Bridging Li-Ion Batteries and Fuel Cells: From Cathode Leaching Residue to an Atomic-Scale Catalytic System

End-of-life lithium-ion batteries (LIBs) constitute an "urban mine" that offers a great opportunity to repurpose the metal species. However, the direct and cross-domain reuse of their functional materials has been ignored. Herein, we report a case study of upcycling a LIB cathode, LiFePO4 particles embedded in N-doped carbon spheres (LFP/C), to a single-atomic (SA) electrocatalyst for the oxygen reduction reaction (ORR). Using a top-down leaching method, the LFP/C was converted to Fe SA-embedded hollow carbon spheres containing minor FeOx nanoclusters and FePO4 nanoparticles (SAFe/FeOx/FePO4). Our studies indicate that the neighboring FeOx/FePO4 modulate the electronic filling in the antibonding state of SAFe sites and thereby optimize the intermediate adsorption energy at the rate-determining step, leading to the boosted half-cell ORR activity as manifested by a high Eonset of 0.97 V. Furthermore, the membrane electrode fabricated with the SAFe/FeOx/FePO4 demonstrates great potentials in two practical energy conversion devices, an ammonia fuel cell and Zn-air battery, building a bridge across the energy applications.