CN102790215A - Preparation process of lithium iron phosphate materials with complete carbon-coated structures - Google Patents
Preparation process of lithium iron phosphate materials with complete carbon-coated structures Download PDFInfo
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- CN102790215A CN102790215A CN201210294198XA CN201210294198A CN102790215A CN 102790215 A CN102790215 A CN 102790215A CN 201210294198X A CN201210294198X A CN 201210294198XA CN 201210294198 A CN201210294198 A CN 201210294198A CN 102790215 A CN102790215 A CN 102790215A
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Abstract
The invention relates to a preparation method of lithium ion battery anode materials, in particular to a preparation method of lithium iron phosphate materials with complete carbon-coated structures. The preparation method includes: uniformly mixing iron phosphate with lithium carbonate or lithium hydroxide, and then feeding reducing gas to a sealed electric furnace for sintering so that pure-phase lithium iron phosphate is prepared; crushing the pure-phase lithium iron phosphate, and soaking the crushed pure-phase lithium iron phosphate in solution containing carbon source precursors prior to drying, so that each crystal particle is coated by the carbon source precursors; and performing second sintering in the electric furnace to enable a carbon source to crack, so that required completely carbon-coated lithium iron phosphate structures are formed. The lithium iron phosphate materials with the complete carbon-coated structures are prepared by two-step sintering, compact lithium iron phosphate crystals are positioned in the centers of the lithium iron phosphate materials, and the lithium iron phosphate materials are uniformly and completely coated with nano carbon, so that compaction of the materials can be achieved, diffusion distance of lithium ions is shortened, rate of the lithium iron phosphate materials is increased, and low-temperature performance of the lithium iron phosphate materials is improved.
Description
Technical field
Technical scheme of the present invention relates to a kind of preparation method of anode material for lithium-ion batteries, specifically a kind of preparation method with LiFePO 4 material of complete carbon-coating clad structure.
Background technology
LiFePO 4 material is the power lithium-ion battery positive electrode that occurs and obtain extensive commercial application in recent years.This positive electrode has special benefits such as fail safe is good, crystal structure is firm, aboundresources, discharge platform is stable and have extended cycle life.But traditional LiFePO 4 material can not directly use, and must carry out carbon and coat.Chief reason is that the conductivity of LiFePO 4 material is very low, and near insulator, the transmission therein of lithium ion and electronics is difficulty very.In order to improve electric conductivity and lithium ion transmission performance, must there be the firm carbon-coating of combination on the LiFePO4 surface, and promptly carbon coating layer could be realized the excellence performance of LiFePO 4 material performance.
Tradition is made in the LiFePO4 process, all adopts molysite, phosphate and lithium salts to synthesize.In building-up process, directly add carbon source, for example glucose etc. decomposes it in heating process, forms carbon coating layer.Glucose at high temperature at first dissolves formation caramel, further is cracked into carbon again.In this process, carbon can not intactly be coated on the surface of LiFePO4 crystal.Often occur not by the zone of carbon coating.Therefore the cycle performance of material receives very big restriction, does not usually reach 2,000 times cycle life.Carbon sources such as glucose also can be distributed between crystal with state of aggregation, form the carbon agglomerate of bulk, have reduced the bulk density of material, have reduced the available capacity of material.No matter be ferrous oxalate method or carbon thermal reduction manufactured LiFePO 4 material, all exist above problem.
The LiFePO4 industry of China has become bigger industry.But the product of each producer is also unstable.The performance of products fluctuation is a ubiquitous problem in the industry, and this problem and carbon source technology are closely related.What coat is better, and the performance of LiFePO4 just performance is better; Coat badly, the combination property of LiFePO4 is just poor.In order to realize the stable manufacturing of material, must make the carbon coating technology obtain stable performance performance.
Optimum structure should be that the surface of LiFePO 4 material has carbon coating layer, and inside have carbon, could realize the maximization of density of material.Simultaneously, the carbon coating layer on surface should be thin more, densification is good more more.This just requires the presoma of carbon source must have These characteristics, can complete parcel LiFePO4 crystal grain, and can not be very thick.How preparing above LiFePO4 optimum structure, is the problem that the present invention proposes.
Summary of the invention
The present invention provides a kind of preparation method with LiFePO 4 material of complete carbon-coating clad structure, and the LiFePO 4 material that solves existing prepared is because of the bad cycle performance that causes of carbon covered effect, bulk density and the unfavorable defective of available capacity.
Technical scheme of the present invention may further comprise the steps:
(1), after being mixed, ferric phosphate and lithium source carry out the once sintered pure phase lithium iron phosphate that obtains;
(2), pure phase lithium iron phosphate pulverized the back immerse the carbon source precursor liquid solution, mix the back drying and obtain powder, make each crystal grain all superscribe the carbon source precursor body; And the weight of carbon source precursor body is 5 ~ 30% of ferric phosphate weight in the carbon source precursor liquid solution;
(3), powder is carried out the LiFePO 4 material that double sintering obtains having the complete packet coating.
Such scheme also comprises following optimal way:
Lithium source in the said step (1) is lithium carbonate or lithium hydroxide, and the mol ratio of lithium ion is 1 in ferric phosphate and the lithium source: (0.95 ~ 1.05); Once sintered in the said step (1) is 550 ~ 800 ℃ of sintering of control temperature 3 ~ 24 hours in the atmosphere protection electric furnace; Wherein protective atmosphere adopts the mist of nitrogen and hydrogen or carbon monoxide, and hydrogen or the ratio of carbon monoxide in mist are 1 ~ 50%.
Carbon source precursor liquid solution in the said step (2) is the aqueous solution of glucose, sucrose, xylitol or the sorbierite of mass concentration 1 ~ 20%; Powder granularity after pulverizing in the said step (2) is 0.5-10um.
Double sintering temperature in the said step (3) is that 550 ~ 800 ℃, time are 0.5 ~ 10 hour; The carbon-coating thickness of the LiFePO 4 material with complete packet coating in the said step (3) is no more than 100nm.
The present invention is different from the technology of traditional once sintered manufacturing LiFePO4; Being divided into for two steps carries out the LiFePO 4 material with complete carbon coating layer that sintering makes; Its center is fine and close LiFePO4 crystal, and appearance is evenly intactly coating the nanometer carbon-coating, can realize the densification of material; Reduce the diffusion length of lithium ion, increase the multiplying power and the cryogenic property of LiFePO 4 material; In charge and discharge process subsequently, conduction electron and lithium ion effectively.Utilize present technique, the cycle life of LiFePO 4 material is brought up to more than 4,000 times from 2,000 times;-20 ℃ of 0.5C discharge capacities are brought up to about 50% from about 30%; The discharge capability of material is brought up to 40C from 10C; The 1C discharge voltage plateau improves about 0.15V simultaneously, has effectively improved the high-rate discharge ability of material.
Embodiment
Embodiment 1
150.85Kg ferric phosphate and 36.95Kg lithium carbonate (mol ratio is 1:1) are mixed, be placed on sintering in the atmosphere protection electric furnace.Protective atmosphere adopts the mist of 95% nitrogen+5% hydrogen.Sintering temperature is 550 ℃, and sintering time is 24 hours.The LiFePO4 that sintering obtains is ground into the powder of 0.5 μ m, immerses in the aqueous solution that is made into by 160Kg water, 40Kg glucose, mixes, dry oven dry.Dried powder is carried out sintering 1 hour at 800 ℃, obtain having the LiFePO 4 material of complete packet coating.
Embodiment 2
150.85 Kg ferric phosphates and 38.79Kg lithium carbonate (mol ratio is 1:1.05) are mixed, be placed on sintering in the atmosphere protection electric furnace.Protective atmosphere adopts the mist of 80% nitrogen+20% carbon monoxide.Sintering temperature is 800 ℃, and sintering time is 3 hours.The LiFePO4 that sintering obtains is ground into the powder about 10 μ m, immerses in the aqueous solution that is made into by 180Kg water, 20Kg sucrose, mixes, dry oven dry.Dried powder is carried out sintering 4 hours at 550 ℃, obtain having the LiFePO 4 material of complete packet coating.
Embodiment 3
1508.5 Kg ferric phosphates and 227.4Kg lithium hydroxide are mixed, be placed on sintering in the atmosphere protection electric furnace.Protective atmosphere adopts 90% nitrogen+10% hydrogen gas mixture.Sintering temperature is 750 ℃, and sintering time is 6 hours.The LiFePO4 that sintering obtains is ground into the powder about 5 μ m, immerses in the aqueous solution that is made into by 800Kg water, 75.43Kg sucrose, mixes, dry oven dry.Dried powder is carried out sintering 4 hours at 550 ℃, obtain having the LiFePO 4 material of complete packet coating.
Embodiment 4
On the basis of embodiment 1, only change protective atmosphere into the mist of employing 50% nitrogen+50% hydrogen or the mist of 99% nitrogen+1% carbon monoxide, thereby obtain having the LiFePO 4 material of complete packet coating.
Embodiment 5
On the basis of embodiment 2, only change the carbon source precursor body into xylitol or sorbierite by sucrose, thereby obtain having the LiFePO 4 material of complete packet coating.
Embodiment 6
On the basis of embodiment 2, only " dried powder was carried out sintering 4 hours at 550 ℃ " changed into " dried powder was carried out sintering 10 hours at 675 ℃ ", thereby obtain having the LiFePO 4 material of complete packet coating.
LiFePO 4 material to the complete packet coating of embodiment 1-6 preparation detects, and its center of empirical tests is fine and close LiFePO4 crystal, and its appearance is evenly intactly coating the nanometer carbon-coating that thickness is no more than 100nm; And the cycle life of LiFePO 4 material is brought up to more than 4,000 times from 2,000 times;-20 ℃ of 0.5C discharge capacities are brought up to about 50% from about 30%; The discharge capability of material is brought up to 40C from 10C; The 1C discharge voltage plateau improves about 0.15V simultaneously, has effectively improved the high-rate discharge ability of material.
Claims (6)
1. LiFePO 4 material preparation technology with complete carbon-coating clad structure is characterized in that concrete steps are:
(1), after being mixed, ferric phosphate and lithium source carry out the once sintered pure phase lithium iron phosphate that obtains;
(2), pure phase lithium iron phosphate pulverized the back immerse the carbon source precursor liquid solution, mix the back drying and obtain powder; And the weight of carbon source precursor body is 5 ~ 30% of ferric phosphate weight in the carbon source precursor liquid solution;
(3), powder is carried out the LiFePO 4 material that double sintering obtains having the complete packet coating.
2. the LiFePO 4 material preparation technology with complete carbon-coating clad structure according to claim 1; It is characterized in that; Lithium source in the said step (1) is lithium carbonate or lithium hydroxide, and the mol ratio of lithium ion is 1 in ferric phosphate and the lithium source: (0.95 ~ 1.05); Once sintered in the said step (1) is 550 ~ 800 ℃ of sintering of control temperature 3 ~ 24 hours in the atmosphere protection electric furnace; Wherein protective atmosphere adopts the mist of nitrogen and hydrogen or carbon monoxide, and hydrogen or the ratio of carbon monoxide in mist are 1 ~ 50%.
3. the LiFePO 4 material preparation technology with complete carbon-coating clad structure according to claim 1 and 2 is characterized in that the carbon-coating thickness of the LiFePO 4 material with complete packet coating in the said step (3) is no more than 100nm.
4. the LiFePO 4 material preparation technology with complete carbon-coating clad structure according to claim 1 and 2; It is characterized in that the carbon source precursor liquid solution in the said step (2) is the aqueous solution of glucose, sucrose, xylitol or the sorbierite of mass concentration 1 ~ 20%; Powder granularity after pulverizing in the said step (2) is 0.5-10um.
5. the LiFePO 4 material preparation technology with complete carbon-coating clad structure according to claim 4 is characterized in that, the double sintering temperature in the said step (3) is that 550 ~ 800 ℃, time are 0.5 ~ 10 hour.
6. the LiFePO 4 material preparation technology with complete carbon-coating clad structure according to claim 5 is characterized in that the carbon-coating thickness of the LiFePO 4 material with complete packet coating in the said step (3) is no more than 100nm.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103474639A (en) * | 2013-09-08 | 2013-12-25 | 江西江特锂电池材料有限公司 | Lithium-enriched manganese-based positive pole material and preparation method thereof |
| CN104282886A (en) * | 2014-10-14 | 2015-01-14 | 江苏华东锂电技术研究院有限公司 | Carbon coating method for electrode active material of lithium ion battery |
| CN110224128A (en) * | 2019-06-21 | 2019-09-10 | 南京农业大学 | Cobalt acid zinc nano-array material of a kind of PVA pyrolysis carbon coated and preparation method thereof, application |
| CN114162802A (en) * | 2021-12-08 | 2022-03-11 | 河北绿草地新能源股份有限公司 | Method for manufacturing nano lithium iron phosphate positive electrode material with ultralow temperature charge-discharge performance |
| US20230170481A1 (en) * | 2021-02-09 | 2023-06-01 | Btr (Tianjin) Nano Material Manufacture Co., Ltd. | Lithium iron phosphate, preparation method therefor, and lithium-ion battery |
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| CN101830453A (en) * | 2010-05-27 | 2010-09-15 | 谢朝华 | Secondary sintering synthesis method for lithium iron phosphate |
| CN102569794A (en) * | 2011-03-23 | 2012-07-11 | 江苏菲思特新能源有限公司 | Carbon-coating method for lithium iron phosphate anode material |
| CN102556998A (en) * | 2011-12-23 | 2012-07-11 | 彩虹集团公司 | Preparation method of lithium iron phosphate material |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103474639A (en) * | 2013-09-08 | 2013-12-25 | 江西江特锂电池材料有限公司 | Lithium-enriched manganese-based positive pole material and preparation method thereof |
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| CN104282886A (en) * | 2014-10-14 | 2015-01-14 | 江苏华东锂电技术研究院有限公司 | Carbon coating method for electrode active material of lithium ion battery |
| CN104282886B (en) * | 2014-10-14 | 2016-10-12 | 江苏华东锂电技术研究院有限公司 | The carbon method for coating of lithium ion battery electrode active material |
| CN110224128A (en) * | 2019-06-21 | 2019-09-10 | 南京农业大学 | Cobalt acid zinc nano-array material of a kind of PVA pyrolysis carbon coated and preparation method thereof, application |
| US20230170481A1 (en) * | 2021-02-09 | 2023-06-01 | Btr (Tianjin) Nano Material Manufacture Co., Ltd. | Lithium iron phosphate, preparation method therefor, and lithium-ion battery |
| CN114162802A (en) * | 2021-12-08 | 2022-03-11 | 河北绿草地新能源股份有限公司 | Method for manufacturing nano lithium iron phosphate positive electrode material with ultralow temperature charge-discharge performance |
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Application publication date: 20121121 |