Fundamental Study On Selective Leaching Spent Lithium-ion Batteries Cathode Scraps Based On Ammonia-ammonium System

Lithium-ion batteries(LIBs)applications in consumer electronics and electric vehicles are rapidly growing,resulting in boosting resoures demand.So recycling of spent batteries will not only eliminate the poluution of hazardous components,but also release the shortage of rare resources.This paper aims to selectively recovery valuable metals(Li,Ni and Co)of cathode materials from spent LIBs with ammonia-based solution.The process emphasizing on the leaching mechanism,leaching conditions,leaching kinetics of ammonia-based solution selectively leaching valuable metals of LiNi1/3Co1/3Mn1/3O2 and selectively leaching valuable metals from mixed spent batteries powder.(1)Scanning electron microscope(SEM),energy dispersive spectrometer(EDS)and X-ray photoelectron spectroscopy(XPS)were used to characteristic the cathode scrap,the cathode materials dismantling from spent lithium ion batteries and the actual material obtained from mechanical pretreatment of spent LIBs and cathode scarps.Compared with cathode scraps,the cathode materials from spent lithium ions battery was in the state of owe lithium and the structure was damaged because of the Li ions flow between the anode and the cathode during the charging and discharging process.The XPS ananlysis also revealed that the release of Li ions led to the oxidation of Ni in LiNi0.5Co0.2Mn0.3O2.(2)Scanning electron microscope(SEM),energy dispersive spectrometer(EDS),X-ray diffraction,X-ray photoelectron spectroscopy(XPS)were used to ananlysis the leaching mechanism of ammonia-ammonium sulfate leaching system LiNi1/3Co1/3Mn1/3O2 cathode material.It was found that the M-O-M bond was broken and the lamellar structure was destroyed by the reduction reaction during the leaching process.Li was state in solution in the form of Li+,while the Ni,Co and Mn were state in the form of Ni(NH3)n2+,Co(NH3)m2+ and Mn(NH3)i2+.Finally,the unstable Mn(NH3)i2+ was precipitated from the ammonia solution in the form of(NH4)2Mn(SO3)2·H2O.(3)Selectively leaching valuable metals from LiNi1/3Co1/3Mn1/3O2 by ammonia-ammonium solution was studied systematically,and the optimal conditions was obtained.The leaching efficiency of Li,Ni,Co and Mn was 95.3%,89.8%,80.7%and 4.3%under the condition of 4 mol·L-1 NH3,1.5 mol·L-1(NH4)2SO4,0.5 mol·L-1 Na2SO3 at 353K,lOg/L and 300 min.The kinetics of leaching behavior was studied and it was found that the unreacted shrinking core model described it well.The model enabled the activation energy of 83.30 kJ·mol-1 for Li,77.93 kJ·mol-1 for Ni and 87.92 kJ mol-1 for Co,which is likely to be a consequence of chemical reaction.(4)Selectively leaching valuable metals from mixed spent batteries powder by ammonia-ammonium carbonate-ammonia sulphite solution was studied systematically,and the optimal conditions was obtained.The leaching efficiency of Li,Ni,Co and Cu was 75.1%,81.6%,81.9%and 99%,while for Al,Fe and Mn the leaching efficiency was less than 1%,and the total leaching selectivity of Li,Ni,Co was 94.64%under the optimal conditions.