Engineering semicoherent interface with O–Fe–Se coordination for boosting the capacity and rate capability of a battery-type supercapacitor anode

The low capacity and rate capability of the battery-type supercapacitor anode prevent its widespread application. In this paper, we construct a semicoherent heterojunction of Fe2O3/FeSe2 as an advanced battery-type supercapacitor anode to overcome the bottleneck. A series of characterization and first-principles calculations confirm that the special heterointerface manipulation automatically generates a stronger inherent electric field, thereby enhancing the electron transport rate and the OH− adsorption capacity. In addition, it facilitates additional redox reactions between the active materials and OH− and makes the reaction system easier to execute. Taking advantage of these benefits, the prepared anode has a high specific capacity of 199.2 mA h g−1 (1 A g−1) and retains 90.2% of its initial capacity after 5000 cycles at 105.8 mA h g−1 (10 A g−1). In addition, an asymmetric supercapacitor device is fabricated with the prepared Fe2O3/FeSe2 as the anode, which provides a maximum energy density of 52.55 W h kg−1 at 0.8 kW kg−1 and a capacity retention of 91.2% even after 15,000 cycles. In our work, a novel strategy for the optimal design of a battery-type supercapacitor anode with a large capacity and superior rate capability is conceived, significantly advancing the widespread application of transition metal compounds in energy storage systems.