Recycling and regenerating of spent ternary cathode in lithium-ion battery via the corn straw-induced thermal reduction

Abstract

To address the problems in the conventional carbothermal-reduction methods for recovery of the spent ternary cathodes in lithium-ion batteries (LIBs), particularly the low-utilization and high-value reductants, this study introduces an optimized thermal-reduction technique utilizing agricultural waste of corn straw as a reductant. The pyrolysis of corn straw generates highly reductive species of C, H₂, CH₄, and CO, which converts the reaction mechanism from a conventional solid–solid reaction to a combined solid–solid/solid–gas reactions. This significantly enhances the reduction efficiency of LiNi_xCo_yMn_1-x-yO₂ (LNCMO), enabling the reduction of high-value metals into Ni, Co, and MnO, while converting Li into Li₂CO₃. Notably, the optimal corn straw-induced thermal-reduction temperature is 700 °C with the high-utilization efficiency of corn straw. Under the optimal conditions, Li can achieve a high recovery rate of 95.8 %, which exceeds that of the conventional carbothermal reduction techniques. Additionally, the reduction products can be successfully regenerated into LiNi_0.6Co_0.2Mn_0.2O₂. The discharge specific capacity and coulombic efficiency of the regenerated LiNi_0.6Co_0.2Mn_0.2O₂ is 163.9 mA h g⁻¹ and 94.6 %, respectively. This study provides a novel strategy for the utilization of agricultural waste to achieve high-efficiency recovery of the ternary cathode materials from spent LIBs.