CN103187567B - Preparation method of anode material lithium iron (II) phosphate for lithium ion cell - Google Patents

Preparation method of anode material lithium iron (II) phosphate for lithium ion cell Download PDF

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CN103187567B
CN103187567B CN201110459901.3A CN201110459901A CN103187567B CN 103187567 B CN103187567 B CN 103187567B CN 201110459901 A CN201110459901 A CN 201110459901A CN 103187567 B CN103187567 B CN 103187567B
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lithium
iron
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phosphate
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CN103187567A (en
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张向军
顾远
卢世刚
阚素荣
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China Automotive Battery Research Institute Co Ltd
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Beijing General Research Institute for Non Ferrous Metals
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Abstract

The invention discloses a preparation method of anode material lithium iron (II) phosphate for a lithium ion cell. The preparation method mainly comprises the following two steps: (1) synthesis of precursor Li3Fe2(PO4)3, blending a lithium source, an iron source and a phosphorus source according to that the molar ratio of Li to Fe to P is 3:2:3, taking deionized water, absolute ethanol or acetone as a medium, ball-milling for 0.5-24 h, drying the obtained slurry, thermally treating for 3-24 hours at the temperature of 500-900 DEG C to obtain the precursor Li3Fe2(PO4)3; and (2) blending the obtained precursor Li3Fe2(PO4)3 and iron powder according to the molar ratio of 1:1, taking deionized water, absolute ethanol or acetone as the medium, ball-milling for 0.5-24 h, drying the obtained slurry, placing the dried slurry into a high-temperature furnace, under the atmosphere of inoxidizability, baking the dried slurry for 5-24 h at the temperature of 500-800 DEG C, and at last preparing the lithium iron (II) phosphate material. By adopting the principle that the lithium iron (II) phosphate material is synthesized by oxidation reduction between zero-valent iron and ferric iron source Li3Fe2(PO4)3 at high temperature, firstly, the pure phase Li3Fe2(PO4)3 intermediate is synthesized in advance, and then reacted with the zero-valent iron to synthesize the lithium iron (II) phosphate, so that the reaction process is easy to control. The synthesized product Li3Fe2(PO4)3 is high in chemical purity, good in electrochemical performance and high in batch stability.

Description

A kind of method preparing lithium ferrous phosphate as anode material of lithium ion battery
Technical field
The invention belongs to technical field of energy material, relate to a kind of preparation method of anode material for lithium ion battery LiFePO 4.
Background technology
Lithium ion battery have energy density high, have extended cycle life, the feature such as self discharge is little, memory-less effect, environmental friendliness, small-scale lithium ion cell occupies monopoly status in information terminal product (mobile phone, portable computer, camcorder), its application is extended to the field such as electric tool, LEV (Light Electric Vehicle), hybrid electric vehicle, telecommunications standby electricity, space from mobile phone, notebook at present, has broad application prospects.
LiFePO 4it is one of current more concerned anode material for lithium-ion batteries, have thermal stability high, have extended cycle life, the inexpensive feature such as abundant, environmentally friendly of raw material, be very suitable for the battery applications field very responsive to fail safe, cycle life, power characteristic, use cost etc.Be that the lithium ion battery of positive electrode owing to can meet the performance requirement of current Development of Electric Vehicles in safety, cost, life-span, environmental protection with ferrousphosphate lithium material, it is the preferred material of lithium-ion-power cell of new generation, become the important directions of countries in the world competitively R and D, in recent years, due to the rapid advances of ferrousphosphate lithium material technology, widely applied in electric tool, electric vehicle field.
The synthetic method of lithium iron phosphate cathode material is a lot, mainly comprise carbothermic method, high temperature solid-state method (for being different from carbothermic method, it is that iron material prepares the method for LiFePO 4 by high-temperature heat treatment that the high temperature solid-state method at this place refers in particular to divalent iron salt), microwave process for synthesizing, sol-gal process, molten salt growth method etc., wherein high temperature solid-state method, carbothermic method are the main method of current ferrousphosphate lithium material industrial-scale production.
High temperature solid-state method is with ferrous compound if ferric oxalate is for precursor, and with lithium salts if lithium carbonate, phosphorus source such as ammonium dihydrogen phosphate are that material system prepares the method for LiFePO 4 by high-temperature heat treatment, in course of reaction, iron determination is constant, is divalent.As patent US6,514,640 disclose ferrousphosphate lithium material and preparation method thereof first, adopt the Li of stoichiometrically proportioning 2cO 3(or LiOH), Fe(CH 2cOOH) 2, NH 4h 2pO 4for raw material under an inert atmosphere, be first heated to 300-350 DEG C and remove NH 3, H 2o, CO 2, at 800 DEG C, be then incubated synthesis in 24 hours obtain LiFePO 4.
Carbothermic method is with ferric iron if iron oxide, ferric phosphate are for precursor, is material system with lithium salts, phosphorus source, and the method being prepared LiFePO 4 by carbothermic method under high temperature in the presence of carbon, in course of reaction, iron determination is reduced to divalent by 3 valencys.Ferrousphosphate lithium material and material modified method thereof is prepared as US 6528033 discloses carbon thermal reduction first, di-iron trioxide, ferric phosphate or tri-iron tetroxide is adopted to be the raw material of iron, mix with lithium salts, phosphorus source and carbon, the method for high-temperature process synthesizing lithium ferrous phosphate under inert atmosphere.
In actual building-up process, often find, for ferric phosphate, lithium carbonate, organic carbon source as the reaction system of sucrose, at high temperature carbothermic method is prepared in LiFePO 4 process, can be found (accompanying drawing 1) by powder x-ray diffraction methods analyst, at about 450 DEG C, ferrous phosphate lithium grain starts to be formed, but there is Li simultaneously 3fe 2(PO 4) 3deng the difraction spectrum of material, show to exist in LiFePO 4 forming process to generate Li 3fe 2(PO 4) 3side reaction or competitive reaction; Further raising reaction temperature also extends temperature retention time, Li 3fe 2(PO 4) 3crystal can react further with iron containing compounds, and diffraction maximum will weaken gradually, but finally often more or less there is the dephasign of ferriferous oxide, phosphoric acid lithium salts etc.Document (Feng Yu, Jingjie Zhanga, Reaction mechanism and electrochemical performance of LiFePO 4/ C cathode materials synthesized by carbothermal method [J] .Electrochimica Acta.2009) analysis to the reaction mechanism mechanism of reaction in ferrousphosphate lithium material building-up process, also demonstrate this point, due to the existence of side reaction or competitive reaction, when making synthesizing lithium iron phosphate materials, course of reaction is difficult to control, lot stability is poor, there is impurity or dephasign in product, reduces the chemical property of material.
PCT/US/9706671 discloses Li 3fe 2(PO 4) 3for a kind of doff lithium compound, but lower (the 2.8v vs Li of its discharge platform +/ Li), the lower about 100 ~ 120mAh/g of specific capacity, is difficult to obtain practical application in the secondary lithium battery of high specific energy requirement.The present invention will with Li 3fe 2(PO 4) 3for preparing the intermediate product of LiFePO 4, prepare LiFePO 4 by the redox reaction of itself and fe.
Summary of the invention
The object of this invention is to provide a kind of novel method preparing lithium ferrous phosphate as anode material of lithium ion battery, its course of reaction is easy to control, synthesized product LiFePO 4chemical purity high, chemical property is good, and lot stability is high.
To achieve these goals, the present invention takes following technical scheme:
First presoma Li is synthesized 3fe 2(PO 4) 3, then with iron powder in molar ratio 1:1 prepare burden, by the two redox reaction synthesizing lithium ferrous phosphate under non-oxidizing atmosphere medium and high temperature condition.Comprise the steps:
(1) presoma Li 3fe 2(PO 4) 3synthesis, be that Li:Fe:P=3:2:3 prepares burden, with deionized water, absolute ethyl alcohol or acetone for medium ball milling 0.5-24h, after gained slurry drying in molar ratio by Li source compound, source of iron, P source compound, in 500-900 DEG C, lower heat treatment 3-24 hour under oxidizing atmosphere, obtains presoma Li 3fe 2(PO 4) 3;
(2) the presoma Li obtained 3fe 2(PO 4) 3with iron powder be in molar ratio 1:1 batching, with deionized water, absolute ethyl alcohol or acetone for medium ball milling 0.5-24h, after gained slurry drying, put into high temperature furnace, in non-oxidizing atmosphere, roasting 5-24 hour at 500-800 DEG C, obtained ferrousphosphate lithium material.
Described Li source compound is lithium hydroxide, lithium carbonate, lithium oxalate, lithium acetate, or lithium dihydrogen phosphate.
Described source of iron is iron powder, divalence or ferric oxide (preferred FeO, FeOOH, Fe 2o 3, Fe 3o 4), divalence or ferric nitrate (Fe (NO 3) 2, Fe (NO 3) 3), divalence or ferric acylate (preferred ferric acetate, ferrous acetate, ferric oxalate and ferrous oxalate).
Described P source compound is ammonium dihydrogen phosphate, diammonium hydrogen phosphate, lithium dihydrogen phosphate.
Described ball-milling medium is deionized water, absolute ethyl alcohol or acetone.
Described drying mode can be spraying dry, vacuumize.
Described oxidizing atmosphere is air, oxygen concentration is the mist of 21%-100%.
Described nonoxidizing atmosphere is at least one in nitrogen and argon gas, also can is reducing atmosphere.
In step 1, synthesis presoma Li 3fe 2(PO 4) 3in, the stoichiometry in lithium source, source of iron, phosphorus source is Li:Fe:P=3:2:3 batching in molar ratio.
In step 2, in synthesizing lithium ferrous phosphate, Li 3fe 2pO 3be 1:1 batching with the stoichiometry of iron powder by material mol ratio.
Advantage of the present invention is:
The object of this invention is to provide a kind of novel method preparing LiFePO 4, its basic thought is based on ferric iron source Li 3fe 2(PO 4) 3and redox reaction at high temperature occurs between fe obtain LiFePO 4, without the need to other reducing agent additional, in course of reaction, iron determination becomes divalent from 3 valencys and zeroth order by redox reaction, is different from two patented methods in prior art from reaction principle.
Preparation process comprises two steps, and the first step first synthesizes presoma Li 3fe 2(PO 4) 3be that Li:Fe:P=3:2:3 prepares burden, with deionized water, absolute ethyl alcohol or acetone for medium ball milling 0.5-24h, after gained slurry drying in molar ratio by Li source compound, source of iron, P source compound, heat treatment 3-24 hour at 500-900 DEG C, obtains presoma Li 3fe 2(PO 4) 3; Second step is by obtained presoma Li 3fe 2(PO 4) 3with iron powder be in molar ratio 1:1 batching, with deionized water, absolute ethyl alcohol or acetone for medium ball milling 0.5-24h, after gained slurry drying, put into high temperature furnace, in non-oxidizing atmosphere, roasting 5-24 hour at 500-800 DEG C, obtained ferrousphosphate lithium material.
Another feature of the present invention is Li 3fe 2(PO 4) 3synthesis can oxidation or air atmosphere in carry out, course of reaction be easy to control, be convenient to obtain the persursor material that chemical purity is high, crystal structure is complete; Again by second step process, by Li 3fe 2(PO 4) 3to mix with iron powder by material mol ratio 1:1 and carry out high-temperature process, be easy to chemical constituent and the phase composition of the LiFePO 4 synthesized by controlling, avoid occurring that in single step reaction synthesis, reaction not exclusively, the unmanageable problem of product dephasign.
For improving the electric conductivity of ferrousphosphate lithium material further, can add a small amount of carbon forming agent in step 2 maybe to be mixed with the even ball milling of a small amount of carbonaceous material by the ferrousphosphate lithium material of synthesis, its object is only limitted to the electronic conduction ability improving ferrousphosphate lithium material.
Accompanying drawing explanation
Accompanying drawing 1 is that the alternating temperature XRD of LiFePO 4 building-up process tests spectrogram;
Accompanying drawing 2 is XRD temperature variation testing spectrograms of 400 DEG C, 450 DEG C, 500 DEG C temperature ranges, and wherein illustration is the amplification of the temperature variation testing spectrogram to angle of diffraction 20-40 degree interval;
Accompanying drawing 3 is according to the obtained Li of the inventive method embodiment 1 3fe 2(PO 4) 3xRD spectra;
Accompanying drawing 4 is the XRD spectra according to the obtained ferrousphosphate lithium material of the inventive method embodiment 1;
Accompanying drawing 5 is according to the obtained ferrousphosphate lithium material of the inventive method embodiment 1.
Embodiment
Below in conjunction with case study on implementation and accompanying drawing, the present invention is further detailed:
Accompanying drawing 1 is that the alternating temperature XRD of LiFePO 4 building-up process tests spectrogram, accompanying drawing 2 is the XRD temperature variation testing spectrograms in angle of diffraction 20-40 degree interval at 400 DEG C, 450 DEG C, 500 DEG C temperature, as can be seen from attached Fig. 1 and 2, in 450 DEG C of-500 DEG C of temperature ranges,, when 500 DEG C, there is LiFePO in the XRD spectra generation significant change of reaction system 4and Li 3fe 2(PO 4) 3, Fe 2o 3diffraction maximum.Show LiFePO 4crystal generates temperature about about 500 DEG C; Along with the carbothermic reduction reaction generating LiFePO4, exist simultaneously and generate Li 3fe 2(PO 4) 3side reaction.Along with the rising of reaction temperature, Li 3fe 2(PO 4) 3and Fe 2o 3diffraction maximum die down gradually, LiFePO 4crystal is regular and growth gradually, and Li is described 3fe 2(PO 4) 3and Fe 2o 3can reduce further and generate LiFePO 4, but still there is a certain amount of impurity or dephasign in end product, as a small amount of Li 3pO 4and Fe 2o 3deng the diffraction maximum of dephasign.Show the existence due to side reaction or competitive reaction, when making synthesizing lithium ferrous phosphate, course of reaction is difficult to control, and product exists impurity or dephasign, will directly affect the chemical property of material.
Embodiment 1
By lithium carbonate, di-iron trioxide and ammonium dihydrogen phosphate are prepared burden according to Li:Fe:P mol ratio 3:2:3, and in ethanol medium, ball milling obtained slurry after 100 minutes; Above-mentioned slurry is carried out vacuumize and obtains presoma, insert roasting in Muffle furnace after presoma being filled alms bowl, programming rate is 5 DEG C/min, and 700 DEG C of insulation 5h, cool to room temperature with the furnace, obtain Li 3fe 2(PO 4) 3presoma;
By Li 3fe 2(PO 4) 3presoma and iron powder are according to 1:1 mol ratio, and in ethanol medium, ball milling is after 30 minutes, obtains slurry; Above-mentioned slurry is carried out vacuumize and obtains presoma, by presoma at nitrogen protection vacuum well type kiln roasting, programming rate is 5 DEG C/min, and 600 DEG C of insulation 5h, cool to room temperature with the furnace, obtain ferrousphosphate lithium material.
Assembly simulation battery is to the LiFePO of above-mentioned preparation 4positive electrode carries out electrochemical property test.Take aluminium foil as plus plate current-collecting body, wherein positive active material (i.e. LiFePO 4), the mass ratio of acetylene black, Kynoar (PVDF) is 8:1:1, negative electricity is metal lithium sheet very, and barrier film is import Celgard-2300,1mol/L LiPF 6the mixed solution of/ethylene carbonate (EC)+diethyl carbonate (DEC)+dimethyl carbonate (DMC) (volume ratio 1: 1: 1) is electrolyte.Being assemblied in glove box of battery is carried out, and the voltage range of constant current charge-discharge test is 2.5 ~ 4.2V.Discharge and recharge system calculates according to the theoretical capacity of 170mAh/g, and namely 1C is 170mA/g.Recording its 0.05C specific capacity is 133mAh/g.
The Li that accompanying drawing 3 obtains according to the inventive method embodiment 1 3fe 2(PO 4) 3xRD spectra; As seen from Figure 1, the Li prepared by the present invention 3fe 2(PO 4) 3the xrd spectrogram of material and monoclinic system Li 3fe 2(PO 4) 3standard spectrogram consistent (pdf#47-0107), belong to P21/n(14) space group, do not find the diffraction maximum of other dephasigns, show obtained Li 3fe 2(PO 4) 3material is pure phase.
Accompanying drawing 4 is the XRD spectra according to the obtained ferrousphosphate lithium material of the inventive method embodiment 1, and all diffraction maximums all index can turn to the LiFePO of olivine structural 4, belong to Pnma space group, do not find the diffraction maximum of other dephasigns, show obtained LiFePO 4material is pure phase.
Accompanying drawing 5 is according to the obtained ferrousphosphate lithium material of the inventive method embodiment 1, assembling button cell (negative pole is lithium sheet), the discharge curve under 0.05C multiplying power.Recording its 0.05C specific capacity is 133mAh/g, compared with specific capacity (125 mAh/g) the high 8mAh/g of pure phosphoric acid ferrous lithium (PCT/US/9706671) prepared by conventional high temperature solid phase method.
Embodiment 2
By lithium hydroxide, ferric nitrate and diammonium hydrogen phosphate are prepared burden according to Li:Fe:P mol ratio 3:2:3, and in medium-acetone, ball milling obtained slurry after 12 hours; Above-mentioned slurry is carried out spraying dry and obtains presoma, presoma is filled alms bowl and insert roasting in Muffle furnace, programming rate is 5 DEG C/min, and 900 DEG C of insulation 3h, cool to room temperature with the furnace, obtain Li 3fe 2(PO 4) 3presoma;
By Li 3fe 2(PO 4) 3presoma and iron powder are according to 1:1 mol ratio, and in aqueous medium, ball milling is after 12 hours, obtains slurry; Above-mentioned slurry is carried out spraying dry and obtains presoma, by presoma hydrogen content be 5% nitrogen and the mixed atmosphere of hydrogen mid-enter roasting in pit-type furnace, programming rate is 5 DEG C/min, 600 DEG C of insulation 10h, cool to room temperature with the furnace, obtain ferrousphosphate lithium material.
Assembly simulation battery is to the LiFePO of above-mentioned preparation 4positive electrode carries out electrochemical property test.Take aluminium foil as plus plate current-collecting body, wherein positive active material (i.e. LiFePO 4), the mass ratio of acetylene black, Kynoar (PVDF) is 8:1:1, negative electricity is metal lithium sheet very, and barrier film is import Celgard-2300,1mol/L LiPF 6the mixed solution of/ethylene carbonate (EC)+diethyl carbonate (DEC)+dimethyl carbonate (DMC) (volume ratio 1: 1: 1) is electrolyte.Being assemblied in glove box of battery is carried out, and the voltage range of constant current charge-discharge test is 2.5 ~ 4.2V.Discharge and recharge system calculates according to the theoretical capacity of 170mAh/g, and namely 1C is 170mA/g.Recording its 0.05C specific capacity is 1300mAh/g.
Embodiment 3
Ferric oxalate and lithium dihydrogen phosphate are prepared burden according to Li:Fe:P mol ratio 3:2:3, in ethanol medium, ball milling obtained slurry after 24 hours; Above-mentioned slurry is carried out spraying dry and obtains presoma, presoma is filled alms bowl and insert roasting in Muffle furnace, programming rate is 5 DEG C/min, and 800 DEG C of insulation 15h, cool to room temperature with the furnace, obtain Li 3fe 2(PO 4) 3presoma;
By Li 3fe 2(PO 4) 3presoma and iron powder are according to 1:1 mol ratio, and in medium-acetone, ball milling is after 24 hours, obtains slurry; Above-mentioned slurry is carried out spraying dry and obtains presoma, presoma is inserted roasting in pit-type furnace in nitrogen atmosphere, programming rate is 5 DEG C/min, and 800 DEG C of insulation 5h, cool to room temperature with the furnace, obtain ferrousphosphate lithium material.
Assembly simulation battery is to the LiFePO of above-mentioned preparation 4positive electrode carries out electrochemical property test.Take aluminium foil as plus plate current-collecting body, wherein positive active material (i.e. LiFePO 4), the mass ratio of acetylene black, Kynoar (PVDF) is 8:1:1, negative electricity is metal lithium sheet very, and barrier film is import Celgard-2300,1mol/L LiPF 6the mixed solution of/ethylene carbonate (EC)+diethyl carbonate (DEC)+dimethyl carbonate (DMC) (volume ratio 1: 1: 1) is electrolyte.Being assemblied in glove box of battery is carried out, and the voltage range of constant current charge-discharge test is 2.5 ~ 4.2V.Discharge and recharge system calculates according to the theoretical capacity of 170mAh/g, and namely 1C is 170mA/g.Recording its 0.05C specific capacity is 129mAh/g.
Embodiment 4
Lithium acetate, iron powder and diammonium hydrogen phosphate are prepared burden according to Li:Fe:P mol ratio 3:2:3, in ethanol medium, ball milling obtained slurry after 12 hours; Above-mentioned slurry is carried out spraying dry and obtains presoma, presoma is filled alms bowl and insert roasting in Muffle furnace, programming rate is 5 DEG C/min, and 600 DEG C of insulation 24h, cool to room temperature with the furnace, obtain Li 3fe 2(PO 4) 3presoma;
By Li 3fe 2(PO 4) 3presoma and iron powder are according to 1:1 mol ratio, and in aqueous medium, ball milling is after 12 hours, obtains slurry; Above-mentioned slurry is carried out spraying dry and obtains presoma, presoma is inserted roasting in pit-type furnace in nitrogen atmosphere, programming rate is 5 DEG C/min, and 650 DEG C of insulation 10h, cool to room temperature with the furnace, obtain ferrousphosphate lithium material.
Assembly simulation battery is to the LiFePO of above-mentioned preparation 4positive electrode carries out electrochemical property test.Take aluminium foil as plus plate current-collecting body, wherein positive active material (i.e. LiFePO 4), the mass ratio of acetylene black, Kynoar (PVDF) is 8:1:1, negative electricity is metal lithium sheet very, and barrier film is import Celgard-2300,1mol/L LiPF 6the mixed solution of/ethylene carbonate (EC)+diethyl carbonate (DEC)+dimethyl carbonate (DMC) (volume ratio 1: 1: 1) is electrolyte.Being assemblied in glove box of battery is carried out, and the voltage range of constant current charge-discharge test is 2.5 ~ 4.2V.Discharge and recharge system calculates according to the theoretical capacity of 170mAh/g, and namely 1C is 170mA/g.Recording its 0.05C specific capacity is 135mAh/g.
Embodiment 5
Lithium oxalate, ferrous oxide and diammonium hydrogen phosphate are prepared burden according to Li:Fe:P mol ratio 3:2:3, in aqueous medium, ball milling obtained slurry after 12 hours; Above-mentioned slurry is carried out spraying dry and obtains presoma, presoma is filled alms bowl and insert roasting in Muffle furnace, programming rate is 10 DEG C/min, and 800 DEG C of insulation 10h, cool to room temperature with the furnace, obtain Li 3fe 2(PO 4) 3presoma;
By Li 3fe 2(PO 4) 3presoma and iron powder are according to 1:1 mol ratio, and in ethanol medium, ball milling is after 12 hours, obtains slurry; Above-mentioned slurry is carried out spraying dry and obtains presoma, presoma is inserted roasting in pit-type furnace in nitrogen atmosphere, programming rate is 8 DEG C/min, and 750 DEG C of insulation 10h, cool to room temperature with the furnace, obtain ferrousphosphate lithium material.
Assembly simulation battery is to the LiFePO of above-mentioned preparation 4positive electrode carries out electrochemical property test.Take aluminium foil as plus plate current-collecting body, wherein positive active material (i.e. LiFePO 4), the mass ratio of acetylene black, Kynoar (PVDF) is 8:1:1, negative electricity is metal lithium sheet very, and barrier film is import Celgard-2300,1mol/L LiPF 6the mixed solution of/ethylene carbonate (EC)+diethyl carbonate (DEC)+dimethyl carbonate (DMC) (volume ratio 1: 1: 1) is electrolyte.Being assemblied in glove box of battery is carried out, and the voltage range of constant current charge-discharge test is 2.5 ~ 4.2V.Discharge and recharge system calculates according to the theoretical capacity of 170mAh/g, and namely 1C is 170mA/g.Recording its 0.05C specific capacity is 134mAh/g.
Embodiment 6
Lithium carbonate, ferrous acetate and diammonium hydrogen phosphate are prepared burden according to Li:Fe:P mol ratio 3:2:3, in medium-acetone, ball milling obtained slurry after 30 minutes; Above-mentioned slurry is carried out spraying dry and obtains presoma, presoma is filled alms bowl and insert roasting in Muffle furnace, programming rate is 10 DEG C/min, and 800 DEG C of insulation 15h, cool to room temperature with the furnace, obtain Li 3fe 2(PO 4) 3presoma;
By Li 3fe 2(PO 4) 3presoma and iron powder are according to 1:1 mol ratio, and in ethanol medium, ball milling is after 12 hours, obtains slurry; Above-mentioned slurry is carried out spraying dry and obtains presoma, presoma is inserted roasting in pit-type furnace in nitrogen atmosphere, programming rate is 8 DEG C/min, and 750 DEG C of insulation 10h, cool to room temperature with the furnace, obtain ferrousphosphate lithium material.
Assembly simulation battery is to the LiFePO of above-mentioned preparation 4positive electrode carries out electrochemical property test.Take aluminium foil as plus plate current-collecting body, wherein positive active material (i.e. LiFePO 4), the mass ratio of acetylene black, Kynoar (PVDF) is 8:1:1, negative electricity is metal lithium sheet very, and barrier film is import Celgard-2300,1mol/L LiPF 6the mixed solution of/ethylene carbonate (EC)+diethyl carbonate (DEC)+dimethyl carbonate (DMC) (volume ratio 1: 1: 1) is electrolyte.Being assemblied in glove box of battery is carried out, and the voltage range of constant current charge-discharge test is 2.5 ~ 4.2V.Discharge and recharge system calculates according to the theoretical capacity of 170mAh/g, and namely 1C is 170mA/g.Recording its 0.05C specific capacity is 133mAh/g.
Embodiment 7
Lithium carbonate, FeOOH and diammonium hydrogen phosphate are prepared burden according to Li:Fe:P mol ratio 3:2:3, in aqueous medium, ball milling obtained slurry after 10 hours; Above-mentioned slurry is carried out vacuumize and obtains presoma, presoma is filled alms bowl and insert roasting in Muffle furnace, programming rate is 10 DEG C/min, and 500 DEG C of insulation 24h, cool to room temperature with the furnace, obtain Li 3fe 2(PO 4) 3presoma;
By Li 3fe 2(PO 4) 3presoma and iron powder are according to 1:1 mol ratio, and in ethanol medium, ball milling is after 20 hours, obtains slurry; Above-mentioned slurry is carried out spraying dry and obtains presoma, presoma is inserted roasting in pit-type furnace in argon gas atmosphere, programming rate is 8 DEG C/min, and 500 DEG C of insulation 24h, cool to room temperature with the furnace, obtain ferrousphosphate lithium material.
Assembly simulation battery is to the LiFePO of above-mentioned preparation 4positive electrode carries out electrochemical property test.Take aluminium foil as plus plate current-collecting body, wherein positive active material (i.e. LiFePO 4), the mass ratio of acetylene black, Kynoar (PVDF) is 8:1:1, negative electricity is metal lithium sheet very, and barrier film is import Celgard-2300,1mol/L LiPF 6the mixed solution of/ethylene carbonate (EC)+diethyl carbonate (DEC)+dimethyl carbonate (DMC) (volume ratio 1: 1: 1) is electrolyte.Being assemblied in glove box of battery is carried out, and the voltage range of constant current charge-discharge test is 2.5 ~ 4.2V.Discharge and recharge system calculates according to the theoretical capacity of 170mAh/g, and namely 1C is 170mA/g.Recording its 0.05C specific capacity is 131mAh/g.

Claims (8)

1. a preparation method for anode material for lithium ion battery LiFePO 4, is characterized in that, comprises the steps:
(1) presoma Li 3fe 2(PO 4) 3synthesis, be Li:Fe:P=3:2:3 batching in molar ratio by Li source compound, source of iron, P source compound, with deionized water, absolute ethyl alcohol or acetone for medium ball milling 0.5-24h, after gained slurry drying, in 500-900 DEG C of temperature, lower heat treatment 3-24 hour under oxidizing atmosphere, obtains presoma Li 3fe 2(PO 4) 3;
(2) the presoma Li obtained 3fe 2(PO 4) 3with iron powder be in molar ratio 1:1 batching, with deionized water, absolute ethyl alcohol or acetone for medium ball milling 0.5-24h, after gained slurry drying, put into high temperature furnace, in non-oxidizing atmosphere, roasting 5-24 hour at 500-800 DEG C, obtained ferrousphosphate lithium material.
2. preparation method as claimed in claim 1, is characterized in that: described Li source compound is lithium hydroxide, lithium carbonate, lithium oxalate, lithium acetate, or lithium dihydrogen phosphate.
3. preparation method as claimed in claim 1, is characterized in that: described source of iron is iron powder, divalence or ferric oxide, ferrous nitrate, ferric nitrate or divalence or ferric acylate.
4. preparation method as claimed in claim 3, is characterized in that: described divalence or ferric oxide are FeO, FeOOH, Fe 2o 3or Fe 3o 4.
5. preparation method as claimed in claim 3, is characterized in that: described divalence or ferric acylate are ferric acetate, ferrous acetate, ferric oxalate or ferrous oxalate.
6. preparation method as claimed in claim 1, is characterized in that: described P source compound is ammonium dihydrogen phosphate, diammonium hydrogen phosphate, lithium dihydrogen phosphate.
7. preparation method as claimed in claim 1, is characterized in that: in described step (1) and step (2), drying mode is spraying dry or vacuumize.
8. preparation method as claimed in claim 1, is characterized in that: in described step (2), and described nonoxidizing atmosphere is at least one in nitrogen and argon gas, or reducing atmosphere.
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