystallinity.
Embodiment 3
(1) coprecipitation coating presoma is synthetic
Accurately take and analyze pure level Li
2cO
3, (NH
4)
2fe (SO
4)
26H
2o, (NH
4)
2hPO
4with each 2.956g of Vc (0.04mol), 31.371g (0.08mol), 10.564g (0.08mol), 1.408g (0.00mol).The reactor of synthetic presoma is placed in to heated at constant temperature magnetic agitation water-bath, when the temperature stabilization of water-bath is during at 100 ℃, in reactor, adds reactant carbonic acid lithium solid, then add the ammonium dibasic phosphate solution ((NH taking
4)
2hPO
4be dissolved in 20mL deionized water), under magnetic agitation effect, make two kinds of reactants be uniformly mixed into slurry, finally add the solution ((NH taking of six ferrous sulfate hydrate ammoniums
4)
2fe (SO
4)
26H
2o is dissolved in 40mL deionized water, adds the Vc taking simultaneously), the pH value of adjusting suspension-turbid liquid, makes it be stabilized in pH=7, and it is stirred 3 minutes under magnetic stirring apparatus effect, obtains uniform coprecipitation coating presoma.
(2) hydrothermal synthesis reaction
The coprecipitation coating presoma that (1) step is obtained is transferred to hydrothermal reaction kettle, and sealing hydrothermal reaction kettle, is placed in baking oven, in 180 ℃ of reaction 16h.
(3) the washing of product, filtration and dry
After (2) step completes, hydrothermal reaction kettle is shifted out to baking oven, be cooled to room temperature, open hydrothermal reaction kettle, product is filtered, twice of deionized water pulp washing of the filter cake obtaining, absolute ethyl alcohol pulp washing one time, again filter and obtain pure filter cake, last filter cake, in 120 ℃ of vacuumize 2h, obtains 10.918g canescence iron phosphate powder.
X-ray diffraction spectrogram and the LiFePO of this example product
4standard spectrogram (JCPDS card 40-1499) contrast, in the XRD spectra of product, there is no the diffraction maximum of impurity, simultaneously from the half-peak breadth at spectrum peak compared with I to find out that obtaining LiFePO4 product has higher degree of crystallinity.
Embodiment 4
(1) coprecipitation coating presoma is synthetic
Accurately take and analyze pure level Li
2cO
3, (NH
4)
2fe (SO
4)
26H
2o, (NH
4)
2hPO
4with each 0.478g of Vc (0.02mol), 15.686g (0.04mol), 5.282g (0.04mol), 0.704g (0.004mol).The reactor of synthetic presoma is placed in to heated at constant temperature magnetic agitation water-bath, when the temperature stabilization of water-bath is during at 100 ℃, in reactor, adds reactant carbonic acid lithium solid, then add the ammonium dibasic phosphate solution ((NH taking
4)
2hPO
4be dissolved in 20mL deionized water), under magnetic agitation effect, make two kinds of reactants be uniformly mixed into slurry, finally add the solution ((NH taking of six ferrous sulfate hydrate ammoniums
4)
2fe (SO
4)
26H
2o is dissolved in 40mL deionized water, adds the Vc taking simultaneously), the pH value of adjusting suspension-turbid liquid, makes it be stabilized in pH=7, and makes it under magnetic stirring apparatus, act on stirring 3 minutes, obtains uniform coprecipitation coating presoma.
(2) hydrothermal synthesis reaction
The coprecipitation coating presoma that (1) step is obtained is transferred to hydrothermal reaction kettle, and sealing hydrothermal reaction kettle, is placed in baking oven, in 120 ℃ of reaction 16h.
(3) the washing of product, filtration and dry
After (2) step completes, hydrothermal reaction kettle is shifted out to baking oven, be cooled to room temperature, open hydrothermal reaction kettle, product is filtered, twice of deionized water pulp washing of the filter cake obtaining, absolute ethyl alcohol pulp washing one time, again filter and obtain pure filter cake, last filter cake, in 120 ℃ of vacuumize 2h, obtains 6.071g canescence iron phosphate powder.
X-ray diffraction spectrogram and the LiFePO of this example product
4standard spectrogram (JCPDS card 40-1499) contrast, in the XRD spectra of product, there is no the diffraction maximum of impurity, from the half-peak breadth at spectrum peak, can find out that more greatly to obtain the degree of crystallinity of LiFePO4 product not high enough.
Embodiment 5
(1) coprecipitation coating presoma is synthetic
Accurately take and analyze pure level Li
2cO
3, (NH
4)
2fe (SO
4)
26H
2o, (NH
4)
2hPO
4with each 0.478g of Vc (0.02mol), 15.686g (0.04mol), 5.282g (0.04mol), 0.704g (0.004mol).The reactor of synthetic presoma is placed in to heated at constant temperature magnetic agitation water-bath, when the temperature stabilization of water-bath is during at 100 ℃, in reactor, adds reactant carbonic acid lithium solid, then add the ammonium dibasic phosphate solution ((NH taking
4)
2hPO
4be dissolved in 20mL deionized water), under magnetic agitation effect, make two kinds of reactants be uniformly mixed into slurry, finally add the solution ((NH taking of six ferrous sulfate hydrate ammoniums
4)
2fe (SO
4)
26H
2o is dissolved in 40mL deionized water, adds the Vc taking simultaneously), the pH value of adjusting suspension-turbid liquid, makes it be stabilized in pH=7, and makes its lower stirring 3 minutes under magnetic stirring apparatus effect, obtains uniform coprecipitation coating presoma.
(2) hydrothermal synthesis reaction
The coprecipitation coating presoma that (1) step is obtained is transferred to hydrothermal reaction kettle, and sealing hydrothermal reaction kettle, is placed in baking oven, in 180 ℃ of reaction 4h.
(3) the washing of product, filtration and dry
After (2) step completes, hydrothermal reaction kettle is shifted out to baking oven, be cooled to room temperature, open hydrothermal reaction kettle, product is filtered, twice of deionized water pulp washing of the filter cake obtaining, absolute ethyl alcohol pulp washing one time, again filter and obtain pure filter cake, last filter cake, in 120 ℃ of vacuumize 2h, obtains 6.081g canescence iron phosphate powder.
X-ray diffraction spectrogram and the LiFePO of this example product
4standard spectrogram (JCPDS card 40-1499) contrast, in the XRD spectra of product, there is no the diffraction maximum of impurity, simultaneously from the half-peak breadth at spectrum peak compared with I to find out that obtaining LiFePO4 product has higher degree of crystallinity.
Embodiment 6
(1) coprecipitation coating presoma is synthetic
Accurately take and analyze pure level Li
2cO
3, (NH
4)
2fe (SO
4)
26H
2o, (NH
4)
2hPO
4with each 0.478g of Vc (0.02mol), 15.686g (0.04mol), 5.282g (0.04mol), 0.704g (0.004mol).The reactor of synthetic presoma is placed in to heated at constant temperature magnetic agitation water-bath, when the temperature stabilization of water-bath is during at 100 ℃, in reactor, adds reactant carbonic acid lithium solid, then add the ammonium dibasic phosphate solution ((NH taking
4)
2hPO
4be dissolved in 20mL deionized water), under magnetic agitation effect, make two kinds of reactants be uniformly mixed into slurry, finally add the solution ((NH taking of six ferrous sulfate hydrate ammoniums
4)
2fe (SO
4)
26H
2o is dissolved in 40mL deionized water, adds the Vc taking simultaneously), the pH value of adjusting suspension-turbid liquid, makes it be stabilized in pH=7, and it is stirred 3 minutes under magnetic stirring apparatus effect, obtains uniform coprecipitation coating presoma.
(2) hydrothermal synthesis reaction
The coprecipitation coating presoma that (1) step is obtained is transferred to hydrothermal reaction kettle, and sealing hydrothermal reaction kettle, is placed in baking oven, in 180 ℃ of reaction 8h.
(3) the washing of product, filtration and dry
After (2) step completes, hydrothermal reaction kettle is shifted out to baking oven, be cooled to room temperature, open hydrothermal reaction kettle, product is filtered, twice of deionized water pulp washing of the filter cake obtaining, absolute ethyl alcohol pulp washing one time, again filter and obtain pure filter cake, last filter cake, in 120 ℃ of vacuumize 2h, obtains 5.908g canescence iron phosphate powder.
X-ray diffraction spectrogram and the LiFePO of this example product
4standard spectrogram (JCPDS card 40-1499) contrast, in the XRD spectra of product, there is no the diffraction maximum of impurity, simultaneously from the half-peak breadth at spectrum peak compared with I to find out that obtaining LiFePO4 product has higher degree of crystallinity.
Claims (24)
1. the method for preparing LiFePO4, is characterized in that comprising the steps:
A, by molar part, get 1.6～2.4 parts of the ammonium salts of 0.8～1.2 part of lithium carbonate, phosphoric acid, be dissolved in water to the ammonium salt concentration of phosphoric acid be 0.4～3.2mol/L, mix formation slurry; Separately get 0.16～0.24 part of reducing agent, be dissolved in water, and in solution, add the ferrous salt with the identical molar part of ammonium salt of phosphoric acid, mix formation reducing agent/ferrous salt mixed solution; Then above-mentioned slurry is mixed with reducing agent/ferrous salt mixed solution, and regulate mixed suspension-turbid liquid pH value to 6.5～7.5, stir, make it in 90～100 ℃ of fully reactions, obtain coprecipitation coating presoma; Wherein, described reducing agent is at least one in ascorbic acid, glucose, sucrose, hydrazine hydrate;
B, by coprecipitation coating presoma under airtight condition, 120～180 ℃ reaction 4～16h;
C, cooling, filters, washs extremely without SO
4 2-till being detected, obtain filter cake, filtration cakes torrefaction, obtains LiFePO4;
The ammonium salt of described phosphoric acid is at least one in ammonium phosphate, diammonium hydrogen phosphate; Described ferrous salt is at least one in ferrous sulfate, iron ammonium sulfate, six ferrous sulfate hydrate ammoniums.
2. the method for preparing LiFePO4 according to claim 1, is characterized in that: in a step, by molar part, lithium carbonate is that 1 part, the ammonium salt of phosphoric acid are 2 parts, and reducing agent is 0.2 part.
3. the method for preparing LiFePO4 according to claim 1 and 2, is characterized in that: in a step, the average grain diameter of the lithium carbonate adding is 0.8～1.2 μ m.
4. the method for preparing LiFePO4 according to claim 3, is characterized in that: in a step, the average grain diameter of the lithium carbonate adding is 1 μ m.
5. the method for preparing LiFePO4 according to claim 1 and 2, is characterized in that: in a step, in reducing agent/ferrous salt mixed solution, ferrous ion concentration is 0.2～1.6mol/L.
6. the method for preparing LiFePO4 according to claim 3, is characterized in that: in a step, in reducing agent/ferrous salt mixed solution, ferrous ion concentration is 0.2～1.6mol/L.
7. the method for preparing LiFePO4 according to claim 1 and 2, is characterized in that: in a step, adopt ammoniacal liquor to regulate mixed suspension-turbid liquid pH value.
8. the method for preparing LiFePO4 according to claim 3, is characterized in that: in a step, adopt ammoniacal liquor to regulate mixed suspension-turbid liquid pH value.
9. the method for preparing LiFePO4 according to claim 5, is characterized in that: in a step, adopt ammoniacal liquor to regulate mixed suspension-turbid liquid pH value.
10. the method for preparing LiFePO4 according to claim 6, is characterized in that: in a step, adopt ammoniacal liquor to regulate mixed suspension-turbid liquid pH value.
11. methods of preparing LiFePO4 according to claim 1 and 2, is characterized in that: in c step, mode of washing, for first using deionized water pulp washing 2～3 times, is then used absolute ethyl alcohol pulp washing 1 time.
12. methods of preparing LiFePO4 according to claim 3, is characterized in that: in c step, mode of washing, for first using deionized water pulp washing 2～3 times, is then used absolute ethyl alcohol pulp washing 1 time.
13. methods of preparing LiFePO4 according to claim 5, is characterized in that: in c step, mode of washing, for first using deionized water pulp washing 2～3 times, is then used absolute ethyl alcohol pulp washing 1 time.
14. methods of preparing LiFePO4 according to claim 7, is characterized in that: in c step, mode of washing, for first using deionized water pulp washing 2～3 times, is then used absolute ethyl alcohol pulp washing 1 time.
15. methods of preparing LiFePO4 according to claim 8, is characterized in that: in c step, mode of washing, for first using deionized water pulp washing 2～3 times, is then used absolute ethyl alcohol pulp washing 1 time.
16. methods of preparing LiFePO4 according to claim 9, is characterized in that: in c step, mode of washing, for first using deionized water pulp washing 2～3 times, is then used absolute ethyl alcohol pulp washing 1 time.
17. methods of preparing LiFePO4 according to claim 10, is characterized in that: in c step, mode of washing, for first using deionized water pulp washing 2～3 times, is then used absolute ethyl alcohol pulp washing 1 time.
18. methods of preparing LiFePO4 according to claim 11, is characterized in that: in c step, filter cake, in 110～130 ℃ of vacuumize 1.5～2.5h, obtains LiFePO4.
19. methods of preparing LiFePO4 according to claim 12, is characterized in that: in c step, filter cake, in 110～130 ℃ of vacuumize 1.5～2.5h, obtains LiFePO4.
20. methods of preparing LiFePO4 according to claim 13, is characterized in that: in c step, filter cake, in 110～130 ℃ of vacuumize 1.5～2.5h, obtains LiFePO4.
21. methods of preparing LiFePO4 according to claim 14, is characterized in that: in c step, filter cake, in 110～130 ℃ of vacuumize 1.5～2.5h, obtains LiFePO4.
22. methods of preparing LiFePO4 according to claim 15, is characterized in that: in c step, filter cake, in 110～130 ℃ of vacuumize 1.5～2.5h, obtains LiFePO4.
23. methods of preparing LiFePO4 according to claim 16, is characterized in that: in c step, filter cake, in 110～130 ℃ of vacuumize 1.5～2.5h, obtains LiFePO4.
24. methods of preparing LiFePO4 according to claim 17, is characterized in that: in c step, filter cake, in 110～130 ℃ of vacuumize 1.5～2.5h, obtains LiFePO4.
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| CN103647045A (en) * | 2013-11-15 | 2014-03-19 | 成都兴能新材料有限公司 | Preparation method of cathode material LiFePO4-C |
| CN105680044B (en) * | 2016-03-18 | 2018-03-20 | 王海峰 | A kind of method that hydro-thermal method equimolar prepares LiFePO4 |
| CN108390057A (en) * | 2018-03-07 | 2018-08-10 | 南京理工大学 | The preparation method of additive Mn lithium iron phosphate electrode material |
| CN109244461A (en) * | 2018-10-29 | 2019-01-18 | 张美芳 | The preparation method of LiFePO 4 material |
| CN110600735B (en) * | 2019-09-27 | 2020-11-13 | 东莞理工学院 | Method for preparing lithium iron phosphate cathode material at low cost and application |
| CN110817830A (en) * | 2019-11-30 | 2020-02-21 | 西北有色金属研究院 | Method for preparing lithium iron phosphate electrode material from guanidino raw material |
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| CN101315981A (en) * | 2008-06-16 | 2008-12-03 | 合肥工业大学 | Lithium iron phosphate anode material for lithium ion battery and modification method |
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