以三元锂电池回收的末端废渣为原料制备的高效核壳结构催化剂性能及机理研究

随着新能源汽车的推广和普及，锂离子电池的装机量呈爆发式增长，随之而来的是大量锂电池的报废，亟待回收处理. 已有锂电池回收技术提取锂、镍、钴、锰等金属后仍残留有一定量过渡金属的末端废渣，若不加以处理处置直接丢弃到环境中会造成重金属的环境污染风险. 本研究提出一种以锂电池回收的末端废渣为原料，与三聚氰胺固体粉末混合后热解的方法，制备出具有核壳结构的高性能催化剂，用于催化过硫酸盐氧化剂氧化去除有机污染物，实现其高值化再利用. 结果表明:①新制备的催化剂具有明显的核壳结构，核为镍钴氮化物和锰氧化物，壳为厚度约5.7~13.1 nm的石墨化碳层. ②以单过硫酸盐(PMS)为氧化剂，对新制备催化剂(NCM1)的催化性能进行了测试，发现其可高效催化PMS降解苯甲酸、苯酚等一系列难降解有机污染物，当NCM1的投加量为0.03 g/L时，浓度为0.05 mmol/L的难降解有机物—2,4-二氯苯酚，在吸附后2 h内降解完全. NCM1/PMS降解体系受环境条件的影响较纯自由基体系小. ③循环试验的结果表明，该材料可实现多次循环利用且催化效率基本保持稳定. ④对降解完成后体系中的金属离子进行测定发现，新制备的催化剂在催化降解过程中，金属离子仅有微量溶出，而原始废渣则大量溶出金属离子，说明与三聚氰胺混合热解可有效固定废渣中的金属. ⑤经淬灭试验、D₂O替换和EPR测试等一系列试验，证明新催化剂催化单过硫酸盐降解有机污染物体系中硫酸根自由基和单线态氧均具有一定贡献，但还存在其他未被探明的机理. 研究显示，新制备的NCM1具有高PMS催化活性以及良好的稳定性和环境友好性，展现出巨大的应用潜力，对锂电池回收废渣的处理处置具有参考意义. 

Performance and Mechanism of a Core-Shell Catalyst Prepared from End Waste of Recycled Ternary Lithium Battery

With the promotion and popularization of new energy vehicles, the installed amounts of lithium-ion batteries have exploded, followed by a large number of scrapped lithium batteries, which urgently need to be recycled. There is a certain amount of transition metals in the residues after extracting lithium, nickel, cobalt, and manganese. If these residues are directly disposed into the environment without treatment, it will cause serious environmental pollution. The results demonstrates that: (1) A catalyst (NCM1) with a core-shell structure was prepared by mixing the residue with melamine. Both NCM1 and the original residue were fully characterized. It was confirmed that NCM1 had an obvious core-shell structure, with the core was composed of nickel-cobalt nitrite and manganese oxide, and the shell was composed of a graphitized carbon layer with a thickness of about 5.7-13.1 nm. (2) The catalytic performance of NCM1 was tested with peroxymonosulfate as oxidant, the catalytic performance of NCM1 was tested. It was found that NCM1 efficiently catalyzed PMS to degrade a series of organic pollutants, including benzoic acid, nitrobenzene, phenol, etc., and it was less affected by environmental conditions than traditional free radical degradation systems. Under the condition of 0.03 g/L NCM1, the absorbed 0.05 mmol/L 2,4-Dichlorophenol was competely removed within 2 hours. (3) The results of cyclic experiments showed that NCM1 could be recycled several times with stable catalytic efficiency. (4) Small amount of metal ions were dissolved after the degradation in NCM1/PMS system, while large amount of metal ions were dissolved in the original residue/PMS system, indicating that the metal ions in the residue were effectively fixed through the mixed pyrolysis with melamine. (5) A series of experiments including quenching experiments, D₂O replacement and EPR tests demonstrated that sulfate radical and singlet oxygen contributed to the degradation of pollutants in the NCM1/PMS system, but there are still unexplored mechanisms. The research shows that NCM1 has high catalytic activity and good stability and environmental friendliness, showing great application potential, which is of significance for dealing with the end waste of recycled lithium battery.