CN101519195A

CN101519195A - Preparation method of high-density non-ball shape ferric phosphate powder body

Info

Publication number: CN101519195A
Application number: CN200910064455A
Authority: CN
Inventors: 常照荣; 吕豪杰; 汤宏伟; 李华吉; 李苞
Original assignee: Henan Normal University
Current assignee: Henan Normal University
Priority date: 2009-03-24
Filing date: 2009-03-24
Publication date: 2009-09-02

Abstract

The invention discloses a preparation method of a high-density non-ball shape ferric phosphate powder body which relates to a ferric compound. The invention aims to provide the preparation method of a high-density non-ball shape ferric phosphate powder body, and the ferric phosphate prepared by the method has high jolt density, small granule size and high specific surface area. The adopted technical scheme is as follows: a mixed water solution with a certain concentration of (FeNO3)3.9H2O and H3PO4 is prepared, (the mole ratio of Fe and P is 0.9:1.0); the mixed water solution is placed into a reactor, an ammonia solution is gradually added under a certain temperature and agitation until the pH value of the reaction liquid reaches 1 to 4 to obtain ferric phosphate slurry; the slurry is injected into a plate and frame filter press to obtain a filtered cake by pressing and filtration, the filtered cake is dried, soluble impurity ions are removed by water washing, and the washed material is dried again, pulverized and sieved to obtain the ferric phosphate powder body. The invention is used for the anode material of lithium ion batteries.

Description

A kind of preparation method of high-density non-ball shape ferric phosphate powder body

Technical field:

The invention belongs to a kind of compound of iron, particularly a kind of high-density tertiary iron phosphate (FePO ₄) preparation method of powder.

Technical background:

Olivine-type LiFePO 4 LiFePO ₄Have nontoxicly, environmentally friendly, safety performance is good, has stable high-temperature performance abundant raw materials, low price, specific storage height (170mA.h.g ^-1) and advantage such as good cycle, be expected to replace the higher LiCoO of cost ₂Become anode material for lithium-ion batteries of new generation.But there are two main drawbacks in LiFePO 4, the one, and extremely low electronic conductivity and diffusion of protons speed cause high-rate charge-discharge capability poor, and actual specific capacity is low; The 2nd, tap density is low, causes volume and capacity ratio low, and these two shortcomings have hindered the practicalization of this material.In recent years, people mixed Mg by to LiFePO 4 particle surface coated with conductive carbon material or conductive metal particle to the LiFePO 4 intracell ²⁺, Cu ²⁺, Al ³⁺, Ti ⁴⁺And Zr ⁴⁺Plasma improves electronic conductivity and diffusion of protons speed, perhaps adopts method such as collosol and gel to make the LiFePO 4 particle reach nano level, shortens the diffusion admittance of ion in solid phase, and these measures have solved the low problem of material electric conductivity basically.But for the low shortcoming bibliographical information of tap density seldom, commodity LiCoO ₂Tap density be generally 2.0-2.6g.cm ^-3, and the tap density of LiFePO 4 only is 1.1-1.3g.cm ^-3, low tap density makes the volume and capacity ratio of electrode reduce greatly, also makes the advantage of this material have a greatly reduced quality, therefore, the tap density that improves LiFePO 4 has the decision meaning to its practicability.

According to bibliographical information, solid-phase synthesis is adopted in synthesizing of LiFePO 4 mostly, material ball millings such as lithium salts, divalent iron salt and phosphoric acid salt is mixed to be placed under the protection of inert gas forming through high temperature sintering.In order to improve material homogeneity and to reduce cost, a lot of documents adopt the raw material of tertiary iron phosphate as synthesizing lithium ferrous phosphate, for example: CN101172594A, CN101172595A, CN101237042A, CN1800003A, reports such as CN101237043A or related to the preparation of tertiary iron phosphate, these methods not only relate to adds oxygenant, tensio-active agent etc., and the tertiary iron phosphate tap density of preparing is low, can not effectively improve the tap density of ferrousphosphate lithium material.CN101244813A has reported by the alkali formula ammonium ferric phosphate that synthesizes and has obtained tertiary iron phosphate than high tap density through high temperature sintering again, but complex process, energy consumption is higher.CN101337666A has reported by the method for spherical hypophosphite monohydrate iron as the spherical high-density LiFePO 4 of feedstock production, with divalent iron salt and phosphoric acid mixed solution, ammoniacal liquor, materials such as oxygenant according to dosage pump into simultaneously reactor continuously, strict control pH value and temperature of reaction, material overflows from the reactor outlet, makes ball shape ferric phosphate.Because iron phosphate grains pattern spherical in shape has higher tap density, can make the LiFePO 4 that synthesizes have higher tap density as raw material.But this ball shape ferric phosphate preparation process condition is comparatively harsh, and the spheroidal particle particle diameter is bigger, and specific surface is less, causes the diffusion admittance lengthening of lithium ion in solid phase, and the solid-liquid contact surface is little, has influenced the LiFePO 4 high rate during charging-discharging.

Summary of the invention

The preparation method who the purpose of this invention is to provide a kind of high-density non-ball shape ferric phosphate powder body, with the ferric phosphate powder body tap density height of this method preparation, particle diameter is little, and specific surface is big.Technical scheme of the present invention is, a kind of preparation method of high-density non-ball shape ferric phosphate powder body, it is characterized in that: include following operation: the preparation of (1) solution, by the Fe:P mol ratio is 0.9:1.0 preparation solubility trivalent iron salt and phosphoric acid mixed aqueous solution, and the trivalent soluble ferric iron salt is selected from any of nitrate, vitriol and hydrochloride and acetate; (2) chemical reaction, after elder generation put into reactor with above-mentioned mixing solutions, temperature was controlled at 30-80 ℃, under agitation adds ammonia soln gradually, and pH value is controlled at 1.0-4.0, and reaction generates FePO ₄Gum size; (3) slurry that generates is squeezed into plate-and-frame filter press with pump, obtain filter cake through press filtration; (4) with filter cake 80-140 ℃ of drying, the soluble impurity ion is removed in washing then; (5) material after the washing is dried under 80-140 ℃ of condition, and crushing screening obtains high-density non-ball shape hypophosphite monohydrate iron powder body.(6) Hong Gan material can obtain anhydrous iron phosphate 500-600 ℃ of following dehydration.

Adopt the technology of the present invention route synthetic ferric phosphate powder body to be aspherical particle, particle diameter is little, specific surface area is big, the tap density height, the reactive behavior height, lithium ferrous phosphate as anode material of lithium ion battery as the presoma preparation has high tap density, can improve the volume and capacity ratio of material greatly; And the selected prices of raw and semifnished materials of the technology of the present invention are low, technology simple controllable, environmental friendliness.

Description of drawings:

Fig. 1 is the x-ray diffraction pattern of embodiment sample anhydrous phosphoric acid iron powder body

Fig. 2 is the x-ray diffraction pattern of LiFePO 4

Embodiment:

In conjunction with following example the present invention is elaborated,

Embodiment 1

(1) solution preparation, preparation 1..0mol.dm ^-3Fe (NO ₃) ₃.9H ₂O and H ₃PO ₄Mixed aqueous solution (the Fe:P mol ratio is 0.9:1.0).

(2) above-mentioned mixing solutions is put into reactor, temperature of reaction is set in 50 ℃, under agitation adds ammonia soln (ammonia concn is 25%) gradually and reaches till 1.5 up to reacting liquid pH value, continues reaction 2h then, obtains the tertiary iron phosphate slurry.

(3) slurry is squeezed into plate-and-frame filter press, pressurize 10h obtains filter cake under 0.5Mpa.

(4) with filter cake dry 8h under 120 ℃ of conditions, the soluble impurity ion is removed in washing then.

(5) material of cleaning is dry under 120 ℃ of conditions again, crushing screening obtains the hypophosphite monohydrate iron powder body, tap density 1.55g.cm then ^-3

(6) with hypophosphite monohydrate iron at 550 ℃ of sintering 8h, obtain the anhydrous phosphoric acid iron powder body.

The anhydrous product tap density of this example is 1.65g.cm ^-3, particle diameter 0.2-5um, specific surface area 56m ².g ^-1, with Li ₂CO ₃, glucose and ferric phosphate powder body press certain mol proportion example mixed grinding, at Ar ₂(95%) and H ₂(5%) the following 750 ℃ of sintering 20h of atmosphere obtain the LiFePO of carbon content 3.0wt% ₄/ C sample, its tap density 2.15g.cm ^-3, volume and capacity ratio reaches 270mA.h.cm ^-3(0.2C multiplying power discharging).Under the similarity condition, adopting the hypophosphite monohydrate iron powder body is the LiFePO that raw material makes carbon content 3.0wt% ₄The tap density of/C sample is 2.08g.cm ^-3, volume and capacity ratio reaches 265mA.h.cm ^-3(0.2C multiplying power discharging).

Embodiment 2

(1) solution preparation, preparation 2.0mol.dm ^-3Fe ₂(SO ₄) ₃And H ₃PO ₄Mixed aqueous solution (the Fe:P mol ratio is 0.9:1.0).

(2) above-mentioned mixing solutions is put into reactor, temperature of reaction is set in 70 ℃, under agitation adds ammonia soln (ammonia concn is 12.5%) gradually and reaches till 2.5 up to reacting liquid pH value, continues reaction 2h then, obtains the tertiary iron phosphate slurry.

(3) slurry is squeezed into plate-and-frame filter press, pressurize 5h obtains filter cake under 0.8Mpa.

(4) with filter cake dry 6h under 130 ℃ of conditions, the soluble impurity ion is removed in washing then.

(5) material of cleaning is dry under 100 ℃ of conditions again, crushing screening obtains the hypophosphite monohydrate iron powder body, tap density 1.45g.cm then ^-3

(6) with hypophosphite monohydrate iron at 500 ℃ of sintering 10h, obtain the anhydrous phosphoric acid iron powder body.

This example anhydrous iron phosphate product tap density is 1.62g.cm ^-3, particle diameter 0.5-7um, specific surface area 45m ².g ^-1, with Li ₂CO ₃, glucose and ferric phosphate powder body press certain mol proportion example mixed grinding, at Ar2 (95%) and H ₂(5%) the following 750 ℃ of sintering 20h of atmosphere obtain the LiFePO of carbon content 3.0wt% ₄/ C sample, its tap density 2.01g.cm ^-3, volume and capacity ratio reaches 255mA.h.cm ^-3(0.2C multiplying power discharging).

Comparative example 1

Preparation 1.0mol.dm ^-3Fe (NO ₃) ₃.9H ₂O and H ₃PO ₄Mixed aqueous solution (the Fe:P mol ratio is 0.9:1.0).Above-mentioned mixing solutions is put into reactor, and temperature of reaction is set in 50 ℃, under agitation adds ammonia soln (ammonia concn is 25%) gradually and reaches till 1.5 up to reacting liquid pH value, continues reaction 2h then, obtains the tertiary iron phosphate slurry.Foreign ion is removed in the direct washing of slurry, dry under 120 ℃ of conditions, obtain the hypophosphite monohydrate iron powder body through crushing screening, again through 550 ℃ of sintering 8h, obtain the anhydrous phosphoric acid iron powder body and obtain comparative sample, its tap density is 1.04g.cm ^-3, particle diameter 0.3-8um, specific surface area 48m ².g ^-1, with Li ₂CO ₃, glucose and ferric phosphate powder body press certain mol proportion example mixed grinding, at Ar ₂(95%) and H ₂(5%) the following 750 ℃ of sintering 20h of atmosphere obtain the LiFePO of carbon content 3.0wt% ₄/ C sample, its tap density 1.36g.cm ^-3, volume and capacity ratio reaches 200mA.h.cm ^-3(0.2C multiplying power discharging).

Claims

1, a kind of preparation method of high-density non-ball shape ferric phosphate powder body is characterized in that: include following operation:

(1) solution preparation is 0.9:1.0 preparation solubility trivalent iron salt and phosphoric acid mixed aqueous solution by the Fe:P mol ratio, and the trivalent soluble ferric iron salt is selected from any of nitrate, vitriol and hydrochloride and acetate;

(2) chemical reaction, after elder generation put into reactor with above-mentioned mixing solutions, temperature was controlled at 30-80 ℃, under agitation adds ammonia soln gradually, and pH value is controlled at 1.0-4.0, and reaction generates FePO ₄Gum size;

(3) slurry that generates is squeezed into plate-and-frame filter press with pump, obtain filter cake through press filtration;

(4) with filter cake 100-140 ℃ of drying, the soluble impurity ion is removed in washing then;

(5) material after the washing is dried under 80-140 ℃ of condition, and crushing screening obtains high-density non-ball shape hypophosphite monohydrate iron powder body.

(6) Hong Gan material can obtain anhydrous iron phosphate 500-600 ℃ of following dehydration.