Epitaxial array of Fe3O4 nanodots for high rate high capacity conversion type lithium ion batteries electrode with long cycling life

With the energy density of intercalation electrodes approaching the ceiling, there are tremendous interests in developing metal oxide conversion type electrodes for lithium ion batteries, which involve more lithium ions in electrochemical reactions. Nevertheless, the cyclic and rate performances of conversion electrodes are rather poor, due to their large volume changes during charging and discharging, poor contact with current collector, and accumulated internal passivation over cycling. Here by carefully designing epitaxial array of Fe3O4 nanodots as a binder-free conversion electrode, we accomplish excellent rate performance under current density as high as 60C with long cycling life and good capacity, and the detailed scanning transmission electron microscopy in combination with comprehensive electrochemical analysis suggest that the success can be attributed to the synergic effects of released internal stress, slowed internal passivation, and good structure integrity all rendered by the nanodot array architecture of Fe3O4. Our study thus overcome materials breakdown, contact failure, and internal passivation of conventional conversion electrodes, providing new insight into optimizing conversion electrodes for practical applications.