Recycling Of Spent NCM523 Type Battery Cathode Material

Lithium-ion batteries,with their portability,long cycle life and high energy density,have been widely used in mobile phones,electric vehicles,aviation and other fields,and the demand is still increasing year by year.However,the battery will be scrapped because of its service life or failure and other reasons.The cathode materials contain Ni,Co,Mn,Li and other valuable metal resources.In view of environmental protection and comprehensive utilization of resources,it is necessary to recycle them.This paper mainly explores the wet process to recover valuable metals Ni,Co and Li from cathode materials of NCM523 lithium-ion battery.In the pretreatment stage,the positive active substance was removed from the collector by selective dissolution method,which delved the influence of the amount of solution and dissolution time on the removal rate of positive active substance powder.The experimental results showed that when solution of 210 m L was used for 80 mins,the removal rate of cathode active substance powder could reach 89.6%.In the leaching stage,H₂SO₄ was used as leaching agent,and with H₂O₂ as leaching reducing agent to leach valuable metals,such as Ni,Co and Mn.The orthogonal experiments with 5 factors and 4 levels and 5 single factor experiments were carried out.The interaction effect of leaching factors on the leaching rate of each metal was analyzed.The experimental results showed that when the concentration of H₂SO₄ was 2.5mol/L,the volume fraction of H₂O₂ was 10%,the solid-liquid ratio was1:14g/L,the reaction temperature was 80℃,and the reaction time was 80 mins,the leaching rates of Ni,Co and Mn were 94.03%,99.56% and 14.97%,respectively.Through kinetic analysis,it is known that the chemical reaction is the limiting link in the leaching process.Using KMnO₄ oxidation precipitation method separated out a small amount of Mn in the leaching solution,which delved the influence of the adding amount of KMnO₄ except the rate of Mn.The experimental results show that when 0.9 times of the theoretical amount of KMnO₄ was added into the leach solution,and stirring for 1h,which can make the Mn in the leach solution separate out in the form of reddish brown MnO₂ precipitation,and the Mn removal rate was calculated to be greater than 98%.Using oxalic acid as the precipitation complexing agent,NiCo₂O₄ material was recovered from the purification solution by hydrothermal synthesis-calcination method,which could avoid the waste of reagent and consumption of valuable metal in the process of separating single metal.Firstly,the pure solution prepared was used for single factor experiment,and the effects of additive types,hydrothermal temperature,hydrothermal time,calcination temperature and calcination time on the morphology and phase composition of the product were investigated.After determining the optimal process parameters,the purification solution was used for experiment.The experimental results show that when the additive is 1.5g HMT,the hydrothermal temperature is 140℃,the hydrothermal time is 4h,the calcination temperature is300℃,and the calcination time is 120 mins,the uniform morphology of NiCo₂O₄ strips can be prepared,and the recovery and utilization of Ni and Co in the waste electrode materials are preliminary realized.Li was recovered from the filtrate by Na₂CO₃ precipitation method.First,the filtrate was evaporated and concentrated to a mass concentration of Li greater than2.88mol/L,then excess saturated Na₂CO₃ solution was added,pH of the solution was adjusted to 7,and the reaction time was stirred at 80℃ for 2h.Li in the solution could be precipitated out in the form of Li₂CO₃ crystals,and the precipitation rate of Li was89%.The total recoveries of Ni,Co and Li are 93.44%,95.34% and 83.53%,respectively.