Phase-Transition-Induced Co–Fe2O3 Nanosheets from Upcycling Spent LiFePO4 for Oxygen Evolution

Spent LiFePO4 (LFP) batteries were upcycled into Co-modified Fe2O3 nanosheets (sFe2O3@Co) through an oxidative reconstruction, selective acid leaching, and Co incorporation. Phase-transition-induced confined growth generated defect-rich ultrathin Fe2O3 nanosheets, while Co doping reconstructed the local electronic structure and accelerated the charge transfer. As a result, sFe2O3@Co exhibited excellent OER activity, requiring only 265 mV at 10 mA cm–2 with a Tafel slope of 28.6 mV dec–1 and maintaining 72.6% activity after 350 h. An AEM electrolyzer achieved 100 mA cm–2 at 1.62 V. A techno-economic analysis further demonstrated the superior value of this upcycling strategy over conventional recycling routes.