CN104422665A - Method for detecting content of phosphorus and iron in LiFePO4/C composite material - Google Patents
Method for detecting content of phosphorus and iron in LiFePO4/C composite material Download PDFInfo
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Abstract
The invention relates to a method for detecting content of phosphorus and iron in a LiFePO4/C composite material. The method comprises the steps of mixing the LiFePO4/C composite material with concentrated hydrochloric acid and concentrated nitric acid, heating to enable the LiFePO4/C composite material to be dissolved, and filtering an insoluble black substance to obtain a LiFePO4/C composite material to-be-detected solution; drawing a phosphorus standard curve; adding an ascorbic acid solution into the LiFePO4/C material to-be-detected solution, enabling ferric iron in the solution to be reduced to ferrous iron, adding an ammonium molybdate solution, carrying the color development, measuring the absorbance of the obtained solution at a position of 720nm in a spectrophotometer by utilizing a cuvette, and finding the to-be-detected content of phosphorus (P) on the phosphorus standard curve according to the absorbance; drawing an iron standard curve; adding a hydroxylamine hydrochloride solution, a sodium acetate-acetic acid buffer solution as well as a phenanthroline solution into the LiFePO4/C composite material to-be-detected solution, carrying out the color development, measuring the absorbance of the solution at the position of 510nm by utilizing the cuvette, and finding the to-be-detected content of iron (Fe) on the iron standard curve according to the absorbance; calculating the content of P and Fe in the LiFePO4/C material. According to the method, the interactive effect of the P and Fe ions and the color influence caused by different C coating can be eliminated.
Description
Technical field
The present invention relates to a kind of LiFePO
4the method of testing of iron and phosphorus in/C composite.
Background technology
It is high that lithium ion battery has energy density, good cycle, the advantages such as stable operating voltage, market to its demand also in continuous increase, especially in electrokinetic cell field.LiFePO
4/ C composite (abbreviation LiFePO 4) positive electrode has the excellent chemical property such as unrivaled security performance, high-energy-density, long-life, outstanding high-temperature stability and chemical stability, uses pilot on a large scale in pure electric automobile battery, energy-storage battery field at present.
LiFePO
4the chemical composition of/C composite determines the chemical property of positive electrode, and its consistance of producing and stability are the key factors restricting this Materials.This material element Fe/P ratio is seized of and consequence.The stability of Fe/P ratio has vital effect to material consistance, if the content that can measure accurately and fast Fe and P in LiFePO 4 will play decisive help to material shipment consistance.
Mainly can be summarized as in the method for test iron and phosphorus content at present: (1) chemical titration; (2) gravimetric method test P content; (3) ICP tests the content of Fe and P; (4) content of ultraviolet spectrophotometry test Fe and P.But in this several methods, although the high complicated operation of chemical titration precision, very high to personnel requirement, the different instability therefore causing test error and test of the judgement of different personnel to titration end-point.Although and this method measuring stability simple to operate is better during operating weight method measurement P content, test process not only needs sample preparation and reaction, and before and after whole process, container needs constant weight consuming time longer, can not draw results needed fast.Although quick from preparing sample to detection operation in ICP test, and to most elements test accurately, but owing to being applicable to trace element test, constant test in need extension rate more artificially increase error, moreover Fe and P excite comparatively close to also easily interfering with each other in testing, extremely difficult stable testing.
And use uv-spectrophotometric to test LiFePO
4fe and P in/C composite, and it is simple to operate, have good stability, such as in (synthesizing mensuration, the Zhang Kun of iron and phosphorus content in positive electrode material LiFePO 4 of lithium) article, author uses molybdenum yellow method to test P content, use nonyl phenol test Fe content, although method of testing is simple, is through checking and finds because chromogenic reaction is for yellow, Fe
3+the color of solution is also yellow, therefore, can have certain interference, the transmitance of light to chromogenic reaction, can bring very large deviation equally to the accuracy of test.
To sum up, those skilled in the art are badly in need of finding a kind of LiFePO stablizing, can test Fe and the P content in sample quickly and accurately simultaneously
4the detection method of phosphorus and iron content in/C composite.
Summary of the invention
A kind of LiFePO is provided herein
4the detection method of phosphorus and iron content in/C composite, use spectrophotometer is quick, Measurement accuracy LiFePO
4phosphorus and iron content in/C composite.
For achieving the above object, the present invention proposes a kind of LiFePO
4in/C composite, the detection method of phosphorus and iron content, comprises the steps:
Step 1: by LiFePO
4/ C composite mixes with concentrated hydrochloric acid and red fuming nitric acid (RFNA), and heating for dissolving also filters out insoluble atrament, obtains LiFePO
4/ C composite solution to be measured;
Step 2: draw phosphorus typical curve;
Step 3: the LiFePO obtained in step 1
4ascorbic acid solution is added in/C composite solution to be measured, trivalent Fe in solution is reduced into ferrous iron, and adds ammonium molybdate solution, colour developing, measure the absorbance of solution with cuvette in 720nm place, on the phosphorus typical curve of step 2, search P test amounts according to described absorbance;
Step 4: draw iron typical curve;
Step 5: the LiFePO obtained in step 1
4hydroxylamine hydrochloride solution, sodium acetate-hac buffer and Phen solution is added in/C composite solution to be measured, colour developing, measure the absorbance of solution with cuvette in 510nm place, on the iron typical curve of step 2, search Fe test amounts according to described absorbance;
Step 6: calculate LiFePO
4p and Fe content in/C composite, computing formula is:
In formula: x is LiFePO
4total phosphorus or Fe percentage composition in/C composite;
C is the content of the phosphorus found from phosphorus typical curve or the content of iron found from iron typical curve;
M is LiFePO
4the quality of/C composite.
Wherein, in described step 1, every gram of LiFePO
4/ C composite mixes with 5ml ~ 10ml concentrated hydrochloric acid and 5ml ~ 10ml red fuming nitric acid (RFNA).
Atrament described in described step 1 is carbon.
In described step 1, heating for dissolving temperature is 60 DEG C ~ 80 DEG C.
Wherein, described step 3 repeats 3 times, and obtain three P test amounts, average, described step 5 repeats 3 times, obtains three Fe test amounts, averages.
Wherein, in described step 2, described ammonium molybdate solution is the mixed solution of ammonium molybdate and sulfuric acid and potassium antimonyl tartrate.
Wherein, in described step 3, described LiFePO
4/ C composite solution to be measured, before adding ascorbic acid solution, is cooled to room temperature after heating 20-40min in boiling water bath.
LiFePO of the present invention
4the detection method of phosphorus and iron content in/C composite, molybdenum blue method test P content, Phen test Fe is adopted by spectrophotometer, and improve preparation method and eliminate the coated impact that testing result is brought of C in LiFePO 4, thus obtain comparatively accurately and fast, easy method of testing, the quality control for ferrousphosphate lithium material provides reliable, simple, easy-operating analytical approach.
Accompanying drawing explanation
Fig. 1 is the P typical curve drawn in embodiment 1;
Fig. 2 is the Fe typical curve drawn in embodiment 1;
Fig. 3 is the process sequence diagram of detection method.
Embodiment
The present invention proposes a kind of LiFePO
4the detection method of phosphorus and iron content in/C composite, comprises the steps (as Fig. 3):
Step 1: by LiFePO
4/ C composite mixes with concentrated hydrochloric acid and red fuming nitric acid (RFNA), and heating for dissolving also filters out insoluble atrament, obtains LiFePO
4/ C composite solution to be measured, by Li in solution
+, Fe
2+, Fe
3+, PO
4 3+, Cl
-, NO
3 -, H
+plasma forms, and owing to also having undissolvable black carbon slag in solution, solution is black troubled liquor;
Step 2: draw phosphorus typical curve;
Step 3: the LiFePO obtained in step 1
4ascorbic acid solution is added in/C composite solution to be measured, trivalent Fe in solution is reduced into ferrous iron, and add ammonium molybdate solution, colour developing, in spectrophotometer, measure the absorbance of solution with cuvette in 720nm place, on the phosphorus typical curve of step 2, search P test amounts according to described absorbance;
Step 4: draw iron typical curve;
Step 5: the LiFePO obtained in step 1
4hydroxylamine hydrochloride solution, sodium acetate-hac buffer and Phen solution is added in/C composite solution to be measured, colour developing, in spectrophotometer, measure the absorbance of solution with cuvette in 510nm place, on the iron typical curve of step 2, search Fe test amounts according to described absorbance;
Step 6: calculate LiFePO
4p and Fe content in/C composite, computing formula is:
In formula: x is LiFePO
4total phosphorus or Fe percentage composition in/C composite;
C is the content of the phosphorus found from phosphorus typical curve or the content of iron found from iron typical curve;
M is LiFePO
4the quality of/C composite.
Wherein, in described step 1, every gram of LiFePO
4/ C composite mixes with 5ml ~ 10ml concentrated hydrochloric acid and 5ml ~ 10ml red fuming nitric acid (RFNA).Atrament described in described step 1 is carbon.Heating for dissolving temperature is 60 DEG C ~ 80 DEG C.
Wherein, in described step 2, described ammonium molybdate solution is the mixed solution of ammonium molybdate and sulfuric acid and potassium antimonyl tartrate.
Wherein, described step 3 repeats 3 times, and obtain three P test amounts, average, described step 5 repeats 3 times, obtains three Fe test amounts, averages.
Wherein, in described step 3, described LiFePO
4/ C composite solution to be measured, before adding ascorbic acid solution, is cooled to room temperature after heating 20-40min in boiling water bath.
Wherein, the phosphorus typical curve in step 2 and step 4 and iron typical curve can adopt the method for any routine in this area to draw.
Specifically, the solution of the present invention is implemented by following preferred mode:
A kind of high precision test LiFePO
4in/C composite, the method for phosphorus and iron content mainly comprises the following steps.
1, LiFePO is prepared
4/ C composite liquid to be measured
Take 0.1 ~ 0.2g sample to mix with 5 ~ 10ml concentrated hydrochloric acid and 5 ~ 10ml red fuming nitric acid (RFNA), heating for dissolving 10 ~ 20min at 60 ~ 80 DEG C, cover surface plate during heating and prevent acid solution from volatilizing.After sample dissolves completely, the residual C in Filter paper filtering removing LiFePO4, and the Liquid Residue repeatedly washed on beaker and filter paper is to ensure raw material free of losses, proceeds to constant volume in 250ml volumetric flask and obtains LiFePO 4 sample treatment liquid.
2, the test of phosphorus content in sample
(1) preparation of reagent:
Ammonium molybdate solution: take 8 ~ 12g ammonium molybdate [(NH respectively
4)
2moO
4] and 0.3 ~ 0.5g potassium antimonyl tartrate [K (SbO) C
4h
4o
6] constant volume moves to 100ml volumetric flask respectively.Under constantly stirring, ammonium molybdate solution is slowly joined in the sulfuric acid of 200ml concentration 50%, mixed solution is poured into antimony tartrate potassium solution, mix, and move into 500ml volumetric flask constant volume.
Ascorbic acid solution: take the dissolving of 4 ~ 6g Vitamin C bolt and be placed on constant volume in 50ml volumetric flask, be stored in brown bottle.
Phosphorus standard solution: the P titer pipetting 1ml, 1000ppm, is diluted in 100ml volumetric flask, adds deionized water constant volume, obtains the phosphorus standard solution of 10mg/L.
(2) phosphorus Specification Curve of Increasing and sample test
Pipette the phosphorus standard solution 0.00,0.50,1.00 of 10.0mg/L respectively, 3.00,5.00,7.00,9.00mL is in 50mL volumetric flask, adding distil water is diluted to about 25mL, add 1 ~ 4mL ascorbic acid solution, add 2mL ammonium molybdate solution after 1min, adding distil water is diluted to scale, shake up, be configured to concentration be 0,0.1,0.2,0.6,1,1.4, the solution of 1.6mg/L.After colour developing 15min, in spectrophotometer, measure the absorbance of solution in 720nm place with 1cm cuvette.
(3) in sample, phosphorus content detects
Measure in LiFePO 4 sample treatment liquid 0.5ml to 100ml volumetric flask, adding distil water is diluted to 50ml, adds 1 ~ 4ml ascorbic acid solution, and the trivalent Fe in solution is reduced into ferrous iron, such colour developing is blue, avoids the yellow produced with ferric iron element to influence each other.Add 2 ~ 6ml ammonium molybdate solution after 1min, adding distil water is diluted to scale, shakes up.After colour developing 15min, in spectrophotometer, measure the absorbance of solution in 720nm place with 1cm cuvette.Above-mentioned detecting step carries out three groups of parallel laboratory tests and observes stability, and phosphorus typical curve is searched P test amounts, and three groups of test datas are averaged.
3, the test of iron content in sample
(1) preparation of reagent
Iron standard solution: the Fe titer pipetting 1ml, 1000ppm, is diluted in 100ml volumetric flask, adds deionized water constant volume, obtains the iron standard solution of 10mg/L.
(2) iron Specification Curve of Increasing and sample test
Pipette in the volumetric flask of 10mg/L iron standard solution 5ml, 10ml, 15ml, 20ml, 25ml to 100ml respectively, obtain the iron standard solution of 0.5mg/L, 1mg/L, 1.5mg/L, 2mg/L, 2.5mg/L respectively, add 10% hydroxylamine hydrochloride solution of 1 ~ 2ml, the sodium acetate-hac buffer of 5 ~ 10mlPH=4.5, the 0.15% Phen solution of 2 ~ 4ml successively, be diluted to scale.After colour developing 30min, in spectrophotometer, carry out colorimetric estimation with 510nm, obtain iron typical curve.
(3) detection of iron content in sample
Measure in LiFePO 4 sample treatment liquid 0.5ml to 100ml volumetric flask, adding distil water is diluted to 50ml, add 10% hydroxylamine hydrochloride solution of 1 ~ 2ml, the sodium acetate-hac buffer of 5 ~ 10mlPH=4.5, the 0.15% Phen solution of 2 ~ 4ml successively, be diluted to scale.After colour developing 30min, in spectrophotometer, measure the absorbance of solution in 510nm place with 1cm cuvette.Above-mentioned detecting step carries out three groups of parallel laboratory tests and observes stability, and iron typical curve is searched Fe test amounts, and three groups of net results are averaged calculating.
4, the calculating of P and Fe content in sample
In formula: x is LiFePO
4total phosphorus or Fe percentage composition in/C composite;
C is the content of the phosphorus found from phosphorus typical curve or the content of iron found from iron typical curve, unit mg/L;
M is LiFePO
4the quality of/C composite, unit mg.
A kind of high precision test LiFePO of the present invention
4the method of phosphorus and iron content in/C composite, accurate testing degree is high, and operation is relatively simple, can obtain result fast.Compared with existing method of testing, the present invention can test Fe and P two kinds of elements on spectrophotometer simultaneously, through the conversion of colour developing, can get rid of Fe when P develops the color
2+and Fe
3+on the impact of result, add the accuracy of Fe and P in spectrophotometric method test LiFePO4, in the process preparing sample, undissolvable C powder is separated with solution by we, further increases the accuracy of test.
Embodiment 1
1, LiFePO 4 liquid to be measured is prepared:
Take 0.1g sample in 50ml beaker, add 6ml concentrated hydrochloric acid and 6ml red fuming nitric acid (RFNA), beaker is placed on heating for dissolving 10min on 80 DEG C of heating plates, prevents acid solution from volatilizing when noting heating at beaker upper cover upper surface ware.After sample dissolves completely, be filtered in 250ml volumetric flask the insoluble carbon impurity of the black removed in sample through double-layer filter paper, and the Liquid Residue repeatedly washed on beaker and filter paper is to ensure raw material free of losses.Finally add distillation and be diluted to scale, obtain LiFePO 4 sample treatment liquid.
2, the test of phosphorus content in sample
(1) preparation of reagent:
Ammonium molybdate solution: take 10g ammonium molybdate and 0.3g potassium antimonyl tartrate and dissolve with a small amount of distilled water and be transferred to respectively in 100ml volumetric flask, adding distil water is diluted to scale.Under constantly stirring, ammonium molybdate solution is slowly joined in 200ml (1+1) sulfuric acid, mixed solution is poured into antimony tartrate potassium solution, mix, and move into 500ml volumetric flask constant volume.
Ascorbic acid solution: take the dissolving of 5g Vitamin C bolt and be placed on constant volume in 50ml volumetric flask, be stored in brown bottle.
Phosphorus standard solution: the P titer pipetting 1ml, 1000ppm, is diluted in 100ml volumetric flask, adds deionized water constant volume, obtains the phosphorus standard solution of 10mg/L.
(2) phosphorus Specification Curve of Increasing and sample test
Pipette the phosphorus standard solution 0.00,0.50,1.00 of 10.0mg/L respectively, 3.00,5.00,7.00,9.00mL is in 50mL volumetric flask, adding distil water is diluted to about 25mL, add 1mL ascorbic acid solution, add 2mL ammonium molybdate solution after 1min, adding distil water is diluted to scale, shake up, be configured to concentration be 0,0.1,0.2,0.6,1,1.4, the solution of 1.6mg/L.After colour developing 15min, use 1cm cuvette, in spectrophotometer, measure the absorbance of solution in 720nm place, typical curve as shown in Figure 1.
(3) test of phosphorus content in sample
Draw in LiFePO 4 sample treatment liquid 0.5ml to 100ml volumetric flask, adding distil water is diluted to about 50mL, adds 1mL ascorbic acid solution, and add 2mL ammonium molybdate solution after 1min, adding distil water is diluted to scale, shakes up.After colour developing 15min, measure the absorbance of solution in 720nm place with 1cm cuvette.Above-mentioned experiment is carried out three groups of parallel laboratory tests and is observed stability, and working curve is searched P test amounts, checks in three groups detect P content and be respectively 0.3926mg/L, 0.3928mg/L, 0.3825mg/L according to typical curve, and to try to achieve its mean value be 0.3926mg/L.Three testing standard deviations 0.000153, the relative standard deviation RSD value of P content results and test surveyed for three times by the mark-on experimental data that has good stability such as table 1:(LiFePO4 sample)
3, the test of iron content in sample
(1) preparation of reagent
Iron standard solution: the Fe titer pipetting 1ml, 1000ppm, is diluted in 100ml volumetric flask, adds deionized water constant volume, obtains the iron standard solution of 10mg/L.
(2) iron Specification Curve of Increasing and sample test
Pipette in the volumetric flask of 10ug/ml iron standard solution 5ml, 10ml, 15ml, 20ml, 25ml to 100ml respectively, obtain the iron standard solution of 0.5mg/L, 1mg/L, 1.5mg/L, 2mg/L, 2.5mg/L respectively, add 10% hydroxylamine hydrochloride solution of 1ml, the sodium acetate-hac buffer of 5mlPH=4.5, the 0.15% Phen solution of 2ml successively, be diluted to scale.After colour developing 30min, use spectrophotometer to carry out colorimetric estimation at 510nm, obtain iron typical curve, Fe marks liquid typical curve as shown in Figure 2.
(3) test of iron content in sample
Draw respectively in 2 parts of LiFePO 4 sample treatment liquid 0.5ml to 100ml volumetric flasks, adding distil water is diluted to 50mL, add 10% hydroxylamine hydrochloride solution of 1ml, the sodium acetate-hac buffer of 5mlPH=4.5, the 0.15% Phen solution of 2ml successively, be diluted to scale.After colour developing 30min, measure the absorbance of solution in 510nm place with 1cm cuvette.Above-mentioned experiment is carried out three groups of parallel laboratory tests and is observed stability, and working curve is searched Fe test amounts.Check in three groups of detection Fe content according to typical curve and be respectively 0.7038mg/L, 0.7041mg/L, 0.7037mg/L, and to try to achieve its mean value be 0.7039mg/L, three testing standard deviations 0.00035, data such as table 2(LiFePO4 sample surveys Fe content results and relative standard deviation RSD value three times):
4, the calculating of P and Fe content in sample
Calculate according to formula:
P content=19.63%
Fe content=35.2%
Fe/P=(0.352*30.974)/(0.1963*55.845)=0.9946
Embodiment 2
1, LiFePO 4 liquid to be measured is prepared:
Take 0.11g sample in 50ml beaker, add 10ml concentrated hydrochloric acid and 10ml red fuming nitric acid (RFNA), beaker is placed on heating for dissolving 5min on 70 DEG C of heating plates, prevents acid solution from volatilizing when noting heating at beaker upper cover upper surface ware.After sample dissolves completely, be filtered in 250ml volumetric flask the insoluble carbon impurity of the black removed in sample through double-layer filter paper, and the Liquid Residue repeatedly washed on beaker and filter paper is to ensure raw material free of losses.Finally add distillation and be diluted to scale, obtain LiFePO 4 sample treatment liquid.
2, the test of phosphorus content in sample
(1) preparation of reagent:
Ammonium molybdate solution: take 10g ammonium molybdate and 0.5g potassium antimonyl tartrate and dissolve with a small amount of distilled water and be transferred to respectively in 100ml volumetric flask, adding distil water is diluted to scale.Under constantly stirring, ammonium molybdate solution is slowly joined in 200ml (1+1) sulfuric acid, mixed solution is poured into antimony tartrate potassium solution, mix, and move into 500ml volumetric flask constant volume.
Ascorbic acid solution: take the dissolving of 6g Vitamin C bolt and be placed on constant volume in 50ml volumetric flask, be stored in brown bottle.
Phosphorus standard solution: the P titer pipetting 1ml, 1000ppm, is diluted in 100ml volumetric flask, adds deionized water constant volume, obtains the phosphorus standard solution of 10mg/L.
(2) phosphorus Specification Curve of Increasing and sample test
Pipette the phosphorus standard solution 0.00,0.50,1.00 of 10.0mg/L respectively, 3.00,5.00,7.00,9.00mL is in 50mL volumetric flask, adding distil water is diluted to about 25mL, add 1mL ascorbic acid solution, add 1.5mL ammonium molybdate solution after 1min, adding distil water is diluted to scale, shake up, be configured to concentration be 0,0.1,0.2,0.6,1,1.4, the solution of 1.6mg/L.After colour developing 15min, use 1cm cuvette, in spectrophotometer, measure the absorbance of solution in 720nm place, and draw phosphorus typical curve.
(3) test of phosphorus content in sample
Draw in LiFePO 4 sample treatment liquid 0.5ml to 100ml volumetric flask, adding distil water is diluted to about 50mL, adds 1mL ascorbic acid solution, and add 1.5mL ammonium molybdate solution after 1min, adding distil water is diluted to scale, shakes up.After colour developing 15min, measure the absorbance of solution in 720nm place with 1cm cuvette.Above-mentioned experiment is carried out three groups of parallel laboratory tests and is observed stability, and working curve is searched P test amounts, checks in three groups detect P content and be respectively 0.4315mg/L, 0.4319mg/L, 0.4317mg/L according to typical curve, and to try to achieve its mean value be 0.4317mg/L.
3, the test of iron content in sample
(1) preparation of reagent
Iron standard solution: the Fe titer pipetting 1ml, 1000ppm, is diluted in 100ml volumetric flask, adds deionized water constant volume, obtains the iron standard solution of 10mg/L.
(2) iron Specification Curve of Increasing and sample test
Pipette in the volumetric flask of 10ug/ml iron standard solution 5ml, 10ml, 15ml, 20ml, 25ml to 100ml respectively, obtain the iron standard solution of 0.5mg/L, 1mg/L, 1.5mg/L, 2mg/L, 2.5mg/L respectively, add 10% hydroxylamine hydrochloride solution of 1ml, the sodium acetate-hac buffer of 8mlPH=4.5, the 0.15% Phen solution of 1.5ml successively, be diluted to scale.After colour developing 30min, use spectrophotometer to carry out colorimetric estimation at 510nm, obtain iron typical curve.
(3) test of iron content in sample
Draw respectively in 2 parts of LiFePO 4 sample treatment liquid 0.5ml to 100ml volumetric flasks, adding distil water is diluted to 50mL, add 10% hydroxylamine hydrochloride solution of 1ml, the sodium acetate-hac buffer of 8mlPH=4.5, the 0.15% Phen solution of 1.5ml successively, be diluted to scale.After colour developing 30min, measure the absorbance of solution in 510nm place with 1cm cuvette.Above-mentioned experiment is carried out three groups of parallel laboratory tests and is observed stability, and working curve is searched Fe test amounts.Check in three groups according to typical curve to detect Fe content and be respectively 0.7742mg/L, 0.7734mg/L, 0.7731mg/L, and to try to achieve its mean value be 0.7736mg/L.
4, the calculating of P and Fe content in sample
Calculate according to formula:
P content=19.62%
Fe content=35.16%
Fe/P=(0.3516*30.974)/(0.1962*55.845)=0.9939
The present invention uses spectrophotometer can detect Fe, P two kinds of element method, and the present invention tests in P content process and in the yellow developer of traditional phosphorus molybdenum, adds reductive agent solution is developed the color become blueness from the yellow of original recipe, even if simultaneously containing Fe in solution
2+(green) solution and Fe
3+(yellow) also can not impact chromogenic reaction absorption at a particular wavelength, adds accurate testing degree.And in the process preparing sample, find that the undulatory property of test also obviously reduces by after undissolved carbon slag removing, further increase test accuracy.Operation is relatively simple, and accurate testing degree is high, has conclusive help to production quality control.
Certainly; the present invention also can have other various embodiments; when not deviating from the present invention's spirit and essence thereof; those of ordinary skill in the art can make various corresponding change and distortion according to the present invention, but these change accordingly and are out of shape the protection domain that all should belong to the claims in the present invention.
Claims (7)
1. a LiFePO
4in/C composite, the detection method of phosphorus and iron content, is characterized in that, comprises the steps:
Step 1: by LiFePO
4/ C composite mixes with concentrated hydrochloric acid and red fuming nitric acid (RFNA), and heating for dissolving also filters out insoluble atrament, obtains LiFePO
4/ C composite solution to be measured;
Step 2: draw phosphorus typical curve;
Step 3: the LiFePO obtained in step 1
4ascorbic acid solution is added in/C composite solution to be measured, trivalent Fe in solution is reduced into ferrous iron, and adds ammonium molybdate solution, colour developing, measure the absorbance of solution with cuvette in 720nm place, on the phosphorus typical curve of step 2, search P test amounts according to described absorbance;
Step 4: draw iron typical curve;
Step 5: the LiFePO obtained in step 1
4hydroxylamine hydrochloride solution, sodium acetate-hac buffer and Phen solution is added in/C composite solution to be measured, colour developing, measure the absorbance of solution with cuvette in 510nm place, on the iron typical curve of step 2, search Fe test amounts according to described absorbance;
Step 6: calculate LiFePO
4p and Fe content in/C composite, computing formula is:
In formula: x is LiFePO
4total phosphorus or Fe percentage composition in/C composite;
C is the content of the phosphorus found from phosphorus typical curve or the content of iron found from iron typical curve;
M is LiFePO
4the quality of/C composite.
2. LiFePO according to claim 1
4in/C composite, the detection method of phosphorus and iron content, is characterized in that, in described step 1, and every gram of LiFePO
4/ C composite mixes with 5ml ~ 10ml concentrated hydrochloric acid and 5ml ~ 10ml red fuming nitric acid (RFNA).
3. LiFePO according to claim 1
4in/C composite, the detection method of phosphorus and iron content, is characterized in that, atrament described in described step 1 is carbon.
4. LiFePO according to claim 1
4in/C composite, the detection method of phosphorus and iron content, is characterized in that, in described step 1, heating for dissolving temperature is 60 DEG C ~ 80 DEG C.
5. LiFePO according to claim 1
4in/C composite, the detection method of phosphorus and iron content, is characterized in that, described step 3 repeats 3 times, and obtain three P test amounts, average, described step 5 repeats 3 times, obtains three Fe test amounts, averages.
6. LiFePO according to claim 1
4in/C composite, the detection method of phosphorus and iron content, is characterized in that, in described step 2, described ammonium molybdate solution is the mixed solution of ammonium molybdate and sulfuric acid and potassium antimonyl tartrate.
7. LiFePO according to claim 1
4in/C composite, the detection method of phosphorus and iron content, is characterized in that, in described step 3, and described LiFePO
4/ C composite solution to be measured, before adding ascorbic acid solution, is cooled to room temperature after heating 20-40min in boiling water bath.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105021556A (en) * | 2015-07-22 | 2015-11-04 | 浙江瑞邦科技有限公司 | Detection method of iron content in lithium iron phosphate |
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| CN105021556A (en) * | 2015-07-22 | 2015-11-04 | 浙江瑞邦科技有限公司 | Detection method of iron content in lithium iron phosphate |
| CN105115922A (en) * | 2015-09-21 | 2015-12-02 | 浙江瑞邦科技有限公司 | Method for detecting iron content of lithium iron phosphate-carbon composite material |
| CN112213279A (en) * | 2020-10-13 | 2021-01-12 | 北京清新环境技术股份有限公司 | Method for measuring iron ions in denitration absorption liquid |
| CN112557146A (en) * | 2020-12-28 | 2021-03-26 | 苏州欣影生物医药技术有限公司 | Method for measuring content of amino PEG (polyethylene glycol) -coated nano iron oxide |
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