Recycovery Of Cathode Materials In Spent Lithum-ion Batteries Via Reducing Roasting Method

Lithium-ion batteries were widely used in portable electronic devices and new energy vehicles due to their excellent performance advantages.However,the limited lifespan of lithium-ion batteries has led to a rapid increase in the number of spent lithium-ion batteries in a short period of time.And the heavy metal elements of cathode materials were harmful to the environment and human health when the spent lithium-ion batteries were discarded without proper treatment.Therefore,there is a great significance of the recycling of the spent lithium-ion batteries.On the other hand,the recovery of heavy metal elements of cathode materials could also relieve pressure of current resource shortages.The pyrometallurgical route has become one of the current research hotspots in the recovery of cathode materials for spent lithium-ion batteries due to the characteristics of short process,high efficiency and easy industrial application.In this paper,the reducing roasting method is used to realize the recovery and regeneration of the cathode materials in spent linthium-ion batteries,which can be divided into three parts:recovery of spent LiCoO2 by carbothermic reduction,recovery of spent LiCoO2 by ammonium sulfation roasting and recovery of spent LiNi0.6Co0.2Mn0.2O2 by ammonium sulfation roasting.The main process contents are as follows:(1)The reducibility of graphite from the anode was used to convert LiCoO2 to Co/CoO and Li2CO3 to achieve the purpose of recovery in carbothermic reduction method.Firstly,the electroactive materials were separated from the current collectors at 400 oC for 1 h by vacuum pyrolysis.Then,single-factor experiments were used to study on the effect of roasting temperature,reactant mass ratio,roasting time and solid-liquid ratio on the recovery rates of Li and Co in the process of carbothermic reduction-water leaching.And based on the optimal process conditions that roasting temperature was 700℃,roasting time was 45 min,mass ratio of pyrolyzed powder and C was 5:1,solid-liquid ratio was 25 g/L,the recovery rates of Li and Co were 93.2%and 99%,respectively.Finally,the recovered CoO and Li2CO3 was used to regenerated LiCoO2 that delivered a specific capacity of 145 mAh/g at 1 C and retaining 93.4%of the initial capacity after 100 cycles.(2)Li and Co in the sepnt LiCoO2 were converted to Li2SO4 and CoSO4 by ammonium sulfate roasting,and it also achieved the purpose of recovery and regeneration via a chemical precipitation-high temperature solid phase calcination method.Firstly,singlefactor experiments were used to study on the effect of roasting temperature,roasting atmosphere,reactant mass ratio and roasting time on the recovery rates of metal elements of py roly zed powder in the process of ammonium sulfate roasting-water leaching.And based on the optimal process conditions that roasting temperature was 400℃,roasting time was 2 h,atmosphere was Ar,mass ratio of(NH4)2SO4 and pyrolyzed powder was 4:1,the recovery rates of Li and Co were 98.2%and 98.6%,respectively.Finally,Co(OH)2 and Li2CO3 obtained by precipitated were used to regenerate LiCoO2 that delivered a specific capacity of over 154 mAh/g at 1 C with capacity retention of 94%after 100 cycles.(3)The recovery rotue of spent LiNi0.6Co0.2Mn0.2O2 by ammonium sulfate roasting was a low-temperature pyrometallurgical rotute,which can detroy the crystal structure in LiNi0.6Co0.2Mno.2O2 and convert the metal elements to the corresponding water-souble sulfate.Firstly,single-factor experiments were used to study on the effect of roasting temperature,roasting atmosphere,reactant mass ratio and roasting time on the recovery rates of metal elements of LiNi0.6Co0.2Mn0.2O2 in the process of ammonium sulfate roasting-water leaching.And based on the optimal process conditions that roasting temperature was 350℃,roasting time was 2 h,atmosphere was Air,mass ratio of(NH4)2SO4 and LiNi0.6Co0.2Mn0.2O2 was 4:1,the recovery rates of Li,Ni,Co and Mn were 99.2%,99.4%,98.8%and 98.5%,respectively.In addition,thermodynamic analysis found that a temperature higher than 300℃ was required to enable the rapid roasting kinetics associated with the assistance of liquid phases.Finally,Ni0.6Co0.2Mn0.2(OH)2 and Li2CO3 obtained by precipitated were used to regenerate LiNio.6Coo.2Mno.2O2 that delivered a specific capacity of over 160 mAh/g at 0.5 C with capacity retention of 94%after 100 cycles.