电位滴定法用于富锂锰基正极材料中钴的测定

钴含量的准确分析对控制富锂锰基正极材料电化学性能有重要意义。锰会对电位滴定测定钴产生干扰,而富锂锰基正极材料中锰含量较高,因此电位滴定测定钴时需要考虑锰的干扰。实验采用盐酸、硝酸溶解样品,加入氯酸钾将锰(II)氧化为二氧化锰沉淀并过滤分离。滤液中加入柠檬酸铵-氯化铵-氨水混合溶液及铁氰化钾标准溶液,使钴氧化完全,过量的铁氰化钾用钴标准滴定溶液进行电位滴定。二氧化锰沉淀连同滤纸用硫酸、硝酸硝化后,电感耦合等离子体原子发射光谱法(ICP-AES)测定沉淀中残留的钴。电位滴定法测定的钴量和沉淀中残留钴量的合量为样品中的钴含量。按照实验方法对1个富锂锰基正极材料实际样品和2个富锂锰基正极材料合成样品进行测定,测定结果的相对标准偏差(RSD,n=11)在0.26%~0.33%。采用实验方法对富锂锰基正极材料实际样品进行测定,并与ICP-AES进行对照试验,结果表明,两种方法的测定值相吻合。

Application of potentiometric titration in the determination of cobalt in lithium-rich manganese-based cathode materials

The accurate analysis of cobalt content has importance significance to control the electrochemical property of lithium-rich manganese-based cathode materials. Manganese has interference during the potentiometric titration of cobalt. Since the content of manganese in lithium-rich manganese-based cathode materials is high, the interference of manganese should be considered during the determination of cobalt by potentiometric titration. The sample was dissolved with hydrochloric acid and nitric acid. Potassium chlorate was added to oxidize manganese (II) into manganese dioxide precipitate, which was then filtrated for separation. The mixed solution of ammonium citrate-ammonium chloride-ammonia and the standard solution of potassium ferricyanide were added into the filtrate to completely oxidize cobalt. The excessive potassium ferricyanide was potentiometrically titrated with the standard titration solution of cobalt. Manganese dioxide together with the filter paper was nitrified with sulfuric acid and nitric acid. The residual cobalt in the precipitate was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES). The sum of cobalt content determined by potentiometric titration and the residual content in the precipitate was the cobalt content in the sample. One actual sample and two synthetic samples of lithium-rich manganese-based cathode materials were determined according to the experimental method. The relative standard deviations (RSD, n=11) of determination results were between 0.26% and 0.33%. The experimental method was used to determine the actual samples of lithium-rich manganese-based cathode material, and the comparison test was carried out with ICP-AES. The results show that two methods were consistent.