摘要/Abstract

针对当前退役锂离子电池有价金属提取工艺选择性差、环境风险突出的瓶颈问题, 提出了碳/硫协同选择性提锂的新思路. 首先在系统考察(NH₄)₂SO₄、NH₄HSO₄、NaHSO₄和H₂SO₄分别作为焙烧剂对退役锂离子电池LiNi_1/3Co_1/3Mn_1/3O₂正极粉末中锂的浸出选择性、环境友好性和经济性影响的基础上, 确定H₂SO₄为最佳焙烧剂. 基于此, 研究了石墨添加量对LiNi_1/3Co_1/3Mn_1/3O₂中锂的浸出选择性的影响, 揭示了C/S协同强化锂的浸出选择性的转化路径及其机制. 结果表明, 在LiNi_1/3Co_1/3Mn_1/3O₂与H₂SO₄物质的量比为2∶1、石墨添加量为20% (w)、焙烧温度为600 ℃、焙烧时间为120 min的最优条件下, LiNi_1/3Co_1/3Mn_1/3O₂中锂的浸出率高达93%, 回收的Li₂CO₃纯度高于电池级Li₂CO₃纯度要求; Ni、Co和Mn均进入渣相, 经分离纯化后可作为合成正极材料的前驱物, 分离得到的石墨可回用于硫化焙烧过程的添加剂. 通过对LiNi_1/3Co_1/3Mn_1/3O₂混合粉末(含20 wt.%石墨)硫化焙烧热行为及其产物X射线衍射(XRD)表征表明, 石墨的添加降低了硫化焙烧的反应温度, 通过C/S协同作用强化了LiNi_1/3Co_1/3Mn_1/3O₂中锂的选择性浸出, 且不产生SO_x等有毒有害气体. 本工作结合硫化焙烧和碳热还原优势, 为退役锂离子电池正负极材料的同步循环利用开辟了新思路, 实现了LiNi_1/3Co_1/3Mn_1/3O₂中锂的高效选择性清洁提取和废石墨负极的循环利用.
关键词: 退役锂离子电池, 硫化焙烧, 废石墨, 选择性提取, 锂
Recycling of spent lithium-ion batteries (LIBs) has attracted ever-growing attention globally owing to the scarcity of critical metals and potential environmental risk. To solve the bottlenecks including poor selectivity and prominent environmental risks during the recovery of valuable metals from spent LIBs, the work proposed a novel process for selectively recovery of lithium synergized by carbon and sulfur elements. Firstly, H₂SO₄ was determined as the optimal roasting reagent by systematically investigating the effects of various roasting reagents including NaHSO₄, (NH₄)₂SO₄, NH₄HSO₄ and H₂SO₄ on the leaching selectivity of lithium from the LiNi_1/3Co_1/3Mn_1/3O₂ active material in spent LIBs, environmental impact and cost of reagents. Then, the effect of graphite dosage on the selectivity of lithium from LiNi_1/3Co_1/3Mn_1/3O₂ is investigated. Finally, the conversion path and mechanism under the synergistic effect of C and S elements for enhancing the selectivity of lithium is revealed. It is found that the leaching efficiency can achieve 93% under the following optimal conditions: the molar ratio of LiNi_1/3Co_1/3Mn_1/3O₂ to H₂SO₄ of 2∶1, graphite dosage of 20% (w), roasting temperature of 600 ℃, and roasting time of 120 min. The purity of the precipitated Li₂CO₃ from the obtained leachate is higher than that of battery grade Li₂CO₃. Ni, Co and Mn from LiNi_1/3Co_1/3Mn_1/3O₂ almost remains in the leaching residue which can be employed as the precursor materials for synthesizing cathode materials after separation and purification treatment. In addition, the separated graphite can be reused as roasting additive during the sulfation roasting of LiNi_1/3Co_1/3Mn_1/3O₂. By analyzing the thermal behavior of the mixed powder of LiNi_1/3Co_1/3Mn_1/3O₂ and graphite, along with the X-ray diffraction (XRD) characterization of the roasting products, it is found that the roasting temperature can be reduced by the addition of waste graphite, the selectivity of lithium can be enhanced under the synergistic effect of C and S elements. Most importantly, no hazardous gases such as SO_x are generated. This work proposed a new solution for simultaneous recycling of cathode and anode materials by combing the advantages of sulfation roasting and carbothermal reduction, thus the efficient, selective and cleaner extraction of lithium and the circulating utilization of waste graphite can be achieved.
Key words: spent lithium-ion battery, sulfation roasting, waste graphite, selective recovery, lithium


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