Oxygen-rich Modified-Graphite Recycled from Spent Lithium Batteries for Improved Lithium-Ion Storage: Adsorption and Intercalation Mechanisms

The flourishing lithium-ion industry has catalyzed the growth of the battery recycling sector. The regeneration of waste graphite into anode materials has emerged as the predominant practice. However, the practical application of recovered graphite is impeded by poor initial coulombic efficiency (ICE), due to the adherence of carbon black (CB) and residual binder. In this study, the variation in activation energies was validated using the Flynn-WallOzawa (FWO) models. A viable method was implemented to separate binder and residual amorphous carbon from recycled graphite by controlling the atmosphere during pyrolysis, simultaneously introducing oxygen atoms as functional groups. When reused as an anode in lithium-ion batteries (LIBs), the recycled graphite electrode achieved a high ICE exceeding 92 %, surpassing the commonly observed similar to 80 %. Notably, a high reversible capacity of 130 mAh/g and excellent cycling stability (99.97 % after 100 cycles) were achieved at a charge/discharge rate of 1C. Density functional theory (DFT) calculations and experimental results reveal that ether, carbonyl, and carboxyl groups significantly impact ICE due to their high adsorption energy for lithium ions. Graphite and carbon black were effectively separated under specific pyrolysis conditions, introducing oxygen- containing functional groups into the regenerated graphite structure, thereby significantly enhancing its electrochemical performance.