3D Copper Foam@FeOx Nanoarrays as a High Areal Capacity and Stable Electrode for Lithium-Ion Batteries

Despite remarkable development in high capacity iron oxide-based electrodes for lithium-ion batteries (LIBs), the low mass loading and poor areal capacity still impede their practical applications. In this report, novel FeOx nanoarrays were directly constructed on three-dimensional (3D) copper foam current collector (denoted as CF@FeOx NAs) via facile hydrothermal growth followed by a postannealing process. The nanoarrays were stacked by numerous FeOx porous nanoblocks, exhibiting a unique hierarchical structure. The loading density of FeOx in the CF@FeOx NAs reached 2.5 mg cm–2 owing to the hierarchical structure of the novel 3D nanoarray electrode. When tested as an anode for LIBs, the 3D integrated electrode delivered high areal capacities of 3.33 and 2.61 mAh cm–2 at 0.25 and 1.25 mA cm–2, respectively. A high areal capacity of 2.12 mAh cm–2 was retained at 2.5 mA cm–2 after 500 cycles, which is the best electrochemical performance in terms of areal capacity for the iron oxide-based electrodes reported so far. Even at a higher current density of 12.5 mA cm–2, the areal capacity was still maintained at 0.96 mAh cm–2, demonstrating good rate capability. A lithium full cell test was also conducted using LiNi0.8Co0.05Al0.15 (NCA) as a cathode and the CF@FeOx NAs as an anode, which exhibited a good areal capacity of 0.94 mAh cm–2 at 2.5 mA cm–2 after 50 cycles. This work offers a promising pathway to greatly enhance the loading density and areal capacity of metal oxide-based electrodes for electrochemical energy storage.