基于高效回收废旧锂离子电池正极材料的低共熔溶剂的筛选

To resolve the secondary pollution and high energy consumption caused by the recycling of spent lithium-ion batteries(LIBs), a green and efficient method for leaching valuable metals from spent LIBs cathode materials is developed. Choline chloride and different hydrogen bond donors(oxalic acid, malonic acid, glutaric acid and benzenesulfonic acid) were used to synthesize choline chloride/acid binary deep eutectic solvent(DES), chlorine choline/acid/H₂O and choline chloride/acid/ethanol ternary DES. The formation process of the hydrogen bond between choline chloride and acid was characterized by means of Fourier transform infrared spectroscopy(FTIR) and nuclear magnetic resonance spectroscopy(NMR). The impacts of carboxylic acid alkyl chain length, acidity and addition of water and ethanol on the leaching of spent LiCoO₂ were investigated. The results show that the leaching capacity of DES decrease with the increase of the carboxylic acid alkyl chain length. The acidity of the acid cannot be concluded as the main reason for the higher ability to dissolve metal oxides. The equimolar addition of water has little effect on the leaching efficiency of DES, while the equimolar addition of ethanol will affect the hydrogen bond structure of DES, which has a greater impact on the leaching efficiency. At last, choline chloride/benzenesulfonic acid/ethanol DES was screened as a green and efficient leaching agent for spent LiCoO₂, leaching efficiencies of Li and Co were as high as 98.6% and 95.2%, respectively.