Quenching of spent graphite: Upcycling regeneration with tailoring subsurface and in-plane defects towards high-rate properties

Abstract

Attracted by short processes and low costs, strategies for directly regenerating spent electrode materials receive considerable attention. As the main anode of lithium-ion batteries, numerous spent graphite materials stack without suitable treatments, leading to serious environmental pollution and resource waste. Although progress has been made in recycling spent graphite, challenges such as high energy consumption and suboptimal sub-surface structural integrity remain unresolved. In this study, we successfully tailor the sub-surface traits, including pore distribution and in-plane defects, by employing short-time sintering and quenching techniques. As a Li-storage anode, the regenerated samples display a considerable capacity of approximately 300 mAh∙g⁻¹ after 500 cycles at 1.0C. Even at 5.0C, their fast-charge capacity reaches up to 258 mAh∙g⁻¹. Detailed electrochemical and kinetic analyses reveal that the introduction of interlayer gaps broadens ion-shuttling pathways by increasing the diffusion coefficient, while the designed in-plane defects provide effective growth sites for Li deposition. This facilitates the transformation from Li dendrites to Li particles, enhancing battery performance and safety. Consequently, this work sheds light on the role of sub-surface traits and offers effective strategies for the upcycling and regeneration of spent graphite, contributing to more sustainable lithium-ion battery technologies.