Pyrolysis kinetics and reaction mechanism of the electrode materials during the spent LiCoO2 batteries recovery process.

The spent lithium-ion batteries (LIBs) have potentially serious environmental hazards but contain various valuable metals. Pyrolysis has been preliminarily proven to be an efficient method to dispose spent LIBs and recycle valuable metals. However, the kinetics and reaction mechanism during this pyrolysis process still remain unclear. Therefore, in this study, the pyrolysis kinetics and reaction mechanism of a typical spent LIB (LiCoO2 battery) was investigated and revealed in depth. The results indicated that the reactions happened to the electrode materials (LiCoO2, C) were mainly in the range of 500-800 °C. Two iso-conversion methods (Kissinger-Akahira-Sunose model and Flynn-Wall-Ozawa model) could both well describe the pyrolysis process, and the corresponding activation energies obtained were 389.61 and 405.67 kJ/mol respectively. The physicochemical properties of the pyrolysis products were detailedly characterized to reveal the reaction mechanism. The pyrolysis reaction mechanism of the electrode materials was firstly proposed and divided into three stages: firstly, LiCoO2 was decomposed into CoO, O2 and Li2O; then Li2O reacted with CO2 to form Li2CO3; finally CoO was reduced and converted into Co. This study is expected to provide a comprehensive understanding of the pyrolysis kinetics and reaction mechanism during the spent LiCoO2 batteries recovery process.