Upcycling spent graphite anodes into cobalt/pre-treated spent graphite composites for high-performance microwave absorption

As lithium-ion batteries and electronic devices proliferate rapidly, recycling spent batteries and developing advanced electromagnetic microwave absorbers have become increasingly crucial. Upcycling spent graphite anodes into high-performance microwave-absorbing materials provides a value-added pathway for graphite resource reutilization while mitigating electromagnetic pollution. In this study, spent graphite anode waste was directly upcycled to construct PSG@Co (Pre-treated Spent Graphite @ Cobalt) composites via a liquid-phase impregnation followed by a carbothermal reduction process. The cobalt loading and morphology of PSG@Co composites were readily tuned by adjusting the concentration of the cobalt precursor solution, thereby further altering microwave absorption performance. Benefiting from the retained bulk graphitic structure and abundant defective sites of the pre-treated spent graphite, the composites exhibited excellent conductive loss and defect polarization. Moreover, cobalt incorporation significantly improved interfacial polarization, magnetic loss, and impedance matching. Under an optimal cobalt precursor concentration of 0.34 M, the PSG@Co-2 composite delivered remarkable microwave absorption performance, achieving minimum reflection loss of − 63.12 dB at 11.20 GHz and a maximum effective absorption bandwidth of 5.68 GHz at a thickness of only 1.65 mm. The study offers a practical and value-added approach to transforming spent graphite anode waste into high-performance microwave-absorbing materials.