CN102867962B

CN102867962B - Preparation method of LiFePO4 composite positive electrode material modified by CePO4

Info

Publication number: CN102867962B
Application number: CN201210369390.0A
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: 2015-05-06
Anticipated expiration: 2032-09-27
Also published as: CN102867962A

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

One CePO 4carry out the LiFePO modified 4the preparation method of composite positive pole

Technical field

The present invention relates to one CePO ₄carry out the LiFePO modified 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

Also a series of significant problems such as environmental pollution, energy shortage, ecological disruption have been there is while 20th century human social economy's high speed developments.Developing green new forms of energy are task of top priority.As one of the representative of new forms of energy, lithium rechargeable battery has broad application prospects.By the end of at present, lithium ion battery substantially covers nearly all portable type electronic product 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 ₄have the advantage of its uniqueness, comprise high thermal stability, environment friendly, with low cost, higher voltage platform and specific discharge capacity, these advantages determine LiFePO ₄it will be the anode material for lithium-ion batteries having very much application prospect.

But LiFePO ₄self also have comparatively significantly defect, its electronic conductivity and ion diffusivity are very low, this greatly limits its use under 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: one is refinement of particle size, optimizes pattern, reduces Li ⁺the evolving path.Two is that to carry out carbon coated, to improve intergranular electronic conductivity.Three is adulterated by high volence metal ion to improve its ion diffusivity.

Applicant has invented one and pass through CePO ₄modify to improve LiFePO ₄the preparation method of electrical property, at LiFePO ₄particle surface decorated nanometer CePO ₄, significantly suppress growing up of particle, significantly shorten Li ⁺the evolving path.

Summary of the invention

The object of the present invention is to provide one CePO ₄carry out the LiFePO modified ₄the preparation method of composite positive pole.This method is easy, feasible, and can significantly improve LiFePO ₄the electrical property of composite positive pole.

Technical solution of the present invention: one CePO ₄carry out the LiFePO modified ₄the preparation method of composite positive pole, the method concrete steps are as follows:

Step one: obtain solution: by 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 amount of substance ratio of 0.2:x carries out weighing that (x is CePO ₄the ratio of amount of substance in the composite, x=0.003-0.02).By LiOHH ₂o and H ₃pO ₄be dissolved in deionized water and stirring and evenly form a kind of milky solution, then by FeSO ₄7H ₂o, C ₆h ₈o ₆with Ce (NO ₃) ₃3H ₂o is slowly dissolved in deionized water and stirring and evenly forms another kind of solution.By two kinds of solution mixing, wherein FeSO ₄concentration be 0.4-0.6mol/L, regulate the pH value of mixed solution to be 7-8 with ammoniacal liquor.

Step 2: prepared by hydro-thermal: proceeded to rapidly in the reactor that Teflon tank is housed by solution, then reactor is placed in constant temperature oven, control heating-up temperature is 160-190 DEG C, and heating time is 10-14 hour.

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

Step 4: calcination processing: dried powder is put into porcelain boat, proceeds in atmosphere furnace and calcine.Control heat treatment temperature is 650-750 DEG C, and constant temperature time is 1-2 hour, and heating rate is 3-5 DEG C/min, and the argon gas that atmosphere is 2-4% by hydrogen volume content provides.What finally obtain is LiFePO ₄/ C/CePO ₄composite positive pole.

Advantage of the present invention is: the CePO playing modification ₄by H in hydrothermal reaction process 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.

Accompanying drawing explanation

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

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

Fig. 2 is LiFePO ₄/ C/CePO ₄tEM photo

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

Embodiment

See Fig. 3, one CePO of the present invention ₄carry out the LiFePO modified ₄the preparation method of composite positive pole, the method concrete steps are as follows:

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

Embodiment 1

Take the LiOHH of 6.294g ₂the H of O and 5.768g ₃pO ₄(85wt%), add 50ml deionized water, use magnetic stirrer 30min, form emulsion liquid.Separately take the FeSO of 13.9g ₄7H ₂the C of O, 1.76g ₆h ₈o ₆with the Ce (NO of 0.1g ₃) ₃3H ₂o slowly adds in 50ml deionized water, and is stirred to whole dissolving gently.Subsequently by two kinds of solution mixing, regulate pH value to be 7 with ammoniacal liquor, proceed to rapidly in the reactor that Teflon tank is housed.Reactant heats 12 hours at 180 DEG C in constant temperature oven.To be cooled to room temperature, the primary sample generated after hydro-thermal reaction is carried out suction filtration, washs 2 times with deionized water and acetone, afterwards filter cake is placed in vacuum drying chamber, at 70 DEG C, vacuumize 4 hours.Last proceeding to again in atmosphere furnace carries out calcining heat treatment, and temperature is 700 DEG C, heating rate 5 DEG C/min, constant temperature 1 hour.The argon gas that reducing environment is 3% by hydrogen volume content provides.What finally obtain is LiFePO ₄/ C/0.5CePO ₄composite positive pole (CePO ₄addition is 0.5%).Electric performance test result shows, 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, be obviously better than not modifying CePO ₄liFePO ₄the electrical property of/C composite positive pole.

Embodiment 2

LiFePO is prepared in hydro-thermal ₄in the raw material of composite positive pole, change the CePO added ₄content be 1%, namely take the Ce (NO of 0.2g ₃) ₃3H ₂o, all the other all carry out according to the step of example 1, and what finally obtain is labeled as LiFePO ₄/ C/CePO ₄composite positive pole.SEM and TEM photo is as shown in Fig. 1 a, Fig. 1 b, Fig. 2.The particle size comparatively unmodified CePO of material can be found out from Fig. 1 a, Fig. 1 b ₄liFePO ₄composite positive pole has had obvious refinement, CePO as can be seen from Figure 2 ₄nano particle can be embedded at LiFePO as nail ₄particle surface and inside, effectively inhibit LiFePO ₄growing up of particle size.During electric performance test is subsequently analyzed, its specific discharge capacity under 0.1C, 1C and 10C discharge-rate is respectively 158.4,137.6 and 101.3mAhg ^-1, electrical property is unmodified CePO comparatively ₄liFePO ₄/ C composite positive pole has had and has significantly promoted, and also shows along with CePO simultaneously ₄the increase of modification amount, the further refinement of particle size of meeting, improves the electrical property of material.

Embodiment 3

Continue to change CePO ₄addition be 1.5%, all the other steps are all carried out according to example 1, and the material marking of preparation is LiFePO ₄/ C/1.5CePO ₄.Its 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 have appropriate value.

Claims

1. one kind with CePO ₄carry out the LiFePO modified ₄the preparation method of composite positive pole, is characterized in that: the method concrete steps are as follows:

Step one: obtain solution: by LiOHH ₂o, FeSO ₄7H ₂o, H ₃pO ₄(85wt%), ascorbic acid and Ce (NO ₃) ₃3H ₂o is according to Li:Fe:P:C ₆h ₈o ₆: Ce=3:1:(1+x): the amount of substance ratio of 0.2:x weighs, and x is CePO ₄the ratio of amount of substance in the composite, x=0.003-0.02; By LiOHH ₂o and H ₃pO ₄be dissolved in deionized water and stirring and evenly form a kind of milky solution, then by FeSO ₄7H ₂o, ascorbic acid and Ce (NO ₃) ₃3H ₂o is slowly dissolved in deionized water and stirring and evenly forms another kind of solution; By two kinds of solution mixing, wherein FeSO ₄concentration be 0.4-0.6mol/L, regulate the pH value of mixed solution to be 7-8 with ammoniacal liquor;

Step 2: prepared by hydro-thermal: proceeded to rapidly in the reactor that Teflon tank is housed by solution, then reactor is placed in constant temperature oven, control heating-up temperature is 160-190 DEG C, and heating time is 10-14 hour;

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

Step 4: calcination processing: dried powder is put into porcelain boat, proceeds in atmosphere furnace and calcine; Control heat treatment temperature is 650-750 DEG C, and constant temperature time is 1-2 hour, and heating rate is 3-5 DEG C/min, and the argon gas that atmosphere is 2-4% by hydrogen volume content provides, and what finally obtain is LiFePO ₄/ C/CePO ₄composite positive pole.