Reconstruction-tunable upcycling of spent LiFePO4 cathodes for oxygen evolution electrocatalysis: from defect legacy to operating active interfaces

Spent lithium iron phosphate (LFP) cathodes offer limited economic value through conventional metal recovery routes, but their Fe–P framework and cycling-induced structural heterogeneity make them promising precursors for oxygen evolution electrocatalysts. This review develops a reconstruction-centered framework that connects battery degradation with catalyst evolution under anodic polarization. Rather than treating inherited defects as intrinsic active sites, this review evaluates how cycling-induced defects, lattice disorder, phase boundaries, and vacancy chemistry regulate the susceptibility of reconstruction. Reported upcycling routes are classified according to precursor structural continuity into direct electrochemical activation, component- and interface-modulated reconstruction, and framework conversion coupled with secondary reconstruction. Despite their distinct precursor structures, many reported systems evolve toward Fe/Ni-based (oxy)hydroxide-rich operating interfaces, although their composition, coordination environment, and reconstruction pathway remain highly dependent on precursor chemistry and electrochemical conditions. Performance is compared beyond overpotential by considering feedstock origin, activation history, current density, cell voltage, temperature, and operational lifetime. Key unresolved challenges are further discussed, including defect–reconstruction relationships, reconstruction kinetics, substrate-derived contributions, feedstock variability, and phosphate stability during saline electrolysis. This review positions spent LFP as a reconstruction-tunable pre-catalyst platform and discusses mechanistic, device-level, and sustainability considerations for practical anion exchange membrane water electrolysis (AEMWE).