Oxygen-free calcination for enhanced leaching of valuable metals from spent lithium-ion batteries without a reductant

Drawbacks such as reductant need in leaching process or high energy consumption in pre-treatment step exist in current approaches for recycling spent lithium-ion batteries (LIBs). Here, we report an energy-saving pre-treatment process that can increase the metals leaching efficiency of spent LiNixCoyMn1-x-yO2 LIBs in H2SO4 solution. In the proposed process, the spent electrode material was calcined in a nitrogen (oxygen-free) atmosphere, resulting in the easy leaching of metals by H2SO4 without adding reductant. Calcination conditions were examined, and calcination at 350 degrees C for 1.5 h resulted in the optimal leaching rates of Li, Ni, Co, and Mn (>99%). Mechanism analysis revealed how calcination improves the leaching efficiency. We found the proposed calcination pre-treatment can destroy the well-defined layered crystal structure of spent LiNixCoyMn1-x-yO2 without changing its original phase composition. As a result, refinement of crystalline size, increase of defect, amorphization, and specific surface area (with the emergence of cracks and voids) of the cathode particles enhance the leaching of metals. This study may provide an energy-saving and cost-effective pre-treatment process that can remarkably improve metals leaching rates from spent LIBs without adding reductants.

Automated summary

By calcining the spent electrode material in a nitrogen atmosphere, the proposed energy-saving pre-treatment process allows for easy leaching of metals from spent LIBs in H2SO4 solution without the need for reductants. This method destroys the layered crystal structure of the cathode material, enhancing metals leaching rates through refinement of crystalline size, increased defects, and amorphization. This study offers a cost-effective approach to improve metals leaching efficiency from spent LIBs.