CN102332564A - A kind of processing method of lithium iron phosphate material - Google Patents
A kind of processing method of lithium iron phosphate material Download PDFInfo
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- CN102332564A CN102332564A CN201010609521A CN201010609521A CN102332564A CN 102332564 A CN102332564 A CN 102332564A CN 201010609521 A CN201010609521 A CN 201010609521A CN 201010609521 A CN201010609521 A CN 201010609521A CN 102332564 A CN102332564 A CN 102332564A
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Abstract
The invention relates to the technical field of lithium ion batteries, in particular to a treatment method of a lithium iron phosphate material. Compared with the prior art, the method has the advantages that the iron impurities remained in the raw materials and the synthesis process are effectively removed by adopting the acid solution to carry out constant-temperature treatment on the lithium iron phosphate, the dissolution of iron elements in the circulation process is reduced, the circulation stability of the material is improved, the ion conductivity of the material is improved and the high rate performance of the material is improved due to the etching of the particle surface layer by the acid.
Description
Technical field:
The present invention relates to technical field of lithium ion, refer in particular to a kind of processing method of LiFePO 4 material.
Background technology:
Along with the rise of low-carbon economy, lithium ion battery is also just energetically towards direction develop activelies such as power vehicle and electrical network energy storage, but the lithium ion battery of exploitation fast charging and discharging and the harsh service condition of adaptation power vehicle becomes the emphasis of research.Anode material for lithium-ion batteries is the bottleneck of decision lithium ion battery development, and it is determining the performance and the price of lithium ion battery.Therefore, research and develop high performance anode material for lithium-ion batteries and become lithium ion battery development key place.
[the A.K.Padhi of Goodenough research group in 1997; K.S.Nanjundaswarmy, B.Goodenough, J.electrochem.SOC; 144 (1997)] synthesized LiFePO4 first; And find that this material has high theoretical specific capacity (170mAh/g) as anode material for lithium-ion batteries, and under low range, discharging and recharging, its doff lithium efficient almost can reach 100%.Positive electrodes such as LiFePO4 and cobalt acid lithium, lithium nickelate, LiMn2O4 are compared, and this material has best heat stability (350 ℃ still can keep structure constant), in electrolyte, has minimum solubility (solubility does not change with variation of temperature).In addition, do not contain precious metal in the LiFePO4, nontoxic, environmental friendliness, raw material sources are extensive, and are cheap.Based on above advantage, this year, this material received much concern as the novel energy-storing lithium ion battery electrode material, especially had in the motive-power battery field and studied largely and use.
The principal element that present restriction LiFePO4 is used in macrocell such as hybrid vehicle is relatively poor high rate performance, and this mainly is because it has low electronic conductivity.In addition, (especially more than or equal to 60 ℃ the time) this material list has revealed relatively poor cyclical stability under the hot conditions.LiFePO
4The defective of high electronics resistance coat through the surface and the mode of element doping has obtained good solution, (S.L.Bewlay, K.Konstantinov; G.X.Wang, S.X.Dou, H.K.Liu; Mater.Lett.58; 2004,1788) of above-mentioned non-patent literature, adopt sputter pyrolysis technology to carry out making its electronic conductivity to improve nearly 7 one magnitude on the LiFePO4 surface.
To make that the chemical property of this material is influenced by particle size bigger for 1D lithium ion migrating channels in the olivine structural ferric phosphate, and very sensitive to the impurity and the lattice stacking defective that possibly cause passage to stop up.(K.Zaghi, N.Ravet, M.Gauthier, F.Gendron; A.Mauger, J.B.Goodenough, C.M.Julien, Journal of Power Sources 163; 2006,560-566) of above-mentioned non-patent literature, in the LiFePO4 olivine structural, detected various ferrous contaminants, like γ-Fe2O3; Fe3O4, Fe2P2O7, Fe2P, Fe3P and Fe75P15C10 etc.Nearest research shows that in high temperature (especially more than 60 ℃) cyclic process, the stripping of iron can take place the LiFePO4 negative electrode, and the deposition of iron of stripping influences the lithium ion migration in the anode SEI film, thereby causes bigger capacity attenuation to anode surface.
Summary of the invention:
The object of the invention is exactly the processing method that a kind of processing LiFePO 4 material is provided to the deficiency of prior art existence.
To achieve these goals, the technical scheme of the present invention's employing is:
A kind of processing method of LiFePO 4 material, form by following steps:
A, iron phosphate powder is distributed in the acid solution;
B, transfer in the container of sealing, under 25 ℃～100 ℃, the constant temperature stir process obtains black suspension;
C, with the black suspension cool to room temperature, suction filtration is used washed with de-ionized water, vacuumize, temperature is controlled at 80 ℃～200 ℃, water content is controlled at below the 5000ppm;
Grind D, cooling back, obtains acid-treated LiFePO 4 material.
The present invention is with respect to prior art; Preparation technology is simple and practical, is suitable for industrial applications, handles LiFePO 4 material with acid solution; Remove ferrous contaminants residual in synthetic raw material and the building-up process; When adopting this material, can reduce the stripping of iron in the high temperature circulation process, improve and adopt high temperature circulation stability and the high-temperature storage performance of this material as the battery of active material as the active substance of lithium ion battery anode material.The battery that the active material of handling without this method prepares, through after the high temperature circulation, the quantity of the iron of anodic deposition is 2000-3000ppm.And the battery that the active material that uses this method to handle prepares, through after the high temperature circulation, the quantity of the iron of anodic deposition is reduced to 200-300ppm.In addition, acid has certain corrasion to the material list surface layer in the acid treatment process, can effectively improve the high rate capability of material.Therefore, the acid treatment LiFePO4 through the present invention obtains has not only improved ionic conductivity, and high rate capability has kept high reversible electrochemical capacity and excellent cycle performance, has more improved the high-temperature behavior of material.
The acid solution of said steps A is one or more in hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, the phosphoric acid, and these acid obtain and low price easily, and raw material satisfy easily.
The acid solution of said steps A is one or more in hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, the phosphoric acid.
Said steps A acid solutions is unrestricted.
The LiFePO 4 material of said steps A is the LiFePO 4 material that carbon coats.Handle after the carbon of LiFePO4 is covered to complete, can effectively carry out etching, increase and lead the passage of lithium ion, thereby improve the rate charge-discharge performance of material the carbon-coating of densification.In addition, the hydrogen fluoride trealment process of LiFePO4 can generate the LiF composition that one deck is similar to anode SEI membrane component, thereby the protection cathode surface improves the high temperature cyclic performance of battery.
Black suspension among the said step B is the suspension-turbid liquid of iron content.
The pH value of the black suspension among the said step B is 6～10.
Said step C control water content is controlled at below the 5000ppm.
Description of drawings:
Fig. 1 is the Fe content curve chart of black suspension pH value of filtrate in the application 1 example of the present invention and ICP test;
Fig. 2 is for 100ppm hydrofluoric acid treatment gained acid treatment in 24 hours LiFePO4 in the application 1 example of the present invention with without the cyclic curve figure of acid-treated LiFePO4 under 60 ℃;
Fig. 3 is for 100ppm hydrofluoric acid treatment gained acid treatment in 24 hours LiFePO4 in the application examples 1 of the present invention with without the multiplying power discharging curve chart under the acid-treated LiFePO4 normal temperature;
Fig. 4 handles 24 hours gained acid treatment LiFePO4s for HCl in the application examples 2 of the present invention and without the multiplying power discharging curve chart under the acid-treated LiFePO4 normal temperature.
Embodiment:
Below in conjunction with embodiment the present invention is further described.
Embodiment 1
Preparation 100ppm HF aqueous solution 150ml adds the iron phosphate powder that 50g carbon coats, and container is carried out encapsulation process; Be transferred to after mixing in 60 ℃ of constant temperature ovens; Constant temperature stir process 24 hours obtains black suspension, with the black suspension cool to room temperature; Suction filtration, filtrating pH value and stripping Fe content are shown in accompanying drawing 1.Leach thing and use washed with de-ionized water repeatedly, in baking oven, be transferred to 130 ℃ of vacuumize 24h of constant temperature in the vacuum drying oven behind the preliminarily dried, obtain the acid treatment iron phosphate powder after the grinding, the powder water content is 2400ppm.Grind the cooling back, obtains the LiFePO 4 material that HF handles.
Embodiment 2
Preparation 9000ppm aqueous hydrochloric acid solution 150ml adds the 50g iron phosphate powder, and container is carried out encapsulation process; Be transferred to after mixing in 26 ℃ of constant temperature ovens, constant temperature stir process 15 hours obtains black suspension; With the black suspension cool to room temperature, suction filtration, filtrating pH value is 7.5.Leach thing and use washed with de-ionized water repeatedly, in baking oven, be transferred to 200 ℃ of vacuumize 21h of constant temperature in the vacuum drying oven behind the preliminarily dried, obtain the acid treatment iron phosphate powder after the grinding, the powder water content is 5000ppm.Grind the cooling back, obtains the LiFePO 4 material of salt acid treatment.
Embodiment 3
Preparation 50ppm aqueous solution of nitric acid 150ml adds the 50g iron phosphate powder, and container is carried out encapsulation process; Be transferred to after mixing in 100 ℃ of constant temperature ovens, constant temperature stir process 32 hours obtains black suspension; With the black suspension cool to room temperature, suction filtration, filtrating pH value is 7.7.Leach thing and use washed with de-ionized water repeatedly, in baking oven, be transferred to 80 ℃ of vacuumize 25h of constant temperature in the vacuum drying oven behind the preliminarily dried, obtain the nitric acid treatment iron phosphate powder after the grinding, the powder water content is 3000ppm.Grind the cooling back, obtains the LiFePO 4 material of nitric acid treatment.
Embodiment 4
Preparation 2000ppm aqueous sulfuric acid 150ml adds the 50g iron phosphate powder, and container is carried out encapsulation process; Be transferred to after mixing in 70 ℃ of constant temperature ovens, constant temperature stir process 24 hours obtains black suspension; With the black suspension cool to room temperature, suction filtration, filtrating pH value is 8.1.Leach thing and use washed with de-ionized water repeatedly, in baking oven, be transferred to 120 ℃ of vacuumize 24h of constant temperature in the vacuum drying oven behind the preliminarily dried, obtain the sulfuric acid treatment iron phosphate powder after the grinding, the powder water content is 3000ppm.Grind the cooling back, obtains the LiFePO 4 material of sulfuric acid treatment.
Preparation 1000ppm phosphate aqueous solution 150ml adds the 50g iron phosphate powder, and container is carried out encapsulation process; Be transferred to after mixing in 60 ℃ of constant temperature ovens, constant temperature stir process 24 hours obtains black suspension; With the black suspension cool to room temperature, suction filtration, filtrating pH value is 8.0.Leach thing and use washed with de-ionized water repeatedly, in baking oven, be transferred to 120 ℃ of vacuumize 24h of constant temperature in the vacuum drying oven behind the preliminarily dried, obtain phosphoric acid after the grinding and handle iron phosphate powder, the powder water content is 2500ppm.Grind the cooling back, obtains the LiFePO 4 material that phosphoric acid is handled.
Embodiment 6
Preparation 50ppm phosphate aqueous solution 75ml, configuration 50ppm HF aqueous solution 75ml adds the 50g iron phosphate powder; Container is carried out encapsulation process, be transferred in 60 ℃ of constant temperature ovens constant temperature stir process 24 hours after mixing; Obtain black suspension; With the black suspension cool to room temperature, suction filtration, filtrating pH value is 7.5.Leach thing and use washed with de-ionized water repeatedly, in baking oven, be transferred to 120 ℃ of vacuumize 24h of constant temperature in the vacuum drying oven behind the preliminarily dried, obtain phosphoric acid after the grinding and handle sour iron lithium powder, the powder water content is 2500ppm.Grind the cooling back, obtains acid-treated LiFePO 4 material.
Application examples 1
Take by weighing HF processing iron phosphate powder among the 9g embodiment 1, add Kynoar (PVDF) binding agent that 0.5g conductive black and 0.5g are dissolved in N-N '-dimethyl pyrrolidone (NMP), be coated in after mixing and be prepared into positive plate on the aluminium foil.In the glove box of argon shield, be to electrode with metal lithium sheet, the barrier film of Celgard company 2400 models, 1MLiPF6+ ethylene carbonate (EC)+dimethyl carbonate (DMC) is an electrolyte, is assembled into button cell (imaginary point is the LFP-HF sample in the accompanying drawing 2).For comparing, adopt above-mentioned method not to be assembled into button cell (real point is the LFP sample in the accompanying drawing 2) through the acid-treated iron phosphate powder of HF.In 2.0V～3.65V voltage range, battery is carried out high temperature circulation and multiplying power discharging test.Accompanying drawing 2 be battery under 60 ℃ of constant temperatures, the cyclic curve that the 0.5C charge-discharge test obtains.From figure, can see that reversible specific capacity is up to 161mAh/g, cyclical stability has had raising by a relatively large margin.(imaginary point is the LFP-HF sample to accompanying drawing 3 in the accompanying drawing 3; Real point is the LFP sample) for battery at normal temperatures; With the 0.2C charging, with the multiplying power discharging curve of 1C, 5C, 10C and 15C multiplying power discharging, from figure, can see respectively; High-rate discharge ability through the LiFePO4 after the HF acid treatment has had significantly raising, improves nearly 1.25 times like 10C multiplying power discharging capacity.Handling after should use-case the carbon of LiFePO4 being covered to complete, is because the present invention can effectively carry out etching to the carbon-coating of densification, increases and leads the passage of lithium ion, thereby improve the rate charge-discharge performance of material; In addition, the hydrogen fluoride trealment process of LiFePO4 can generate the LiF composition that one deck is similar to anode SEI membrane component, thereby the protection cathode surface improves the high temperature cyclic performance of battery.
Application examples 2
Should use-case and application examples 1 difference be: the LiFePO 4 material that should use-case adopts embodiment 2 to handle.Take by weighing HCl processing iron phosphate powder among the 9g embodiment 2, add Kynoar (PVDF) binding agent that 0.5g conductive black and 0.5g are dissolved in N-N '-dimethyl pyrrolidone (NMP), be coated in after mixing and be prepared into positive plate on the aluminium foil.In the glove box of argon shield, be to electrode with metal lithium sheet, Celgard2400 is a barrier film, 1M LiPF6+ ethylene carbonate (EC)+dimethyl carbonate (DMC) is an electrolyte, is assembled into button cell (imaginary point is the LFP-HCl sample in the accompanying drawing 4).For comparing, adopt above-mentioned method not to be assembled into button cell (real point is the LFP sample in the accompanying drawing 4) through the acid-treated iron phosphate powder of HCl.In 2.0V～3.65V voltage range, battery is carried out the multiplying power discharging test.Accompanying drawing 4 be battery at normal temperatures, with 0.2C charging, respectively with the multiplying power discharging curve of 1C, 5C, 10C and 15C multiplying power discharging; From figure, can see; High-rate discharge ability through the LiFePO4 after the HCl acid treatment has had significantly raising, and like 10C, 15C multiplying power discharging capacity improves.Handling after should use-case the carbon of LiFePO4 being covered to complete, is because the present invention can effectively carry out etching to the carbon-coating of densification, increases and leads the passage of lithium ion, thereby improve the rate charge-discharge performance of material.
According to the announcement and the instruction of above-mentioned specification, those skilled in the art in the invention can also carry out suitable change and modification to above-mentioned execution mode.Therefore, the embodiment that discloses and describe above the present invention is not limited to also should fall in the protection range of claim of the present invention modifications more of the present invention and change.In addition, although used some specific terms in this specification, these terms are explanation for ease just, the present invention is not constituted any restriction.
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Citations (4)
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| JP2003157845A (en) * | 2001-11-22 | 2003-05-30 | Kyushu Univ | Method for producing positive electrode material for secondary battery, and secondary battery |
| CN101276909A (en) * | 2007-02-28 | 2008-10-01 | 三洋电机株式会社 | Method of producing active material for lithium secondary battery, method of producing electrode for lithium secondary battery, method of producing lithium secondary battery, and method of monitoring |
| CN101794879A (en) * | 2010-03-04 | 2010-08-04 | 上海电力学院 | Preparation method of iron phosphate lithium of lithium ion battery positive-electrode materials |
| CN101847763A (en) * | 2010-04-09 | 2010-09-29 | 奇瑞汽车股份有限公司 | Comprehensive recovering method of waste lithium iron phosphate battery |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003157845A (en) * | 2001-11-22 | 2003-05-30 | Kyushu Univ | Method for producing positive electrode material for secondary battery, and secondary battery |
| CN101276909A (en) * | 2007-02-28 | 2008-10-01 | 三洋电机株式会社 | Method of producing active material for lithium secondary battery, method of producing electrode for lithium secondary battery, method of producing lithium secondary battery, and method of monitoring |
| CN101794879A (en) * | 2010-03-04 | 2010-08-04 | 上海电力学院 | Preparation method of iron phosphate lithium of lithium ion battery positive-electrode materials |
| CN101847763A (en) * | 2010-04-09 | 2010-09-29 | 奇瑞汽车股份有限公司 | Comprehensive recovering method of waste lithium iron phosphate battery |
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Application publication date: 20120125 |