Study On The Recycling Of Waste Lithium-ion Batteries By Slurry Electrolysis

With the development of electronic technology and the continuous renewal of electronic products,the actual service life of LIB is greatly shortened,increasing the number of waste LIBs.Waste LIBs have both high economic value and environmental pollution characteristics,which have attracted the attention of many researchers.In this paper,the waste LIBs were treated by slurry electrolysis,then the effects of current on the recovery rate of cobalt,lithium,nickel,copper,mass contribution rate in cathode metal powder,phase and morphology were investigated.In addition,it is also explored whether the cathode material LiCoO2 can be deposited and regenerated in one step.The main conclusions are as follows: 1.Pretreatment of waste LIBs: the waste LIBs were treated with 10 wt.% NaCl solution for 240 min.After mechanical crushing,more positive and negative materials enter into the particle size less than 0.45 mm,which were selected as the follow-up experimental sample.2.Study on the reduction ammonia leaching of the mixture of positive and negative materials of waste LIBs: a high efficiency reduction ammonia leaching system of the mixture of positive and negative materials of waste LIBs was established.The optimum leaching conditions were NH3·H2O 120 g/L,NH4HCO3 75 g/L,n(Na2SO3): n(Co)= 2:1,353 K,240 min.the leaching rates of cobalt,lithium,nickel and copper were 91.16%,97.57%,86.60% and 99.50%,respectively.The result of leaching kinetics shows that the rate limiting step of this process is the control of interfacial chemical reaction.In addition,the leaching residue can be separated and purified,and graphite,manganese carbonate and manganous oxide can be obtained.3.Electrodeposition of the mixture of positive and negative materials of waste LIBs: with the increase of current,the recovery of cobalt,nickel and copper is generally increasing,while the recovery of lithium is relatively low.When the current is 1.0A,the recovery of cobalt,nickel,copper and lithium is 98.15%,99.11%,99.91% and 15.36%,respectively.The proportion of cobalt in the cathode metal powder is the largest,up to 80.71%.The current has little effect on the XRD phase of cathode metal powder.From the morphology of cathode metal powder,increasing the current is conducive to reducing the particle size of cathode powder.4.Recovery of the mixture of positive and negative materials of waste LIBs by slurry electrolysis: with the increase of current,the recovery of cobalt firstly increases,then decreases and then increases.The recovery of nickel,copper and lithium first increases and then decreases.The highest recovery of cobalt,lithium,nickel and copper are 25.66%,99.57%,91.52% and 89.44%,respectively.When the current is 4.5A,the content of cobalt in the cathode metal powder is the highest,which is 86.88%.It shows that increasing the current is beneficial to the deposition of cobalt.The current has little effect on the XRD phase of cathode metal powder.From the morphology of cathode metal powder,increasing the current is conducive to reducing the particle size of cathode powder.In addition,one-step deposition and regeneration of the cathode material LiCoO2 can be realized by increasing the current density and adding electrolyte solution to maintain the current stability.