Resuscitation of spent graphite anodes towards layer-stacked, mechanical-flexible, fast-charging electrodes

The alarming resource shortage of the lithium battery supply chain has triggered new vitality to the close-loop recycling of retired batteries. As compared to hydrometallurgy or pyrometallurgy strategies for the cathode recovery, the proper use of degraded graphite anodes, featuring with the solvated Li⁺ intercalation and in-plane defect formation, is hitherto neglected. In this work, we propose a facile “green route” to extract values from spent graphite anode. Through elucidating the dynamic Li occupancy in graphite lattice, an up-scaling delamination protocol is developed with the aid of in-situ generated H₂ bubbles in the protic mixed solvent, to weaken van der Waals (vdW) bonding of the graphite interlayers and generate few-layer graphene flakes (∼ 2 nm); meanwhile high-purity Li salt could be simultaneously extracted from the residue solvent (∼ 98% Li leaching efficiency). Upon exquisite interfacial modification, the as-exfoliated graphene flakes tend to assemble with the Na₂Ti₆O₁₃ (NTO) nanosheets as a layer-stacked, mechanical-flexible anode, which further demonstrates a robust cycling at various flexing states and extreme power output of 1142 Wkg⁻¹ as paired with the LiFePO₄ cathode (5.3 mg cm⁻²) in the integrated, thin-film battery. This work vividly demonstrates potential add-value market of spent anodes in the flexible power sources.