Gas-phase oxidation modification strategy of spent graphite from spent LiFePO4 with enhanced initial coulombic efficiency for lithium-ion battery anodes

Abstract

Recycling graphite from spent LiFePO₄ batteries plays a significant role in relieving the shortage of environmental protection and waste of valuable resources. However, a low initial coulombic efficiency (ICE) and poor performance at a high current density frustrate its practical application. In this study, a brief method is proposed to recycle spent graphite (SG) via gas-phase oxidation. The electrochemical performance of the oxidation spent graphite (OSG) with different calcination temperatures (450 °C, 550 °C and 650 °C) and times (1 h, 2 h and 3 h) were carefully studied. The ICE of OSG increases first and decreases as the temperature increases, and increases with the extension of calcination time. OSG was prepared by holding for 3 hours at a 550 °C calcination temperature. As an anode for lithium-ion batteries, OSG-550-3 exhibits a remarkable electrochemical performance in terms of ICE (86.9%) and first irreversible capacity (61.1 mA h g⁻¹) compared to those of the SG electrode (64.4% and 186 mA h g⁻¹, respectively). The improvement is attributed to removal of some highly active sites or defects, which weaken the damage effect of solvent molecule co-embedding during the charge/discharge process. The present work highlights the critical roles of gas oxidation in the development of SG anodes for lithium-ion storage.