废旧磷酸铁锂正极粉磷酸浸出过程的优化及宏观动力学

随着新能源汽车产业快速发展，磷酸铁锂动力电池退役量爆发式增长，回收需求迫切，但面临回收利用经济性较差的难题。正极材料价值较高，本文提出采用磷酸浸出废旧正极材料以制备电池用磷酸铁，但铝等杂质的分离是关键。本文以含铝的磷酸铁锂正极粉为原料，开展了磷酸浸出过程优化及宏观动力学研究，重点研究了酸料比、浸出温度、液固比、搅拌速度等参数对磷酸铁锂及铝浸出效果的影响规律，并考察了磷酸铁锂在磷酸溶液中浸出的宏观动力学。研究结果表明，在酸料比1.1mL/g、温度20℃、液固比（5∶1)mL/g、搅拌速度400r/min、浸出时间120min条件下，磷酸铁锂浸出率大于93%，铝浸出率小于20%；磷酸铁锂正极粉磷酸浸出过程符合无固态产物层的收缩核模型，表观活化能为24.62kJ/mol，浸出过程受扩散控制。

Process optimization and kinetics for leaching spent lithium iron phosphate cathode powder by phosphate acid

With the rapid development of new energy vehicles, the amount of spent lithium iron phosphate (LFP) power batteries increase explosively, and the demand for recycling the spent LFP batteries is very urgent, which however still faces the problem of poor economics of recycling. Due to the high value of the cathode materials in LFP battery, we proposed a new method for preparing battery grade iron phosphate from the spent LFP cathode material by using phosphoric acid, whose key is to remove the impurities such as Al. In this paper, the leaching of aluminum-containing lithium iron phosphate cathode powder was optimized and the process kinetics was studied. The effects of the ratio of acid to material, leaching temperature, liquid-solid ratio and stirring speed on the leaching efficiency of lithium iron phosphate and aluminum, as well as the leaching kinetics in phosphoric acid solution, were also investigated. The results showed that under the optimal conditions of ratio of acid to material 1.1mL/g, temperature 20℃, liquid-solid ratio （5∶1）mL/g, stirring speed 400r/min and reaction time 120min, the leaching efficiency of lithium iron phosphate was above 93%, and the leaching efficiency of aluminum is below 20%. The leaching model was fit to the shrinking core model without solid product layer, yielding an apparent activation energy of 24.62kJ/mol with the liquid film diffusion as the rate limiting step.