CN101407319B - Method of preparing lithium iron phosphate having high conductivity and superior low temperature discharge property - Google Patents
Method of preparing lithium iron phosphate having high conductivity and superior low temperature discharge property Download PDFInfo
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- CN101407319B CN101407319B CN2008101616123A CN200810161612A CN101407319B CN 101407319 B CN101407319 B CN 101407319B CN 2008101616123 A CN2008101616123 A CN 2008101616123A CN 200810161612 A CN200810161612 A CN 200810161612A CN 101407319 B CN101407319 B CN 101407319B
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- high conductivity
- low temperature
- phosphate
- solution
- temperature discharge
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Abstract
The invention relates to a preparation method of lithium iron phosphate, in particular to a preparation method of the lithium iron phosphate having high conductivity and good low-temperature discharge performance. The method mainly aims at solving the defects of low conductivity, poor low-temperature discharge performance and the like of the lithium iron phosphate prepared by the existing method and provides the preparation method of the lithium iron phosphate having high conductivity and good low-temperature discharge performance. The main technical proposal of the preparation method is as follows: a soluble ferrous iron salt solution is adopted for mixing with a phosphoric acid solution or a soluble phosphate solution, then alkali is used for neutralization to obtain a superfine Fe3(PO4)2.xH2O precipitate with particle D50 being 1-5[mu]m, and then the precipitate is mixed with lithium phosphate and a conductive agent for sintering at high temperature.
Description
Technical field
The present invention relates to a kind of method preparing phosphate iron lithium, relate in particular to a kind of method preparing phosphate iron lithium with high conductivity and superior low temperature discharge property.
Background technology
LiFePO
4Be the preferred material of following power cell, but this material ionic conductivity and electronic conductivity are very low, are difficult to satisfy actual needs.Its major cause is the decline that preparation technology has caused material property.Method preparing phosphate iron lithium mainly contains following several at present.
Publication number is the mechanical solid phase synthesis process of a kind of lithium ion battery anode material lithium iron phosphate of CN1581537, its main method: with metal iron powder, tertiary iron phosphate, Trilithium phosphate, mix up element phosphor hydrochlorate, conductive agent or conductive agent presoma and mix in proportion, place the ball mill container of filling inert atmosphere, ball milling 18-36 hour; Gained ball milling product is put into High Temperature Furnaces Heating Apparatus, in inert atmospheres such as nitrogen or argon gas, heat up with 10-30 ℃/MIN heating rate, in 450-750 ℃ of constant temperature roast 10-60MIN, be cooled to room temperature with 10-30 ℃/MIN cooling rate then, make iron phosphate powder or mix up iron phosphate powder.
Publication number is lithium iron phosphate positive material of CN1767238 and preparation method thereof; its main method: form by iron lithium phosphate and calcium boride; press mass ratio; iron lithium phosphate: calcium boride=100: (1.01～5.26); earlier synthetic pure iron lithium phosphate during preparation: with ferrous salt, phosphoric acid salt and lithium salts; with alcohol is the lubricant ball milling, and the mixture heating up behind the ball milling is a shielding gas with the rare gas element.Synthetic iron lithium phosphate and calcium boride ball milling, the mixture calcining behind the ball milling, passing to rare gas element is shielding gas, promptly makes target product.
More than two kinds all can be described as " solid phase method " synthesizing iron lithium phosphate.The prepared iron lithium phosphate electric conductivity of its technology is low, low temperature discharge property is poor, and the application of iron lithium phosphate is produced a very large impact.
Summary of the invention
The present invention mainly is defectives such as the iron lithium phosphate electric conductivity that makes at present method is low, low temperature discharge property difference, and a kind of method preparing phosphate iron lithium with high conductivity and superior low temperature discharge property energy is provided.
Above-mentioned technical problem of the present invention is implemented by the following technical programs:
Have the method preparing phosphate iron lithium of high conductivity and superior low temperature discharge property, it may further comprise the steps:
A) prepare ultra-fine Fe
3(PO
4)
2XH
2O: at first solubility divalent iron salt solution is mixed with phosphoric acid solution or soluble phosphoric acid salts solution, blending ratio is an iron: mix phosphorus mol ratio 3:2.0～2.5, add strong base solution neutralization and stirring then in above-mentioned mixed solution fast, moment obtains ultra-fine Fe
3(PO
4)
2XH
2The O precipitation is with ultra-fine Fe
3(PO
4)
2XH
2O washing of precipitate final vacuum drying;
B) mixing raw material: with the mol ratio of 1:0.1:1 with Trilithium phosphate and conductive agent and dried ultra-fine Fe
3(PO
4)
2XH
2The O uniform mixing;
C) sintering iron lithium phosphate: the mixture that the B step is obtained sintering 0.1～20 hour in 500 ℃～800 ℃ obtains LiFePO 4 material.
Above-mentioned method preparing phosphate iron lithium with high conductivity and superior low temperature discharge property, as preferably, described ultra-fine Fe
3(PO
4)
2XH
2O deposit seeds D
50Between 1-5 μ m.
Above-mentioned method preparing phosphate iron lithium with high conductivity and superior low temperature discharge property, as preferably, the Trilithium phosphate granularity D that uses during described sintering
50(less than the grain diameter of this value account for cumulative volume 50%) at 1～5 μ m
Above-mentioned method preparing phosphate iron lithium with high conductivity and superior low temperature discharge property, as preferably, described conductive agent is sucrose or glucose etc.
Above-mentioned method preparing phosphate iron lithium with high conductivity and superior low temperature discharge property, as preferably, described iron salt solutions volumetric molar concentration is 0.1～2mol/L; Described phosphoric acid solution or soluble phosphoric acid salts solution volumetric molar concentration are 0.01～2mol/L.
Above-mentioned method preparing phosphate iron lithium with high conductivity and superior low temperature discharge property, as preferably, in the described solution and the time temperature between-20 ℃～20 ℃.
Above-mentioned method preparing phosphate iron lithium with high conductivity and superior low temperature discharge property, as preferably, described strong base solution is ammoniacal liquor or sodium hydroxide or the potassium hydroxide solution of volumetric molar concentration 0.1～10mol/L.
Can make iron lithium phosphate according to the method described above with high conductivity and superior low temperature discharge property.
Can make the lithium ion battery of lithium iron phosphate positive material according to the method described above with high conductivity and superior low temperature discharge property; Its-20 ℃/0.5C loading capacity has reached more than 80% of normal temperature.
In sum, the present invention compares with prior art and has following advantage:
The present invention adopts special process, by synthetic presoma Fe
3(PO
4)
2XH
2O obtains iron lithium phosphate, and this method can effectively reduce synthetic middle grain-size, shortens the lithium ion the evolving path, the low temperature performance of strongthener.
Synthetic iron lithium phosphate of the present invention, when effectively improving material ionic conductivity and electronic conductivity, the crystal size of control material and pattern obtain good low-temperature performance.Adopt this synthetic route crystallization grain-size can be about 30 nanometers, size distribution be even, and large current discharging capability is strong, and low-temperature performance is good, and-20 ℃/0.5C loading capacity has reached more than 80% of normal temperature, and general material has only about 70%.
Description of drawings
Fig. 1 is the SEM figure of product;
Fig. 2 is four kinds of discharge curves under the state;
Among Fig. 2 from top to bottom four curves be respectively 0.5C, 20 ℃; 0.5C, 10 ℃; 0.5C, 0.C; 0.5C, the curve in the time of-20 ℃.
Embodiment
Below by embodiment, and in conjunction with the accompanying drawings, technical scheme of the present invention is described in further detail:
Embodiment 1:
The molysite volumetric molar concentration is that the copperas solution of 0.1mol/L mixes with phosphoric acid solution, mixing condition is iron: phosphorus mol ratio 3:2.5 then in temperature-20 ℃, is that the ammoniacal liquor of 0.1mol/L neutralizes fast with the volumetric molar concentration, in and the time stirred solution accelerate in and speed, moment obtains ultra-fine Fe
3(PO
4)
2XH
2The O precipitation, ultra-fine Fe
3(PO
4)
2XH
2O deposit seeds dimension D
50At 4 μ m, with Fe
3(PO
4)
2XH
2O washing of precipitate final vacuum drying is then with 1:1:0.1 mixed in molar ratio Fe
3(PO
4)
2XH
2O, Trilithium phosphate, conductive agent, conductive agent is a sucrose, after mixing, obtains LiFePO 4 material in 20 hours with 550 ℃ of following sintering, the Trilithium phosphate particle size D that uses during sintering
50At 1 μ m.
Embodiment 2:
The molysite volumetric molar concentration is that the copperas solution of 0.25mol/L mixes with phosphoric acid solution, mixing condition is iron: phosphorus mol ratio 3:2.4 then in temperature-10 ℃, is that the ammoniacal liquor of 0.5mol/L neutralizes fast with the volumetric molar concentration, in and the time stirred solution accelerate in and speed, moment obtains ultra-fine Fe
3(PO
4)
2XH
2The O precipitation, ultra-fine Fe
3(PO
4)
2XH
2O deposit seeds dimension D
50At 3 μ m, with Fe
3(PO
4)
2XH
2O precipitates vacuum-drying, then with 1:1:0.1 mixed in molar ratio Fe
3(PO
4)
2XH
2O, Trilithium phosphate, conductive agent, conductive agent is a glucose, after mixing, obtains LiFePO 4 material in 10 hours with 600 ℃ of following sintering, the Trilithium phosphate particle size D that uses during sintering
50At 5 μ m.
Embodiment 3:
The molysite volumetric molar concentration is that the copperas solution of 0.5mol/L mixes with phosphoric acid solution, mixing condition is iron: phosphorus mol ratio 3:2.3 then 0 ℃ of temperature, is that the sodium hydroxide solution of 1mol/L neutralizes fast with the volumetric molar concentration, in and the time stirred solution accelerate in and speed, moment obtains ultra-fine Fe
3(PO
4)
2XH
2The O precipitation, ultra-fine Fe
3(PO
4)
2XH
2O deposit seeds dimension D
50At 5 μ m, with Fe
3(PO
4)
2XH
2O precipitates vacuum-drying, then with 1:1:0.1 mixed in molar ratio Fe
3(PO
4)
2XH
2O, Trilithium phosphate, conductive agent, conductive agent is a sucrose, after mixing, obtains LiFePO 4 material in 5 hours with 650 ℃ of following sintering, the Trilithium phosphate particle size D that uses during sintering
50At 3 μ m.
Embodiment 4:
The molysite volumetric molar concentration is that the copperas solution of 1mol/L mixes with phosphoric acid solution, mixing condition is iron: phosphorus mol ratio 3:2.2 then 10 ℃ of temperature, is that the potassium hydroxide solution of 5mol/L neutralizes fast with the volumetric molar concentration, in and the time stirred solution accelerate in and speed, moment obtains ultra-fine Fe
3(PO
4)
2XH
2The O precipitation, ultra-fine Fe
3(PO
4)
2XH
2O deposit seeds dimension D
50At 2 μ m, with Fe
3(PO
4)
2XH
2O precipitates vacuum-drying, then with 1:1:0.1 mixed in molar ratio Fe
3(PO
4)
2XH
2O, Trilithium phosphate, conductive agent, conductive agent is a sucrose, after mixing, obtains LiFePO 4 material in 2 hours with 700 ℃ of following sintering, the Trilithium phosphate particle size D that uses during sintering
50At 4 μ m.
Embodiment 5:
The molysite volumetric molar concentration is that the copperas solution of 1.5mol/L mixes with phosphoric acid solution, mixing condition is iron: phosphorus mol ratio 3:2.0 then 20 ℃ of temperature, is that the ammoniacal liquor of 10mol/L neutralizes fast with the volumetric molar concentration, in and the time stirred solution accelerate in and speed, moment obtains ultra-fine Fe
3(PO
4)
2XH
2The O precipitation, ultra-fine Fe
3(PO
4)
2XH
2O deposit seeds dimension D
50At 2 μ m, with Fe
3(PO
4)
2XH
2O precipitates vacuum-drying, then with 1:1:0.1 mixed in molar ratio Fe
3(PO
4)
2XH
2O, Trilithium phosphate, conductive agent, conductive agent is a glucose, after mixing, obtains LiFePO 4 material in 1 hour with 750 ℃ of following sintering, the Trilithium phosphate particle size D that uses during sintering
50At 3 μ m.
Each concentration of component of table 1 raw material
| Iron salt solutions (mol/L) | Phosphate/phosphor acid solution (mol/L) | Strong base solution (mol/L) | Neutral temperature (℃) | |
| Embodiment 1 | 0.1 | 0.083 | 0.1 | -20 |
| Embodiment 2 | 0.25 | 0.2 | 0.5 | -10 |
| Embodiment 3 | 0.5 | 0.38 | 1 | 0 |
| Embodiment 4 | 1 | 0.73 | 5 | 10 |
| |
1.5 | 1 | 10 | 20 |
Table 2 sintering process parameter table
| Sintering temperature (℃) | Sintering time (hour) | |
| Embodiment 1 | 550 | 20 |
| Embodiment 2 | 600 | 10 |
| Embodiment 3 | 650 | 5 |
| Embodiment 4 | 700 | 2 |
| |
750 | 1 |
The comparative example:
Record the grain-size of the foregoing description by the X-ray powder diffraction analysis.See Table 3.
Application examples:
The foregoing description gained material is made button cell (negative pole is the lithium metal), and its loading capacity (representative value) and low temperature capability retention see Table 3.
The low temperature capability retention: with 0.5C, the capacity in the time of 20 ℃ is set at 1, records 0.5C then, remaining capacity under-20 ℃ of conditions.
Each embodiment performance comparison table of table 3
At specific embodiment described herein only is that the present invention's spirit and part experiment are illustrated.Those skilled in the art in the invention can make various modifications or replenish or adopt similar mode to substitute described specific embodiment, but can't depart from spirit of the present invention or surmount the defined scope of appended claims.
Claims (7)
1. method preparing phosphate iron lithium with high conductivity and superior low temperature discharge property, it may further comprise the steps:
A, prepare ultra-fine Fe
3(PO
4)
2XH
2O: at first solubility divalent iron salt solution is mixed with phosphoric acid solution or soluble phosphoric acid salts solution, blending ratio is an iron: phosphorus mol ratio 3: 2.0～2.5, in above-mentioned mixed solution, add the strong base solution neutralization then fast, and moment obtains ultra-fine Fe
3(PO
4)
2XH
2The O precipitation is with ultra-fine Fe
3(PO
4)
2XH
2O washing of precipitate final vacuum drying;
B, mixing raw material: the mol ratio with 1: 1: 0.02～0.2 is with Trilithium phosphate and dried ultra-fine Fe
3(PO
4)
2XH
2O and conductive agent uniform mixing;
C, sintering iron lithium phosphate: the mixture that the B step is obtained sintering 0.1～20 hour in 500 ℃～800 ℃ obtains LiFePO 4 material.
2. the method preparing phosphate iron lithium with high conductivity and superior low temperature discharge property according to claim 1 is characterized in that, described ultra-fine Fe
3(PO
4)
2XH
2O deposit seeds dimension D
50Between 1-5 μ m.
3. the method preparing phosphate iron lithium with high conductivity and superior low temperature discharge property according to claim 1 is characterized in that, the Trilithium phosphate particle size D that uses during described the mixing
50Between 1-5 μ m.
4. the method preparing phosphate iron lithium with high conductivity and superior low temperature discharge property according to claim 1 is characterized in that, described conductive agent is sucrose or glucose.
5. the method preparing phosphate iron lithium with high conductivity and superior low temperature discharge property according to claim 1 is characterized in that, described iron salt solutions volumetric molar concentration is 0.1～2.0mol/L; Described phosphoric acid solution or soluble phosphoric acid salts solution volumetric molar concentration are 0.01～2.0mol/L.
6. according to claim 1 or 2 or 3 or 4 or 5 described method preparing phosphate iron lithium, it is characterized in that with high conductivity and superior low temperature discharge property, in the described solution and the time temperature between-20 ℃～20 ℃.
7. according to claim 1 or 2 or 3 or 4 or 5 described method preparing phosphate iron lithium, it is characterized in that described strong base solution is ammoniacal liquor or sodium hydroxide or the potassium hydroxide solution of volumetric molar concentration 0.1～10mol/L with high conductivity and superior low temperature discharge property.
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|---|---|---|---|
| CN2008101616123A CN101407319B (en) | 2008-09-16 | 2008-09-16 | Method of preparing lithium iron phosphate having high conductivity and superior low temperature discharge property |
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| Publication Number | Publication Date |
|---|---|
| CN101407319A CN101407319A (en) | 2009-04-15 |
| CN101407319B true CN101407319B (en) | 2011-04-27 |
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