CN100420075C - Method for preparing lithium ion battery anode material lithium ion phosphate - Google Patents

Method for preparing lithium ion battery anode material lithium ion phosphate Download PDF

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CN100420075C
CN100420075C CNB2005101117916A CN200510111791A CN100420075C CN 100420075 C CN100420075 C CN 100420075C CN B2005101117916 A CNB2005101117916 A CN B2005101117916A CN 200510111791 A CN200510111791 A CN 200510111791A CN 100420075 C CN100420075 C CN 100420075C
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lithium
phosphate
iron
ion battery
lithium ion
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CNB2005101117916A
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Chinese (zh)
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CN1803591A (en
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王保峰
杨立
邱亚丽
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上海交通大学
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Abstract

The present invention discloses a method for preparing anode material lithium iron phosphate of a lithium ion battery. Trivalent iron salt, lithium salt, microcosmic salt and reductant are mixed in solvent to react, and amorphous lithium iron phosphate is obtained after the reaction of 0.5 to 30 hours and is calcined for 20 to 600 min at constant temperature by rising the temperature to 450 to 800 DEG C at the heating rate of 5 to 30 DEG C /min in a nitrogen or argon or mixing gas atmosphere. Then, the amorphous lithium iron phosphate is cooled to room temperature at the temperature decreasing rate of 1 to 20 DEG C /min, and crystal anode material lithium iron phosphate powder of the lithium ion battery is manufactured. The method of the present invention for synthesizing lithium iron phosphate materials adopts ferric iron, and the lithium iron phosphate is generated when the reductant reduces the ferric iron to ferrous iron. The lithium iron phosphate obtained by the technology has advantages of high specific capacity and fine cycle performance. The present invention is provided with a stable charge and discharge voltage platform, and charge and discharge efficiency for the first time achieves 100%.

Description

A kind of preparation method of lithium ion battery anode material lithium iron phosphate

Technical field

The invention belongs to a kind of preparation method of anode material for lithium-ion batteries, particularly a kind of method that adopts wet processing to prepare lithium ion battery anode material lithium iron phosphate.

Background technology

The positive electrode of lithium ion battery is the bottleneck of restriction lithium ion battery development, and it is determining performance, price and the development thereof of lithium ion battery.Therefore, research and develop the key point that high performance positive electrode has become the lithium ion battery development.[the A.K.Padhi of Goodenough research group in 1997, K.S.Nanjundaswarmy, .B.goodenough, J.Electrochem.Soc., 144 (1997))] synthesizing iron lithium phosphate first, and find to have high theoretical specific capacity (170mAh/g) as anode material for lithium-ion batteries with this material, greater than commercial LiCoO 2Actual discharge specific capacity 140mAh/g.Consider that it is nontoxic, environmentally friendly, price that raw material sources is abundant, cheap and good characteristics such as thermal stability, and receive researcher's very big concern, and be considered to the anode material for lithium-ion batteries of new generation of tool development and application potentiality.

The method of synthesizing iron lithium phosphate mainly contains high temperature solid-state method, sol-gel process, hydro thermal method, liquid phase oxidation reducing process etc. at present.

Widely used high temperature solid-state method ([J] P.P.Prosini et al Electrochem Acta for example; 46 (2001) 3517-3523) be with molysite such as ferrous oxalate or ferric nitrate; with ammonium dihydrogen phosphate and lithium salts such as lithium carbonate or lithium hydroxide by metering than mixing; under inert atmosphere such as nitrogen or argon shield, through two one-step baking synthesizing iron lithium phosphates.This method makes synthetic material particle size wider distribution easily, and is difficult to obtain pure LiFePO4.Chinese patent CN1581537A is that directly to adopt metal iron powder and ferric phosphate be source of iron, is the lithium source with the lithium phosphate, through 36 hours high-energy ball millings, and, make LiFePO4 in 600 ℃ of constant temperature calcining 60min.Though this technology is simple, the high-energy ball milling time is long, and energy consumption is big.

F.croce etc. are at [J] Electrochemical and Solid-State Letters, and adopting sol-gel process among 2002,5 (3) A47-A50 is presoma with ferric acetate or ferric nitrate, add ascorbic acid behind the LiOH of mixed chemical metering ratio, join H then 3PO 4In, regulate pH value with ammoniacal liquor, be heated to 60 ℃ and obtain gel.In blanket of nitrogen, made gel decomposition in 12 hours then, obtained LiFePO4 in 24 hours at 800 ℃ of sintering at last 350 ℃ of heating.Jingsi Yang etc. are at document [J] Electrochemical and Solid-StateLetters, 2004,7 (12), among the A515-A518 lithium acetate, ferrous acetate, phosphoric acid are dissolved in the glycol water with stoichiometric proportion, after vigorous stirring, get gel, through 700 ℃ of following constant temperature 12 hours, promptly get iron phosphate powder then.Though utilize the synthetic material uniformity of this method better, conditional request is harsh, wayward in preparing gel.

S.Fanger etc. among 2002,5 (10) A231-A223, adopt hydro thermal method with Fe at [J] Electrochem Solid-State Letter 3(PO 4) 2And Li 3PO 4Be presoma, at 220 ℃, reaction made iron phosphate powder in 1 hour under the 240bar condition in autoclave.This synthetic method need be used autoclave, and reaction must be carried out under HTHP, so cost is higher.

Pier Paolo etc. are at [J] Journal of the Electrochemical Society, among 2002,149 (7) A886-890, with Fe (NH 4) 2(SO 4) 2, NH 4H 2PO 4And H 2O 2Be the at first synthetic FePO of raw material 4, reduce FePO with LiI then 4, heating preparation in 1 hour LiFePO4 under 550 ℃ of reducing atmospheres.This method can make the chemical property excellent material, but used LiI costs an arm and a leg improper suitability for industrialized production.

Summary of the invention:

The present invention proposes a kind of wet preparation method of lithium ion battery anode material lithium iron phosphate, simplifies preparation technology, improves product purity, improves the material electric conductivity.The present invention need not to prepare in advance or use the ferrous salt of easy oxidation in air, and adopt trivalent iron salt, lithium salts and phosphate is presoma, utilize the clean type reducing agent in precursor solution, under the low temperature ferric iron to be reduced into ferrous iron, thus the lithium ion battery anode material lithium iron phosphate of preparation purity height, chemical property excellence.

The preparation method of a kind of lithium ion battery anode material lithium iron phosphate of the present invention mainly adopts low temperature liquid phase redox synthesis technique, and concrete preparation method is as follows:

With trivalent iron salt, lithium salts, phosphate and reducing agent are mixed in the solvent and react, iron in the trivalent iron salt wherein, lithium in the lithium salts, the phosphorus in the phosphate and the mol ratio of reducing agent are 1: 0.95-1.05: 1: 0.25-2, the concentration of iron in the molysite in solvent is 0.1-2mol/L, reacted 0.5-30 hour, 60-100 ℃ of following solvent flashing also washs resultant unbodied LiFePO4 precipitation, unbodied LiFePO4 is deposited in nitrogen or argon gas or the gaseous mixture atmosphere then, be warming up to 450-800 ℃ with the 5-30 ℃/min rate of heat addition, constant temperature calcining 20-600min, be cooled to room temperature with 1-20 ℃/min rate of temperature fall then, make the lithium ion battery anode material lithium iron phosphate of crystal formation.

Employed trivalent iron salt is ferric nitrate, iron chloride or ferric phosphate among the present invention.

Employed lithium salts is lithium carbonate, lithium hydroxide, lithium acetate or lithium nitrate among the present invention.

Employed phosphate is diammonium hydrogen phosphate, ammonium dihydrogen phosphate or ferric phosphate among the present invention.

Reducing agent used in the present invention is hydrazine hydrate, stannous chloride, sodium borohydride or ascorbic acid.

Solvent used in the present invention is deionized water, absolute ethyl alcohol, ethylene glycol or glycerine.

The used ferric phosphate of the present invention can use the commercial goods, also can make by oneself.The method for preparing ferric phosphate is: with equimolar Fe (NH 4) 2(SO 4) 2.6H 2O and NH 4H 2PO 4Be dissolved in respectively in the deionized water, be made into 0.025-0.1mol/L solution, after two kinds of solution were mixed, in the vigorous stirring, every liter of solution added the H of 1-4mL30% 2O 2The aqueous solution continues to stir 2 hours, and the gained precipitation makes FePO through filtration, washing, drying 4

The method that the present invention adopts the low temperature liquid phase redox to prepare lithium ion battery anode material lithium iron phosphate has following remarkable advantage: 1) reducing agent of the present invention's employing can be reduced into ferrous iron with ferric iron in low temperature liquid phase, generates unbodied LiFePO4 precipitation simultaneously; 2) the lithium ion battery anode material lithium iron phosphate powder of gained is a nano-scale particle, and chemical analysis and thing be uniform ingredients mutually; 3) low temperature liquid phase reduction synthesis technique of the present invention prepares the method for LiFePO4, material composition and product prescription are controlled easily, electro-chemical test shows the LiFePO 4 material that adopts the present invention to synthesize, the specific capacity height, cycle performance is good, has stable charging/discharging voltage platform and first charge-discharge efficiency and reaches 100%.

Description of drawings

Fig. 1 presses the X-ray diffracting spectrum of the prepared LiFePO4 of embodiment 1.

Fig. 2 presses the stereoscan photograph of the prepared LiFePO4 of embodiment 1.

Fig. 3 presses the charging and discharging curve of the prepared LiFePO4 of embodiment 1.

Embodiment

The electrochemical property test condition that following examples adopt is: voltage range 2.5V~4.2V, electrolyte are 1mol/L LiPF 6/ EC: DMC (1: 1) is a metal lithium sheet to electrode, and charging and discharging currents is 17mAg -1, probe temperature is 20 ± 2 ℃.

Embodiment 1:

Take by weighing 0.01molFe (NH 4) 2(SO 4) 26H 2O and 0.01molNH 4H 2PO 4Be dissolved in respectively in the 500ml deionized water, after two kinds of solution mix, under agitation add 4mL concentration and be 30% H 2O 2The aqueous solution continues to stir 2 hours.The sediment that generates is filtered, washs the dry FePO of getting 4With 0.02molLiAc2H 2O, 0.01molFePO 4, the 0.01mol ascorbic acid is mixed in the 50mL ethanol, stirring reaction 10 hours, 60 ℃ of following solvent flashings also wash the unbodied LiFePO4 precipitation of gained, then unbodied LiFePO4 precipitation are placed high temperature furnace, at mixed atmosphere (95%Ar+5%H 2) in, heat up with the 5 ℃/min rate of heat addition, in 600 ℃ of constant temperature calcinings 2 hours, be cooled to room temperature with 20 ℃/min rate of temperature fall then, make the lithium ion battery anode material lithium iron phosphate powder of crystal formation.Fig. 1 is an X-ray diffractogram, and the iron phosphate powder of analyzing gained is pure olivine-type rhombic system phase structure.Fig. 2 is the stereoscan photograph of iron phosphate powder, and the product particle size has the agglomeration of particle substantially less than 3 microns.

Take by weighing 0.4 restrain iron phosphate powder, add the polyvinylidene fluoride binding agent that 0.05 gram acetylene black and 0.05 gram are dissolved in N-N ' dimethyl pyrrolidone, be applied to after mixing and make positive plate on the aluminium foil.In the argon gas atmosphere dry glove box, be to electrode with metal lithium sheet, UB3025 (PP/PE/PP) is a barrier film, ethylene carbonate (EC)+dimethyl carbonate (DMC)+1ML LiPF 6Be electrolyte, be assembled into battery.

Under normal temperature (20 degree), battery is carried out the constant current charge-discharge test in 2.5V~4.2V voltage range.Fig. 3 is with 0.1C multiplying power (17mAg -1) charging and discharging curve, as seen from the figure, gained LiFePO 4 material discharge voltage is about 3.4V, reversible specific capacity is 96% of theoretical specific capacity up to 163mAh/g.Cycle performance of battery is also very superior.

Embodiment 2:

Take by weighing 0.01molLiAc2H 2O, 0.01mol FePO 4(by embodiment 1 preparation), 0.005mol ascorbic acid are dissolved in the 25mL ethanol, stirring reaction 20 hours, 60 ℃ of following solvent flashings also wash gained LiFePO4 precipitation, at last the LiFePO4 precipitation is placed high temperature furnace, in argon gas atmosphere, heat up with the 5 ℃/min rate of heat addition, in 700 ℃ of constant temperature calcinings 10 hours, be cooled to room temperature with 10 ℃/min rate of temperature fall then, promptly get the lithium ion battery anode material lithium iron phosphate powder.The specific discharge capacity of this material is about 130mAh/g.

Embodiment 3:

Take by weighing 0.01molLiAc2H 2O, 0.01molFePO 4(by embodiment 1 preparation), 0.01mol ascorbic acid are dissolved in the 25mL ethanol, stir after 20 hours, with sedimentation and filtration, washing, drying, then at mixed atmosphere (95%Ar+5%H 2) in heat up with the 5 ℃/min rate of heat addition, in 650 ℃ of constant temperature calcinings 15 hours, be cooled to room temperature with 10 ℃/min rate of temperature fall then, promptly get the lithium ion battery anode material lithium iron phosphate powder.The specific discharge capacity of this material is about 140mAh/g.

Claims (6)

1. the preparation method of a lithium ion battery anode material lithium iron phosphate is characterized in that the preparation method is as follows:
With trivalent iron salt, lithium salts, phosphate and ascorbic acid are mixed in the solvent and react, iron in the trivalent iron salt wherein, lithium in the lithium salts, the phosphorus in the phosphate and the mol ratio of ascorbic acid are 1: 0.95-1.05: 1: 0.25-2, the concentration of iron in the molysite in solvent is 0.1-2mol/L, reacted 0.5-30 hour, 60-100 ℃ of following solvent flashing also washs resultant unbodied LiFePO4 precipitation, unbodied LiFePO4 is deposited in nitrogen or argon gas or the gaseous mixture atmosphere then, be warming up to 450-800 ℃ with the 5-30 ℃/min rate of heat addition, constant temperature calcining 20-600min, be cooled to room temperature with 1-20 ℃/min rate of temperature fall then, make the lithium ion battery anode material lithium iron phosphate of crystal formation.
2. the preparation method of a kind of lithium ion battery anode material lithium iron phosphate according to claim 1 is characterized in that trivalent iron salt is ferric nitrate, iron chloride or ferric phosphate.
3. the preparation method of a kind of lithium ion battery anode material lithium iron phosphate according to claim 1 is characterized in that lithium salts is lithium carbonate, lithium oxalate or lithium nitrate.
4. the preparation method of a kind of lithium ion battery anode material lithium iron phosphate according to claim 3 is characterized in that lithium salts substitutes with lithium hydroxide.
5. the preparation method of a kind of lithium ion battery anode material lithium iron phosphate according to claim 1 is characterized in that phosphate is diammonium hydrogen phosphate, ammonium dihydrogen phosphate or ferric phosphate.
6. the preparation method of a kind of lithium ion battery anode material lithium iron phosphate according to claim 1 is characterized in that solvent is deionized water, absolute ethyl alcohol, ethylene glycol or glycerine.
CNB2005101117916A 2005-12-22 2005-12-22 Method for preparing lithium ion battery anode material lithium ion phosphate CN100420075C (en)

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CN100448772C (en) * 2006-08-11 2009-01-07 广州市鹏辉电池有限公司 High density ultrafine composite ferric lithium phosphate anode material and preparation method
CN101567439B (en) * 2009-06-01 2011-01-12 南京工业大学 Method for synthesizing nanometer LiFePO4 lithium ion power battery cathode material by ferric iron source
US9073760B2 (en) 2010-12-24 2015-07-07 Shoei Chemical Inc. Manufacturing method and manufacturing device for multiple oxide
CN102205955A (en) * 2011-03-25 2011-10-05 江苏国泰锂宝新材料有限公司 Preparation method for battery anode material LiMPO4
CN102795611B (en) * 2011-05-26 2015-08-26 比亚迪股份有限公司 A kind of preparation method of LiFePO 4 material and a kind of lithium ion battery
CN102881876B (en) * 2012-10-15 2014-12-17 福建师范大学 Method for preparing lithium-rich solid solution cathode material through reduction co-precipitation
KR101561373B1 (en) 2013-01-10 2015-10-19 주식회사 엘지화학 Method for preparing lithium iron phosphate nanopowder
KR101561378B1 (en) 2013-01-10 2015-10-20 주식회사 엘지화학 Method for preparing lithium iron phospate nanopowder coated with carbon
KR101561376B1 (en) 2013-01-10 2015-10-19 주식회사 엘지화학 Method for preparing lithium iron phosphate nanopowder
CN103311547B (en) * 2013-05-24 2016-08-17 武汉工程大学 The preparation method of lithium iron phosphate /carbon composite powder
CN103500829B (en) * 2013-08-15 2016-12-28 江苏华东锂电技术研究院有限公司 The preparation method of LiFePO 4
CN103633326B (en) * 2013-12-18 2016-01-20 益阳生力材料科技有限公司 The production method of LiFePO4

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