CN102616764B

CN102616764B - Preparation method of porous LiFePO4 powder

Info

Publication number: CN102616764B
Application number: CN201110315594.1A
Authority: CN
Inventors: 刘洪权; 郝飞祥; 王焱; 谷亦杰
Original assignee: Shandong University of Science and Technology
Current assignee: Shandong University of Science and Technology
Priority date: 2011-10-10
Filing date: 2011-10-10
Publication date: 2014-04-02
Anticipated expiration: 2031-10-10
Also published as: CN102616764A

Abstract

Relating to a preparation method of a positive electrode material, the invention provides a preparation method of porous LiFePO4 powder. The method solves the practical problems of porous shape control, element homogenization control and the like of LiFePO4, and lays a solid foundation for industrial promotion of doped LiFePO4 and charge-discharge dynamic regulation of LiFePO4. The invention is implemented in the following steps of: (1) preparing a metal ion solution; (2) selecting an appropriate phosphate or phosphoric acid, and introducing a phosphate ion into the above solution; (3) adding a monomer and a crosslinking agent in appropriate proportion; (4) adding an initiator into the solution in step 3 so as to form a gel; (5) drying the gel rapidly; and (6) roasting the dried gel in an inert atmosphere protection furnace, thus obtaining the porous LiFePO4 powder. The method of the invention prepares porous LiFePO4 powder, which is in favor of reducing the solid-state diffusion distance of lithium ions and speeding up the electrochemical reaction kinetic process. Powder of different porous forms can be formed through regulation of different parameters. The prepared porous LiFePO4 powder has good element homogenization and realizes atomic level mixing, and is conducive to industrial research of LiFePO4 doped materials.

Description

A kind of porous LiFePO 4the preparation method of powder

Technical field

The present invention relates to a kind of anode material for lithium-ion batteries LiFePO ₄the preparation method of porous powder, belongs to energy and material technical field.

Background technology

Battery technology is the key that promote in battery applications field, and improve battery performance, depends on battery electrode material and other assemblies.The new electrode materials with excellent electrochemical performance finds to have important significance of times.With respect to metal oxide electrode material, new electrode materials should guarantee on the basis of respective battery performance to possess the acceptable low cost in good security and stability and market simultaneously.Iron lithium phosphate (LiFePO ₄) as far back as 1997, be just used as positive electrode material and be applied in lithium ion battery, along with the improvement of its battery performance, become gradually the Typical Representative of new positive electrode material.Iron lithium phosphate has the advantages such as low cost, high cycle characteristics, high security, high open circuit voltage (3.5 volts), also has the native defect that specific conductivity is low simultaneously.

At present, LiFePO ₄low range characteristic perplexing its application always, especially, under an urgent demand of large power, electrically electrical automobile application demand high-rate charge-discharge capability, improve LiFePO ₄the urgent task of chemical property is to improve its high rate performance.At present, people are mainly improved specific conductivity, are improved its high rate performance by modes such as doping, coated, morphology control.

The high rate performance of battery also depends on transporting of current carrier in electrode, electrolytic solution, and lithium ion exchanged occurs in material interface, and battery performance also depends on the surface topography of electrode materials.Battery performance depends on the electrochemical reaction dynamic process of electrode materials, and this dynamic process is subject to the control of electro-chemical reaction equations, reaction table area and carrier diffusion speed.Due to LiFePO ₄electrochemical reaction is definite, and the rate of diffusion of reaction table area and current carrier is controlled becomes the important solution route that improves its battery performance.Small-particle provides high-specific surface area, short diffusion length, thereby its chemical property obviously improves.Short grained eutectic area will be narrower, is conducive to form sosoloid, improves its specific conductivity.Yet nano particle can increase reactive behavior, this will reduce the stability of battery.There is the electrode materials of granularity in the middle of reporting to show better battery performance.

Porous nano Si-C composite material is applied to power cell, can make battery storage electric weight be promoted to 3 times of conventional batteries, is regarded as the major technological breakthrough in power cell field.In recent years, porous LiFePO ₄because its specific surface area is large, accelerate lithium ion transmission route, improve the power density of material and receive much concern, improve the battery performance etc. of material.Recently have and report that the micron electrode materials ratio nano particle performance with nanoporous goes out more excellent battery performance.

From above-mentioned LiFePO ₄analysis on development, low range performance is restriction LiFePO ₄one of bottleneck of development, and high rate performance depends on the dynamic process discharging and recharging.Morphology control is the crucial controlling factor that solves high-rate charge-discharge capability; Porous material can effectively be avoided the reunion, insecurity of nano particle etc., has reduced lithium ion solid-state diffusion path simultaneously, is conducive to improve material use efficiency, increase capacity, improves the performance of the high power charging-discharging of material.Porous LiFePO ₄preparation technology's research plays an important role for its industrialization promotion.

Summary of the invention

LiFePO ₄powder preparation method, its synthesis step is as follows:

(1) preparing metal solion: the LiNO that is 1: 1 by mol ratio ₃and Fe (NO ₃) ₃9H ₂o is dissolved in water, the concentration range 0.40～0.84mol/L of lithium ion in solution, the concentration range 0.40～0.80mol/L of iron ion; (2) in solution, add phosphate anion: according to the mol ratio of iron ion and phosphate anion 1: 1, primary ammonium phosphate (or Secondary ammonium phosphate) is dissolved in above-mentioned solution.(3) solution stirring temperature-rise period adds monomer (acrylamide) and linking agent (N-N methylene-bisacrylamide): solution stirring is heated to 80 ℃, in temperature-rise period, add monomer and linking agent, every 100mL solution adds monomer 3-6g, and linking agent adds according to 20% of monomer mass.(4) in step 4, add initiator, form gel: when monomer and linking agent dissolve completely, after 80 ℃ of temperature are above, every 100mL solution adds initiator (optional Diisopropyl azodicarboxylate or ammonium persulphate) 0.01～0.05g.Remain on 85 ℃ of constant temperature until form gel.(5) fast dewatering: gel is heated at 200～300 ℃, and fast dewatering, obtains xerogel.(6) roasting obtains LiFePO ₄precursor powder: by xerogel roasting 5～15 hours at 500～700 ℃, obtain porous LiFePO ₄powder.

Accompanying drawing explanation:

Fig. 1 is the specific embodiments LiFePO that for example prepared by a technique ₄the XRD figure spectrum of porous powder, by obtaining the LiFePO of pure phase under this technique of XRD figure spectrum confirmation ₄powder.Fig. 2 is the specific embodiments LiFePO that for example prepared by a technique ₄powder porous pattern (SEM photo), left figure has confirmed that powder granule, at tens microns, exists a large amount of holes on particle, has micron-sized macropore, also has the aperture of submicron order; In the enlarged view of right figure, can find out, in micron-sized macropore, cover has submicron order or nano level aperture.

Fig. 3 is the specific embodiments LiFePO that for example prepared by two techniques ₄the XRD figure spectrum of porous powder, by obtaining the LiFePO of pure phase under this technique of XRD figure spectrum confirmation ₄powder.Fig. 4 is the specific embodiments LiFePO that for example prepared by two techniques ₄powder porous pattern (SEM photo), left figure has confirmed that powder granule is still at tens microns, on particle, hole obviously reduces (with Fig. 2 contrast), has micron-sized macropore, also has the aperture of submicron order; In the enlarged view of right figure, can find out, in micron-sized macropore, cover has submicron order or nano level aperture.

Fig. 5 is the specific embodiments LiFePO that for example prepared by three techniques ₄the XRD figure spectrum of porous powder, by obtaining the LiFePO of pure phase under this technique of XRD figure spectrum confirmation ₄powder.Fig. 6 is the specific embodiments LiFePO that for example prepared by three techniques ₄powder porous pattern (SEM photo), left figure has confirmed that powder granule, at tens microns, exists a large amount of holes on particle, but the size in hole is less than the size of Fig. 2 mesopore; In the enlarged view of right figure, can find out, in micron-sized macropore, cover has submicron order or nano level aperture.

Known by Fig. 1-Fig. 6, can be by controlling synthesis technologic parameter as temperature, concentration, the porous form of regulation and control particle.

Specific embodiments is given an example:

Specific embodiments gives an example one:

(1) preparing metal solion; By the LiNO of 0.02mol ₃fe (NO with 0.02mol ₃) ₃9H ₂o is dissolved in 50mL water, and concentration of metal ions is 0.4mol/L; (2) in solution, add phosphate anion: according to the mol ratio of iron ion and phosphate anion 1: 1, primary ammonium phosphate is dissolved in above-mentioned solution.(3) solution stirring temperature-rise period adds acrylamide and N-N methylene-bisacrylamide: in solution stirring heat-processed, to solution, add acrylamide 3g, N-N methylene-bisacrylamide 0.6g.(4) in step 4, add ammonium persulphate, form gel: when acrylamide and N-N methylene-bisacrylamide dissolve completely, after 80 ℃ of temperature, to solution, add ammonium persulphate 0.02g.Remain on 85 ℃ of constant temperature until form gel.(5) fast dewatering: gel is heated at 250 ℃, and fast dewatering, obtains xerogel.(6) LiFePO is prepared in roasting ₄powder: xerogel is put into N ₂in gas protection tube furnace, 600 ℃ of roastings 10 hours, obtain LiFePO ₄powder.

The precursor powder that this scheme obtains be LiFePO ₄pure phase, the XRD figure spectrum by Fig. 1 is confirmed, Fig. 2 shows LiFePO under this technique ₄powder porous pattern.

Specific embodiments gives an example two:

(1) preparing metal solion; By the LiNO of 0.02mol ₃fe (NO with 0.02mol ₃) ₃9H ₂o is dissolved in 50mL water, and concentration of metal ions is 0.4mol/L; (2) in solution, add phosphate anion: according to the mol ratio of iron ion and phosphate anion 1: 1, the primary ammonium phosphate of 0.02mol is dissolved in above-mentioned solution.(3) solution stirring temperature-rise period adds acrylamide and N-N methylene-bisacrylamide: in solution stirring heat-processed, to solution, add acrylamide 3g, N-N methylene-bisacrylamide 0.6g.(4) in step 4, add ammonium persulphate, form gel: when acrylamide and N-N methylene-bisacrylamide dissolve completely, after 80 ℃ of temperature, to solution, add ammonium persulphate 0.02g.Remain on 85 ℃ of constant temperature until form gel.(5) fast dewatering: gel is heated at 250 ℃, and fast dewatering, obtains xerogel.(6) LiFePO is prepared in roasting ₄powder: xerogel is put into N ₂in gas protection tube furnace, 700 ℃ of roastings 10 hours, obtain LiFePO ₄powder.

The precursor powder that this scheme obtains be LiFePO ₄pure phase, the XRD figure spectrum by Fig. 3 is confirmed, Fig. 4 shows LiFePO under this technique ₄powder porous pattern.

Specific embodiments gives an example three:

(1) preparing metal solion; By the LiNO of 0.03mol ₃fe (NO with 0.03mol ₃) ₃9H ₂o is dissolved in 50mL water, and concentration of metal ions is 0.6mol/L; (2) in solution, add phosphate anion: according to the mol ratio of iron ion and phosphate anion 1: 1, primary ammonium phosphate is dissolved in above-mentioned solution.(3) solution stirring temperature-rise period adds acrylamide and N-N methylene-bisacrylamide: in solution stirring heat-processed, to solution, add acrylamide 3g, N-N methylene-bisacrylamide 0.6g.(4) in step 4, add ammonium persulphate, form gel: when acrylamide and N-N methylene-bisacrylamide dissolve completely, after 80 ℃ of temperature, to solution, add ammonium persulphate 0.02g.Remain on 85 ℃ of constant temperature until form gel.(5) fast dewatering: gel is heated at 250 ℃, and fast dewatering, obtains xerogel.(6) LiFePO is prepared in roasting ₄powder: xerogel is put into N ₂in gas protection tube furnace, 600 ℃ of roastings 10 hours, obtain LiFePO ₄powder.

The precursor powder that this scheme obtains be LiFePO ₄pure phase, the XRD figure spectrum by Fig. 5 is confirmed, Fig. 6 shows LiFePO under this technique ₄powder porous pattern.

Claims

1. a porous LiFePO ₄powder preparation method, is characterized in that synthesis step is as follows:

(1) preparing metal solion; By the LiNO of 0.03mol ₃fe (NO with 0.03mol ₃) ₃9H ₂o is dissolved in 50mL water, and concentration of metal ions is 0.6mol/L; (2) in solution, add phosphate anion: according to the mol ratio 1:1 of iron ion and phosphate anion, primary ammonium phosphate is dissolved in above-mentioned solution; (3) solution stirring temperature-rise period adds acrylamide and N-N methylene-bisacrylamide: in solution stirring heat-processed, to solution, add acrylamide 3g, N-N methylene-bisacrylamide 0.6g; (4) in step 3, add ammonium persulphate, form gel: when acrylamide and N-N methylene-bisacrylamide dissolve completely, after 80 ℃ of temperature, to solution, add ammonium persulphate 0.02g, remain on 85 ℃ of constant temperature until form gel; (5) fast dewatering: gel is heated at 250 ℃, and fast dewatering, obtains xerogel; (6) LiFePO is prepared in roasting ₄powder: xerogel is put into N ₂in gas protection tube furnace, 600 ℃ of roastings 10 hours, obtain LiFePO ₄powder.