Zhang Beilei, Qu Xin, Chen Xiang, Liu Dongxu, Zhao Zhuqing, Xie Hongwei, Wang Dihua, Yin Huayi
Key Laboratory for Ecological Metallurgy of Multimetallic Mineral of Ministry of Education, School of Metallurgy, Northeastern University, Shenyang 110819, PR China.
School of Resource and Environmental Science, Wuhan University, Wuhan 430072, PR China.
J Hazard Mater. 2022 Feb 15;424(Pt C):127586. doi: 10.1016/j.jhazmat.2021.127586. Epub 2021 Oct 27.
Mild-temperature (<1000 °C) carbothermic reduction has been proven as an effective way to recover Li and transition metals by converting lithium transition metal oxides to transition metals/alloys and LiCO. However, LiFePO cannot be reduced by carbon because of its thermodynamically stable olivine structure. Herein, LiFePO is converted to Fe and lithium salts by carbon with the assistance of NaCO that acts as an activating agent to break down the chemical bonds of LiFePO and thereby enable the carbothermic reduction. Using NaCO as the activating agent, LiFePO was reduced to Fe, NaLiPO, and LiNa(PO) which can be separated by magnetic separation with a Li recovery rate of 99.2%. Using NaOH as the activating agent, LiFePO was oxidized to FeO, NaLiPO and LiNa(PO) at 600 °C, and the roasted products can be separated by magnetic separation process with a Li recovery rate of 92.7%. Various sodium salts were tested to screen proper salts for the reduction process, and a 400-g scale roasting-separation process has been demonstrated. Overall, the salt-assisted roasting is a promising way to recycle spent LiFePO batteries without using strong mineral acids and shows great potential for the industrial-scale implementation.
温和温度（<1000°C）碳热还原已被证明是一种通过将锂过渡金属氧化物转化为过渡金属/合金和碳酸锂来回收锂和过渡金属的有效方法。然而，磷酸铁锂由于其热力学稳定的橄榄石结构而不能被碳还原。在此，在作为活化剂的碳酸钠的辅助下，碳将磷酸铁锂转化为铁和锂盐，碳酸钠充当活化剂以破坏磷酸铁锂的化学键，从而实现碳热还原。以碳酸钠作为活化剂，磷酸铁锂被还原为铁、磷酸钠锂和磷酸锂钠，可以通过磁选分离，锂回收率为99.2%。以氢氧化钠作为活化剂，磷酸铁锂在600°C下被氧化为氧化亚铁、磷酸钠锂和磷酸锂钠，焙烧产物可以通过磁选工艺分离，锂回收率为92.7%。测试了各种钠盐以筛选用于还原过程的合适盐，并展示了一个400克规模的焙烧-分离过程。总体而言，盐辅助焙烧是一种在不使用强无机酸的情况下回收废旧磷酸铁锂电池的有前景的方法，并且在工业规模实施方面具有巨大潜力。
