Facile conversion from spent graphite to N-doped graphite with high cycling performance

Abstract

Recovery of graphite from spent lithium-ion batteries (LIBs) is of great importance to sustainable development of battery industry and environmental protection. Herein, we propose a novel and simple strategy for the reconstruction and recovery of waste graphite. By roasting mixture of waste graphite and melamine, N-doping and interlayer broadening for graphite are achieved simultaneously. The formation of CN bond induces defect generation, and the gases produced from melamine decomposition enlarge the interlayer spacing, both of which are conducive to the transport and storage of lithium ion. Density functional theory analysis shows that the regenerated N-doped graphite (NG) has a lower adsorption energy than commercial graphite. NG electrode exhibits excellent cycling stability. It delivers a high specific capacity of 406 mAh g⁻¹ at 1C after 1000 cycles, which exceeds that of commercial graphite. In situ XRD analysis further demonstrates that NG electrode has good reversibility and superior lithium-ion storage ability. This research provides a facile method to accomplish the closed-loop utilization of graphite in LIBs.