Radical-driven upcycling of spent graphite into defect-controllable nitrogen-doped graphene for sustainable energy storage

Abstract

The pursuit of sustainable energy technologies demands high-performance electrode materials manufactured with minimal environmental impact. Leveraging our recently proposed radical-driven wedge-cleavage (RDWC) mechanism, we develop an upcycling strategy that directly transforms spent graphite from lithium-ion batteries into high-quality, heteroatom-doped graphene, bypassing the defective graphene oxide (GO) pathway. •OH selectively activate graphite edges, while SO4•- decouple the layers, a cooperative mechanism that confines defects to the periphery and preserves the long-range conductive sp2-hybridized lattice. This GO-free paradigm enables versatile doping sequences. The exfoliation-doping route employs RDWC to exfoliate spent Li-ion battery graphite (SG) into edge-confined defective graphene, replacing oxygen-containing edge sites with pyrrolic and pyridinic nitrogen through doping modification and delivering OER activity comparable to GO-derived analogues but with far superior capacitive rate capability (83.5% vs. 49.1% retention at 20 A g-1). The doping-exfoliation route leverages •OH to selectively replace edge pyridinic-N, yielding a material rich in stable graphitic-N and delivering a specific capacitance of 94.83 F g-1 at 0.5 A g-1 with outstanding rate performance (84.36% retention at 20 A g-1, rivaling graphene derived from commercial graphite). Crucially, life-cycle assessment confirms the green profile of this circular strategy, showing a >54% reduction in global warming potential and achieving a significant mitigation of relative ecotoxicity versus conventional synthesis. This work establishes a scalable, mechanism-guided platform for synthesizing advanced graphene materials that unites high electrochemical performance with sustainable manufacturing.