Recycling Of Waste Lithium Ion Batteries By Direct Reduction And Melting

The study is one part of the project called "HEV/EV batteries reclcying" which is sponsored by the State-Owned Enterprise Electric Vehicle Industry Alliance and the major project "The technological development and industrial application for the valuable metals recovery of spent lithium ion batteries by combining smeling reduction and hydrometallur-gy processes" which sponsored by Changsha Research Institute of Mining & Metallurgy CO., LTD.. Several kinds of bateteris such as with Al can or steel cans and polymer includ-ing Mn or not were investigated. XRD and SEM-EDS were used for the analysis of the structure and composition of the slag. The major conclusions can be summrized as follows:(1) For the smeling process of spent lithium ion batteries, Co, Ni and Cu are the aimed elements, Al, Mn and Cr are crital elements, oxygen partical pressure and smeling temperature are the crital factors which significantly influence the result of smelting pro-cess. In order to make sure the appropriate slag qualities, the higher oxygen parital pressure should be used for the polymer li-ion batteries containing Mn; however, the lower oxygen parital pressure should be used for the li-ion batteries with steel cans containing Cr. The FeO-SiO2-Al2O3 slag system is more suitable for the smelting reduction process of spent lithium ion batteries with higher Al or Mn content.(2) The satisfied valuable metals recovery can be obtained for various kinds of spent lithium ion batteries by smeling reduction based on CaO-SiO2-Al2O3 slag system. The slag composition is suitable under CaO/SiO2=0.83-1.28 (w/w),8.44～13.33 wt.% Al2O3 content, 4.0～7.5 wt.% MgO content. The Cr containing spent li-ion batteries with steel cans mainly entered the alloy; the most of Mn containing spent li-ion polymer batteries entered the slag. Under the best condition of 10kg-scale medium frequency induction furnace experiment (slag former addition 5.0 (w/w), CaO/SiO2=1.50 (w/w), smelting temperature 1500℃, smelting time 40min), the Co, Ni and Cu recoveries were 99.01%,99.22%, and 97.33%, respectively. This copied the result of lab-scale experiment very well.(3) The FeO-SiO2-Al2O3 slag system is more suitable for the smelting reduction process of spent lithium ion batteries with higher Al or Mn content. The slag compositon is suituable under FeO/SiO2=0.58-1.03 (w/w) or (FeO+MnO)/SiO2=0.50～1.08 (w/w),17～22 wt.% Al2O3 content. Co, Ni and Cu recoveries were more than 95%under the best experi-ment conditions(smelting temperature 1450℃ and smelting time 15～30min). Under the best condition of 10kg-scale medium frequency induction furnace experiment, the Co, Ni and Cu recoveries were 97.21%,98.93% and 93.60%, respectively. This copied the result of lab-scale experiment very well.(4) The slag which was obtained by using the FeO-SiO2-Al2O3 slag system mainly consists of fayalite, hercynite. Cu existed in slags in the formation of matte. The content of Cu (matte) in the slag is closely related with the structure of fayalite. The structure of fayal-ite should be in fine discontinued in shape in order to decrease the Cu content in the slag.(5) The roast-smelting process (10kg-scale medium frequency induction furnace experiment) was used for the recovery of valuable metal of spent lithium ion battery. The 95.19% Co,96.58% Ni and 90.93% Cu recoveries were obtained under the best experi-mental condition of slag-making addition 3.0 (w/w), roasting temperatue 800℃, roasting time 70min, smelting temperature 1450℃ and smelting time 20min.(6) The slag forming is obvious when the smeling process of spent lithium ion bat-tery used the FeO-SiO2-Al2O3 slag system, which exsits safe risk. However, it is benefit for the mass and thermal transfer. The two methods including roasing-smelting and optimized slag system can effectively control the behavior of slag forming.