CN102841122A - Fe<2+> content rapid analysis method for LiFePO4 (lithium iron phosphate)/C (carbon) composite anode material - Google Patents
Fe<2+> content rapid analysis method for LiFePO4 (lithium iron phosphate)/C (carbon) composite anode material Download PDFInfo
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- CN102841122A CN102841122A CN2012103101058A CN201210310105A CN102841122A CN 102841122 A CN102841122 A CN 102841122A CN 2012103101058 A CN2012103101058 A CN 2012103101058A CN 201210310105 A CN201210310105 A CN 201210310105A CN 102841122 A CN102841122 A CN 102841122A
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Abstract
The invention discloses a Fe<2+> content rapid analysis method for a LiFePO4/C composite anode material, which comprises the following steps of: a, dissolving the LiFePO4/C composite anode material by hydrochloric acid under the inert gas protection; and b, with the adoption of a potentiometric titrator, directly detecting the Fe<2+> content in the LiFePO4/C composite material through potassium dichromate as a dripping agent under the inert gas protection. The Fe<2+> content rapid analysis method provided by the invention simplifies the steps of removing carbon, prevents the reduction state and oxidation state materials from interfering detection, reduces the errors of an artificial judgment end point, simplifies the operation of adjusting the acidity and the temperature, greatly improves the defects of the existing method, and has the advantages of simplicity in operation, reliable data and the like. The basis is provided for the performances of the LiFePO4/C composite material.
Description
Technical field
The present invention relates to the cell positive material quality detection technology, especially a kind of LiFePO
4/ C composite positive pole Fe
2+The content rapid analysis.
Background technology
Present LiFePO
4Advantages such as that/C compound substance has is nontoxic, pollution-free, material source is extensive, cheap are desirable lithium electricity positive electrodes, are widely used in recent years.LiFePO
4/ C compound substance has good circulating and reversible performance and high-rate discharge ability, especially high temperature circulation reversibility as anode material for lithium-ion batteries.At synthetic LiFePO
4In the positive electrode process, there is impurity F e
3+Be inevitably, Fe
3+Can cause LiFePO
4The positive electrode specific storage descends, so Fe
3+Content is to weigh LiFePO
4The important indicator that the positive electrode performance is good and bad.Method of testing commonly used is to measure total iron and Fe in the sample respectively
2+Amount, ask its difference to draw Fe
3+Content.Fe
2+How therefore the mountain accurately measure LiFePO in very easily oxidation
4Fe in the/C compound substance
2+It is particularly important that content seems.
Measure the method for iron content in the LiFePO 4 at present, mainly contain AAS, gravimetric method, chemical titration, VA polarographic method, coulometric titration etc.
Wherein AAS is through measuring the absorbance log of measured matter light in certain wave strong point or certain wavelength coverage, this material being carried out the method for qualitative and quantitative analysis.Utilize ferric ion can form the characteristics of colored complex with some reagent; Can adopt ferrous content in the absorption photometry test LiFePO 4, but test need be carried out the filtration in advance of the necessary quilt of carbon dust in the solution of clear; Ferrous meeting is oxidized in filtering carbon dust; Therefore be difficult to guarantee the accuracy of measuring, so this method only is suitable for measuring the content of the full iron in the LiFePO4, and can't realizes the mensuration of ferrous content.
Gravimetric method is meant ferrous oxidation, and to be ferric iron be converted into iron oxide according to the quality determination of iron oxide and analyze the content of iron in the former material with ammoniacal liquor with the ferric iron deposition again.This method only is applicable to the content of measuring full iron in the sample, and is not suitable for measuring ferrous content in the LiFePO 4.
Chemical titration is to adopt ferrous content in potassium permanganate or the potassium dichromate method titration LiFePO 4; With the sulfosalicylic acid is indicator; In the practical operation in order to reduce the influence that causes because of carbon absorption to endpoint observation; Need before the titration to filter carbon and cyclic washing 5-10 time earlier, the part ferrous oxidation is a ferric iron in this process, so measurement result is not accurate enough.Therefore chemical titration also is more suitable in the amount of the total iron of titration.
The VA polarographic method is analyzed according to the electrode potential-current curve in the electrolytic process; The relation that is directly proportional with material concentration through peak height in the polarogram; Adopt the standard solution method of adding concentration known, can accurately measure content ferrous in the LiFePO 4, but this method need select suitable complexing agent to distinguish the ORP of ferrous ion and ferric ion; And need to adopt DME, in the process of the preparation of electrode and use, all there is drawback.
Coulometric titration is the electric weight that is consumed when measuring electrolysis; Obtain ferrous content indirectly; This method electric weight that requirement is consumed when measuring all is used for the electrode reaction of tested material; Must avoid on working electrode, taking place other subsidiary reactions; Simultaneously in order to measure the electric weight coulombmeter of need in electric current, connecting, and how to select suitable directing terminal method, accurately measure electric weight hydrogen-oxygen coulombmeter preparation and how to guarantee that the problem of current efficiency 100% is restricting the application of this method in the lithium ferrous phosphate composite material actual analysis.
Make a general survey of above-mentioned analytical approach, the subject matter of existence be how to prevent ferrous oxidized in analytic process, how to avoid carbon dust to the interference of indicator, to the interference of penetrability and to the judgement of terminal colour.Therefore study LiFePO simple and practical, reliable results
4/ C composite positive pole Fe
2+The rapid analysis of content is the important topic that the researchist faces.
Summary of the invention
The objective of the invention is provides a kind of LiFePO for overcoming the deficiency of above-mentioned prior art
4/ C composite positive pole Fe
2+The content rapid analysis, this method needn't be filtered carbon, can avoid oxidation ferrous in the analytic process, and step is simple, terminal point is easy to judge, reliable results, can be and judges LiFePO
4The performance of/C composite positive pole provides direct foundation.
For realizing above-mentioned purpose, the present invention adopts following technical proposals:
A kind of LiFePO
4/ C composite positive pole Fe+ content rapid analysis may further comprise the steps:
1). take by weighing 0.3～0.4g LiFePO
4/ C composite positive pole specimen sample is put in the beaker, and at inert gas (not limitting kind) or CO 2 gas-shielded following, the use massfraction is 18% dissolve with hydrochloric acid solution LiFePO
4/ C composite positive pole, dissolution time was advisable in 5～10 minutes; Wherein, every 100mg LiFePO
4The required massfraction of/C composite positive pole sample is that 18% hydrochloric acid solution is advisable with 2mL～5mL;
2). adopting potentiometric titration, under inert gas shielding, is that titrant is measured ferrous content with the potassium dichromate.
Said step 2) need under stirring condition, to carry out, concentration is even everywhere to guarantee solution.
Said step 2) automatical potentiometric titrimeter is adopted in the potentiometric titration in, is indicator electrode with the platinum combination electrode, and perhaps adopting platinum electrode is indicator electrode, and Ag/AgCl is a contrast electrode.
Said step 2) in is that titrant is measured ferrous content and is specially with the potassium dichromate, is redox reaction titrant with the 0.005mol/L potassium bichromate solution of standard, with automatical potentiometric titrimeter titration Fe
2+, judge titration end-point according to potential break, according to the titration Rapid Dose Calculation Fe of stoichiometric point consumption
2+Content.
Need not to filter carbon dust in the process of the present invention, simplified experimental procedure, at utmost avoided in the analysis titration process mountain to make ferrous oxidation, the accuracy that influence is measured in filter carbon; Experiment is an indicator electrode with the platinum combination electrode, and perhaps adopting platinum electrode is indicator electrode, and Ag/AgCl is a contrast electrode.Potassium dichromate with standard is a redox reaction titrant, uses the automatical potentiometric titrimeter titration, judges titration end-point with potential break, according to the titration Rapid Dose Calculation Fe of stoichiometric point consumption
2+Content.Experiment is carried out under stirring condition, and concentration is even everywhere to guarantee solution.
The invention has the beneficial effects as follows: the present invention has simplified carbon removing step; Needn't filter carbon, prevent oxidation ferrous in the analytic process, avoid going back ortho states and of the interference of oxidation state material measuring; Reduced the error of artificial judgement terminal point; Simplify adjusting acidity and temperature operation, greatly improved the defective of existing method, had advantages such as simple to operate, that terminal point is easy to judge, data are reliable.Be LiFePO
4The judgement of/C composite positive pole performance provides foundation.
Embodiment
Below in conjunction with embodiment the present invention is further specified.
LiFePO
4/ C composite positive pole Fe
2+Assay
Analytical procedure:
Take by weighing an amount of (as shown in table 1) LiFePO
4/ C sample in the 150mL beaker, in inert gas shielding with LiFePO
4It is 18% hydrochloric acid solution 6mL dissolving that/C sample uses massfraction, with distilled water diluting to 50mL.Adopting automatical potentiometric titrimeter, is indicator electrode with the platinum combination electrode, with the 0.0502mol/L potassium bichromate solution titration Fe of standard
2+, confirm titration end-point through the hop of current potential.
Agents useful for same: concentrated hydrochloric acid, distilled water, the pure potassium dichromate of analysis.
Required instrument: automatical potentiometric titrimeter (perhaps potentiometric titrimeter, potentiostat), platinum combination electrode (or platinum electrode and Ag/AgCl electrode), magnetic stirring apparatus.
Then:
mFe
2+＝6×0.05585CV
Wherein: mFe
2+Ferrous content in----alleged sample, g
The concentration of C----potassium dichromate standard solution, mol/L
The volume that V----potassium dichromate standard solution consumes, mL
Table 1 LiFePO
4Fe in the/C sample
2+The assay data
Said method has been simplified carbon removing step; Needn't filter carbon, prevent oxidation ferrous in the analytic process, avoid going back ortho states and of the interference of oxidation state material measuring; Reduced the error of artificial judgement terminal point; Simplify adjusting acidity and temperature operation, greatly improved the defective of existing method, had advantages such as simple to operate, that terminal point is easy to judge, data are reliable.For the judgement of LiFePO4/C composite positive pole performance provides foundation.
Though above-mentioned specific embodiments of the invention is described; But be not restriction to protection domain of the present invention; One of ordinary skill in the art should be understood that; On the basis of technical scheme of the present invention, those skilled in the art need not pay various modifications that creative work can make or distortion still in protection scope of the present invention.
Claims (4)
1. LiFePO
4/ C composite positive pole Fe
2+The content rapid analysis is characterized in that, may further comprise the steps:
1) takes by weighing 0.3～0.4g LiFePO
4/ C sample is put in the beaker, and at inert gas (not limitting kind) or CO 2 gas-shielded following, the use massfraction is 18% dissolve with hydrochloric acid solution LiFePO
4/ C composite positive pole, dissolution time was advisable in 5～10 minutes); Wherein, every 100mg LiFePO
4The required massfraction of/C composite positive pole sample is that 18% hydrochloric acid solution is advisable with 2mL～5mL;
2) adopting potentiometric titration, under inert gas shielding, is that titrant is measured ferrous content with the potassium dichromate.
2. the method for claim 1 is characterized in that, said step 2) need under stirring condition, to carry out, concentration is even everywhere to guarantee solution.
3. the method for claim 1 is characterized in that, said step 2) in potentiometric titration adopt automatical potentiometric titrimeter, be indicator electrode with the platinum combination electrode, perhaps adopting platinum electrode is indicator electrode, Ag/AgCl is a contrast electrode.
4. the method for claim 1 is characterized in that, said step 2) in be that titrant is measured ferrous content and is specially with the potassium dichromate, be redox reaction titrant with the potassium bichromate solution of standard, with automatical potentiometric titrimeter titration Fe
2+, judge titration end-point according to potential break, according to the titration Rapid Dose Calculation Fe of stoichiometric point consumption
2+Content.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103616428A (en) * | 2013-12-18 | 2014-03-05 | 齐齐哈尔大学 | Potentiometric titration method for measuring concentration of Fe<2+> in solution |
| CN105784816A (en) * | 2016-03-28 | 2016-07-20 | 苏州久润能源科技有限公司 | Method for determining total iron concentration in Fe/Cr flow battery electrolyte |
| CN106198532A (en) * | 2016-09-05 | 2016-12-07 | 江苏德林环保技术有限公司 | The dual wavelength autocontrol method of a kind of quick photometric titration and device |
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| CN101949911A (en) * | 2010-08-09 | 2011-01-19 | 中钢集团安徽天源科技股份有限公司 | Method for measuring ferrous ions in carbon-coated lithium iron phosphate |
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| CN101464413A (en) * | 2007-12-21 | 2009-06-24 | 深圳市比克电池有限公司 | Method for measuring ferrous iron and ferric iron content in lithium iron phosphate anode material |
| CN101949911A (en) * | 2010-08-09 | 2011-01-19 | 中钢集团安徽天源科技股份有限公司 | Method for measuring ferrous ions in carbon-coated lithium iron phosphate |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103616428A (en) * | 2013-12-18 | 2014-03-05 | 齐齐哈尔大学 | Potentiometric titration method for measuring concentration of Fe<2+> in solution |
| CN103616428B (en) * | 2013-12-18 | 2016-02-03 | 齐齐哈尔大学 | Fe in a kind of mensuration solution 2+the potentiometric titration of concentration |
| CN105784816A (en) * | 2016-03-28 | 2016-07-20 | 苏州久润能源科技有限公司 | Method for determining total iron concentration in Fe/Cr flow battery electrolyte |
| CN106198532A (en) * | 2016-09-05 | 2016-12-07 | 江苏德林环保技术有限公司 | The dual wavelength autocontrol method of a kind of quick photometric titration and device |
| CN106198532B (en) * | 2016-09-05 | 2018-09-04 | 江苏德林环保技术有限公司 | A kind of the dual wavelength autocontrol method and device of quick photometric titration |
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