由电解磷铁废渣制备的FePO4合成LiFePO4研究

在磷酸水溶液中,以磷铁废渣为阳极、石墨为阴极,恒流无膜电解后溶液由无色变为黄色,用氨水调节pH值,经过滤、洗涤、干燥,得到淡黄色粉体,XRD和热分析结果表明该粉体组成为FePO4.2H2O.在电解产物中加入LiOH.H2O和葡萄糖,用乙醇作溶剂充分研磨形成流变相前驱体,在700℃氩气气氛中焙烧得到LiFePO4/C复合物.用动电位极化方法分析了磷铁的电解过程,用XRD、SEM和循环伏安法(CV)研究了LiFePO4/C复合物的结构、形貌及电化学性能.测试结果表明LiFePO4/C复合物没有磷铁原料的杂质峰,氧化电位和还原电位分别在3.54和3.33 V,说明经过阳极袋电解能够消除磷铁原料中的杂质元素影响及锂离子脱/嵌过程中极化较小.

Synthesis of LiFePO4 Using FePO4 Produced by Electrolyzing Fe1.5P Waste Slag

Fe1.5P waste slag was galvanostatically electrolyzed without separator in a H3PO4 aqueous solution using graphite as the cathode,and the electrolyte color turned from achromatism to yellow after electrolysis.Light yellow powder was finally obtained by adjusting the value of pH using ammonia water,filtering,washing and drying in sequence.The results of XRD and TG-DTA showed that the as-electrolyzed product was FePO4.2H2O.The as-obtained FePO4.2H2O was mixed well with LiOH.H2O and glucose to form a rheological phase precursor by using ethanol as a dispersing agent.LiFePO4/C composite was synthesized successfully by calcining the above precursor at 700℃ in an Ar atmosphere.The electrolysis process was investigated via a potentiodynamic polarization method.The structure,morphology and electrochemical performance of the as-synthesized LiFePO4/C composite were characterized by XRD,SEM and cyclic voltammetry,respectively.There was no impurity indexed peaks from Fe1.5P raw material,and the oxidization potential and the reduction potential were at 3.54 V and 3.33 V,respectively.The good experimental results indicated that electrolysis of Fe1.5P waste slag using an anode bag can eliminate the effect of impurities from raw material and the polarization between lithium ion intercalation and de-intercalation was low.