Black-Fe2O3 Polyhedron-Assembled 3D Film Electrode with Enhanced Conductivity and Energy Density for Aqueous Solid-State Energy Storage

The construction of advanced Fe2O3 materials with high energy density for energy storage faces challenges due to the defects of conventional widely-known red-brown Fe2O3 such as poor electronic conductivity and insufficient physical/chemical stability. Unlike previous work, we successfully synthesize a novel black Fe2O3 (B-Fe2O3) thin film electrode by adopting simple hydrothermal strategy. Physical characterizations indicate that the as-made B-Fe2O3 product is composed of polyhedrons (mainly exhibit 4-8 sides) with a micrometer grade size range. Besides, the Fe-based thin film electrode with this 3D structure has stronger affinity and high electronic conductivity. As anode of aqueous solid-state energy storage devices, the as-synthesized B-Fe2O3 film electrode exhibits excellent volume energy density of 14.349 kWh m−3 at power density of 1609 kW m−3, which is much higher than the best result of previous works (∼8 kWh m−3). This study may provide new insights into the development of the Fe2O3 series on developing high-efficiency Fe-based anode materials for solid-state energy storage.