Study On Recycling Lithium-ion Battery Electrode Materials By Deep Eutectic Solvents Method

As the last link in the use of power batteries,recycling waste LIBs is conducive to realizing resource return and avoiding pollution and potential risks of toxic and harmful substances in the environment.Because green and cheap deep eutectic solvent（DES）shows high selectivity and excellent leaching efficiencies for valuable metals in cathode materials,using DES for leaching them has become a new means of the LIBs recovery.In this thesis,the dissolution of valuable metals from electrode materials and the leaching mechanism were investigated by regulating the components and leaching reaction conditions of DES.The specific conclusions are as follows:First,the effects of microwave enhancement strategies and DES surface chemistry on the recovery of waste electrode materials were investigated.A microwave-enhanced approach was used to short the leaching time of Li Co O₂（LCO）cathode materials in the urea/lactic acid:Ch Cl:ethylene glycol DES system.Over 90%of Li and Co can be fast leached at 4 min and 160 W in the urea/lactic acid:Ch Cl:ethylene glycol DES system.Meanwhile,during the leaching process,the surfaces of the leached residues in the urea-based DES and lactic acid-based DES systems were porous and smooth,respectively,indicating that the materials underwent the leaching modes of dot-etching and layer peeling,respectively.And the dot-etching can be attributed to the synergistic effect of reduction and coordination,the layer-peeling process depends on neutralization.Then,to further reduce the recovery cost,an ultra-cheap new DES consisting of aluminum chloride hexahydrate and ethylene glycol（EA DES）was proposed.Further analysis shows that EA DES has good reducibility and acidity.At the same time,it shows an excellent recovery effect,whether it is conventional Li Co O₂ cathode,Li Ni_0.5Co_0.2Mn_0.3O₂ cathode,or spent industrial black powder(the mixture of spent Li Ni_0.5Co_0.2Mn_0.3O₂ cathode and graphite anode)with a more complex structure.Li Co O₂ can be leached entirely at 80 ^oC for 60 min,and the leaching efficiency of Li Ni_0.5Co_0.2Mn_0.3O₂ also exceeds 83.90%;In addition,EA DES was also used to leach,separate,and purify the industrial black powder.Finally,in combination with EA DES leaching and a short heat treatment process,we obtained graphite material.In the last part,two types of alkaline DES consisting of Li OH/Na OH and ethylene glycol were used to achieve the separation between the Li Co O₂ cathode material and the collector.The results show that both types of alkaline DES have a destructive effect on the binder and the collector,allowing the cathode material to be easily peeled off from the collector.The destructive effects of both types of DES on the binder are mainly reflected in the severe impact on-CF₂ and-CH₂.Finally,the exfoliated cathode material was roasted in a muffle furnace for regenerative repair.The XPS and TEM results show that the cathode material after heat treatment has a better crystal structure and lower defects.The heat-treated cathode material has better rate performance and cycling stability.The discharge-specific capacity is maintained at108 m Ah/g after 500 charge/discharge cycles at 5 C.