Fe_2O_3 Nanoparticle Seed Catalysts Enhance Cyclability on Deep (Dis)charge in Aprotic LiO_2 Batteries

摘要

Although the high energy density of Li-O-2 chemistry is promising for vehicle electrification, the poor stability and parasitic reactions associated with carbon-based cathodes and the insulating nature of discharge products limit their rechargeability and energy density. In this study, a cathode material consisting of alpha-Fe2O3 nanoseeds and carbon nanotubes (CNT) is presented, which achieves excellent cycling stability on deep (dis)charge with high capacity. The initial capacity of Fe2O3/CNT electrode reaches 805 mA h g(-1) (0.7 mA h cm(-2)) at 0.2 mA cm(-2), while maintaining a capacity of 1098 mA h g(-1) (0.95 mA h cm(-2)) after 50 cycles. The operando structural, spectroscopic, and morphological analysis on the evolution of Li2O2 indicates preferential Li2O2 growth on the Fe2O3. The similar d-spacing of the (100) Li2O2 and (104) Fe2O3 planes suggest that the latter epitaxially induces Li2O2 nucleation. This results in larger Li2O2 primary crystallites and smaller secondary particles compared to that deposited on CNT, which enhances the reversibility of the Li2O2 formation and leads to more stable interfaces within the electrode. The mechanistic insights into dual-functional materials that act both as stable host substrates and promote redox reactions in Li-O-2 batteries represent new opportunities for optimizing the discharge product morphology, leading to high cycling stability and coulombic efficiency.