关键词: 废旧锂电池, 回收, 浸出, 共沉淀, 三元正极材料

Abstract:

In this study, phosphoric acid was employed as efficient leaching reagent for the leaching of different valuable metals from waste cathode materials of spent lithium ion batteries (LIBs). Based on the leaching results, about 96.3% Co, 100% Li, 98.8% Mn and 99.5% Ni can be dissolved in phosphoric acidic medium under the optimized leaching conditions of acid concentration-2 mol/L, reductant dosage- 4% H₂O₂, retention time- 60 min, reaction temperature- 60°C and pulp density- 20 mL/g. After adjusting the molar ration with addition of a certain proportion of metal ions to the leachate, the precursor materials of (Ni_1/3Co_1/3Mn_1/3)C₂O₄ can be obtained by co-precipitation method (adding stoichiometric oxalic acid to leaching solution). And phosphoric acid can be simultaneously regenerated during the above precipitating reaction. According to the circulating leaching results, it can be concluded that the regenerated acid can be reused to as leaching reagent with relatively sound leaching efficiencies for valuable metals (90.1% for Li and over 75.0% for Co, Mn and Ni) after 5 cycles of leaching. Finally, cathode materials of Li(Ni_1/3Co_1/3Mn_1/3)O₂ can be reprepared by calcination the precursor materials of (Ni_1/3Co_1/3Mn_1/3)C₂O₄ with pure Li₂CO₃ in appropriate molar ratio. Analysis results of electrochemical performances of the regenerated cathode material indicated that the initial discharge capacity of Li(Ni_1/3Co_1/3Mn_1/3)O₂ was 136.4 mA·h/g with a remained capacity rate of 97.2% after 50 cycles at 0.2 C under the optimized synthesis temperature of 800 ^oC.

Key words: spent lithium ion batteries, recovery, leaching, co-precipitation, Li(Ni_1/3Co_1/3Mn_1/3)O₂ materials