Study On The Preparation And Modification Of LiNi_0.6Co_0.2Mn_0.2O₂ With Spent Lithium Ion Batteries

Lithium ion batteries(LIBs)are widely used as power source in 3C field(computer,communication and consumer electronics)owing to their excellent electrochemical performance such as low self-discharge,high battery voltage and high energy density.However,a majority of spent LIBs were discarded due to a sharp attenuation of discharge capacity after several years of service.Because of the existence of heavy metals and organic compound in these spent LIBs,they can not be simply disposed for environmental reasons.In addition,due to the limitation of natural resources and the growing demand for energy,it is necessary to recycle the valuable metals in spent LIBs.Compared with the traditional LiCoO2 cathode material,the new generation of layered nickel rich material LiNixCoyMn1-x-yO2(NCM,X≥0.6)has higher specific capacity and lower cost.In the research of this paper,a process has been proposed to recover cobalt and lithium elements from spent LiCoO2 batteries,then these elements were used as raw materials for the synthesis of LiNi0.6Co0.2Mn0.2O2 material.Moreover,the influence of calcination temperature on the electrochemical properties of NCM622 was also investigated,and aluminum ion was selected as a dopant to modify the LiNi0.6Co0.2Mn0.2O2 material.The optimal concentration of sulfuric acid and H2O2 for the recovery of waste LiCoO2 battery was studied.The results showed that the optimal concentration of sulfuric acid was 2 mol·L-1,and the concentration of H2O2 was 3vol%.Under this condition,the leaching efficiency of Li and Co was 97.1%and 96.8%,respectively.In addition,the best sintering temperature of LiNi0.6Co0.2Mn0.2O2 was also studied.The experimental results showed that 800℃ is the best sintering temperature.In order to further improve the cyclic and rate properties of ncm622 materials,aluminum ions were incorporated into NCM622 materials by simple physical mixing and calcination.The obtained materials were characterized by X-ray diffraction,scanning electron microscopy,electrochemical impedance spectroscopy and charge-discharge tests.The XRD results showed that the aluminum doped material with a mass fraction of 1%had a lower degree of cation mixing and a more stable structure.Li(Ni0.6Co0.2Mn0.2)0.99Al0.01O2 cathode material provided a high discharge specific capacity of 181.82 mAh·g-1 at 0.1 C and maintained a capacity of about 92.60%after 100 cycles.When the current density was 2 C,it still retained a discharge specific capacity of 128.96 mAh·g-1,which was a huge improvement compared to that of pure LiNi0.6Co0.2Mn0.2O2.In general,it may be a good way to reduce the adverse effect of spent LIBs on the environment by recycling the high value-added metals in spent LIBs to synthesize new cathode materials.