Regeneration of spent graphite via TEATFB-assisted surface cleaning and defect healing

Abstract

Reviving graphite anodes from spent lithium-ion batteries presents a critical pathway to mitigate resource waste and environmental pollution. However, the structural damage of graphite and the accumulation of surface byproducts during prolonged cycling substantially increase the energy barrier for restoration under mild conditions. Herein, we propose a low-temperature regeneration strategy based on tetraethylammonium tetrafluoroborate (TEATFB) assistance, whose pyrolysis products enable dual functions of surface cleaning and structural reconstruction. In particular, the acidic atmosphere and Lewis-acidic BF₃ generated from TEATFB pyrolysis synergistically remove residual inorganic SEI species and oxygen-containing functional groups at defect sites. Notably, the deep elimination of oxygen functionalities significantly lowers the repair energy barrier, which facilitates carbon framework reconstruction and graphitization at defective regions by pyrolytic carbonaceous intermediates under low-temperature conditions. The revitalized graphite delivers a reversible capacity of 376 mAh g⁻¹ at 0.2C and maintains 358 mAh g⁻¹ at 1C, alongside a capacity retention of 87.5% after 500 cycles, underscoring the excellent rate capability and interfacial stability. Techno-economic analysis reveals that, compared with conventional recycling methods, this strategy offers superior environmental and economic benefits. This work provides a new technological paradigm for the green and high-value recycling of anode materials from spent lithium-ion batteries and holds significant implications for constructing sustainable battery material circular systems.