Kinetic Study and Pyrolysis Behaviors of Spent LiFePO₄ Batteries

Abstract

Pyrolysis is an important way to deal with spent lithium ion batteries (LIBs). This study investigated the pyrolysis process and pyrolysis behaviors of the main components in spent LIBs. Kinetic studies on the pyrolysis process of spent LIBs were conducted using isoconversional method. The pyrolysis process of spent LIBs could be classified into four stages and the average of active energy was 85.36 kJ/mol. After the pyrolysis process, more than 96 wt % electrolyte, about 88 wt % separator, and 50 wt % poly(vinylidene difluoride) were converted into pyrolytic gas and oil, which were mainly composed of small molecular compounds, such as short-chain hydrocarbons and HF. Most of the harmful element fluorine contained in spent LIBs was converted into HF gas, which can be adsorbed by alkaline solution. Meanwhile, the pyrolysis residues of spent LIBs were mainly composed of carbon powder, fluorocarbon, hydrocarbons, active materials, copper, and aluminum foils. The active materials containing LiFePO4 and C were not destroyed after the pyrolysis; thus, they can be reused as raw materials for producing new LIBs.