Upcycling Spent Graphite via a Robust SiO x /C Coating for High-Capacity and Stable Lithium Storage

The recycling of spent graphite is crucial for the environmental protection and resource sustainability within the lithium-ion battery life cycle. However, conventional recycling methods often suffer from inadequate performance restoration and high energy consumption. Herein, we propose an efficient and facile upcycling strategy that converts spent graphite into a high-performance anode via in situ construction of a robust amorphous SiOx/C coating. This coating, synthesized via a sol−gel method followed by thermal treatment, serves as a multifunctional layer that enhances interfacial stability and promotes efficient ion and electron transport. The resulting SG@SiOx/C composite delivers a high specific capacity of 463.9 mA h g−1 at 0.15 A g−1 and exhibits exceptional cyclability, with 91.3% capacity retention after 600 cycles at 1.0 A g−1. Moreover, when paired with a LiFePO4 cathode in a full cell, the anode demonstrates remarkable durability and superior rate performance in practical application, delivering a stable discharge capacity of 132.8 mAh g−1 after 200 cycles at 1C with 85.4% capacity retention. This work provides a sustainable and effective route for revalorizing spent graphite, offering considerable economic and ecological benefits.