Recovery of valuable metals from spent LiNixCoyMnzO2 cathode material via phase transformation and stepwise leaching

Recycling of spent lithium-ion batteries becomes increasingly important due to the presence of valuable metals and great harm to the environment. In this work, a combined method of reduction roasting with methane, carbonation water leaching and acid leaching was proposed to recover valuable metals from spent lithium-ion batteries. Firstly, thermodynamic analysis was applied to predict the reaction products after reduction roasting. It indicates that the presence of Al will lead to the formation of water-insoluble LiAlO2. Then, pre-alkali leaching was used to preferentially separate Al to facilitate the Li leaching. The effects of roasting temperature, time and methane flow rate on reduction roasting have been further studied. The results show that under the optimal roasting conditions (temperature: 600 ?C, time: 30 min, methane flow rate: 300 mL/min), about 88% of Li can be preferentially extracted and over 98% of Mn, Ni and Co are subsequently acid-leached without the employment of reducing agent. Additionally, the removal of organic matters during the roasting process decreases the concentration of F, P and COD in the leachate and further reduces the cost of wastewater treatment. Finally, the preliminary economic analysis of proposed process confirms that the process has high potential for the industrial production.