Study On The Efficient Recovery Of The Valuable Metals In Cathode From Spent Lithium Ion Batteries

In 1980,Goodenough and others invented lithium cobaltic dioxide as the cathode material of lithium-ion battery in Oxford University.In 1990,the Sony Corporation commercialized lithium-ion secondary battery,so lithium cobaltic dioxide was widely used in lithium-ion batteries,and then a large number of waste lithium cobaltic dioxide batteries were produced.The recovery of valuable metals（such as cobalt and lithium）from the spent lithium-ion batteries can not only alleviate the scarcity of valuable metals,but also protect the environment.The recovery of waste lithium-ion batteries has been widely studied,but in general,the recovery processes are complex,the costs of recovery are high,and secondary pollution will occur.In this paper,citric acid-hydrogen peroxide and citric acid-glucose were used to recover the valuable metals from waste lithium cobaltic dioxide batteries.In this paper,a more simple and efficient method was used to recover the valuable metals in the cathode of waste lithium-ion batteries.The cathode plate was directly immersed in the mixed solution of citric acid and hydrogen peroxide without the pretreatment of N-methylpyrrolidone（NMP）immersion or calcination.At the same time,the effects of leaching conditions such as citric acid concentration,H₂O₂ dosage,reaction temperature,reaction time and solid-liquid ratio on the leaching rate were discussed.The results showed that under the conditions of citric acid concentration of1.0 mol/L,hydrogen peroxide dosage of 8%,reaction temperature of 70℃,leaching time of 70 min and solid-liquid ratio of 40 g/L,the comprehensive leaching rate of cobalt and lithium reached 99%.The leaching solution can be used to prepare new cathode materials for lithium-ion batteries,and the separated aluminum foil can be recycled.The results of UV-vis.and FT-IR spectra showed that the chelates formed by cobalt ions,lithium ions and citrate anions played an important role in improving the leaching rate.Glucose is a more economical and environmentally friendly reducing agent than hydrogen peroxide.Therefore,this paper also discussed the acid leaching of citric acid-glucose system to recover the valuable metals in the cathode of waste lithium-ion batteries,and discussed the effects of leaching conditions such as citric acid concentration,glucose dosage,reaction temperature,reaction time and solid-liquid ratio on the leaching rate.The results showed that under the conditions of citric acid concentration of 1.5 mol/L,glucose dosage of 1.0 g/g（glucose dosage/cathode dosage）,reaction temperature of 100℃,leaching time of 3 h and solid-liquid ratio of 20 g/L,the comprehensive leaching rate of cobalt and lithium reached 98%.After acid leaching,the separated aluminum foil is recycled,and then oxalic acid and sodium carbonate were added into the filtrate successively to precipitate cobalt ions and lithium ions.The mechanism of acid leaching showed that enough citric acid can provide enough hydrogen ions for lithium cobaltic dioxide to produce complete acid leaching reaction,but excessive citric acid will inhibit the formation of citric acid anions,thus affect the formation of Co^II-L coordination ion,which has a negative impact on the acid leaching reaction of lithium cobaltic dioxide.The coordination and combination of cobalt ions and lithium ions with citrate anions plays an important role in improving the leaching rate.The results of precipitation showed that Co^II-L can react with oxalic acid to form Co C₂O₄ precipitate,while Li₂CO₃ cannot be precipitated by carbonate because of its large solubility product constant.