微波焙烧-水浸回收废旧锂离子电池中有价金属新工艺的研究

STUDY ON RECOVERY OF METALS FROM CATHODE MATERIALS OF SPENT LITHIUM-ION BATTERIES BY MICROWAVE ROASTING-WATER LEACHING PROCESS

刘振达

11930267

硕士

材料工程

徐政和(Zhenghe Xu)

2021-05-15

2021-06-23

南方科技大学

深圳

近年来，随着锂离子电池产业的持续高速增长，废旧锂离子电池所带来的环境及资源问题日益突出。如何无害化、高值化地回收利用这种二次资源已逐渐成为国内外的研究热点。本论文提出了一种“微波低温焙烧+水浸”回收金属新工艺。在微波辅助作用下，利用温和的硫酸盐（(NH4)2SO4）将正极粉末中的LiCoO2焙烧转化为水溶性的硫酸盐（CoSO4、Li2SO4），然后通过水浸工艺得到含目标金属的水溶液。本论文将主要考察：废旧锂离子电池正极材料和(NH4)2SO4的吸波特性研究；微波辅助硫酸盐焙烧的工艺优化及相关动力学研究；焙烧渣的水浸及钴酸锂正极材料的微波辅助再生和电化学性能研究。主要研究内容及结论如下：研究了(NH4)2SO4、LiCoO2废料和混合物料的介电特性和升温特性曲线，结果表明：LiCoO2废料具有极好的介电特性，其吸波特性明显优于(NH4)2SO4；对于(NH4)2SO4和LiCoO2的混合物，随着(NH4)2SO4用量增加，混合物料的吸波特性逐渐变差。考察了微波焙烧温度、微波焙烧时间和(NH4)2SO4用量对Co、Li回收率的影响，结果表明在焙烧温度为400 ℃、焙烧时间30 min、= 3:1的最佳条件下，Co与Li的回收率均超过90%；焙烧动力学研究表明，Co的焙烧过程符合未反应收缩核模型，且受内扩散步骤控制；经计算，微波焙烧的表观活化能为24.99 KJ/mol，明显低于常规焙烧过程的表观活化能（33.26 KJ/mol），结果表明微波有助于提高焙烧过程的动力学。采用沉淀法从焙烧-水浸液中制备得到Co3O4和Li2CO3，并利用固相合成法再生制备得到LiCoO2。结果表明，相比于传统合成方法，微波加热合成LiCoO2可以更快地得到合格的LiCoO2产品。微波辅助再生所得LiCoO2具有如下电化学性能：起始容量为121 mAh g-1，库伦效率82%，循环100圈后容量还有80 mAh g-1。综上所述，本论文着重研究了微波在电池回收及再生中的运用，并成功探索出了一种高效、环保的废旧钴酸锂的回收及再生新工艺，为废旧电池的资源化利用提供了新思路。

With rapid growth of lithium-ion battery industry in recent years, environmental problems and depleting natural resources caused by spent lithium-ion batteries have become increasingly a major challenge to battery and electrical vehicle industries. How to recycle this secondary resource in an environmentally benign and high-value manner has become a research focus both in China and abroad. In respond to such situation, this thesis proposes a new "microwave-assisted low-temperature roasting-water leaching" process. With the aid of the microwave treatment, a sulfate salt ((NH4)2SO4 ) is used to calcinate LiCoO2 in the positive electrode powder into water-soluble metal sulfates (CoSO4, Li2SO4).The water-soluble sulfates formed are leached out by water to obtain an aqueous solution containing the target metals. This thesis project investigates mainly: the absorption characteristics of microwave radiation by spent lithium ion battery cathode materials and (NH4)2SO4; optimization of microwave-assisted roasting process and kinetics of sulphuration roasting; aqueous leaching characteristics of roasting slags, and microwave-assisted regeneration of lithium cobalt oxide cathode materials and their electrochemical performance. The main research contents and conclusions are as follows:Study the dielectric properties and temperature profiles of pure (NH4)2SO4, spent LiCoO2 materials and their mixture under microwave radiation. The results show that spent LiCoO2 has excellent dielectric properties with significantly better absorbing properties of microwave radiation than (NH4)2SO4. For the mixture of (NH4)2SO4 and LiCoO2, the microwave absorbing properties deteriorate gradually with increasing the amount of (NH4)2SO4 in the mixture.The effect of microwave roasting temperature, microwave roasting time and the amount of (NH4)2SO4 on the recovery of Co and Li was investigated. The results showed that under the optimal conditions of roasting temperature 400 ℃, roasting time 30 min, and ratio of 3:1, the recovery for both Co and Li exceeded 90%. The roasting kinetics study revealed that the roasting process of Co follows the unreacted shrinkage nucleus model and is controlled by the internal diffusion. The calculation showed an apparent activation energy of microwave-assisted roasting to be 24.99 KJ/mol, which is significantly lower than the apparent activation energy of the conventional roasting process (33.26 KJ/mol). The results indicate that microwave roasting helps to improve the kinetics of the roasting process.Co3O4 and Li2CO3 are prepared from roasting-water leaching solution by precipitation method, while LiCoO2 is prepared by solid-phase synthesis method for regeneration of cathode materials. The results showed that the synthesis of LiCoO2 by microwave heating can produce high quality LiCoO2 faster than by traditional synthesis methods. The LiCoO2 obtained by microwave-assisted regeneration has the following electrochemical properties: the initial capacity of 121 mAh g-1, the coulombic efficiency of 82%, and the capacity of 80 mAh g-1 after 100 cycles.In summary, this thesis focuses on the application of microwave in spent lithium battery recycling and regeneration, and successfully explored a high-efficiency and environmentally friendly recycling and regeneration process for lithium cobalt oxide in spent battery, which is a valuable resource of cobalt. The research in this thesis thus provides new ideas for the utilization of spent batteries while resolving environmental issues of spent battery disposal.

废旧锂离子电池 微波焙烧 钴酸锂 硫酸铵 材料再生

spent lithium-ion batteries microwave roasting lithium cobalt oxide ammonia sulfate materials regeneration

中文

独立培养

南方科技大学

刘振达. 微波焙烧-水浸回收废旧锂离子电池中有价金属新工艺的研究[D]. 深圳. 南方科技大学,2021.