| 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... |
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