Preparation And Modification Of Nickel Rich Cathode Materials Based On The Recovery Of Ternary Battery

At present,the demand of battery in the field of electric vehicles is mainly dominated by ternary lithium-ion batteries.According to the surveies,in the first three months of 2018,the proportion of ternary lithium-ion batteries in the power battery field has reached to 66%,up nearly 18%year-on-year.Therefore,the recycling of used ternary batteries is particularly important.The resources of nickel and cobalt in China are scarce and mainly depend on foreign imports.In this circumstance,the raw material resources of power battery will inevitably become more tense.It can be predicted that the direction of recycling of used lithium-ion batteries will become a research hotspot in the future.The nickel rich cathode material belongs to the ternary material system,and the nickel rich battery has high specific capacity due to the high Ni content.However,this material show low efficiency during the first cycle,poor cycle performance,and poor thermal stability.These problems hindered its development.In this study,the waste ternary lithium ion battery is recovered by the wet separation process.The positive and negative electrode sheets and the active material are separated by using the sodium hydroxide solution to dissolve the positive and negative electrode sheets,as the same time,the copper foil is recovered.Separated positive and negative active materials are dissolved in a strong acid solution to obtain a leaching solution of transition metal ions,and the untreated leaching solution contains a large amount of AL³⁺and Cu²⁺impurity ions.Adjust pH of the leachate to 4,in which most of the impurity ions in the solution were converted into hydroxide precipitates.The organic phosphate extractant is used to deeply remove the impurity.Results show that when the ratio of oil phase and water are 1:1,the extractant is diluted by 75%,and the saponification is 60%,at pH=3.5,the two-stage extraction of the leachate can ensure the recovery of Ni²⁺,Co²⁺and Li⁺while minimizing the impurity ions.The nickel rich material was prepared by coprecipitation method after adjusting the concentration of transition metal ions in the recovered liquid.At the first cycle,its capacity can reach to 186 mAh/g at 0.1 C with a efficiency of 78%.However,the cycle performance of the material was poor.After 100 cycles,its capacity was attenuated from169 mAh/g to 116 mAh/g at 1 C,and the capacity retention rate was 71%.The nickel rich material was coated by MoO₃ with MoO₃ as molybdenum source.In the SEM and TEM images,it can be clearly observed that the active material is coated by MoO₃coating layer with a thickness of about 5 nm.XRD and XPS results show that the structure and element valence state of the modified material have not changed.The electrochemical performance results show that the capacity retention of the 2mass%MoO₃ coated material after 100 cycles under the same conditions is 88%,which is17%higher than the raw material.In addition,the coating modification also reduces the polarization phenomenon and the battery impedance.