Study On Crushing Mechanical Properties Of Spent Lithium-ion Batteries

Lithium-ion batteries (LIBs) are widely used in digital products, vehicles and other modern-life appliances due to the advantages of light weight, high capacity, and availability. There will be a large number of spend LIBs due to the limited life span of 1³ years.On the other hand, the analysis showed that LIBs usually contain 12% to 18% (w/w) cobalt, 1.2¹.8% lithium, 8¹0% copper and 4⁸% aluminum. Therefore, the large number of LIBs abandoned can pollute environment and be wasteful of metal resource.At present, the research on the resource utilization of LIBs is still focus on the recovery of valuable metals such as Co and Li by chemical treatment mostly, and seldom on the pretreatment of LIBs. In fact, the pretreatment to strip the plastics to obtain electrode by artificial disassembling method plays an important role in recycling advancement of LIBs.In order to solve the problem which is disadvantage of low efficiency and high cost of artificial disassembling, a process involving mechanical crushing and sieving is vital important. Therefore, to design the suitable crusher for effective crushing LIBs is another key to substitute for artificial disassemble. In this paper, the crushing mechanical properties of spent LIBs are introduced to provide the design parameter of crusher.Crushing mechanical properties of compressive strength, tensile strength, bending-strength and impact resistance about spent lithium-ion batteries were tested by electromechanical testing systems CMT4000 and pendulum impact testing machine ZBC-25A on the basis of determination methods of plastics national standards.The results show that Stress-strain relationship of compressive strength, tensile strength and bending-strength has the typical features of plastic curves and the three relationships can obey the Gaussian distribution function which R² is above 0.99. On the other hand, the law that compressive strength is less than tensile strength which less than bending-strength can be found, and the Modulus'law are the same. Impact resistance is poor and its Stress-strain relationship shows lithium-ion batteries are tough and soft. However, the material of inner core within electrolyte is very soft, and can be yielded and fractured easily; in the case of tensile strength, the inner core won't be fractured when the shell is fractured, they are in relative independence. Therefore, crushing equipment having an impact force attached should be selected in the comminution of waste lithium-ion battery.Spent lithium-ion batteries were broken into pieces by wet impact crusher MX, and the characteristics of the product, including surface morphology, structure and surface components, were investigated bydigital camera, invert microscope, XRD, SEM and EDS.The results show that the spent lithium-ion batteries were crushed highly efficiently in the condition of different crushing time, different water consumption and different dosage of batteries. The plastic shell, Isolation sheet, copper foil and aluminium foil were enriched in the +0.25mm crushing product, while the LiCoO₂ and C were mainly enriched in the -0.25mm crushing product. So, all the components of the product were liberated completely. Most of Al,Cu,C and LiCoO₂ were in the -0.25+0.125mm and -0.125+0.075mm crushing product, the -0.075mm product mainly contain C and LiCoO₂. LiCoO₂ was enriched in the -0.125+0.075mm product, the content of Co and O was 75.08%. However, the contents of C enriched in the -0.25+0.125mm and -0.075mm product were respectively 73.39% and 72.65%.Ammoniacal solution system containing ammonia and ammonium carbonate was used as leaching media for the removal of copper in the +0.5mm crushing product from the spent lithium-ion batteries (LIBs). Leaching test was carried out at room temperature and under normal atmospheric pressure conditions by introduction of air.The experimental results showed that when the aeration was 50L/h, the reaction time was 7 h, and the solution was not stirred, all copper could be absolutely leached out in the 1:9(v/v) solution systems with a leaching rate of 100%, copper in the 1:19 and 1:14 solution system while the leaching rate was 94.71% and 66.62%. When the aeration was 25L/h, leaching out all the copper in the 1:9 solution needed 23 h, but stirring can quicken the reaction speed, in this case, the leaching time could be reduced from 23 h to 3 h, while under the condition the aeration was 50 L/h, the leaching time was reduced from 7 h to 2 h; Besides, the pH presents the regularity of gradually decreasing in the process.