磷酸体系应用于失效磷酸铁锂电池正极材料回收的研究

Application of Phosphoric Acid System in Positive Electrode Material Recovery from Invalid Lithium Iron Phosphate Batteries

以H_3PO_4-H2O_2溶液对除铝后的失效磷酸铁锂电池正极材料进行浸出锂实验,采用ICP-OES测定浸出液中Li+和Fe3+浓度,研究了H2O_2及H_3PO_4加入量、液固质量比(L/S)、反应温度、搅拌转速、反应时间及体系终态pH值对Li浸出率的影响,并对终态pH值为3.5得到的滤渣进行XRD分析,结果表明,Li浸出率随H2O_2及H_3PO_4加入量的增加而增大,但当H2O_2与H_3PO_4用量分别高于1.2倍、1.1倍反应计量时,锂浸出率增速趋缓;随着液固质量比的增大,Li浸出率呈现先增大后减小的趋势;在30~60℃反应温度对Li浸出率影响不明显;Li浸出率随搅拌转速的提高和反应时间的延长而增大,但搅拌转速高于30 r×min^(-1)、反应时间超过3.0 h后Li浸出率变化不明显;体系终态pH为3.5时,锂浸出率为99.21%、铁沉淀率为99.99%,浸出渣为Fe PO_4·2H2O。

H_3PO_4-H_2O_2 solutions were used in Li leaching from iron phosphate batteries after aluminum separation, and the concentrations of Li＋ and Fe3＋ were calibrated by ICP-OES. Effects of H_2O_2 and H_3PO_4 percentage, liquid solid mass ratio, reaction temperature, stirring speed, reaction time and final pH value on Li leaching ratio were studied and leaching residues at final pH value of 3.5 was analyzed by XRD. Experimental results indicate that Li leaching ratio increases with the increase of H_2O_2 and H_3PO_4 addition. However, when the dosages of H_2O_2 and H_3PO_4 are higher than 1.2 and 1.1 times of reaction stoichiometry respectively, the increase of Li leaching ratio slows down. Li leaching ratio increases first and then decreases with the increase of liquid solid mass ratio. Reaction temperature（30~60℃） has few effects on Li leaching ratio which increases along with the increase of stirring speed and reaction time, and the ratio remains almost constant when the two parameters are higher than 30 r×min^（-1） and 3.0 h respectively. When the final pH value of the system is adjusted to 3.5, Li leaching ratio is 99.21% and the precipitation ratio of iron is 99.99%. The leaching residue is FePO_4·2 H_2O.