CN102867962A

CN102867962A - Preparation method of LiFePO4 composite positive electrode material modified by CePO4

Info

Publication number: CN102867962A
Application number: CN2012103693900A
Authority: CN
Inventors: 张俊英; 权威
Original assignee: Beihang University
Current assignee: Beihang University
Priority date: 2012-09-27
Filing date: 2012-09-27
Publication date: 2013-01-09
Anticipated expiration: 2032-09-27
Also published as: CN102867962B

Abstract

The invention relates to a preparation method of a LiFePO4 composite positive electrode material modified by CePO4. The preparation method comprises four major steps of: step 1: preparing a solution; step 2: performing hydrothermal preparation; step 3: performing suction filtration, water washing and drying; and step 4: performing calcination treatment to finally obtain the LiFePO4/C/CePO4 composite positive electrode material. The CePO4 playing a modifying role in the preparation method disclosed by the invention is generated by reaction of H3PO4 and Ce(NO3)3 during the hydrothermal reaction process and is insoluble in water, the particle size is only tens of nanometers, and the CePO4 can inhibit the growth of the particle size of LiFePO4 like a nail, so that the particle size can be thinned, the diffusion path of Li+ can be greatly shortened, and the electrical properties of the material can be improved.

Description

A kind of CePO that uses 4The LiFePO that modifies 4The preparation method of composite positive pole

Technical field

The present invention relates to a kind of CePO of using ₄The LiFePO that modifies ₄The preparation method of composite positive pole, it is a kind of to LiFePO ₄Positive electrode carries out modification, to improve the method for its electrical property, belongs to the fields such as material, electrochemistry, new forms of energy.

Background technology

A series of significant problems such as environmental pollution, energy shortage, ecological disruption have also appearred when human social economy's high speed development in 20th century.The developing green new forms of energy are task of top priority.As one of representative of new forms of energy, lithium rechargeable battery has broad application prospects.By the end of at present, lithium ion battery has covered nearly all portable type electronic product substantially such as mobile phone, notebook computer etc., and pure electric automobile and hybrid-electric car also come out.In numerous anode material for lithium-ion batteries, LiFePO ₄Its unique advantage is arranged, comprise high thermal stability, environment friendly, with low cost, higher voltage platform and specific discharge capacity, these advantages have determined LiFePO ₄It will be the anode material for lithium-ion batteries that application prospect is arranged very much.

But LiFePO ₄Comparatively significantly defective is also arranged self, and its electronic conductivity and ion diffusivity are very low, and this has greatly limited its use under the high current charge-discharge condition.At present for LiFePO ₄Research mainly concentrate on how to improve its electronic conductivity and ion diffusivity.Sum up research in recent years, main modification mode mainly comprises following three aspects: the one, and refinement of particle size is optimized pattern, reduces Li ⁺The evolving path.The 2nd, carry out carbon and coat, to improve intergranular electronic conductivity.The 3rd, mix to improve its ion diffusivity by high volence metal ion.

The applicant has invented a kind of CePO of passing through ₄Modification is to improve LiFePO ₄The preparation method of electrical property is at LiFePO ₄Particle surface decorated nanometer CePO ₄, significantly suppressed growing up of particle, significantly shorten Li ⁺The evolving path.

Summary of the invention

The object of the present invention is to provide a kind of CePO of using ₄The LiFePO that modifies ₄The preparation method of composite positive pole.This method is easy, and is feasible, and can significantly improve LiFePO ₄The electrical property of composite positive pole.

Technical solution of the present invention: a kind of CePO that uses ₄The LiFePO that modifies ₄The preparation method of composite positive pole, the method concrete steps are as follows:

Step 1: obtain solution: with LiOHH ₂O, FeSO ₄7H ₂O, H ₃PO ₄(85wt%), C ₆H ₈O ₆(ascorbic acid) and Ce (NO ₃) ₃3H ₂O is according to Li:Fe:P:C ₆H ₈O ₆: Ce=3:1:(1+x): the molar ratio of 0.2:x carries out weighing, and (x is CePO ₄The ratio of the amount of substance in composite material, x=0.003-0.02).With LiOHH ₂O and H ₃PO ₄Be dissolved in deionized water and stirring and evenly form a kind of milky solution, then with FeSO ₄7H ₂O, C ₆H ₈O ₆And Ce (NO ₃) ₃3H ₂O slowly is dissolved in deionized water and stirring and evenly forms another kind of solution.Two kinds of solution are mixed, wherein FeSO ₄Concentration be 0.4-0.6mol/L, the pH value of regulating mixed solution with ammoniacal liquor is 7-8.

Step 2: hydro-thermal preparation: solution is changed over to rapidly in the reactor that the Teflon tank is housed, then reactor is placed constant temperature oven, the control heating-up temperature is 160-190 ℃, and be 10-14 hour heating time.

Step 3: suction filtration, washing and drying: after the hydro-thermal reaction, remove the supernatant liquor of product, remainder adopts the mode of suction filtration, repeatedly cleans 2-3 time with deionized water and acetone respectively.Afterwards filter cake is placed in the vacuum drying chamber, under 60-80 ℃, dry 3-4 hour.

Step 4: calcination processing: dried powder is put into porcelain boat, change in the atmosphere furnace and calcine.The control heat treatment temperature is 650-750 ℃, and constant temperature time is 1-2 hour, and heating rate is 3-5 ℃/min, and atmosphere is provided by the argon gas of hydrogen volume content for 2-4%.What obtain at last is LiFePO ₄/ C/CePO ₄Composite positive pole.

Advantage of the present invention is: the CePO that plays modification ₄In hydrothermal reaction process by H ₃PO ₄With Ce (NO ₃) ₃Reaction generates, and it is water insoluble, and particle size only has tens nanometer, can suppress LiFePO as nail ₄Growing up of particle size, thus reach refinement of particle size, improve the effect of material electrical property.

Description of drawings

Fig. 1 a is LiFePO ₄The SEM photo of/C (a)

Fig. 1 b is LiFePO ₄/ C/CePO ₄(b) SEM photo

Fig. 2 is LiFePO ₄/ C/CePO ₄The TEM photo

Fig. 3 is FB(flow block) of the present invention

Embodiment

See Fig. 3, a kind of CePO that uses of the present invention ₄The LiFePO that modifies ₄The preparation method of composite positive pole, the method concrete steps are as follows:

The present invention is described in detail below in conjunction with embodiment, but protection scope of the present invention is not limited in the following example, should comprise the full content in the application for patent.

Embodiment 1

Take by weighing the LiOHH of 6.294g ₂The H of O and 5.768g ₃PO ₄(85wt%), add the 50ml deionized water, use magnetic stirrer 30min, form emulsion liquid.Other takes by weighing the FeSO of 13.9g ₄7H ₂The C of O, 1.76g ₆H ₈O ₆Ce (NO with 0.1g ₃) ₃3H ₂O slowly adds in the 50ml deionized water, and is stirred to gently whole dissolvings.Subsequently two kinds of solution are mixed, regulating pH value with ammoniacal liquor is 7, changes over to rapidly in the reactor that the Teflon tank is housed.Reactant is 180 ℃ of lower heating 12 hours in constant temperature oven.To be cooled to room temperature, the primary sample that generates after the hydro-thermal reaction is carried out suction filtration, with deionized water and acetone washing 2 times, afterwards filter cake is placed in the vacuum drying chamber, under 70 ℃, vacuumize 4 hours.Change over to more at last and calcine heat treatment in the atmosphere furnace, temperature is 700 ℃, 5 ℃/min of heating rate, constant temperature 1 hour.Reducing environment is provided for 3% argon gas by hydrogen volume content.What obtain at last is LiFePO ₄/ C/0.5CePO ₄Composite positive pole (CePO ₄Addition is 0.5%).Electric performance test is the result show, under the discharge-rate of 0.1C, 1C and 10C, the specific discharge capacity of material is respectively 150.3,130.1 and 92.2mAhg ^-1, obviously be better than not modifying CePO ₄LiFePO ₄The electrical property of/C composite positive pole.

Embodiment 2

Prepare LiFePO in hydro-thermal ₄In the raw material of composite positive pole, change the CePO that adds ₄Content be 1%, namely take by weighing the Ce (NO of 0.2g ₃) ₃3H ₂O, all the other all carry out according to the step of example 1, and what make at last is labeled as LiFePO ₄/ C/CePO ₄Composite positive pole.SEM and TEM photo such as Fig. 1 a, Fig. 1 b, shown in Figure 2.Can find out that from Fig. 1 a, Fig. 1 b the particle size of material is than unmodified CePO ₄LiFePO ₄Composite positive pole has had obvious refinement, as can be seen from Figure 2 CePO ₄Nano particle can be embedded at LiFePO as nail ₄Particle surface and inside, establishment LiFePO ₄Growing up of particle size.During subsequently electric performance test was analyzed, its specific discharge capacity under 0.1C, 1C and 10C discharge-rate was respectively 158.4,137.6 and 101.3mAhg ^-1, electrical property is than unmodified CePO ₄LiFePO ₄/ C composite positive pole has had significantly lifting, also shows along with CePO simultaneously ₄The increase of modification amount, the further refinement of particle size of meeting, the electrical property of raising material.

Embodiment 3

Continue to change CePO ₄Addition be 1.5%, all the other steps are all carried out according to example 1, the material marking of preparation is LiFePO ₄/ C/1.5CePO ₄Its specific discharge capacity under the discharge-rate of 0.1C, 1C and 10C is respectively: 156.4,135.7 and 97.4mAhg ^-1, test result has had further lifting than example 1, but is not so good as the excellent material performance of example 2, and this illustrates CePO ₄Addition an amount of value is arranged.

Claims

1. use CePO for one kind ₄The LiFePO that modifies ₄The preparation method of composite positive pole is characterized in that: the method concrete steps are as follows:

Step 1: obtain solution: with LiOHH ₂O, FeSO ₄7H ₂O, H ₃PO ₄(85wt%), C ₆H ₈O ₆And Ce (NO ₃) ₃3H ₂O is according to Li:Fe:P:C ₆H ₈O ₆: Ce=3:1:(1+x): the molar ratio of 0.2:x carries out weighing, and x is CePO ₄The ratio of the amount of substance in composite material, x=0.003-0.02; With LiOHH ₂O and H ₃PO ₄Be dissolved in deionized water and stirring and evenly form a kind of milky solution, then with FeSO ₄7H ₂O, C ₆H ₈O ₆And Ce (NO ₃) ₃3H ₂O slowly is dissolved in deionized water and stirring and evenly forms another kind of solution; Two kinds of solution are mixed, wherein FeSO ₄Concentration be 0.4-0.6mol/L, the pH value of regulating mixed solution with ammoniacal liquor is 7-8;

Step 2: hydro-thermal preparation: solution is changed over to rapidly in the reactor that the Teflon tank is housed, then reactor is placed constant temperature oven, the control heating-up temperature is 160-190 ℃, and be 10-14 hour heating time;

Step 3: suction filtration, washing and drying: after the hydro-thermal reaction, remove the supernatant liquor of product, remainder adopts the mode of suction filtration, repeatedly cleans 2-3 time with deionized water and acetone respectively; Afterwards filter cake is placed in the vacuum drying chamber, under 60-80 ℃, dry 3-4 hour;

Step 4: calcination processing: dried powder is put into porcelain boat, change in the atmosphere furnace and calcine; The control heat treatment temperature is 650-750 ℃, and constant temperature time is 1-2 hour, and heating rate is 3-5 ℃/min, and atmosphere is provided by the argon gas of hydrogen volume content for 2-4%, and what obtain at last is LiFePO ₄/ C/CePO ₄Composite positive pole.