Study On Extraction And Recovery Of Valuable Metals From Spent Lithium Ion Batteries

Lithium-ion batteries(LIBs)have been used more and more widely in daily life and productions due to their electrochemical superiorities in terms of long service life,small size,convenience,environmental protection and energy conservation.However,LIBs were exhausted after their end-life of services around 3-6 years,so the amount of waste LIBs has increased year by year.On the one hand,the cathode materials in the waste LIBs contains a large amount of valuable metals such as Co,Li,Mn and Ni.On the other hand,there are some toxic chemical substances such as fluoride and hydride.Improper disposal of spent LIBs will not only cause long-term environmental impact,but also leads to significant waste of resources.Therefore,the recovery and reuse of valuable metals in cathode materials of LIBs is important to reduce environmental pollution and alleviate social resources.In view of these problems,this paper mainly studied the recovery and reuse of waste LIBs with different types(LiCoO2,LiMn2O4,LiFePO4 and LiNixCoyMnzO2)as cathode materials.The research contents are as follows:(1)First,the pretreatment of LIBs included discharge,disassembly,and mechanical separation to obtain the cathode materials and Al-foil.Subsequently,the cathode materials were obtained at a certain temperature by calcination.For the LiCoO2 material,100%Li can be selectively extracted in a short-cut process under an acidic medium(0.8 mol/L H3PO4)and Co recovered as Co3(PO4)2.When the acid concentration of 2.0 mol/L,Co and Li completely dissolved under the optimized leaching conditions.The different leaching behaviors of Co and Li in the phosphoric acid medium indicated that they can be selectively recovered according to the phosphoric acid concentration.In addition,the effect of cycles of phosphoric acid on the leaching of Co and Li showed that the leaching rates remain 80%after 5 cycles of leaching.The effects of impurities included Cu,Al and Fe on the leaching of waste LiCoO2 materials were also investigated.From the leaching results and reaction kinetics of different metals,the leaching reaction orders of different metals are Li>Cu-Co>Fe>Al(in 0.8 mol/L H3PO4)and Cu>Al?Li>Fe>Co(in 2.0 mol/L H3PO4),respectively.(2)In the different cathode materials of LiCoO2,LiMn2O4,LiFePO4 and LiNixCoyMnzO2,phosphoric acid was used as the leaching agent and hydrogen peroxide as the reducing agent.In the lower concentration of 0.8 mol/L phosphoric acid,100%Li can be selectively leached and purified to obtain Li3PO4.The leaching-precipitation reaction of different cathode materials in the phosphoric acid medium was carried out to extract Li.The leaching rates of Co,Li,Mn and Ni were 96.3%,100%,98.8%and 99.5%at a higher concentration of 2.0 mol/L,respectively.The Ni1/3Co1/3Mn1/3C2O4 precursor was obtained by selective precipitation with oxalic acid.The leaching rate of Fe is relatively low at 3%,the pure FePO4 can be obtained by separation and purification and applied to the preparation of the FeLiPO4.The leaching kinetics studies showed that the leaching reactions of Co,Li,Mn and Ni controlled by chemical reactions,and the higher apparent activation energy which revealing the interrelationship and mechanism of synergistic separation and regeneration of metals and acids in mixed systems.(3)After leaching of the valuable metals Co,Li,Mn,and Ni in the mixed materials by phosphoric acid and selectively precipited the metals with precipitant(H2C2O4),then calcinated at 500 ? for 5 hours to obtain the precursor Ni1/3Co1/3Mni1/3C2O4.and added lithium source to obtain LiNi1/3Co1/3Mn1/3O2.In this study,parameters of different calcination temperatures,different lithium sources and the amount of lithium sources are investiged.The results showed that the optimal preparation temperature is 800?,calcination time is 12 h,lithium source is LiC2O3 and addition amount of 3%.The results were characterized by XRD and SEM showed that the prepared cathode active material with well structured LiNi1/3Co1/3Mn1/3O2.Finally,it was assembled into a button battery for charge and discharge test,and the first discharge specific capacity was 136.4 mAh/g at 0.1C in the voltage range of 2.8-4.3 V.In this paper,the process of "pretreatment-leaching-material preparation" is used to recover valuable metals in waste LIBs,which has good application value for reducing environmental pollution and mitigating social resources.