Influence of vacuum filtration decarbonization on the determination of iron in carbon-coated lithium iron phosphate

The presence of carbon might affect the dissolution of carbon-coated lithium iron phosphate.Vacuum filtration decarbonization could benefit the determination of iron in carbon-coated lithium iron phosphate(LiFePO4/C).In order to check out whether the decarbonization affect the determination results,the sample was dissolved in hydrochloric acid under 160℃for 10 min,before vacumm decarbonization,potassium dichromate oxidation and titanium trichloride reduction titration determination of Fe in the material.X-ray diffraction(XRD)characterization showed the XRD spectrum of carbon residue and amorphous carbon were quite similar and characteristic peak was not observed,indicating the abscence of lithium iron phosphate.In addition,deducting the carbon content,iron content by titration is similar to theoretical content.Iron content in carbon slag solution was determined with ICPAES,indicating non-detected,which further denied the loss of lithium iron phosphate during decarbonization.Analysis was conducted on Fe of three LiFePO4/C practical samples.The relative standard deviation(RSD)was not more than 0.06%.When the solution was analyzed by titration and ICPAES after vacuum filtration,the relative error was lower than 0.50%.Since the testing result of highcontent component by ICP-AES was not quite stable,this method is more suitable to the determination of iron in carbon-coated lithium iron phosphate with mass production.