Study on Pyrolysis Pretreatment Characteristics of Spent Lithium-Ion Batteries

Abstract

In recent years, the rapid development of the new energy vehicle industry has led to an increase in the production of used lithium-ion batteries. The recycling of waste lithium-ion batteries is expected to alleviate the shortage of valuable metals in battery materials. The electrode material is adhered to the collector by a viscous organic binder such as PVDF. A key step in recycling is to separate the anode material and aluminum foil from the waste lithium batteries to obtain materials rich in valuable metals. Compared with chemical dissolution and decomposition, pyrolysis pretreatment is a simple and feasible method. By reducing the binding force between the binder and the positive active substance at a high temperature, organic matter can be eliminated by thermal decomposition at a high temperature. At the same time, the organic component of PVDF has a high calorific value, and the energy can be recycled and reused, which can save energy. The pyrolysis process and pyrolysis behavior of spent LIBs materials were studied in this paper. FWO, Friedman and KAS conversion methods were spent to compare the pyrolysis kinetics of positive electrode materials. Thermogravimetric analysis shows that the cathode material is decomposed into three stages with mass losses of 1.7%, 1.2% and 3.3%, respectively. The activation energy (Eα) calculated by the three model-free methods is best fitted by the FWO method. During the pyrolysis process, the concentration of F decreases gradually with the increase in temperature, and the concentrations of Ni, Mn, Co and Li remain stable. Most of the harmful element (F) in spent LIBs is converted into HF gas, which can be adsorbed by alkaline solution. The analysis of pyrolysis kinetics and pyrolysis products is of great significance for large-scale pretreatment of spent lithium-ion batteries.