退役锂离子电池碳/硫协同选择性提锂技术

Selective Recovery of Lithium from Spent Lithium-ion Batteries Synergized by Carbon and Sulfur Elements

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(NH_(4))_(2)SO_(4)、NH_(4)HSO_(4)、NaHSO_(4)和H_(2)SO_(4)分别作为焙烧剂对退役锂离子电池LiNi_(1/3)Co_(1/3)Mn_(1/3)O_(2)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H_(2)SO_(4)为最佳焙烧剂.基于此,研究了石墨添加量对LiNi_(1/3)Co_(1/3)Mn_(1/3)O_(2)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_(1/3)Co_(1/3)Mn_(1/3)O_(2)与H_(2)SO_(4)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_(1/3)Co_(1/3)Mn_(1/3)O_(2)中锂的浸出率高达93%,回收的Li_(2)CO_(3)纯度高于电池级Li_(2)CO_(3)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_(1/3)Co_(1/3)Mn_(1/3)O_(2)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_(1/3)Co_(1/3)Mn_(1/3)O_(2)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_(1/3)Co_(1/3)Mn_(1/3)O_(2)中锂的高效选择性清洁提取和废石墨负极的循环利用.

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,H_(2)SO_(4) was determined as the optimal roasting reagent by systematically investigating the effects of various roasting reagents including Na HSO_(4),(NH_(4))_(2)SO_(4),NH_(4)HSO_(4)and H_(2)SO_(4) on the leaching selectivity of lithium from the Li Ni_(1/3)Co_(1/3)Mn_(1/3)O_(2) active material in spent LIBs,environmental impact and cost of reagents.Then,the effect of graphite dosage on the selectivity of lithium from Li Ni_(1/3)Co_(1/3)Mn_(1/3)O_(2) 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 Li Ni_(1/3)Co_(1/3)Mn_(1/3)O_(2) to H_(2)SO_(4) of 2∶1,graphite dosage of 20%(w),roasting temperature of600℃,and roasting time of 120 min.The purity of the precipitated Li_(2)CO_(3) from the obtained leachate is higher than that of battery grade Li_(2)CO_(3).Ni,Co and Mn from Li Ni_(1/3)Co_(1/3)Mn_(1/3)O_(2) 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 Li Ni_(1/3)Co_(1/3)Mn_(1/3)O_(2).By analyzing the thermal behavior of the mixed powder of Li Ni_(1/3)Co_(1/3)Mn_(1/3)O_(2) 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.