废钴酸锂正极材料悬浮电解一步再生钴酸锂机理研究

Efficient recovery of Li and Co from the spent cathodic active material (i.e. cathodic active material of the spent lithium cobalt oxide battery), which is the core of the recycling of the lithium cobalt oxide battery, is the necessary requirement of avoiding environmental damage, promoting sustainable utilization of the resource, and alleviating the strategic resource shortage of cobalt and lithium in China. The application of suspension electrolysis technology to the treatment of the spent cathodic active material can realize the dissolution, purification and regeneration of Li and Co in one step, providing a new way for its resource utilization. How to construct the suspension electrolysis system to electrodeposit LiCoO2 and separate impurities efficiently is the key to the practical application of this process. In this research, the thermodynamic principle and kinetics mechanism of the suspended electrolytic system of spent cathodic active material are focused on, the law of migration and transformation of Li, Co and impurities are revealed, the thermodynamics and kinetic models of waste Li/Co dissolution-transfer-deposition/impurity separation under suspension electrolysis are established, and an innovative technology based on suspension electrolysis for spent cathodic active material recycling is put forward. The result of this research can provide theoretical support for the further research and application of the new process in the recovery of lithium cobalt oxide from the spent lithium cobalt oxide battery.

废钴酸锂正极材料中Li、Co的高效回收，是废钴酸锂电池资源化的核心，是避免生态环境污染、推动资源可持续利用进程和缓解我国锂钴战略资源短缺的必然要求。将悬浮电解技术应用于废钴酸锂正极材料的处理处置，能一步实现Li、Co的溶出、提纯和再生，为其资源化提供了一条新途径。如何构建废钴酸锂正极材料悬浮电解体系，实现LiCoO2的高效电沉积再生及杂质的高效分离，是该工艺实用化的关键。本课题以废钴酸锂正极材料悬浮电解体系反应热力学原理和动力学机制为核心，揭示不同悬浮电解体系中Li、Co及杂质的迁移转化规律，建立悬浮电解条件下废Li/Co的溶解-迁移-沉积/杂质分离热力学和动力学模型，以提出基于悬浮电解的废钴酸锂正极材料资源化新技术，为该新工艺在废钴酸锂电池资源化方面的进一步研究与应用提供理论支持。

为了实现废LiCoO2的短流程、高效率、清洁化回收和再生，研究了废LiCoO2的NH4HCO3悬浮电解体系、NH4HCO3-NH3·H2O悬浮电解体系、NH4HCO3-(NH4)2SO3悬浮电解体系。通过对悬浮电解再生废LiCoO2的研究，确定了应用NH4HCO3-(NH4)2SO3悬浮电解体系回收再生废LiCoO2的方法，并揭示了其反应过程机理。取得以下研究成果：（1）在NH4HCO3反应体系中，电场可以促进NH3·H2O与LiCoO2反应形成Co-NH3络合物的进程，但反应效率低，Co的浸出率基本在2%以下，Li的浸出率低于9%，且未能实现LiCoO2的阴极再生；（2）NH3·H2O不是该反应的限制性因素，NH4+仅作为NH3络合剂的提供者，几乎没有消耗；SO32-和H2O是该过程消耗的主要试剂；阳极区应定期添加SO32-，阴极区应定期去除SO42-，以促进反应的正向进行；（3）在NH4HCO3-(NH4)2SO3悬浮电解反应体系中，LiCoO2能一步实现阳极浸出和阴极沉积，并得出优化条件：NH4HCO3浓度2.5 mol/L、电流3.5 A、(NH4)2SO3浓度0.7 mol/L、反应时间90 min、温度60℃、固液比4 g/L、氟化钠2.5 g；（4）在以上优化条件下，以纯LiCoO2为实验样品，Li 的浸出率达95.3%，Co的浸出率达88.6%，钴酸锂的再生率达75.2%；以废LiCoO2正极材料为实验样品，Li 的浸出率为71.8%，Co的浸出率为55.4%，钴酸锂的再生率为51.5%。. NH4HCO3-(NH4)2SO3悬浮电解反应体系一步阳极溶解-阴极沉积LiCoO2机理：（1）该反应是络合、还原、氧化、电流传输与离子迁移共同作用的结果；（2）LiCoO2的阳极溶解为两步反应，涉及的反应过程包括：Co-NH3络合、SO32-的还原和电场氧化；（3）LiCoO2的阴极合成非氧化还原反应，涉及的反应过程包括：H2O作为e-受体提供OH-以及电场、铂极板与电解液的共同作用实现LiCoO2的合成。. 本研究首次实现了在一个电化学反应器中、在常压下一步实现钴酸锂的阳极溶出和阴极再沉积，同时未添加任何酸和碱，反应体系仅包含NH4HCO3、(NH4)2SO3和NaF。利用该反应，可清洁化实现废LiCoO2的回收与再生。