【作者】 张涛；

【导师】 何亚群；

【作者基本信息】 中国矿业大学 ， 矿物加工工程， 2015， 博士

【摘要】 我国是世界上最大的锂离子电池生产国和消费国,同时,每年也产生了大量的废弃锂离子电池。废弃锂离子电池中含有高价值金属和有毒有害物质,对其进行二次资源利用,不仅能够防止环境污染,还可以实现资源的循环利用,缓解我国因经济快速发展带来的金属资源紧缺问题,对我国经济、环境的可持续发展具有重要的意义。然而目前对废弃锂离子电池的资源化研究还处于初始阶段,主要集中在通过化学方法实现高价值正极活性材料的分离提纯,对废弃锂离子电池的破碎、分选富集研究较少,致使废弃锂离子电池难以得到高效的资源化综合利用。本文以实现废弃锂离子电池的资源化综合利用为目标,着重解决废弃锂离子电池的高效破碎及高价值电极活性材料的分选富集这两个关键问题。本文通过联合使用多种分析测试手段详细深入分析废弃锂离子电池的工艺矿物学特征,为废弃锂离子电池的破碎、分选富集奠定基础。通过研究废弃锂离子电池的破碎行为,建立其选择性破碎的评价方法,并通过自行设计的破碎机,研究强化选择性破碎的机理,实现废弃锂离子电池的高效破碎解离,为后续分选富集过程创造好的条件。通过对比制造电池用的商品化纯钴酸锂和石墨与废弃锂离子电池回收得到的钴酸锂和石墨颗粒的表面性能和浮选行为,分析富钴破碎产物的浮选特性,并在此基础上,有针对的对回收物料进行表面改性,提高其浮选分离效果,使富钴破碎产物中的钴酸锂和石墨得到有效分离。主要研究分为以下三个部分:1.废弃锂离子电池的工艺矿物学研究。废弃锂离子电池中铜、钴、铝三种金属含量超过45%,极具回收价值,但回收过程中因六氟磷酸锂等有毒物质释放带来的二次污染需得到有效解决;废弃锂离子电池具有较好的选择性破碎特点,破碎过程中应强化这种特性;从电极活性材料钴酸锂和石墨的晶体类型来看,浮选分选富集具有可行性,回收得到的钴酸锂晶格结构变化微小,具有修复后直接用于电池生产的潜力。该部分为后续研究的基础。2.废弃锂离子电池的高效破碎解离研究。废弃锂离子电池中仅电极活性材料与导电骨架间存在PVDF造成的粘结力,其余组分间不存在任何结合力,破碎过程中要确保电极活性材料的解离;提出了矿物组分的选择性破碎行为判据σ,如下所示:和选择性破碎效果判据ε,如下所示:水介质的引入,可以使破碎过程中小于筛网尺寸的破碎产品迅速透过筛网,避免重=√1∑(-)2=1=∑×=1复破碎,但因破碎腔内停留时间短,会造成解离不完全;冲击速度过低,粗粒级产率增加,主要原因在于电极活性材料解理不完全,依然紧密结合在大块的铜箔、铝箔上面,而增加冲击速度,并不会造成中间粒级产率的增加,可以获得更大的电极活性材料解离度,增加细粒级产率;相对于锤片而言,锤头施力方式能够增加摩擦破碎效果,防止隔膜纸、铜箔、铝箔、金属外壳的过破碎,增强电极活性材料的解离效果。3.废弃锂离子电池富钴破碎产物浮选性能改善研究。富钴破碎产物颗粒外面包裹以PVDF和有机碳酸酯残体为主的有机层,呈内核外壳的“核壳结构”,造成表面性质接近,难以浮选分离;在450℃下焙烧15分钟,可以有效的去除表面有机层,同时不会对石墨造成过氧化,达到较好的改性效果;Fenton高级氧化在Fe2+/H2O2比例为1:120,液固比为75:1条件下反应30分钟,可以脱除富钴产物颗粒表面有机包裹层,达到表面改性的目的。富钴破碎产物表面改性后,浮选效果得到极大地改善,其中钴的品位达到40%,回收率超过95%。通过以上对废弃锂离子电池工艺矿物学、选择性破碎以及富钴破碎产物改性浮选的基础研究,为废弃锂离子电池的资源化综合利用提供了重要的理论依据和技术支撑,具有重要的科学意义。更多还原

【Abstract】 China is one of the biggest countries to produce and consume lithium-ion batteries(Li Bs). Large amount of spent Li Bs with hazardous materials and high value metals are produced annually. Recycling of the spent Li Bs cannot only prevent environmental pollution, but also can relieve the shortage of metal resources, which plays a significant role in the sustainable development of resources, environment and economy. However, only preliminary research about the recycling of Li Bs has been conducted. Most of the research focused on the separation and purification of the high value cathode active materials by chemical methods. There are rare research concerning the effective comminution, separation and concentration of Li Bs. Therefore, it is difficult to achieve the efficient comprehensive utilization of spent Li Bs.This paper aims to solve two problems: the effective crushing of spent Li Bs and efficient separation of valuable electrode active materials so as to realize comprehensive utilization of spent Li Bs. Several analyses and testing method were used to investigate the mineralogical characteristics of spent Li Bs in order to lay the foundation for the comminution and separation of spent Li Bs. After studying the comminution behaviors of spent Li Bs, evaluation methodology of selective comminution was developed. As a result, efficient liberation and created favorable conditions for the subsequent separation were achieved. Based on the comparison between commercial and recycled Li Co O2 and graphite, the surface properties and flotation behaviors of Co-enriched crushed products were analysed. Surface modification was made to improve the flotation efficiency. Thus, Li Co O2 and graphite in Co-enriched crushed products were effectively separated. The main content consists of three parts:1. Mineralogical characteristics of spent Li Bs. The total percentage of cobalt, copper and aluminum in spent Li Bs are beyond 45% which indicates a great recovery value, but measures should be taken to avoid secondary pollution because of the emission of toxic material such as hexafluorophosphate lithium. Spent Li Bs were found to have the characteristic of selective crushing, and this property should be strengthened during the crushing process. It is possible to separate Li Co O2 and graphite due to their difference in crystal type. The recycled Li Co O2 changes little in crystal lattice and is potential to be utilized directly in battery manufacture.2. Efficient crushing and liberation of spent lithium-ion batteries. In the spent lithium-ion batteries, binding power caused by PVDF exists only between electrodes active materials and conducting matrix grains. There is no binding power between other components. Hence, only the liberation of electrodes active materials requires to be guaranteed in the crushing process. In addition, σ, the criterion of selective crushing behavior of mineral components is presented as follows: As well as ε, the criterion to evaluate the effect of selective crushing behavior is presented: The introduction of water medium can make those crushed products smaller than the screen mesh size go through the mesh fast. In this way, the repeated crushing can be avoided, but the short residence time in the crushing chamber will cause incomplete liberation. Low impact speed leads to the increase of coarse size fraction are attributed to the incomplete liberation of active materials and adhesion on the copper foil or aluminum foil. Rising impact speed cannot increase the middle size fraction, but can obtain a further liberation of electrodes active materials and an increase of fine size fraction yield. Compared with hammer crusher, the force mechanism of hammer head can strengthen the attrition, avoid the over crushing of diaphragm paper, copper foil, aluminum foil and mental shell, and enhance the liberation of electrodes active materials.3. Improvement of floatability of Co-enriched crushed product of spent lithium-ion batteries. Particles of Co-enriched crushed product are covered by an organic layer whose main components are PVDF and the residue of organic carbon ester which forms the structure as a kernel with cover. Therefore they have the similar surface characteristics and can be hardly separated by flotation. The organic layer on particles’ surface can be effectively removed by being roasted for 15 min at 450℃. While graphite will not be over oxided and this means the successful surface modification. For Fenton advanced oxidation method, when the ratio of Fe2+ and H2O2 is 1:120, and liquid-solid ratio is 75:1, the organic layer can be effectively removed after 30 min reaction. After the surface modification, the floatation results of co-enriched products can be well improved. The grade of Co can reach to 40%, and the recovery is over 95%. = √1∑(-)2=1 = ∑ × =1更多还原